Glossary

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A:  An abbreviation for acre, q.v. 


A:  An abbreviation for anal fin (rays). 


A:  The annual total mortality rate (the number of fish which die during a year divided by the initial number. Also called actual mortality rate, coefficient of mortality (Ricker, 1975)). 


a:  An abbreviation for annum, meaning year. 


a-: (prefix) As in lacking, absence of, not. 


A-ft: An acre-foot (one acre of surface covered with 1 foot of water (1,233,500 L, 1233.5 m3, 325,850 gal). 


A1: An abbreviation for first anal fin (rays). 


A2: An abbreviation for second anal fin (rays). 


A30: The number of anal fin rays anterior to the 31st vertebra, e.g. in Carapidae. 


A100: The number of anal fin rays anterior to the 201st vertebra, e.g. in Nemichthyidae. 


a posteriori classification: A classification made based on the results of experimentation. 

a priori classification: A classification made prior to experimentation. 


A-grade: A freshness grade for fish used in the European community. 

ab- :(prefix) As in from, away from. 



A-band: One of the dark bands which can be seen running across a myofibril in a skeletal
muscle. It corresponds to the location of filaments of the protein myosin.

Abbreviate heterocercal: The type of caudal fin in which the vertebral column extends only a short way into the upper lobe of the fin (which is longer than the lower lobe); a heterocercal caudal fin approaching the homocercal type, e.g. Lepisosteidae, Amiidae. 

Abbreviation: A shortened form of a word or title. In zoological works genus-group names cited in binomial names of species are often abbreviated to one or two letters for convenience, e.g. Salmo trutta may be abbreviated to S. trutta, the abbreviation always being followed by a full stop (or period). The abbreviation should not be used on the first mention of a name. Similarly specific names cited in trinomial names of subspecies may be abbreviated. 

ABC: An allowable biological catch (a term used by a management agency which refers to the range of allowable catch for a species or species group. It is set each year by a scientific group created by the management agency and is the subjectively estimated amount of catch of a given species from a given region. The agency then takes the ABC estimate and sets the annual total allowable catch (TAC)). 

Abdomen: The part of the body containing the viscera; also refers to the lower part of the body of fish, the belly. 

Abdominal: Pertaining to the abdomen. Pelvic fins are said to be abdominal when they lie behind the posterior tip of normally developed pectoral fins. 

Abdominal cavity: The part of the body containing the viscera or guts, liver, ovaries, testes, kidneys, etc. 

Abdominal pore: An external aperture near the vent communicating with the abdominal cavity. Found in Cyclostomata, Elasmobranchii, and in some Teleostomi, e.g. Salmonidae.

Abdominal serra: An abdominal spine, formed from a scale in the ventral region of the fish body. A series of these serrae form a saw-like edge and their numbers can be used in identification of some Clupeidae and Serrasalmidae. 

Abdominal vertebra: One of the anterior vertebrae bearing ribs but lacking the haemal arch, canal and spine of caudal vertebrae, q.v. 

Aberration: A term used to denote a class of individuals within a species. A name which explicitly refers to an aberration unequivocally treated as an infrasubspecific entity is unavailable. 

Abioseston: The non-living components of the seston, q.v. 

Abiotic: A ecological factor which is concerned with the non-living part.

Abnormality: Any condition not found in most fishes.

Aboral: = opposite or away from the oral or mouth area/cavity. 

Abortive: = remaining or becoming imperfect. 

Abraded: = worn or frayed, e.g. fins of fish after spawning. 

Absolute abundance: = the total number of a kind of fish in the population. Usually estimated from relative abundance as it is rarely known. 

Absolute fecundity: = total number of eggs in a female. 

Absolute growth rate: = the actual increase in size of an individual, stock or population over a given time span and under specified conditions. 

Absolute recruitment: = the number of fish which grow into the catchable size range in a unit of time (usually a year)(Ricker, 1975). 

Absolute synonym: A homotypic synonym (a synonym based on the same nomenclatural type). 

Absolute tautonymy: = the identical spelling of a generic or subgeneric name and the specific or subspecific name of one of its originally included nominal species or subspecies. 

Absolute tautonymy: = the identical spelling of a generic and species or subspecies name originally included in the genus. 

Abundance: = degree of plentifulness. The total number of fish in a population or on a fishing ground. Can be measured in absolute or relative terms and may be number per area or per unit fishing effort. 

Abundance index: = data obtained from samples or observations and used as a measure of the weight or number of fish which make up a stock or a segment of a stock such as spawners. Most indices are relative units (as opposed to measuring absolute abundance), and simply indicate relative changes in abundance over time. 

Abyss (adjective abyssal): = water below 4000 metres or 2000 fathoms (= 3660 metres), down to 6000 metres, where light does not penetrate. Occasionally used for depths below 2000 metres. A constant environment with temperatures usually 0-2°C or temperatures are uniform. 

Abyssal benthic: = pertaining to the ocean floor below 400-600 fathoms (730-1100 metres). 

Abyssal depth: = see abyssal for oceans; in fresh water it may mean the maximum depth or the depth at which water temperature remains uniform. 

Abyssal plain: = the area of the generally flat ocean floor excluding ocean trenches below 2000 fathoms (3660 metres, presumably an older version based on fathoms) or 4000 metres. 

Abyssal zone: = the middle zone of the deep sea between 3700 and 6000 metres.

Abyssobenthic: = the depth zone of the ocean floor between 4000 and 6000 metres, or from about 3700 m downward, or below the 4°C isotherm. 

Abyssopelagic: = living in the water column at 4000 to 6000 metres (or 2500-4000 metres, or 4000-7000 metres, sources differ), seaward of the continental shelf-slope break. 

AC: Aseries of ventro-lateral photophores extending between a vertical at the anal fin origin and the end on the caudal peduncle. The AC row may begin posterior to the anal fin origin if it is offset from other ventro-lateral photophores. 

Acanthotrich:: A spiny dorsal or anal fin ray. 

Acanthostedion: The postlarval stage of the Peristediidae characterized by long parietal spines and development of rostral exsertions. 

Acceptable biological catch: The subjectively estimated amount of catch of a given species from a given region. Also called allowable biological catch.

Acceptable catch estimate: An approximate estimate of the catch of a given species that could be taken from a stock in a given region. Also called allowable catch estimate. 

Acceptable impact: A negative, or potentially negative, alteration of the fishery resulting from human activities. The impact is acceptable; since it represents a low risk to the resource. 

Accepted name: A name adopted by an author as the correct name for a taxon where names are in dispute. 

Access: The means by which a person enters a water body, usually with a boat. 

Access right: The authorisation given to a user, e.g. a vessel owner, by a fishery management authority or by legislation, to exploit a resource, a particular species, or a share of a total allowable catch. Access rights may be free of charge or require payment and are usually conditional and used under constraints specified in a management plan. 

Accessibility: The condition of fish occupying a locality where they can be caught. 

Accession: 1) the formal acceptance into museum custody of a specimen or a collection of fishes, and the recording of such, 2) a specimen(s) acquired by a museum for its permanent collection, 3) the act of recording and processing an addition to a permanent collection. 

Accession list: A document in which accessions are recorded, usually chronologically by date of receipt; may be a bound volume and/or a computer file. 

Accession number: A unique number assigned to an accession, usually sequentially in chronological order of receipt. 

Accessioning: Accepting legally a fish collection, containing one to many specimens and species, with date of receipt, ownership, donor, etc. 

Accessory caudal ray: One of a series of short, procurrent rays on the upper and lower margins of the of the caudal peduncle. 

Accessory dorsal branch: A lateral line branch found in some flatfishes, running from the head for varying lengths below the base of the dorsal fin. 

Accessory growth centre: A growth centre outside the core of the fish otolith from which new growth may occur. Also incorrectly called accessory primordia. 

Accessory lateral line: Accessory dorsal branch. 

Accessory male: A male fish which attempts to fertilise eggs of a breeding female at the expense of a dominant male. 

Accessory pectoral scale: Accessory scale, q.v. 

Accessory pelvic appendage: A tapered fleshy lobe above the base of the pelvic fin. May be covered by a scale. 

Accessory primordium: An additional growth centre outside the otolith core but lacking primordial granules. Accessory growth centre is preferred. 

Accessory respiratory organ: A superficial or internal organ which complements the gills in exchange of gases with the environment when the fish is in poorly oxygenated water or in air. In some cases it may also function as a hydrostatic organ. 

Accessory scale: Axillary scale (a small triangular appendage or a modified scale at the upper or anterior base of a paired fin. Also called fleshy appendage. Functions apparently to streamline the fin when held against the body while swimming). 

Accidental catch: Other fishes caught during a fishery directed to a target species. Also called incidental catch or by-catch. 

Acclimation: The process by which fish become used to new circumstances. Often used in adjusting to changes in temperature, water quality, lighting regimes, etc. in aquaculture or aquaria. Fish may be more susceptible to pathogens and eat poorly while acclimating. 

Acclimatisation: Adaptation to a new environment; in fishes temperature, salinity and pollution are often environmental factors. 

Acclivous: Having a gentle upward slope. 

Acentrous: Without vertebral centra, with persistent notochord, e.g. Dipnoi, Holocephali. 

Acequia: An irrigation ditch or canal, often community run (southwest United States). 

Aciculate: Needle-like. 

Acid deposition: The addition of acidic material to the ground or water, usually from sulphur and nitrogen compounds emitted by factories and deposited far from this source. Wet deposition is also called acid rain, q.v., and is the result of rain, snow or fog while dry deposition results from particle fallout or acidic gases. 

Acid lake: Any lake with a pH less than 6.0. 

Acid neutralising capacity: The property of water that reacts with an acid; formerly alkalinity. Abbreviated as ANC. 

Acid pickle: An acid solution for curing or marinating fish. 

Acid rain: Rain falling through an atmosphere containing sulphur dioxide and nitrogen oxide pollutants thus making the rain acidic (pH less than 7.0); in lakes without the ability to neutralise the acid survival of fish eggs and young is compromised. Also referred to as acid deposition and wet deposition. 

Acid-cured fish: Fish preserved or marinated in acidified brine with or without spices. 

Acidity: A measure of the hydrogen ion concentration, a pH less than 7.0, or the quantitative capacity to neutralise a base to a designated pH. 

Acidophilous: Having an affinity for or thriving in acidic conditions, e.g. in a bog or marsh. Also called acidophilic. 

Acinaciform: Slender sword, of scimitar-like form, e.g. acinaciform branchiostegal rays in Perciformes.

Acinus (plural acini): A lobule of a secretory gland formed by a group of exocrine glandular cells, e.g. in the pancreas. 

Acipenserin: A toxic substance reputedly obtained from the gonads of sturgeon, Acipenser. 

Acmic: Referring to periods of seasonal change in an aquatic population. 

Acoustic survey: A method of gathering information on fish availability and abundance by using echo sounders and sonar. 

Acoustic tag: A sound transmitter attached to a fish. 

Acoustico-lateralis system: The sensory system consisting of the lateral line and the inner ear. 

Acquisition: Transfer of title for a specimens(s) to a museum. Acquisitions may be gifts, purchases, bequests, exchanges or the results of field work.

Acre: 4046.9 m2, 0.405 ha, 43,560 ft2, 4840 yd2, 0.00156 mi2.

Acre-foot: One acre of surface covered with 1 foot of water (1,233,500 L, 1233.5 m3, 325,850 gal.). 

Acrodin: Tissue forming a cap on teeth found in ray-finned fishes. 

Acrodont: Type of tooth ankylosed to the jaw along the midline of the jawbone, rather than to the inner edge, the condition in most fishes. Attachment is by connective collagenous tissue with impregnated calcium salts and, in maxillary and mandibular teeth, by a bony piece between the tooth and the bone. 

Acronurus: Postlarval stage of Acanthuridae. 

Acronym: Any abbreviation using the initial letters of the words abbreviated. Museum collections of fishes are catalogued with an acronym and a number; these acronyms are listed in Leviton et al. (1985) and Leviton and Gibbs (1988). 

Acrosome: A cap over the nucleus of spermatozoan heads having enzymes involved in sperm penetration of the egg and possibly fusion of egg and sperm. Absent in most Teleostei. 

Acrylic: A plastic material used in aquaria construction and for aquarium accessories such as filters.. 

Act, nomenclatural: A published act which affects the nomenclatural status of a scientific name or the typification of a nominal taxon; available nomenclatural act is one that is published in an available work; invalid nomenclatural act is any nomenclatural act which is not valid under the provisions of the International Code of Zoological Nomenclature; unavailable nomeclatural act is one published in an unavailable work; valid nomenclatural act is one that is accepted under the provisions of the Code, i.e. the earliest available act not contravening any provision of the Code. 

Actic: Pertaining to rocky shores; between the low and high tides; intertidal; littoral. 

Actinophore: The pterygiophore(s) and the associated fin ray. 

Actinost: One of a series of endochondral bones in the pectoral and pelvic girdle on which the fin rays insert. Most teleosts lack or have greatly reduced pelvic actinosts. Teleosts have one row of actinosts between the fin rays and supporting skeleton (coracoid and scapula for the pectoral, basipterygia for the pelvic) while other fishes may have more rows, referred to as radials.

Actinotrichium (plural actinotrichia) or actinotrich: A slender, horny, flexible, unsegmented fibril which strengthens the embryonic fin fold and which may persist in the outer edge of the adult fin membrane or in the adipose fin. It develops intercellularly rather than cellularly. Persists in fins of Elasmobranchii, Holocephali, and sometimes in Teleostomi distal to the lepidotrichia that replace them. Actinotrichia are translucent, exhibit birefringence (double refraction) and are composed of a scleroprotein called elastoidine. They may be homologous with ceratotrichs found in cartilaginous fishes because of their horny or keratinous nature.

Action: 1) the performance of a fishing rod being the time elapsed between flexion and a return to a straight configuration. Action can be slow (the most flexion) to fast; also referred to as stiff, parabolic, etc. May also refer to the rod strength, a light rod being limber and a heavy rod stout, 2) the gear of fishing reels, 3) the movement and performance of a fishing lure in the water.

Activated carbon: Pure carbon in porous form used in aquaria to adsorb dissolved organic matter.

Active: Fish intent on feeding. Also called positive.

Active fishing: Fishing with gear that is not stationary, e.g. trawls. 

Actophilous: Thriving on rocky shores. 

Actual mesh size: Stretched mesh size of a net as determined by a standard process such as use of a mesh gauge, q.v. 

Aculeiform: Needle-shaped, e.g. pipefishes. 

Acuminate: Tapering gradually to a point, e.g. the tail of Anguilliformes. 

Acute:  1) ending in a sharp point, 2) running a short and intense course as in toxicity or inflammation. 

Acypriniod zone: Those regions lacking Cyprinidae - South America and the tropical Pacific Islands approximately east and south of Wallace's Line including Australia. 

Ad hoc: For the specific purpose, case or situation at hand and for no other. 

Ad int.: Ad interim, meaning for the present, provisionally. 

Ad libitum: To the limit; often meaning fed until satiated. 

Ad- (prefix): To, on the side of. 

Adaptation: The process (or its results, e.g. a structure) wherein individuals, populations or species change to cope with their environment or changes in that environment. 

Adaptive management: A management process involving feedback to test performance and perhaps deliberate intervention to test the fishery system's response. 

Adaptive radiation: Speciation of a taxonomic group to fill numerous previously vacant ecological niches, e.g. Cichlidae in the Great Rift Lakes of Africa, Cottidae in Lake Baikal of Russia.

Adaxial: The paraxial mesoderm subregion developing just adjacent to the chorda mesoderm or notochord rudiment. 

Added-value: Processing of fish before export. 

Additional material: Specimens other than those in the type series; these may be used to describe a new species but have no nomenclatural significance. 

Adductor: A muscle that brings one body part towards another 

Adductor mandibulae: A muscle of the cheek area which acts to close the mouth and compress the lips. It is divided into four parts in the perch (Perca flavescens): part 1 has its origin on the dorsal half of the vertical arm of the preopercle and inserts at the centre of the maxillo-mandibular ligament (q.v.). It is a large muscle below the eye. A third part of the ligament serves as an origin for the fourth part of the muscle. Part 3 originates on the pterygoid bone and inserts with part 2 on the maxillo-mandibular ligament beneath the insertion of part 1. Part 2 is a large muscle below part 1. Part 4 originates on the internal portion of the maxillo-mandibular ligament and inserts on the ventral, internal part of the dentary and so is on the lower jaw. 

Adductor operculi: A muscle originating from the pterotic bone posterior and medial to the origin of the elevator operculi and inserting on the dorso-medial surface of the operculum ventral to the insertion of the levator operculi. 

Adelfophagy: Feeding on retarded siblings within the uterus, e.g. Lamna nasus, Odontaspis taurus, Latimeria chalumnae. 

Adenohypophysis: Part of the pituitary organ of the lower brain involved in hormone control. 

Adenoid organ: A lymphoid structure in the lining of the oesophagus of Elasmobranchii.

Adfluvial: 1) living in lakes and migrating into streams to spawn; juveniles feed in streams but migrate to lakes as subadults for feeding, 2) pertaining to flowing water. 

Adherent: Attached (firmly); sticking; connected with. Said of scales that do not detach easily, for example. 

Adhesive disk: A sucker-like organ for clinging to various surfaces, e.g. the modified pelvic fins in Gobiescoidae and Liparidae, and the dorsal fin in Echeneidae. Also spelt adhesive disc and used for the adhesive organ. 

Adhesive egg: A fish egg that is deposited on sand, gravel, plants, etc. to which it sticks by means of the egg's sticky surface. In aquaculture situations this is inconvenient and the adhesiveness can be removed by milk or tannin. 

Adhesive head gland: Adhesive organ. 

Adhesive organ: Transient larval organs near the mouth used to attach the larvae to the substrate, e.g.in Protopterus, Lepidosiren, Acipenser, Esox, Macropodus. 

Adipose eyelid: Transparent membrane(s) over the anterior and posterior regions of the eye, e.g. in Scombridae, Clupeidae, Albulidae, Mugilidae. It serves for streamlining and protection and may cover much of the eye except for a small central opening. 

Adipose fin: A small fleshy fin lacking rays or spines but reinforced by actinotrichs posterior to the soft dorsal fins (rarely a hard ray or a few soft rays may be developed in the adipose fin of certain catfishes), e.g. in Salmonidae, Osmeridae, Argentinidae, Myctophidae, Ictaluridae, Percopsidae. 

Admissible: The form of a name which can be validly published and the use of a name or epithet in accordance with the provisions of the International Code of Zoological Nomenclature. 

Adnasal bone: A small dermal bone in front of the nasal bone in some fishes, e.g. the middle bone of three in the nasal region of Lepisosteus. 

Adnate: Closely attached to, joined along whole length without a free tip; conjoined; adhering, e.g. adipose fin in Noturus (Ictaluridae). 

Adnate eye: An eye joined by a membrane to the orbit.

Adnexed: Unattached, with a free edge, not united, flag-like e.g. the adipose fin in salmonids. Opposite of adnate. 

Adopt: To use an unavailable name as the valid name of a taxon in a way which establishes it as a new name with its own authorship and date. 

Adpressed: Pressed flat against the body. 

Adtidal: Living immediately below the low tide level. 

Adult: A sexually mature animal. 

Adult fish count: A count of adult fishes passing by a fish-viewing window. Such windows can be placed at the upstream end of fish ladders on dams. Observers count the number of fish according to pre-set criteria, e.g. by species and size, for 50 minutes of every hour for 16 hours per day. Extrapolations can then be made for times when fish are not observed. Separate counts can be made for adults and jacks (precocious male salmonids that can be identified by their smaller size). 

Adult period: This period begins with the first maturation of gametes and is characterised by spawning, either annually or only once, and by a slowed or arrested growth rate. 

Adv.: Advena, alien, introduced. 

Advanced fry: A larval fish that has absorbed the yolk, correctly postlarva.

Advena: Alien, introduced. Abbreviated as adv.

Adventitious: Accidental, occurring at an unusual locality.

Aerial stocking: Releasing fish into a water body from a plane or helicopter. Usually fry are stocked in this way. 

Aerial survey: A method of gathering information on fish shoal movement and density by visual observation and photography from low-flying aircraft. 

Aerial trap: A trap used to take jumping fish, e.g. mullets and flyingfish. Fish are caught on the surface in boxes, rafts, boats and in such nets as veranda nets. The fish may be frightened into jumping out of the water. 

Aerofoil: Modified pectoral and pelvic fins used for gliding.

Aestival pond:  1) a pond containing some water throughout the year but freezing to the bottom in winter, thus supporting only a temporary fish fauna, 2) a pond existing only in summer. 

Aestivation: Dormancy during the dry season or summer, e.g. in Dipnoi. Also spelled estivation.

Aff.: Abbreviation for affinis (related to but not identical with, affinity, relationship, sometimes misleadingly employed as a synonym for phenetic similarity (or akin to)).

Afferent branchial arteries: Those arteries that receive blood from the ventral aorta, extending along the gill arches and sending capillaries into the gill filaments where they join branches which become the efferent branchial arches and so are involved in gaseous exchange. 

Affinis: Related to but not identical with, affinity, relationship, sometimes misleadingly employed as a synonym for phenetic similarity (or akin to). 

Affluent: A stream or river that flows into a larger one or to a standing water body; a tributary; influent, although this may be restricted to a lake having a single inflowing stream (or influent). 

AFO: Number of vertebrae anterior to the anal fin origin, e.g. in larval fishes. 

Afterbay: The tail race or reservoir of a hydroelectric power plant at the turbine outlets. 

Agamy: The condition where no lasting bond is formed between a spawning pair, the male and female separating after spawning, e.g. in some Cichlidae. 

Agape: With jaws open; gaping. 

Age: The number of years of life completed (Ricker, 1975). In fisheries indicated by a numeral, e.g. age 5 or age V. The numeral may be followed by a plus sign to indicate the year of life, e.g. 5+ is a fish in its sixth year of life. 

Age at first capture: The age at which fish are first caught commercially. 

Age at first maturity: Mean or median age at first maturity when 50% of a cohort spawn for the first time.

Age class: Individuals of a given (same) age within a population; a cohort. Usually given in years but may be shorter periods, particularly in the tropics.

Age composition: The proportion of different age groups of fish in a population or in a catch. 

Age determination: The age of fish may be determined by counting the annual rings on a scale (by microscopic examination, projection of the scale or its celluloid imprint with a scale projector, or projecting a photographic negative of the scale), or in bony parts such as vertebrae, otoliths, opercular series of bones, pectoral spines; by the known age method (growing fish in ponds or tagging fish in the wild and recapturing them at intervals); by the length frequency method (the different age groups tend to be different lengths apparent when the sizes are grouped in a length frequency graph, from which age may be deduced). 

Age distribution: The number or percentage of individuals in each age class of a population; age structure. 

Age estimation: Age determination. 

Age frequency: A breakdown of the different age groups of a kind of fish in a population or sample. Also called age structure. 

Age of fishes: The period of time in the earth's history dominated by fishes - the Silurian and Devonian periods. 

Age of maturity: The age when 50% of the fish of a given sex are considered to be reproductively mature. 

Age of recruitment: The age when fish are considered to be recruited to the fishery. In stock assessments, this is usually the youngest age group considered in the analyses, typically age 0 or 1. 

Age specific:  the dependence of a factor, such as fishing mortality, on the age of fish. 

Age specific fecundity: Fecundity or egg potential related to age. 

Age specific mortality: Mortality expressed as a function of age. 

Age specific survival rate: The average proportion of individuals in a particular age group that survive for a given period. 

Age structure: The number or percentage of individuals in each age class of a population. 

Age validation: Confirming that annual growth rings on bony parts do conform to a year's growth. 

Age-cohort analysis: The proportion of each age-group participating in an activity currently used to predict the future sizes of each age-group. 

Age-group: A term denoting the age in years of a fish, or the number of calendar years in which it has existed, as O, I, II, III, etc. Unfortunately a standard definition has not been established. 

Age-length key: A method of assigning ages to fish, given length measurements. Used to convert catch-at-size data into catch-at-age data. The keys specify the probability that fish of a given size belong to one of several age groups.

Age-slicing: Cohort slicing (a method used to assign ages to fish, given length measurements, e.g. used to convert catch-at-size data into catch-at-age data before the application of age-structured assessment models. Cohort slicing assumes that there is a one-to-one correspondence between length and age, i.e. the approach ignores individual variability in growth). 

Age-structured production model: A stock assessment programme based on a deterministic form of a stock-recruitment relationship, with non-equilibrium tuning of abundance indices. Abbreviated as ASPM. 

Ageing: The process of determining the age of a fish or population of fishes. A fish that is less than 1 year old (counted from time of spawning by its parents) is a subyearling, or zero-age. A yearling fish is more than 1 year and less than 2 years old. Ages may be expressed as years or as year with a + sign, e.g. 3+ is a fish in its fourth year of life. Strictly, this term should be used only for the process of becoming older and the associated changes in an individual. 

Ageing technique: A method of determining the ages of fish, most often done by counting rings in hard parts of the fish body, such as otoliths, scales, opercula or vertebrae. 

Aggregate: A group of species, other than a subgenus, within a genus, or a group of species within a subgenus, or a group of subspecies within a species. The aggregate can be indicated by a species-group name interpolated in parentheses. 

Aggregated fishery data: Pooled data. Such data is compiled so that confidential or proprietary data, e.g. on detailed fishing activities of individual fishers or vessels, cannot be determined either from the present release of the data or in combination with other releases. 

Aggregating device: Artificial or natural floating objects placed on the ocean surface, often anchored to the bottom, to attract several schooling fish species underneath, thus increasing their catchability. Used with tuna, for example. Also called fish attracting device. Abbreviated as FAD for fish aggregating device. 

Aggregation: A group of fishes in close proximity, usually of the same species, most of which are not oriented or moving in the same direction, usually responding independently to a common stimulus, e.g. food; as opposed to a school, q.v.

Aggressive mimicry: Mimicry involving at least three species. A predator resembles a non-aggressive species such as a cleaner (q.v.) and thus can attack misled clients who think they are about to be cleaned. 

Aglomerular: Without glomeruli (q.v.). An aglomerular kidney lacks capillaries which filter water and waste from the bloodstream. Found in some Gasterosteiformes. 

Aimed fishing: Fishing directed at a particular, identified group of fishes, such as a school located by sonar. 

Air bladder: Gas bladder, the preferable term since the composition of gases may not be identical to that of air (a thin membranous, sometimes alveolated sac in the dorsal portion of the abdominal cavity. Contains a varying mixture of gases and may be one, two or three chambered. May be connected to the gut by a tube, the ductus pneumaticus (then called physostomous) or unconnected (then called physoclistous). May function as one or more of:- hydrostatic organ, sound producing organ, sound receptor, respiratory organ. Found in Actinopterygii. Often lacking in bottom fishes. Sometimes called swim bladder, a less appropriate term). 

Air blast chilling: Cooling fish product with a blast of cool air to a temperature just above 0°C. 

Air blast freezing: Freezing fish product with high velocity cold air to -35°C. 

Air breathing fishes: A general term for those fishes that can use atmospheric oxygen by means of an accessory respiratory organ, in addition to their gills. Includes fishes in the Clariidae, Channidae, Belontiidae, Osteoglossidae and the lungfishes (Dipnoi). 

Air curtain: Air bubbled through perforated pipes as a barrier to fish movement. 

Air hole: An opening in the frozen surface of a water body. 

Air lift: A device that inserts air into water at depth, displacing both upwards. Used in aquaculture to remove fish from cages for harvest or to lift dead fish from the bottom of cages. Also called air lift system or air water lift. 

Air pump: A pump which supplies air for airstones, lift tubes, skimmers, bubblers, and other devices in an aquarium. The most common type are diaphragm pumps, though cylinder pumps are available for large installations. 

Air vesicle: Hard, hollow spheres of bone in Clupeidae. 

Airstone: A device that attaches to the air pump, q.v., to create various bubble effects in an aquarium and to oxygenate the water. 

Al.: Abbreviation of alii or aliorum, meaning others, of others. 

Ala: Alar scale. 

Ala laminaris: A lateral ridge on the lower part of the cleithrum, forming a site of attachment for some of the pectoral fin muscles. 

Alar scale: One of the enlarged, elongate flap-like scales at the base of the caudal fin, e.g. in Alosa, Sardina, Sardinops, Harengula. Called paracaudal organ in the anchovy. Probably related to fast swimming. 

Alar spine: A spine on the upper surface of the pectoral fin near the tip, in some male Rajidae. 

Alar thorn: Alar spine. 

Alarmist: An individual fish which reacts by movement to alarm substances, warning other school members and drawing attention of the predator upon itself, e.g. many Cypriniformes and Gonorhynchiformes. 

Alarm substance: A substance produced in the round or oval alarm substance cells (previously called “clubcells") in the skin of Ostariophysi (Cypriniformes, Siluriformes) and Gonorhynchiformes, and which is released upon injury of the skin. On scenting the alarm substance members of the same species, and to a lesser extent related fishes, exhibit the fright reaction (q.v.). The dispersal of the alarm substance apparently normally acts to warn of the presence of a preying predator. The alarm pheromone is hypoxanthine-3N-oxide comprising a purine skeleton with N-O functional group and sensitive to relatively weak changes in pH. Also called alarm pheromone or Schreckstoff. 

Alaska Scotch cure: A modified Scotch cure, q.v., used in Alaska for herring processing. 

Albany beef: Cheap sturgeon flesh marketed in nineteenth century America. 

Alcohol: A general term for either ethanol (ethyl alcohol) or isopropanol (iso-propyl alcohol) used to preserve fishes in museums at various concentrations in water (70-80% ethanol, 45-50% isopropanol usually). Denatured alcohol is ethanol rendered unfit for human consumption by addition of methanol (methyl alcohol or wood alcohol) or other substances and is used in some fish collections. 

Alecithal: Eggs with little or no yolk. 

Alevin: A young fish with a yolk-sac; larva of species in which postlarval stages are not recognized; that is, in which the yolk-bearing larva transforms directly into the juvenile, e.g. in Salmonidae; the stage from hatching to end of dependence on the yolk sac as the primary source of nutrition. 

Algae: Simple rootless aquatic plants growing in relative proportion to the amounts of nutrients and sunlight available. They can affect water quality adversely by lowering the dissolved oxygen and thus affecting fish populations but they are also food for fish. 

Algal bloom: The rapid growth of algae on the surface of lakes, streams, or ponds; stimulated by nutrient enrichment. 

Algivore: Feeding on algae. 

Alien: Any species not native (indigenous) to the area under consideration, often a politically defined area (country, province, state, etc.). It includes exotic, introduced, transplanted, non-native, non-indigenous, invasive and escaped species. 

Aliform: Wing-like, usually in reference the pectoral fin. 

Alii: Others. Abbreviated as al. 

Alimentary canal: The passage through which food passes and is digested and absorbed; includes the mouth, oesophagus, stomach, intestine and anus. Also called alimentary tract, digestive tract and gut. 

Alisphenoid: Term misapplied in older literature to the pterosphenoid (q.v.) of fishes. It is not homologous with the alisphenoid of mammals and should not be used.

Alizarin: A bone specific stain, alizarin red S, is used to highlight the osteology of a fish specimen. The viscera are often excised and the flesh macerated or cleared (rendered transparent) by enzymes or potassium hydroxide.

Alkaline cure: Stock fish, q.v., soaked in a solution of lime and soda and then in water for several days. 

Alkaline gland: A paired organ in the genito-urinary apparatus of Raja (and probably other skates and rays) whose cavity is fluid filled. Also called Marshall's gland. 

Alkalinity: The acid-neutralisng capacity of carbonates, bicarbonates and hydroxides in water. Total alkalinity is the total concentration of bases in water, expressed as mg/l of CaCO3. 

All-female species: The production and survival of a clone by gynogenesis, q.v., e.g. in Poeciliidae, Cyprinidae. 

Allec: A fish paste of the ancient world made by fermenting brined fish. 

Allen paradox: The observation that the quantity of benthic invertebrates in a river is insufficient to support the observed fish population.

Allergy:  Humans can be allergic to fish (BWC, personal experience) although not to other seafoods such as crustaceans and molluscs. Gadus morhua allergy has been studied the most and other species are believed to be similar although not all fish species may trigger a reaction. Gad c l, a parvalbumin, is the major cod allergen.

Allo- (prefix): Other. 

Allocation: Division of a fish resource among harvesters and those needed for reproduction. The allocation can be absolute, e.g. a number of tonnes per country based on the TAC, q.v., or relative, e.g. a percentage of the annual allowable catch. May be based on historical harvests. 

Allochronic species: Those species that do not occur in the same geological Period. 

Allochthonous: Food items, organic matter, nutrients etc. that enter an aquatic ecosystem from outside. 

Allolectotype: A type specimen of opposite sex to the lectotype and chosen from the type series subsequent to the original description. 

Allometry: The study of proportional growth rate differences, e.g. how head length changes with respect to increasing body length. 

Alloparalectotype: A paralectotype, q.v., of opposite sex to the lectotype. 

Alloparatype: A paratype, q.v., of the same sex as the allotype. 

Allopatric: Refers to populations or taxa whose ranges do not overlap. 

Alloplesiotype: A plesiotype, q.v., of the same sex as the allotype. 

Allotopic: Species with overlapping ranges not occurring together. 

Allotopotype: A type specimen from the original type locality of the same sex as the allotype, q.v. 

Allotrophic lake: A lake receiving organic matter from the surrounding land by runoff. 

Allotype: A paratype of opposite sex to the holotype and originally designated by the author, a term not regulated by the International Code of Zoological Nomenclature. 

Allowable biological catch: A term used by a management agency which refers to the range of allowable catch for a species or species group. It is set each year by a scientific group created by the management agency and is the subjectively estimated amount of catch of a given species from a given region. The agency then takes the ABC estimate and sets the annual total allowable catch (TAC). Abbreviated as ABC. 

Allowable catch: The catch allowed by a management authority to be taken from a stock of a species or group of species, by a fishery during a specified time period. Often defined as the total allowable catch (TAC). Often allocated explicitly amongst those having a right of access to the stock. 

Allowable catch estimate: Acceptable catch estimate, q.v. 

Allowable quota: A share in a total allowable quota (TAC) usually divided amongst those with a right to participate in the fishery. Also called quota. 

Allowance: An amount set aside from a total allowable catch to allow for the expected catch of harvesters who are not subject to quota management. 

Alluvion: Fine sediment. 

Alluvium (adjective alluvial): Clay, silt, sand, gravel or other material deposited by running water. Often fossil-bearing. 

Alm's Fb coefficient: The ratio of fish caught to total benthic biomass per hectare.

Almas: Golden caviar, i.e., either the eggs of an albino sturgeon with a light and delicate flavour or those of Acipenser gueldenstaedtii at least 60 years of age with a creamy and subtle flavour. 

Alpine lake: A lake in a mountainous area with a cold climate, associated with snow and ice conditions. 

Alternative name: Two names for the same taxon, of the same rank, published simultaneously by an author. 

Altithermal: A warmer period than today, about 4500-7000 B.P. 

Altricial: Young requiring care or nursing after hatching. Opposite of precocial. Also used to describe ontogeny with large numbers of ova with low energy content, poorly-developed larvae and relatively large clutches in early maturing and slow-growing fishes. 

Alveolar: Pocketed or pitted, honeycomb-like 

Alveolar ridge: A bony ridge supporting teeth. 

Alveolus (plural alveoli): A small cavity or space; socket of a tooth; air cell of the lungs.

Amarelo cure: Yellow cure (Portuguese salt cod with some of the salt removed by soaking in water between stages of washing and drying, yellowish in appearance). 

Ambicoloration: Pigmentation of both the eyed and blind side of flatfishes (Pleuronectiformes) in which, ordinarily, only the eyed side is pigmented. 

Ambient: Surrounding on all sides, the conditions in the environment, e.g. temperature. 

Ambiguous name: A name consistently used by different authors for different taxa (nomen ambiguum). 

Ambush predator: A predator that lies in wait for its prey rather than chasing it. See also pursuing predator and tracking predator. 

Amictic: Lakes with a permanent ice cover and so with no circulation. 

Ammocoete: The larval stage of lampreys (Petromyzontiformes) which is characterized by the presence of an oral hood and the lack of a sucking disk, teeth and developed eyes. The term is derived from the genus Ammocoetes in which the larvae were placed before it was realized that they were larval lampreys. 

Amphi- (prefix): Both, on both sides of, e.g. amphi-Atlantic on both sides of the Atlantic, amphi-American on both sides of America, amphi-Pacific on both sides of the Pacific (these terms may include discontinuous and continuous distributions). 

Amphibiotic: Living in water during an early stage of development and on land during the adult stage. 

Amphibious: Able to live or operate on land and in the water, e.g. mudskippers approach this condition. 

Amphiboreal: Pertaining to an interrupted northern circumpolar distribution. 

Amphicoelous: Biconcave vertebrae, having both ends hollowed out, the condition in Elasmobranchii, Amia and most Teleostomi except Lepisosteus (also spelled amphicelous). 

Amphidromous: Fishes which regularly migrate between the sea and fresh water (or vice versa) at some definite stage in their life cycle but not for the purpose of reproduction, e.g. Sicydium, perhaps Megalops and Chanos, some Galaxias (Myers, 1949).

Amphipedal progression: Locomotion using the pectoral fins in a manner similar to that used by humans on crutches, e.g. in mudskippers and frogfishes. Also called crutching. 

Amphistylic: Attachment of the upper jaw to the skull by means of a process on the palatoquadrate and the hyomandibular bone and by a direct connection between the jaw and braincase, e.g. some Elasmobranchii; basal gnathaostomes, other than placoderms).

Amphitropical: Pertaining to a distribution of temperate species interrupted by the tropics. 

Ampullae: Swellings of the end of the semicircular canals. 

Ampullae of Lorenzini: Lorenzini's ampullae (the mucus filled canal system opening on the snout of Elasmobranchii, Polyodon spathula and Plotosus anguillaris. May be electric, pressure or temperature receptors).

Ampullary organ: An electroreceptor consisting of receptor cells sunk into the epidermis or located in an epidermal cavity opening to the surface through a duct and pore. The duct may be filled with jelly, e.g. in certain Gymnotidae, Mormyridae and Siluroidei.

Anabiosis: Inhabiting temporary water bodies and surviving drought by suspended animation, e.g. Dipnoi. 

Anabranch: A diverging branch of a river which re-enters the main stream. 

Anacanthous: Lacking dorsal fin spines. Opposite of phalacanthous. 

Anacat: Fish that live partly in fresh water and partly in the sea and vice versa (from anadromous and catadromous). 

Anadromous: Running up; said of those fishes which spend most of their life in the sea and which migrate to freshwater to reproduce, e.g. Oncorhynchus, Stenodus, Petromyzon, Roccus, Stokellia anisodon (Retropinnidae) (Myers, 1949). The opposite is catadromous. 

Anaemia: Deficiency of red blood corpuscles or haemoglobin; in fish a dietary disease due to a vitamin deficiency. 

Anaerobic: Without oxygen, either as a presence or needed as part of a process. 

Anagenesis: Evolutionary change along an unbranching lineage (no new species arise). 

Anagram: A taxonomic name formed by the rearrangement of the letters of a word or phrase. 

Anal: Pertaining to the anus. 

Anal fin: The median ventral fin or fins behind the anus. Abbreviated as A, or A1 and A2 if there are two. Also called proctopterygium, it functions to maintain equilbrium against rolling. 

Anal fin base length: The distance between the origin and the insertion of the anal fin, i.e. the length of that portion of the anal fin in contact with the body. 

Anal fin depressed length: The depressed length of the anal fin is the distance from the origin to the farthest posterior tip when the fin is flattened down. 

Anal fin height: The distance from the origin to the tip of the longest ray. Sometimes taken as the greatest vertical height from the base. 

Anal fin ray count: Enumeration of the soft anal fin rays. In fishes where the smaller rays in front gradually grade into larger rays, these smaller anterior rays are included in the count, e.g. Ictaluridae, Esocidae, Gadidae. Where the first small rays abruptly change to larger ones or where the first small rays are very variable or difficult to count these are not included; the first unbranched ray reaching nearly to the tip of the fin and the remainder of the rays are then counted - this is called the principal ray count. Where the last two rays are closely approximated at the base some authors consider them as a branched ray counting them as one (although they are not really a single branched ray). In fishes where the last two rays are not closely placed at the base, the rays are usually both counted. However some authors again count the last two rays as one. In some studies, only the branched rays of the anal fin are counted. It may readily be seen that if published counts are to be of use to others the method of counting should be stated.

Anal gland: Rectal gland (an evagination of the terminal portion of the intestine of Elasmobranchii. Function formerly thought to be related to digestion or excretion, but now considered to secrete high concentrations of excess sodium chloride. Found also in the coelacanth Latimeria chalumnae). 

Anal lappet: A small skin flap supported by an internal scale or scales over the anal fin base in Cetomimidae. 

Anal papilla: A fleshy protuberance through which the end of the digestive tract passes. 

Anal photophores: Two rows of light organs, one above the base of the anal fin and the other along the ventrolateral surface of the caudal peduncle. Abbreviated as AO in Myctophidae. 

Anal ring:  One of the dermal plates in members of the Syngnathidae forming a series of rings enclosing the body; the body ring immediately in front of the anus. 

Anal spine: A spine at the origin of the anal fin before the soft rays. In flatfishes this is not a true spine but the free end of the first distal anal pterygiophore under the skin which may protrude through the skin. 

Analog products: Simulated crab, lobster and other shellfish and fish products made from processed fish flesh. 

Analogous: Similar in structure or function but independently evolved, e.g. the hard ray in the dorsal fin of the carp and the spines in the first dorsal fin of the perch are analogous structures. 

Analytical operation: Research study on a fish stock gathering data that cannot be obtained from commercial operations. 

Anamestic bone: One of a series of bones in the cheek region that fill in spaces left by the sensory pit-bearing bones; may be used for any bone lacking sensory canals. 

Anastomosing: Joining in a network, forming a network, e.g. river channels, blood vessels. 

Anatomy: The structure of organisms, often revealed by dissection.

Anaulacorhizid: Vascularisation of a tooth root through scattered foramina of equal size on both outer and inner faces, e.g. in Hexanchidae. A secondarily anaulacorhizid condition occurs where the median groove of a holaulacorhizid type of root is totally overgrown to form a closed tube internally connected or merged with the pulp cavity (Herman et al., 1994).

Anazygalia: Zygalia (four small cranial bones in Osteolepiformes, perhaps formed from elements of the second to the fourth vertebra, a segment of the primordial cranium. The anazygalia are located dorsal to the chorda dorsalis, the catazygalia ventral to the chorda dorsalis).

Ancestor: Any organism, population, or species from which some other organism, population, or species is descended by reproduction.

Anchor ice: Frazil ice that collects on the stream or lake bed, or extends down to the water bottom. 

Anchor seine:  Danish seine (a seine which is hauled over an area of about 2 square kilometres to a stationary vessel, the very long towing ropes disturbing clouds of mud which help herd the fish into the net. Also called anchor seine, Danish seine trawl, Danish trawl).

Anchor worm: A copepod crustacean parasite of the genus Lernaeocera found on fish gills. 

Anchovy butter: Anchovy paste mixed with butter. 

Anchovy cream: Anchovy paste mixed with vegetable oil. 

Anchovy essence: A compound of pounded anchovies and various herbs. May be canned. 

Anchovy paste: Ground anchovies covered with salt, saltpetre, bay salt, sal prunella and cochineal. Sold in jars or cans. 

Ancillary collection: Material retained in addition to the main specimen in a collection, e.g. frozen tissue, thin sections, body parts, DNA, etc. 

Androgamone: Sperm secretions which depress the activity of sperm in the male genital duct and dissolve the egg membranes. 

Angel fillet: Block fillet (a fillet comprising muscle mass from the side of the fish, usually joined at the back or belly. Also called angel fillet, cutlet, double fillet or when smoked golden cutlet).

Angle:   1) the bony protuberance posterior to the jaw gape where the angular, articular and quadrate bones join, 2) old work for a hook.

Angler: A person using an angle to catch fishes, and usually a rod and line too. The fish may be released or kept as food but they are not sold. 

Angler day: One person angling for any part of 1 day.

Angler survey:  A survey of anglers and their catches either off-site by mail, email, telephone, door-to-door, etc. or on-site by access, roving, aerial, etc. 

Angling: Fishing with a rod and reel, usually for sport but also an effective way to catch some species for research purposes (or so ichthyologists maintain). 

Angling machine: An automated rod and line system on the side of a vessel. The machine can jig to catch the fish, rotate to bring the fish on deck, and jerk to release the fish from the hook. 

Anguilliform:   1) sinuous type of swimming as in an eel, 2) eel-like in shape. 

Angular: The triangular, paired dermal bone on the posterior ventral corner of the lower jaw. Also applied to the dermal bone of the lower jaw which articulates posteriorly with the quadrate, in which case the preceding bone is known as the retroarticular. In mammals this bone becomes the malleus of the inner ear. 

Angulate: Having definite angles or corners. 

Animal pole: The location on the fish egg where polar bodies emerge. It corresponds to the point of fertilisation just below where the sperm penetrates the chorion through the micropyle.

Animal-vegetal axis: A line passing through the animal and vegetal poles of the embryo before epiboly.

Anisakiasis: A disease caused by a nematode parasite. Anisakis can infect humans causing gastric problems if raw or lightly processed fish, e.g. cold smoked, is consumed. The parasite is found in the viscera and muscles of such fish as herring. 

Ankylose: To fuse together, e.g. fusion of two bones or teeth to bone to form one part. 

Anlage (plural anlagen, German): The initial clump of cells from which develops an organ or structure; primordium. 

Annual canvas: A compilation of available fishery records made annually. 

Annual fish: A fish which normally completes its life cycle in a year and dies, only the eggs surviving, e.g. certain South American and African cyprinodonts dwelling in ponds which disappear in the dry season, Austrofundulus, Rachovia, Aphia pellucida, Cynolebius. 

Annual flood: The highest peak discharge of a river. 

Annual growth rate: The increase in weight of a fish over one year (final weight divided by initial weight). Abbreviated as h or h (Ricker, 1975).

Annual migrant: A fish that makes regular yearly migrations for spawning and/or feeding. 

Annual mortality: The percentage of fish dying in one year due to natural causes. May also include those taken through fishing. 

Annual mortality rate: The ratio between the number of fish which die during a year from causes other than fishing and the number alive at the beginning of that year. Also called annual natural mortality rate, conditional natural mortality rate, seasonal natural mortality rate. Abbreviated as m or n. 

Annual production:  1) tonnes of market-sized fish produced by an aquaculture facility in one year, 2) the amount of fish produced by a defined area of river or lake.

Annual ring: A growth ring formed over the course of one year.

Annual species: One in which free-swimming individuals live for less than one year, their fertile eggs hibernating in soil during the dry season, e.g. some rivulin Cyprinodontidae. 

Annual total mortality rate: The number of fish which die during a year divided by the initial number. Also called actual mortality rate, coefficient of mortality. Abbreviated as A (Ricker, 1975). 

Annual turnover:  1) the total biomass produced in one year, 2) the spring and fall mixing of water in a lake caused by wind, annual air temperature cycle and heating from the sun.. 

Annular: Ring-shaped. 

Annular sclerite: Annulus, q.v. 

Annulled name: An originally available name that has been suppressed by the International Commission on Zoological Nomenclature and consequently becomes unavailable for purposes of priority. 

Annulled work: A publication that the International Commission on Zoological Nomenclature has ruled must not be used for purpose of nomenclature.

Annulment: The suppression by the International Commission on Zoological Nomenclature of an available name as unavailable for the purposes of priority and homonymy, and the ruling of a work as unavailable. 

Annulus (plural annuli): A ring or rings on a fish scale or in a bony or cartilaginous structure corresponding to a year of growth. In a scale usually consists of closely arranged ridges (circuli). An accessory annulus is a ring caused by retarded or temporarily terminated growth that does not represent an annual cycle. In the tropics annuli may indicate spawning rather than growth. 

Anomaly: Departure from normal. 

Anonymous: Of a name, nomenclatural act or work whose authorship is not stated. Also where the identity of an author cannot be determined from the work itself. 

Anoxia: The lack of oxygen in an environment. 

Ant: A photophore at the anterodorsal margin of the orbit. 

Ante- (prefix): Before, in front of. 

Antecedent stream: A stream already in place before the rise of a mountain range, subsequently cutting through the rock at the same rate as the mountains rise and so maintaining its position. This has consequences for fish distribution, dispersal and migration. 

Antennulae microvillares: Mucopolysaccharide threads or tufts, the mucus filaments on the outermost layer of skin. 

Antepenultimate: The third from the end; one preceding the penultimate. 

Anteriad: In front of; towards the front end. 

Anterial: Towards the anterior end. 

Anterials: Teeth on the anterior field of the oral disc of lampreys. 

Anterior: In front; front (also used for towards the front end, strictly anteriad). Opposite of posterior. 

Anterior anal photophores: The row of light organs just above the base of the anal fin in Myctophidae (abbreviated AOa). 

Anterior cardinal vein: Paired veins draining blood from the head into the common cardinal veins. 

Anterior cerebral vein: A vein draining blood from the rostrum and eye into the lateral head vein, q.v. 

Anterior circumorals: The first row of anterials. 

Anterior intestinal artery: A branch of the coeliac artery that serves the enlarged proximal loop of the intestine and the intestinal diverticula. 

Anterior-posterior axis: The principal axis of the embryo. Also called rostrocaudal axis and embryonic axis. 

Anterohyal: Ceratohyal (the bone articulating dorsally with the interhyal, anteriorly supporting some branchiostegal rays and ventrally joining one or two hypohyals). 

Anterolateral photophores: An old name for VLO photophores (q.v.). 

Anthropogenic: Involving the impact (usually negative) of mankind on nature. 

Anti- (prefix): Opposite, against. 

Anti-fouling agent:  A paint used to protect ships or aquaculture cages from attaching organisms. Now regulated in aquaculture because of their build-up in fish tissues and replaced by biodegradable and less toxic products. 

Anti-kink: Any device used to prevent twisting of fishing line; in angling often achieved by having swivels, q.v. 

Anti-reverse: = a system preventing fishing reels from spinning in reverse. 

anti-tangle lead: = a lead weight used to sink the bait in angling having a long length of silicone tubing on either side to protect the line from abrasion. 

antibody: = a protein (an immunoglobulin or Ig) produced by the B-lymphocytes in the blood in response to the introduction of a foreign substance, an antigen. 

antiboreal: = of the south temperate region. 

antigen: = a substance which induces the formation of antibodies; used to compare relationships among species based on those sharing the same or more antibodies (serum proteins). 

antimere: = the corresponding element on the opposite side of a bilaterally symmetrical organism, as fishes are. 

antipodean: = referring to opposite sides of the world. 

antirostrum: = the anterior and dorsal projection of the sagittal otolith, dorsal to the sulcus. 

antiserum: = a blood serum with specific antibodies. 

antitropical: = the distribution pattern where a group is found north and south of, but not in, the tropics. Includes bipolar, bitemperate distributions, e.g. Sardinops, Engraulis, Squalus, Zeus. 

antitype: = paratype (every specimen, other than the holotype, in the type-series; all the specimens on which the author bases the series, except any that (s)he refers to as variants, or doubtfully associates with the nominal species, or expressly excludes from it). 

antorbital: = a small, paired dermal bone lying lateral to the nasal bone in front of the eye. Sometimes included in the suborbital or infraorbital series because the infraorbital canal crosses it, e.g. in Amiidae, Lepisosteidae, Elops, Osmeridae, some Siluridae. 

antorbital: organ = a photophore on the front and lower edge of the orbit which may manifest itself as the photophore Vn or Dn or as the suborbital light organ. 

antrorse: = angled forward or pointing anteriorly; opposite of retrorse. 

anus: = the posterior opening of the digestive tract by which it communicates with the exterior and through which faeces are voided. Also called vent, although the vent is the opening for reproductive and kidney products too. 

AO: = a row of photophores along the base of the anal fin and lower side of the caudal peduncle (not including the Prc's at the base of the caudal fin) in Myctophidae. Usually divisible into AOa mostly above the anal fin base and AOp mostly on the caudal peduncle. In some older works AO refers to the antorbital photophores. 

AOa: = a row of photophores mostly above the anal fin base in Myctophidae. 

AOp: = a row of photophores mostly on the caudal peduncle in Myctophidae. 

aorta: = the main blood vessel supplying blood to the body from the heart. 

aortic arches: = the pairs of arteries running through the branchial arches, connecting the ventral aorta with the dorsal aorta (or for the first two arches to the internal carotid artery). The last four carry the blood supply to and from the gills. 

aortic radices: = the paired roots of the dorsal aorta, joining posterior to the entrance of the last efferent artery to form the dorsal aorta. 

ap.: = abbreviation for apud, meaning in the work of; used in citing the work of an author contained in another work. 

aparietal: = a form of skull where the parietals are absent, e.g. in Syngnathiformes, Siluruidae. 

apex predator: = a fish at the top of the food chain, relying on smaller fishes for food. 

aphagy: = lacking the ability to feed. 

aphakic space: = the space in the pupil which is not occupied by the lens. The space may be circumlenticular, around the lens as in Stomias, ventral as in Omosudidae, some Myctophidae and Paralepidae, or rostral as in Scopelosauridae. A rostral aphakic space may enhance the forward binocular field of vision. 

aphotic: = areas never reached by natural light in the deep ocean (deeper than about 800 metres). No photosynthesis occurs.

aphytal: = the plantless zone of a lake bottom. 

apical: = at the apex or end. The apical field of a scale is the posterior end normally exposed when in its natural position. 

aplacental: = viviparous reproduction in which embryos are not connected to their mother's blood supply by a placenta, as is the case in some sharks 

aplacental viviparity: = also called ovoviviparity (production of eggs that are fertilised and hatch inside the mother but the embryos lack a placental connection to the oviduct or uterus and so do not feed off the mother. The young are born as miniature adults, free-swimming and feeding). 

aplesodic: = said of a cartilaginous pectoral fin where ceratotrichia, q.v., do not reach the border and so do not offer the support seen in the plesodic fin, q.v. More highly derived fish may have other support for the distal fin region. 

apode fishes: = fishes without pelvic fins, e.g. Anguilla.
 
apomorph: = a derived character differing from the ancestral condition. 

apophysis: = a narrow expansion protruding from the body of a bone. 

apopyle: = the anterior opening of the tube formed by the claspers. 

apogenotype: = a type specimen fixed through substitution, e.g. when a genus is renamed through homonymy, the type species automatically becomes the type of the new genus. 

apomorphy: = a state derived by evolution from a primitive state (plesiomorphy); applied to a character, not a taxon. 

aponeurosis: = flattened tendon.

aposematic: = referring to a colour or structure that warns of a special means of defense against a predator.

apotype: = a specimen used to supplement the description of a type.

apparatus Weberei: = Weberian apparatus (four bones and associated tissues connecting the gas bladder to the inner ear and conveying pressure changes and sound. Usually the definition includes the first four vertebrae (two and three may be fused), a supporting unit or pars sustentaculum comprising two transverse plates projecting downwards from the fourth vertebra enclosing a circular space for the aorta and the neural complex comprising modified neural arches and spines. Found in the Cypriniformes and Siluriformes).

appetency: = an instinctive inclination or propensity in animals to perform certain actions, e.g. a male Betta splendens will display when sighting itself in a mirror.

appertisation: = canned fish. 

appetitive behavior: = searching for the stimulus that can release the activity, e.g. a stickleback that has left its nest shows this behaviour when returning to resume fanning of the nest. 

application:= the use of a name to denote a taxon.

application to the Commission: = any zoologist may submit nomenclatural problems to the Commission. These are published in the Bulletin of Zoological Nomenclature. 

appressed: = held flat against the body, e.g. appressed pectoral fin. 

approach velocities: = water velocities at or near the face of a fish screen, q.v. 

approved: = given approval and promulgated by the International commission on Zoological Nomenclature. 

approved name: = one given approval by the Commission for use in nomenclature. 

aproctal bone: = the ventral element in the priapium of the Phallostethidae on which articulate the ctenactinia (q.v.). Also called axial or pelvic bone. 

apron: = the false belly of the cod end of a trawl used as a chafing gear. 

apron gill net: = an L-shaped net comprising a vertical back wall and a horizontally floating apron. 

apud: = meaning in the work of; used in citing the work of an author contained in another work. Abbreviated as ap. 

aqua- (prefix): = water. 

aquaculture: = the artificial or controlled culture of aquatic organisms, including stripping and fertilisation of eggs and raising of young to a certain size for release or marketing. Also spelled aquiculture, but this also means hydroponics. 

aquamarsh: = a water body almost completely covered with emergent an floating aquatic vegetation.

aquariology: = the care, maintenance and breeding of captive aquatic animals. Includes design of displays and veterinary medicine and pathology. 

aquarium :(plural aquaria) = an artificial tank with glass or plastic sides allowing the fish to be viewed; also a large facility with many aquaria, often open to the public. 

aquatic: = living in or near water or pertaining to water. 

aquaticolous: = living in water or aquatic vegetation. 

aquatoria: = water world or habitat. 

aqueduct of Sylvius: = a posterior channel joining the third and fourth ventricle in the brain. 

aqui- (prefix): = relating to water. 

aquifer: = a water bearing geological formation. Springs and wells depend on aquifers for water. Described as artesian (confined) or water table (unconfined). 

aquiculture := see aquaculture. 

arbitrary: = used of scientific name lacking formal derivation with regard to etymology, e.g. an arbitrary combination of letters, or an etymologically incorrect gender assigned to a name.

arbor: = the centre part of a fly reel where backing and line are wound. 

arborescent: = treelike. 

arborescent organ: = dendritic organ (a small arborescent organ found between the anus and the anal fin in certain Plotosidae (e.g. Plotosus, Cnidoglanis and Euristhmus). Organ with two main cell types, those with parallel groups of cytoplasmic tubules and many mitochondria, and clear cells with a network of cytoplasmic tubules. May have an osmoregulatory function).

arboriform: = form of a tree, branching. 

arch-centra := vertebral centra formed by the growth of the arcualia around the notochord external to the chordal sheath and which fuse to form annual segments which become biconcave centra. Found in Teleostei. 

archetype: = a hypothetical ancestor constructed by elimination of specialised characters. 

archi- (prefix): = first. 

archibenthic := the waters on the slope beyond the outer edge of the continental shelf at depths between 200-400 and 1000-1100 metres or below the 4°C isotherm. 

archicercal: = proterocercal (the type of tail fin primitively symmetrical, both internally and externally, and hence one which has not undergone reduction or modification of the original form, e.g. in Petromyzontiformes). 

archinephros: = the primitive kidney extending the whole length of the body cavity. Found only in embryonic Myxini. 

archipterygium := the primitive lobe-like paired fin. Generally applied to the biserial fin or lobe-fin, e.g. in Crossopterygii, or to the lobe fin of some Elasmobranchii, e.g. Pleurocanthus. 

archival tag := an implanted fish tag that detects and records several environmental variables, e.g. water temperature, over time or internal variables, e.g. body temperature. 

arciform =: bow-shaped. 

arcocentrum: = the cartilaginous arch and its base in the vertebrae of Elasmobranchii. Also used in Pycnodont Actinopterygii (Poyato-Ariza and Wenz, 2002). 

Arctic cities := dense gatherings of trawlers fishing demersally in Arctic waters. 

arcualium (plural arcualia) := an embryonic cartilaginous element from which the vertebrae form. There are primitively two pairs of endoskeletal elements in each metamere and on each side of the notochord, the interdorsals and basidorsals. In the gnathostomes (jawed fishes) there are two additional pairs ventrally to the notochord, the interventrals and basiventrals. All these elements are called arcualia and can fuse to a notochordal calcification, the centrum. Arcualia and centrum make a vertebra. 

arcuate := in a smooth arc, not straight or interrupted. 

area closure := the closure to fishing by particular gear(s) of an entire fishing ground, or a part thereof, for the protection of the population(s) or a section of a population, e.g. spawners, juveniles. The closure is usually seasonal but it could be permanent. 

area swept := the area of the sea floor over which the fishing gear such as a trawl is dragged during its operation . The area is equal to the effective horizontal opening of the gear multiplied by the distance the gear has covered during the period of time considered, e.g during a one hour trawl haul. Combined with information on the fish quantities caught during the considered time period, the area swept allows an estimation of a relative or absolute value of the fish density (and biomass) in the area. 

area temporalis: = an area of high resolution in the retina of the eye, e.g. in Clupeidae. 

areal: = involving a particular area, an area of particular extent.

areola (pl. areolae): = one of a series of normal epidermal cells arranged in circles overlying the mormyromasts, q.v. 

argentea (of choroid): = a silvery guanine layer between the sclera and choroid concealing the melanin in the choroid layer in larvae. 

argentium: = a silvery dermal layer containing crystals of guanine. 

arithmotype := an isotype, q.v., which belongs to a different taxon from the holotype. 

arm := a long and narrow body of water branching from a lake or an inlet of the sea or formed from flooding of an inlet streambed. 

arroyo: = a gully; a small, steep-sided and flat-bottomed channel in an arid area, usually dry but sometimes with permanent water. 

Art := a monotypic species which is not one of a series of species which replace one another geographically (German). Compare Artenkreis and Rassenkreis. 

Art.: = an Article of the International Code of Zoological Nomenclature. 

Artenkreis: = a series of species which replace one another geographically (German); a superspecies or species complex, as opposed to Rassenkreis or Art. 

artesian well := a deep-drilled well where the water is forced to the surface by hydrostatic pressure. Some fishes have been found in such wells. 

arthropterygium := type of pectoral fin covered with external plates and provided with an endoskeleton. Found in Bothriolepis (Pterichthys). 

Article := a section of the International Code of Zoological Nomenclature comprising a mandatory rule or rules. 

articular := the deep, endochondral bone of primitive acanthopterygians in the middle of the lower jaw between the dentary and the angular (or retroarticular) which articulates with the quadrate. It is later invaded by the angular. Divided into the distal part (wanting in Teleostomi) and the proximal part. Occupies the position of Bridge's ossicles b and c in Amia. Found as a distinct structure in Amia, Lepisosteus, Polyodon and Acipenseridae. 

articular process := a projection of the upper border of the premaxilla acting as a fulcrum for the protrusion of the maxilla. 

articulate := to make a joint with, e.g. the mandible articulates with the quadrate; jointed, e.g. soft fin rays. A diarthrosis articulation allows free movement, amphiarthrosis limited movement as between vertebrae and synarthrosis very little movement as between the two mandibles at the jaw tip. May be used instead of segmented for soft fin rays. 

articulated := jointed (like bamboo), e.g. soft fin rays. 

artificial bait := any bait or lure made of plastic, wood, metal, feathers, etc. 

artificial channel: = a short channel designed for spawning or rearing fish that live nearby. 

artificial classification: = a classification based on characters selected for their utility and not indicative of phylogenetic relationships. 

artificial fly := an artificial rendering of an insect used as a bait in fly fishing. Flies may be fished dry (on the surface) or wet (submerged). 

artificial hole: = a cavity in a hollow log, a pipe or made of tile used for fish spawning. 

artificial key: = an identification key based on characters selected for their utility and not indicative of phylogenetic relationships. 

artificial lure := any manufactured device used to attract and hook fishes. Used in angling and includes spoons, spinners and plugs as well as products designed to imitate worms, eggs, fish, crayfish, etc. 

artificial production := the spawning, incubating, hatching and/or rearing of fish in a hatchery. 

artificial propagation := artificial production. May also include stock transfers, creation of spawning habitat, egg bank programs, captive broodstock programs, and cryopreservation of gametes.

artificial reef := materials placed on the sea flood that serve as habitat for marine organisms including fishes. Can be anything from old tires to a sunken ship.

artificial smoking: = adding colour and flavour to a fish product resembling that of naturally smoked fish. 

artificials := artificial baits and lures. 

artisanal fishery := a traditional fishery involving skilled but non-industrialized operators; typically a small-scale, decentralized operation; normally a subsistence fishery although sometimes the catch may be sold. Usually fishing trips are short and inshore and fishing vessels are small but in developed countries may apply to trawlers, seiners or longliners. Also called small-scale fisheries. 

as such: = strictly as cited. 

ascending process: = a vertical process on the anterior part of the premaxillary bone in most teleosts. Not homologous with a similar structure in Holostei (Amia and Lepisosteus), called the nasal process. 

ascr. := abbreviation for ascriptum, meaning ascribed to. 

ascriptum := ascribed to. Abbreviated ascr. 

aspect ratio := a dimensionless ratio expressing how elongated the shape of a flat organ is. In the case of the caudal fin, a high aspect ratio is found in fast swimmers. Calculated as the ratio of height squared to the surface of the fin. 

asperite := a rough, bony excresence. 

asperity = roughness or pricklyness.

aspic: = fish in jelly (fish cooked in acidified brine or vinegar, fried or smoked and then packed in gelatin, gelatin and pectin or aspic. Sometimes includes cucumbers, onions and spices).

aspidin := the acellular bone substance found in the dermal skeletons of Heterostraci.

ASPM: = age-structured production model ( a stock assessment programme based on a deterministic form of a stock-recruitment relationship, with non-equilibrium tuning of abundance indices). 

aspondylous vertebrae := vertebrae lacking a centrum although neural and haemal arches are well-developed, e.g. in Cyclostomata, Holocephali, Dipnoi, Acipenseridae. 

assemblage := a collection of co-existing organisms at a particular locality and at a specific time, not strictly inter-dependent but with unspecified relationships, e.g. trophic ones, between them. 

assembly area: = the place where a pre-spawning concentration of fish occurs, e.g. at stream mouths. 

assessment := the state of a resource, such as a fish stock, as judged by a scientist of scientific body usually for management purposes. The stock may be judged as to size, potential yield, whether it is over- or underexploited, etc. 

assimilation efficiency: = the rate at which an organism converts food into weight. 

associate type:= any of two or more type specimens listed in the original description of a taxon in the absence of a designated holotype. 

associated species: = species that prey upon a target species, are preyed on by it, compete with it for food, living space, etc, or co-occur in the same fishing area and are exploited (or accidentally taken) in the same fishery or fisheries. These interactions can occur at any stage of the life cycle of one or other species and the range of species concerned can therefore be very large. 

astatic: = water bodies with fluctuating surface levels; seasonal astatic water bodies dry up annually, perennial ones rise and fall but do not dry up annually. 

astaxanthin := a carotenoid pigment found in crustaceans that gives the flesh of fish eating them a pink colour. Also found in microalgae which can be used as a source of pigment for fish feed. 

asteriscus := the otolith in the lagena. Also called asterisk or lagenolith. The largest otolith in Cyprinidae but small in other fishes. 

asterisk := asteriscus, q.v. 

asterospondylous := a type of vertebra with radiating calcifications extending to the chordacentrum and autocentrum, e.g. in some Elasmobranchii. 

asymmetrical := lacking symmetry, e.g. Bothidae and Pleuronectidae lack bilateral symmetry, one eye rotating to the other side of the head. 

asymptotic length := a parameter of the von Bertalanffy Growth Function, q.v., expressing the mean length the fish in a stock would attain if they were to grow for an infinitely long period. Not the largest observed size of a species. 

asymptotic weight: = a parameter of the von Bertalanffy Growth Function, q.v., expressing the mean weight the fish in a stock would attain if they were to grow for an infinitely long period. 

at-risk fish stocks: = stocks that have been identified as being in need of rescue or in need of specific management practices because of low or declining populations. 

athalassohaline lake := a saline lake not of marine origin but from evaporation of fresh water in a system dominated by calcium, magnesium and sulphate (as opposed to sodium and chloride in the ocean). Some of these ion concentrations are more toxic to fish than others. 

Atlantic trawl:= a four-seam otter trawl designed in Canada. 

atlas: = the first vertebra which articulates with the skull. 

atom trawl := a wingless, midwater trawl with a square mouth towed between two boats. Also called Larsen midwater trawl, Larsen trawl, floating trawl, Larsen two boat trawl, two boat pelagic trawl. 

atresia (adjective atretic) := the degeneration and loss of an anatomical structure; usually said of ovarian follicles or eggs that may be absorbed. 

atrial pore: = the opening near the anus which leads from the atrium to the exterior in Amphioxi. Also called atriopore. 

atrio-ventricular valve: = the heart valve between the atrium and ventricle. 

atriopore := the opening near the anus which leads from the atrium to the exterior in Amphioxi. Also called atrial pore. 

atrium := a chamber, often specifically applied to a cavity in the heart or the chamber exterior to the branchial bars communicating with the outside through the atrial pore in Amphioxi. In most fishes it collects venous blood from the sinus venosus and delivers it to the ventricle, generating the first of each doubled heart beat. 

attendant male := a male which is not the member of the spawning pair; often a sneaky male. 

attenuate: = drawn out, slender. 

attractant := a flavouring added to bait or ground bait (q.v.) in angling. Flavours can be sweet or spicy. 

attracting device:= fish aggregating device (artificial or natural floating objects placed on the ocean surface, often anchored to the bottom, to attract several schooling fish species underneath, thus increasing their catchability. Used with tuna, for example. Abbreviated as FAD for fish aggregating device). 

attraction: = drawing fish to fishways or spillways of dams through the use of water flow regimes. 

attractor: = 1) fish attractor (any structure placed in the water to create habitat for fishes), 2)a type of fly that is very effective but has little resemblance to a natural food item, usually very flashy and large.. 

auct. or auctt.:= abbreviation for auctorum, meaning of authors. Used to indicate that a name is used in the sense of a number of subsequent authors and not in its different sense as established by the original author. 

auct. non.: = abbreviation for auctorum non, meaning not of authors, used when citing a misapplied name. 

auctorum := of authors. Used to indicate that a name is used in the sense of a number of subsequent authors and not in its different sense as established by the original author. Abbreviated as auct. or auctt. 

auctorum non: = not of authors, used when citing a misapplied name. Abbreviated auct. non. 

auditory capsule: = cartilaginous skeleton about the inner ear in Elasmobranchii, a chondral skeleton in bony fishes. 

auditory ossicle: = one of a series of bones conducting sound, in fishes the four Weberian ossicles, q.v. 

auditory vesicle := sensory anlage from which the ear develops. 

aufwuchs: = organisms and detritus coating rocks and plants in an aquatic environment often fed on by fish specialised as scrapers. 

aural := pertaining to ears or hearing. 

auriculo-ventricular valves := valves at the junction between the atrium and ventricle chambers of the heart. 

austral: = of the south temperate region, between the Antarctic and tropical regions. Opposite of boreal. 

autecology: = the ecology of individual organisms or species. 

author := the person to whom a published work or zoological name is attributed or who first publishes a name satisfying the criteria of availability or valid publication. 

author citation: = the name of the authority (q.v.) for a taxon name, when cited, should follow the taxon name without any intervening marks or punctuation. Its citation is optional and may or may not be followed immediately by the year. 

authorised species: = any species or species group that a vessel is authorized to retain as specified by the fishery management authority. 

authority := the name of the person who originally describes a species, e.g. McAllister is the authority for Lycodes sagittarius. The authors name is placed in parentheses if the species is now placed in a genus other than that in which it was originally described, e.g. Salvelinus fontinalis (Mitchell, 1815). 

authorship: = the author of a taxonomic name is the person who alone is responsible for both the name and for the conditions which make it available (q.v.), i.e. the diagnosis, etc. 

auto- (prefix): = self, automatic, same one. 

autocentrum := an outer ring of cartilage in the vertebrae of Elasmobranchii interrupted by the neural and haemal arches. 

autochthonous: = originating there (zoogeographical or referring to nutrients or organisms fixed or generated within an aquatic system). 

autodiastoly: = jaws suspension where the palatoquadrate is suspended from two articulations with the braincase, perhaps the original form of jaw suspension. 

autogenotype := a genotype, q.v., by original designation. 

autogenous: = ossifying from an independent centre and, by extension, used in the sense of bones that are not fused to the nearest neighbour. 

autograph := a text in the handwriting of the author, either the original or a photocopy. 

autolysis: = the breakdown of proteins, fats and other body components of fish after death caused by the action of enzymes. The rate depends on temperature. 

automatic feeder := a mechanism that dispenses food at preset times and in preset amounts in an aquaculture facility.

automimicry := imitation of oneself or ones own species, e.g. egg dummies in Cichlidae. 

autumn sickness := a disease of fishes causing deaths and occurring in autumn. Of no known cause or signs of disease. 

autumn turnover: = the mixing of the entire lake water mass in the autumn or fall. 

autonym: = an automatically established name, applied to a nominate subordinate taxon. 

autopalatine := a paired deep bone on the roof of the mouth, lateral to the prevomer (or vomer). Often called palatines. Usually overlain by the dermal, often tooth-bearing bone, the dermopalatine. 

autopotamic := 1) pertaining to organisms adapted to and living out their lives in streams, 2) originating in fresh water. 

autopterotic := pterotic (the paired deep bone and the superficial dermal bone covering it forming the lateral roof of the skull between the parietal and the hyomandibular and in contact with the lateral semicircular canal). 

autosphenotic := the deep bone comprising the postorbital process. Often called the sphenotic, it is overlain by the dermosphenotic or postorbital. 

autostylic jaw suspension := a type of suspension where the upper jaw is connected directly to the chondrocranium (instead of fastened to the hyomandibular, the hyostylic suspension) by a process from, or fusion with, the palatoquadrate, e.g. in Dipnoi.. 

autotrophic lake: = a lake where most or all of the organic matter present is derived from within the lake, not from the surrounding land.

autotype := 1) the type, by original designation, of a taxon, 2) a specimen designated by the author of a species subsequent to the original publication as being identical to the holotype. 

auxillary scale := one of the small scales in between the larger scales, e.g. in such Pomacanthidae as Pomacanthoides. 

availability := 1) the part of a fish population which lives in areas where it is susceptible to fishing during a given fishing season. This part receives recruits from or becomes mingled with the non-available part of the stock at other seasons, or in other years (Ricker, 1975). Fish become available through migration, movement in the water column, or growth. Abbreviated as r or r, 2) whether a certain kind of fish of a certain size can be caught by a type of gear in an area, 3) catch per unit of effort, q.v. 

available name := a scientific name of an animal satisfies the provisions of the International Code of Zoological Nomenclature, including publications of the name after 1757 in a latinized form or arbitrary combination of letters constructed so it can be treated as one, in a work consistently applying binomial nomenclature, not first published in a synonymy, etc. Not necessarily the valid name. 

available work := a work published after the starting point that conforms to the provisions of the International Code of Zoological Nomenclature and has not been annulled by its Commission. An available name is not necessarily a valid name (q.v.), as an available name may be in synonymy (q.v.). Conversely a valid name must always be an available one. Available names include nomen inviolatum, nomen conservandum, nomen perfectum, nomen vanum, nomen correctum, nomen substitutum, nomen imperfectum. 

average annual instantaneous size-specific growth rate: = a method for comparing growth rates of fish of equivalent size instead of equivalent age. The average annual instantaneous-growth rate (the average of individual log fork length at age n + 1 minus log fork length at age n) is plotted against the length or weight at the beginning of the year. 

avidity: = the frequency of fishing activity, e.g. the number of days on which fishing trips were made. 

Avidity bias: Bias arising in angler surveys through time spent fishing or frequency of fishing. 

Avoidance: The probability that a fish or fish school will escape capture by swimming out of the path of a ship or trawl, away from or alongside a gill net, or retention by a hook or trap. May be expressed as a function of size or age (avoidance curve). 

Avoidance curve: The relationship between a fish size or age and its probability of being retained by fishing gear after coming in contact with it. 

Avowed substitute: A name explicitly proposed as a substitute for an existing name. 

Avulsed: A stream channel without flow since water has taken a new path. 

Axial: Towards an axis running antero-posteriorly through the middle of the fish; central. Opposite of radial, q.v. 

Axial bone: The ventral element in the priapium of the Phallostethidae on which articulate the ctenactinia (q.v.). Also called aproctal or pelvic bone. 

Axial hypoblast: A hypoblast consisting of mesodermal and probably endodermal precursor cells developing on the dorsal midline. It includes prechordal plate and chorda mesoderm. 

Axial skeleton: The bones in the axis of the body, comprising the neurocranium, the branchial skeleton, the vertebral column and the intermuscular bones and ribs. 

Axial swimming: The usual swimming mode of fishes powered by the myotomal musculature and involving lateral bending of the body and oscillating movement of the tail. 

Axial vein: The unpaired vein in the caudal trunk leading from the caudal vein to the left and right posterior cardinal veins. 

Axil: The region immediately behind or under the pectoral fin.

Axillary gland: A multicellular structure below the skin dorsal to the pectoral fin, e.g. in Ictalurus punctatus, suggested to produce toxin. This is unlikely as no duct allows delivery to the spine tip and production of toxin is known from epithelial spine tissue. 

Axillary process or scale: A small triangular appendage or a modified scale at the upper or anterior base of a paired fin. Also called accessory scale or fleshy appendage. Functions apparently to streamline the fin when held against the body while swimming. 

Axillary scale: A small scale superimposed or interspersed with large ones. 

Axis: 1) a line, 2) the anterior-posterior axis of the embryo. 

Axonost: The pterygiophore (the cartilage or bone on the outer end of which sit the median fin rays or spines), sometimes the proximal pterygiophore. 

Azygost: = the dermal bone in Psettodidae between the prefrontal and the frontal of the lower side. 

























 


Abramites: Omnivorous S. American characins; commonly known as "headstanders" because of the way
they swim. 



Abscisic acid (ABA): A plant growth substance which acts mainly as a growth inhibitor.
It is present in large quantities in dormant buds of some plants. It also is involved in the opening of the stomata.

Absolute growth rate: See Growth Rate

Absorption: The process by which a filter media traps unwanted molecules. 



Acanthophthalmus: An out of date name for S. E. Asian loaches, Family Cobitidae.



Acanthurus: The type genus of the Family Acanthuridae, commonly known as tangs or
surgeonfish.



Acara: Name often used in describing several S. American cichlids.



Acclimation: Process of slowly introducing fish or other organisms into new water conditions

Accomodation: The ability of the eye to change focus so that near and distant objects can be
seen clearly.

Acetabularia: Green marine algae, known as "mermaids wineglass", grows in upright colonies on
hard coral. 

Acetylcholine(ACh): One of the main substances responsible for the transmission of an impulse across
a synapse.

Acid: A chemical compound that dissociates in solution to yeild one or more hydrogen ions
and a negatively charged ion; a solution with a pH less than neutral 7.0.

Acidicty: This is a water condition in your aquarium. Hydrogen ions in the water makes it more 
acid.

Acipenser Sturgeons, primitive fish found in both marine and fresh waters.

Acoelomate: An animal without a coelom, flatworms and tapeworms that belong to the phylum
Platyhelminthes are examples.

Acontia: Filaments extruded from pores at the base of the pedal disk in certain sea
anemones, thought to be for defensive purposes.

Acorus: Sweet flag, a flowering marsh plant of the Family Arum.

Acrosome: A cap like vesicle at the front of a sperm that contains enzymes. Right before
fertilization the membrane that surrounds the this vesicle bursts and the enzymes are released to seperate the cells that surround
the egg.

Acrylic: A plastic material used to construct fish tanks, filters and accessories.

Action spectrum: A graph which shows the proportion of light that is actually used in a particular
process. The action spectrum for photosynthesis is very similar to the absorption spectrum for clorophyll. This shows the 
importance of clorophyll in absorbing the light used in photosynthesis.

Adipose Fin: A small fin located behind the dorsal fin and in front of the caudal fin.


Adsorption: The process by which filter media attracts unwanted molecules to its surface via a 
chemical charge.

Adventitious plant: Plantlets that develop asexually from a parent plant: a rooted plantlet forming on a part of the mother plant.

Aeration: The introduction of air. See Air pumps 



Aerobic: A term used to describe an organism that needs oxygen to survive.



Air pumps: This is a continous supply of air. See Aeration and Filtration. 



Algae: This is a very basic type of plant in a aquarium. There are many types, you can remove it
by brushes, scrapers, and chemical treatments can be used, but will also affect your other plants
in your tank.

Alkaline: This is a water condition in your aquarium. Hydroxide ions in the water makes it more 
alkaline.

Alkaline earths: Earth metals, calcium, magnesium, barrium, strontium, and their mineral salts. 

Ammonia: This is the chemical compound NH3 (Nitrogen, hydrogen) which is one of the first 
compounds in your new aquarium.

Amphibious: An organism able to exist either on land or in the water. 

Anaerobic: Living without oxygen. This is a living situation most commonly associated with "bad"
bacteria.

Angelfish: in freshwater, Pterophylum South American Cichlids of which P. scalare 
is very popular and has been selectively bred into many ornamental strains. Marine angelfish belong to the Family 
Pomacanthidae.

Anglerfish Predatory fish of the Family Anernnaridae, they entice prey with a " pole" 
formed from the first dorsal fin spine.

Angiosperm: A group of plants whose seeds are borne within a matured ovary. 

Anal Fin: Single fin mounted vertically below the fish.

Asexual reproduction:any form of reproduction that does not require the union of male and female reproductive material.
 
Axil: The junction of the leaf or petiole and the stem.

Axillary: Arising from the above junction. 

B
Top!



Bacillus: A rod-shaped bacterial cell.



Bacopa: Freshwater plant in the snapdragon family. Usually grown from cuttings.



Badis: A fish from Indonesia, feeds on small, meaty foods in standing water with heavy 
vegitation.



Beneficial Bacteria: There are useful bacterium in your aquarium, like Nitrosomonas which will
convert ammonia to Nitrite.

Biogenic decalcification:
When there is a carbon dioxide deficiencey in the water, plants can derive CO2 from the hardening
constituents of the carbonate hardness. First they split the hydrogen carbonates into CO2 and 
carbonates. This causes the pH to rise about one step and the largely insoluable carbonates 
precipitate and form rough deposits on the leaves and substrate. Some plants such as Vallisneria
can even destroy the carbonates and obtain CO2 from them. This raises the pH again by another 
step. Biogenic decalcification thus causes the water to be 10 to 100 times more alkaline than it
was previous. In the dark, the process reverses and the pH drops considerably. Thus these 
continous large pH swings can pose asignificant risk to the well being of fish and animals. 
The solution is to add enough CO2 to thewater and have a significant carbonate level to act as a
buffer. 

Biological filtration: This system breaks down any toxic compounds, usually Nitrogenous toxins.

Bipinnate: A leaf formed of several leaflets set on either side of the petiole.

Brackish waters: Water that is mainly freshwater, but also contains smaller amounts of salt.

Bract:  Specialized scale-like leaf found at the base of a flower. 

Breeding Tank: An aquarium set up for the breeding of fish.



Brine shrimp: Becoming very popular with the average aquaritics, high in protien and nice snack 
for many freshwater fish.



Bubble Nest: A term used for a nest which is suspended by a weave of tiny air bubbles. It is used
as a protective coating for the eggs and the newly hatched young. It is most commonly used by the
anabantids. 

Buffer: A substance used to treat the water and to counteract changes in the pH.

Bullate: Blistered, bubbled or puckered in appearance. 

Bulb: Tightly packed fleshy leaves used as a storage organ. Onions and tulips both have bulbs

C


Cation Exchange Capacity (CEC): 
Quantifies the ability of media to provide a nutrient reserve for plant uptake. It is the sum of exchangeable cations, or positively charged ions, media can adsorb per unit weight or volume. It is usually measured in milligram equivalents per 100 g or 100 cm3 (meq/100 g or meq/100 cm3, respectively). A high CEC value characterizes media with a high nutrient-holding capacity that can retain nutrients for plant uptake between applications of fertilizer. Media characterized by a high CEC retains nutrients from leaching. In addition, a high CEC provides a buffer from abrupt fluctuations in media salinity and pH. Important cations in the cation exchange complex in order of adsorption strength include calcium (Ca2+) > magnesium (Mg2+) > potassium (K+) > ammonium (NH4+), and sodium (Na+). Micronutrients which also are adsorbed to media particles include iron (Fe2+ and Fe3+), manganese (Mn2+), zinc (Zn2+), and copper (Cu2+). The cations bind loosely to negatively charged sites on media particles until they are released into the liquid phase of the media. Once they are released into the media solution, cations are absorbed by plant roots or exchanged for other cations held on the media particles. Anion exchange capacity Some media retains small quantities of anions, negatively charged ions, in addition to cations. However, anion exchange capacities are usually negligible, allowing anions such as nitrate (NO3-), chloride (Cl-), sulphate (SO4-), and phosphate (H2PO4-) to leach from the media. 




C1 Pathway: Part of the biochemical pathway of photosynthesis.



Cabomba: Vinelike aquatic plants with feathery, dark green foliage and tiny white flowers borne
at the surface; requires very bright light.



Calcium: A necessary element used by salt water corals and other organisms for their calcium
carbonate skeleton or shell. 



Cannister Filter: A filter which pushes water through an external canister which contains a 
filter media such as filter floss, polyester or carbon.



Carbon: Activated carbon medium in your aquarium helps to break down dissolved substances in
the water. 



Carbon dioxide: Known as CO2, is the biproduct from respiration. If you wanted to keep real 
plants in your aquarium, CO2 is one of the elements needed - Photosynthesis. 



Carnivore: Predatory fish which require live foods.



Caudal Fin: Single fin at the back of a fish-the tail fin.



Chlorine: The enemy to any freshwater fish, chlorine is very toxic to the fish. Letting water
stand over night will remove it, as it evaporates into the air.



Cloudy water : The cause is normally because of a rapid development of bacteria and algae spores.
This in turn is often because the nitrogen cycle isn't completed yet, or, all the filters were
cleaned killing the benificial bacterias such as nitrasomonas and nitrobacter.



Communities: Different species of fish kept in the same aquarium.



Crustaceans: A group of mostly aquatic animals that have an exterior skeleton and antennae; some 
examples of crustaceans include shrimps, lobsters, crabs, and water fleas.



Cuttings: Detached parts of stem plants: they take root after planting and become new plants.






D
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Dace: Any of several species from N. American and European cyprinids in various genera, 
including Erythogaster, Rhinichthys, and others  



Dark reaction: The process in which carbon dioxide is reduced to form carbohydrate during
photosynthesis.



Denitrification: Breakdown of nitrates by anaerobic bacteria into other forms. 



Detritus: Organic waste matter that collects on the bottom of fish tanks.



dGH: Water hardness is expressed in degrees of hardness. 0 - 30 is normally used, 0-4 being very
soft, 5-8 soft, and so forth until 30 which is extremely hard water. Look at Water hardness.



Diseases: Dropsy, Whitespot, fin-rot, Fungus - these are just some of the more common diseases 
that a fish can be attacked by.

Dormant Period: Interruption of growth in an effort to adjust to seasonal periods of stress.

Dorsal Fin: Single fin mounted on top of the fish. Some species have two, one behind the other.

E
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Echinaster: A common sea star.

Echinodermata: The animal phylum containing sea urchins and starfish.



Endcap: A water resistant socket for fluorescent lamps.



Etiolation: The formation of weak, spindly foliage deficient in Chlorophyll, usually occurs in 
light of too low intensity. 



External filters: A filter which is located outside of the tank.



F
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F1: The offspring from parents which are homozygous for a particular characteristic.



FAAS: Federation of American Aquarium Societies.



Family: A term used in the classification of organisms. A family is made up of related Genera.



Filtration: With no filtration, there would be no aquarium. This process removes waste materials
from aquarium water. 



Filter medium: These trap suspended waste as the water is passed through the filter.



Fishless Cycle: Instead of using a few hardy fish to start off the cycle, there is an option to
use liquid ammonia.



Freshwater: Water with no salt content.



Fry: Baby fish, can be very small and need special attention.

Flakes: A great source of food for almost any fish.

G
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Galaxea: A stony coral.

Gall bladder: A small muscular sac or bag found just under the liver. It stores bile between 
meals. It is produced in the liver and passed to the gall bladder then it is released through
the bile duct into the first part of the small intestine. release of bile from the gall bladder
is controlled by the hormone, cholecystokinin

Gravel: Basic substrate for any aquariums, recommeded depth is 2".



Gravel Vac: A Device used to clean gravel substrate without disturbing the fish to much through
methods of syphoning.



Gonopodium: An modified anal fin which is elongated. Only appears on the males, which helps to 
fertilize the females. You would expect to see these organs in Livebearers


H
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H- zone: A lighter area in the center of the A-band of a myofibril in a skeletal
muscle. It is the area where the thick myosin filaments which make up the A-band do not
overlap with the actin filaments.



Habitat: The geographic locality, together with its biological components, in which a species is
typically found.

Hard Water: Water with a high concentration of dissolved salts.

Heater: Needed to heat the aquarium to the appropriate water temperature. 24-25 degrees Celsius
is the average for many tropical freshwater fish.

Herbivore: Fish which eat plants and algae as their main diet.

Heterophyllous: Having leaves of different shapes on the same plant.

Heterostylic: Having flowers which differ in the relative length of their styles and stamens,
such that any one flower is very rarely, if ever, self pollinated.

Hydrometer: A device used to measure salinity of water.



I
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I-band: one of the light bands which can be seen running across a myofibril in a skeletal 
muscle. It corresponds to the location of filaments of the protein  actin.

Ich: An infestation of the skin of a freshwater fish by the ciliated protozoan parasite
Ichthyophthirius multifillis, ich is very common parasitic disease characterized by white 
salt-like specks all over the fish.

Impeller: An electrical impeller, which pumps the water through the filtration system.

Internal filter: A filter which is located inside the aquarium.

Invertebrate: An animal with no backbone.

Iron: The most important trace element for plants. Iron deficiency causes Chlorosis; a disease
that makes the plant leaves Yellow.



J
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Jawfish: Any species in the family Opisthognathidae; these marine fish have large mouths and 
typically burrow into the substrate.

K
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Kalkwasser: German for; limewater, a solution of calcium hydroxide added to marine reef aquariums
as a source of calcium ions.

Kidney: An organ responsible for the formation of urine in a mammal.

Killifishes: These are fish with a low life-span, often only for a year.

L
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Labeo: Freshwater "sharks", actually cyprinids. Larger species can become aggressive.

Labyrinth fish: Fish which are also called Anabantoids.

Lactase: An enzyme that breaks down the milk sugar, lactose.

Lamina: The part of a leaf which is flattened, to a greater or lesser degree. As the Leaf Blade.

Lateral Line: A line of sensory scales along the sides of fish that enables them to detect 
vibrations and electrical impulses from other fish.

Livebearers: These fish are fertilized and hatched within the body, which means they are easier
to breed.

Lumens: A measurement of light intensity. (1 lumen=10.76 lux).

Lux: The standard for measuring light.



M
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MAC: Marine Aquarium Council

Macro-Algae: Complex celled algae found in marine aquaria i.e.: Calurpa. 

Male: The organism, or part of the organism, which is responsible for producing male sex cells or
gametes.

Medication: There are many fish medications to cure illnesses on the market, and many are very
useful.

Mechanical filtration: A way of trapping any waste materials from the aquarium water. See 
Aeration and Filtration.

Micro-Algae: Single celled algae often growing in strands called hair algae.

Milt: Fish Sperm.

N
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NAD: A molecule which picks up hydrogens released during respiration.

Nandus: Type genus of the Family Nandidae. A predatory freshwater fish of S.E. Asia.

Nitrate: Mildly toxic end product of biological filtration. Can be used as a gauge to tell when 
a partial water change is needed.

Nitrite: A compound which is intermediate during the Nitrogen Cycle.

Nitrogen Cycle: The formal name for the biological cycle in which toxins are broken down into 
less harmful products by Aerobic bacteria.

Node: The part of the stem from which one or more leaves arise.


O
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Occiput: The area where the dorsal musculature attatches to the skull of a fish.

Omnivore: Fish which eat both live foods and plants.

Oodinium: Known as velvet disease, similar to ich but more deadly.


P
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Paddlefish: Two primative freshwater fish, Polydon and Pseuphurus, that feed by 
swimming open mouthed to trap planktonic organisms.

Pectoral Fins: Fins located directly behind the head of the fish, these act as the 'stearing' of
the fish.

Pelvic Fin: located on the underside (belly) of a fish that are usually placed between the 
pectoral fins and anal fin.

Phosphates: A byproduct of fish and inverteabte metabolism and decaying organic matter, such as
uneaten food. Can cause algae problems if you have high levels.

pH: A measurement of the acidity or alkalinity of your water.

Plants: Plants come in different sizes and shapes, you can use plastic or real plants.

Power filters: This is a filter which uses a high water flow rate.

PPM: Abbreviation for parts per million, a measurement used in test kits.



Q
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Quarantine tank: An aquarium for the temporary housing of a injured, sick, new, or conditioning
fish.

R
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Rabbitfish: Any member of the Family Siganidae. Herbivorous.

Reverse Osmosis: A process of filtering tap water for use in the aquarium. Water passes through
a membrane which filters out all elements leaving the water very pure. Trace elements you want 
will have to be adjusted as well as the pH.


S
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Sabella: Polychaetes, several species of which have colorful radioles.

Salinity: The measurement of dissolved salts in the aquarium water.

Scales: Small, flat plates which overlap eachother to form the external body covering of a fish.

Soft Water: Water with a low concentration of dissolved salts.

Species Tank: An aquarium where only one type of fish is kept.

Spectrum: Used to describe the wavelengths of light produced by a bulb.

Spray bar: Many use these - e.g. if you had a very strong powerhead, a spray bar can disperse 
the flow across the bar.

Substrate: Material used on the aquarium bottom. Examples include gravel and sand.

Stress: Can cause fish disease so be careful when moving or changing the fishes home.

Swim Bladder: A sac containing gas and air, present in the upper part of the body cavity, that 
aids in creating buoyancy and in the respiration of some fishes. 

T
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Taeniacra: The black striped dwarf cichlid of Brazil, T. candidae.

Tannin acid: You have added bogwood to the tank - and the water has turned orange? Its because 
the wood has leeched its tannin acids into the aquarium - a good boiling and soaking in a bucket for a few weeks, will remove the problem hopefully.

Trace Elements: Minute substances found in water,that are needed for proper plant and fish growth.
Usually replenished with partial water changes.



U
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Uaru: The waroo or triangle cichlid of the Amazon and Guyana, U. amphiacanthoides.

Under-gravel filter: A type of filter placed under the substrate that utilizes an air pump or 
power head to pull water through the gravel and thus oxygenates the bacteria to help in the 
nitrogen cycle. Not recommended for live plant tanks.


V
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Vacuum: Can be used to remove water during a water change (syphon), and can clean the gravel and
remove wastes.

Valenciennea: Marine sleeper gobies, Family Gobidae.

Venturi: A valve which makes bubbles by drawing air into fast flowing water. Especially useful 
in protein skimmers.



W
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Water changes: Removal and replacement.

Water: The great H2O, the water is the basic ingredient in your aquarium. Using test kits will
rate your water.

Water hardness: Water hardness refers to how much Calcium and Magnesium is in your water. Water
rich in Calcium salts is considered "hard". 

Water-turnover: The rate at which water flows through a certain filter. This is normally rated
at LPH (Litres per Hour). In general, water turnover in an aquarium will be 3 to 4 times the tank
capacity an hour.

X
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Xanthophyll: A yellow pigment produced by many plants and algae.

Y
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Yolk sac: A larval structure enclosing stored nutrients derived from the egg.

Z
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Zanclus: The Moorish idols, Family Zanclidae.

Zeolite: A substance used in fresh water aquaria for the removal of ammonia.



	

©Owen Gibson 2003®