Dictionary of Ichthyology

Brian W. Coad and Don E. McAllister^†

Revised: 20 March 2009

I

i.e. = abbreviation for id est or that is.

IBI = index of biotic integrity (the use of fish sampling data to indicate the overall health and integrity of a stream. Measures of fish species composition, trophic composition, reproductive behaviour and abundance and condition are used. Sites with high biotic integrity have relatively high numbers of total species).

ib. = abbreviation for ibidem.

ibid. = abbreviation for ibidem.

ibidem = in the same place; used to indicate same reference or author.

IC = the entire, ventral row of photophores running from the anterior end of the isthmus to the posteriormost photophore on the caudal peduncle.

ice age = a period when glaciers covered significant portions of the planet, eliminating significant freshwater fish habitats, and marine habitats by lowering sea levels as water became locked up in ice. As the ice melted, fish recolonised these habitats, sometimes after speciating in isolation. The last major ice age was during the Pleistocene.

ice anchor = a form of anchor, q.v., with a single hook used to moor a vessel to ice.

ice augur = auger (a device used to drill holes in ice for ice fishing with nets or hook and line. May be powered or operated by hand).

ice fish = ice cooled fish, iced fish as in commercial preparations. Not to be confused with icefishes (Nototheniidae, Channichthyidae).

ice fishing = fishing through holes cut in the ice of lakes or rivers, using specially designed gear and often with a shack positioned over the hole to mitigate the weather conditions. See also ice fishing under Symbols.

ice out = the period just after ice melts or is blown along a shore leaving open water, lasting about two weeks in spring.

ice pack = 1) a large area of floating ice driven closely together.

ice pack = 2) the polar sea ice.

ice shack = a small shelter for ice fishing used as a protection against the weather. Also called ice shanty.

ice shanty = ice shack.

ice shelf = thick ice, fairly flat, along polar coasts, fastened to the shore and often reaching the bottom although the seaward end floats free, sometimes over deep water. Icebergs break off this shelf.

ice-line = ice-fishing apparatus.

ice-up = formation of ice on lakes and rivers.

iceberg = a massive piece of ice broken off a glacier and floating in the ocean.

icebound = covered by ice, as in lakes in winter in northern climes.

Iceland Cod Wars = a series of disputes between Iceland and Britain over the rights to fisheries off the coasts of the former country from 1958 to 1976. On three occasions, the Icelanders extended their territorial limits from 7 km to 19 km, from 19 km to 80 km, and then to 370 km (200 nautical miles). Nets were caught, rammings occurred and some shots fired. The limit was accepted when Iceland threatened to close the NATO base at Keflavik, an important defense against the Soviet Union in the Cold War (and Cod War may be a tabloid press play on words from Cold War).

icer = the person on board a fishing vessel responsible for icing down the fish catch.

ich = 1) abbreviation for ichthyology.

ich = 2) a contagious disease of aquarium and hatchery freshwater fishes, caused by a large protozoan (Ichthyophthirius multifiliis or I. hoferi) and characterized by small white to greyish pustules on the skin and eyes, the encysted mature parasite. Fish become hyperactive, show flashing and may cut themselves on sharp objects as the parasites cause irritation. Severe infections cause respiratory problems and death. Various chemical additives such as malachite green, formalin and methylene blue can be used to treat the aquarium water. Removal of fish from the aquarium will interrupt the parasite life cycle as encysted trophozoites settle to the aquarium bottom and divide into tomites or theronts which re-infect fish skin. Also called white spot and ichthyophthiriasis.

ichnology = the study of fossilised work of an animal.

ichnotaxon = a taxon based on the fossilised work of an animal, e.g. trails, burrows, etc.

ichthic = of, pertaining to, or characteristic of fishes; having the zoological characters of a fish; piscine.

ichthidin = a substance from the egg yolk of bony fishes.

ichthin = a nitrogenous substance resembling vitellin, present in the egg yolk of cartilaginous fishes.

ichthism = poisoning from eating fish.

ichthulin = the globulin portion of fish eggs, analogous to the vitellin of birds eggs. The ichthulin of some fish eggs is poisonous to warm-blooded animals.

ichthus = 1) a representation of a fish; an amulet or talisman shaped like a fish; often a symbol of fertility. Formed from two intersecting arcs, used by early Christians as a secret symbol, and now called the Jesus fish, q.v., appearing commonly on the backs of cars, and used by Alfa Romeo cars as a non-religious symbol. Also spelt ichthys, icthus, ikhthus. See also vesica piscis.

ichthus = 2) an iconographic symbol for Christ from the initials in the Greek phrase Iesous Christos Theou Huios Soter (Jesus Christ Son of God Saviour, ιχθύς in Greek); or representing Jesus as a fisher of men.

ichthy- (prefix) = pertaining to fishes, from the Greek ixoos, ichthys, fish.

ichthyarchy = the domain of fishes.

ichthyic = like, or pertaining to, fishes.

ichthyism = fish poisoning.

ichthyismus = an obsolete clinical term for fish poisoning. See ichthyotoxism.

ichthylepiden = one of two albuminoid proteins found in the scales of many teleost fishes (the other being collagen).

ichthyo- (prefix) = pertaining to fishes, from the Greek ixoos, ichthys, fish.

ichthyoacanotoxism = envenomation from the sting of fishes.

ichthyoacanthotoxin = the poison secreted by the venom apparatus of fishes; fish venom.

ichthyoacanthotoxism = an intoxication (poisoning) resulting from injuries produced by the stings, spines, or "teeth" of venomous fishes.

ichthyoallyeinotoxin = a hallucinogenic fish poison.

ichthyoallyeinotoxism = hallucinogenic fish poisoning caused by ingesting the heads or flesh of certain types of reef fishes in the tropical Pacific and Indian Oceans. The toxicity is sporadic and unpredictable in its occurrence and is not destroyed by ordinary cooking. The symptoms develop within minutes to 2 hours after ingestion, lasting up to 24 hours or more. The poison affects primarily the central nervous system. Symptoms consist of dizziness, loss of equilibrium, lack of motor co-ordination, hallucinations and mental depression. Feelings of chest constriction, of imminent death and nightmares are characteristic. No specific antidotes are known. The stomach should be immediately evacuated, other treatment is symptomatic.

ichthyobiology = the study of the biology of fishes. A term used in Europe, particularly Poland.

ichthyocene = a fish taxocene (a taxonomically related set of species within a community), e.g. the epipelagic ichthyocene. Mostly Russian terminology, not commonly encountered elsewhere.

ichthyocide = a substance which kills fishes, e.g. rotenone; piscicide is also employed.

ichthyocol = isinglass; a glue prepared from the gas bladders of certain fishes and a pure form of gelatin used for clarifying wine and beer, for making jellies, and in various other usages. Ichthyocol is made up of short needles of collagen in the tunica externa of the gas bladder.

ichthyocolia = ichthyocol.

ichthyocolla = variant of ichthyocol.

ichthyocoprolite = fossil faeces of fishes.

ichthyocrinotoxic fishes = those fishes that produce a poison by means of glandular structures often in the skin, independent of a true venom apparatus, i.e. poison glands are present, but there is no traumagenic device (such as a spine), e.g. Myxinidae, Grammistes, Rypticus (Serranidae), and Ostraciidae.

ichthyocrinotoxin = the poison produced by a glandular secretion of fishes which is not associated with a venom apparatus. Glands in the skin release their contents into the water where they are toxic and usually lethal to other fishes.

ichthyocyan = the chemical responsible for the blue and blue-green colours of the serum of Labridae.

ichthyodont = a fossil fish tooth.

ichthyodorulite = fossil spine, plate, tooth or denticle in Elasmobranchii.

ichthyoerythrin = the chemical responsible for the rose pigment in the serum of certain fishes.

ichthyofauna = fish life of a region, fish fauna. The synonym piscifauna is less commonly applied.

ichthyographer = a writer or describer of fishes.

ichthyographia = an article or report about fish; a treatise on fishes.

ichthyography = an article or report about fish; a treatise on fishes.

ichthyohemotoxic fishes = those fishes having poisonous blood, members of the anguilliform families Anguillidae, Congridae, Muraenidae, and Ophichthidae. Most of these are edible fishes, only the absorption or ingestion of fresh blood being harmful.

ichthyohemotoxin = the poison found in the fresh blood of certain anguilliform fishes. These are largely parenteral (entry not through the intestine but through skin, cuts, etc.) poisons, although some individuals have been poisoned by the ingestion of large amounts of the toxin. The poisons have hemolytic, immunological and neurological effects. They are usually destroyed by heat and gastric juices.

ichthyohemotoxism = poisoning from absorption, injection or ingestion of fresh blood of ichthyohemotoxic fishes. Symptoms following ingestion include diarrhoea, bloody stools, vomiting, frothing at the mouth, skin eruptions, cyanosis, apathy, irregular pulse, paralysis, respiratory distress and possibly death. Local application to the eye or tongue produces inflammation and production of tears or saliva. No specific antidote is known. Some laboratory animals develop cellular immunity, others hypersensitivity, following repeated small doses.

ichthyohepatotoxic fishes = poisoning resulting from the consumption of toxic fish livers. One species of each of the following families has been implicated: Scombridae, Serranidae, Sparidae, Trichodontidae.

ichthyohepatotoxin = the poison found in the liver of ichthyohepatotoxic fishes - probably excessive amounts of vitamin A.

ichthyohepatotoxism = poisoning resulting from eating the livers of ichthyohepatotoxic fishes. A high concentration of vitamin A is believed to be an important factor in the poisoning: ordinary cooking does not destroy the poison. Symptoms appear within 1/2 to 12 hours with maximum intensity usually within 7 hours after ingestion and consist of nausea, vomiting, fever and headache. Mild diarrhoea and facial flushing may occur. Large areas of skin may peel off between 3-30 days. Recovery is usually uneventful and no fatalities have been reported.

ichthyoid = 1) fish-like.

ichthyoid = 2) hagfishes and lampreys, similar to fishes but not true fishes.

ichthyoid blood cell = megaloblast, an erythrocyte or an abnormal blood cell in pernicious anaemia.

ichthyol = an oily substance prepared by the dry distillation of a bituminous mineral containing fossil fishes. Used as a remedy in some forms of skin diseases.

ichthyolatrous = adjective of ichthyolatry.

ichthyolatry = the worship of fishes or fish-shaped idols.

ichthyolite = a fossil of whole or part of a fish.

ichthyologic = adjective for ichthyology.

ichthyological = adjective for ichthyology.

ichthyologically = adverb for ichthyology.

ichthyologist = one who studies fish.

ichthyology = from the Greek ἰχθυ, (ikhthu, fish) and λόγος (logos, reason), the study (scientific) of fishes; the natural history of fishes; a treatise on fishes. Usually restricted to the scientific study of and the resulting knowledge about fishes, particularly in the fields of systematics, taxonomy, anatomy, zoogeography and ecology. Commercial fisheries and the study of fish stocks are not usually included under ichthyology. Dictionary definitions include the study of the structure, classification, physiology, history, habits, economic importance, etc. and it is in this more general sense that ichthyology is treated in this Dictionary.

ichthyomancy = divination by the heads or the entrails of fishes.

ichthyomania = an obsession with fishes and their study.

ichthyomantic = adjective for ichthyomancy.

ichthyomantist = someone who uses divination by the heads or the entrails of fishes.

ichthyomass = the amount of fish flesh present in a biotope at any one time; standing crop of fish.

ichthyomorph = fish-shaped.

ichthyomorphic = fish-shaped.

ichthyomorphous = fish-shaped.

ichthyoneuston = the fish part of the neuston, typically fish eggs and fry.

ichthyoneustont = a member of the ichthyoneuston.

ichthyonomy = the arrangement or classification of fishes.

ichthyonosia = a fish allergy.

ichthyootoxic fishes = those fishes that produce a poison that is generally restricted to the gonads of the fish; the musculature and other parts of the fish are usually edible. There is a definite relationship between gonadal activity and toxin production. These fishes are mainly freshwater, but a few marine species have been incriminated. The most dangerous forms are the genera Barbus, Schizothorax, Tinca (Cyprinidae) and Stichaeus (Stichaeidae).

ichthyootoxin = the poison found only in the eggs or gonads of ichthyootoxic fishes (not those also found in the flesh, etc.).

ichthyootoxism = poisoning resulting from eating eggs or gonads of ichthyootoxic fishes. Symptoms which develop soon after ingestion of the roe include abdominal pain, vomiting, diarrhoea, headache, thirst, sensation of chest constriction, low blood pressure, chills, paralysis, coma and death. Recovery is usually made in 3-5 days. There is no known antidote. The stomach should be promptly evacuated and symptomatic treatment be given. Some ichthyootoxins are destroyed by heat, others are not.

ichthyopalaeontology = the study of fossil fishes.

ichthyopatolite = fish-track (fossilised remnants of fish moving over the bottom; traces of pectoral and other fins).

Ichthyophagi = the fish-eating peoples of the Makran coast of Iran and Pakistan mentioned by Nearchus in Classical times. They are said to have eaten fish raw, dried and in fishmeal bread, wore fish skin dresses, and lived in houses with windows and doors made from whale bones. Their nets where made of the inner bark of palm trees and could stretch for a quarter of a mile.

ichthyophagian = ichthyophagist.

ichthyophagist = one who eats, or subsists on, fish.

ichthyophagous = fish-eating or subsisting on fish.

Ichthyophagous Club = a New York club of the nineteenth century devoted to rare and choice fish dinners.

ichthyophagus = ichthyophagist.

ichthyophagy = the practice of fish-eating.

ichthyophile = a lover of fishes.

ichthyophilist = ichthyophile.

ichthyophily = a love of fishes.

ichthyophobia = 1) avoidance of fish in consequence of a taboo.

ichthyophobia = 2) fear of fishes.

ichthyophthalmite = fish eyestone, a white, pale pink, or pale green crystalline mineral.

ichthyophthira = a division of copepod crustaceans, including numerous species parasitic on fishes.

ichthyophthiriais = ich (2).

ichthyoplankton = eggs, larvae and small juveniles, and adult fishes having feeble powers of locomotion; fishes capturable in plankton nets.

ichthyopolism = the sale of fish; the trade in fish.

ichthyopolist = one who sells or deals in fish.

ichthyopterygium = 1) fin (flap-like external organ concerned with locomotion in fishes. See dorsal, adipose, caudal, anal, pelvic (ventral), and pectoral fins).

ichthyopterygium = 2) more narrowly defined as the paired fin skeletons of fishes; girdle.

ichthyosarcephialtilepsis = see preferred synonym ichthyoallyeinotoxism.

ichthyosarcotoxic fishes = those fishes that contain a poison in the flesh (including musculature, viscera, skin, or slime) which when ingested by humans will produce a biotoxication. The toxins are oral poisons believed to be small molecular structures and are generally not destroyed by heat or gastric juices.

ichthyosarcotoxin = poisoning from fish flesh including muscles, viscera, or gonads (not including those due to bacteria).

ichthyosarcotoxism = poisoning from consumption of flesh including musculature, viscera, skin, slime of ichthyosarcotoxic fishes.

ichthyosiform = resembling ichthyosis or of ichthyosis.

ichthyosis = a congenital skin disease in humans where the epidermis becomes hard, rough and scaly. Also called fishskin disease or fish-scale disease.

ichthyosismus = an obsolete term to designate fish poisoning. See ichthyotoxism.

ichthyosporidiosis = a fungal internal infections in fishes caused by Ichthyophonus hoferi or Ichthyosporidium. Symptoms include hollow bellies, emaciation, sluggishness, loss of balance and eventually external black cysts and sores.

ichthyotherapy = the use of fish to treat illness, e.g. certain members of the family Cyprinidae such as Garra rufa and Cyprinion macrostomum living in hot springs near Sivas, Turkey nibble at skin lesions and are said to cure psoriasis. Probably exposure to UV light and to selenium in the water is aided by removal of dead skin.

ichthyothereol = a plant poison interfering with respiration found in members of the family Asteraceae from the Amazon, such as Ichthyothere terminalis. It is a polyacetylene compound. Fish will jump out of the water if leaves are used in bait.

ichthyotic = of or relating to ichthyosis.

ichthyotomist = one skilled in ichthyotomy.

ichthyotomy = the anatomy or dissection of fishes.

ichthyotoxic = 1) poisonous from fish, i.e. the poison is derived from the fish.

ichthyotoxic = 2) poisonous to fish, e.g. reputedly certain strains of Pfiesteria.

ichthyotoxicology = the science which treats poisons found in fishes, their effects, nature, antidotes, and recognition.

ichthyotoxicum = the toxic principle in the blood of certain anguilliform fishes. See ichthyohemotoxin.

ichthyotoxin = a general term used to designate any type of poison derived from fishes.

ichthyotoxism = a general term used to designate any form of intoxication (poisoning) produced by a fish.

ichthyovenin = an obsolete term for poisoning due to histamine in combination with saurine.

ichthys = ichthus.

ichthytaxidermy = taxidermy of fishes; mounting and stuffing fishes for display and preservation, and as fishing trophies.

ichtxocolle = a commercial misspelling (?) of ichthyocolle.

ichtyocolle = French spelling of ichthyocolle, sometimes used in English.

icing = putting ice among fish in a box to chill them to 0 to-0.5°C. There is a whole technology involved in this process.

ick = ich (a contagious disease of tropical marine and freshwater fishes, caused by a protozoan (Ichthyophthirius multifiliis) and characterized by small white to greyish pustules on the skin and eyes. Also called white spot).

iconotype = an illustration on which a new species or subspecies was based.

icosapantaenoic acid = an omega-3-fatty acid, q.v., found in fish oil; its chemical name is all-cis-5,8,11,14,17-icosapentaenoic acid. Said to reduce the risk of heart attacks in humans when ingested at 1800 mg per day. Also called eicosapentaenoic acid and timnodonic acid.

icotype = a specimen used for identification, worked on by the original author, or collected from the type locality, but not one used for the published description.

icthus = ichthus.

ICZN = International Commission on Zoological Nomenclature, the judicial body empowered to enforce and interpret the International Code of Zoological Nomenclature (which presumably has the same acronym).

id est = that is. Abbreviated, and usually seen as, i.e.

-id (suffix) = word-ending anglicising the Latin word for a family, e.g. the perch family Percidae may be referred to as percid.

-idae (suffix) = the formal ending of the Latin name of a family , e.g. Acipenseridae.

idem = the same.

identification = the placing of individual specimens into previously established taxa, by deductive procedures. The determination of the taxonomic identity of an individual.

identification key = a tabulation of characters used to identify a species. Two rubrics form a couplet, the usual arrangement of keys. Each couplet gives an alternative set of characters leading to the species identity or to the next couplet. Artificial key, q.v., bracketed key, q.v., dichotomous key, q.v., indented key (or yoked key), q.v., monothetic key, q.v., natural key, q.v., sequential key, q.v.

ideotype = a specimen examined by the author of a species but not from the type locality. Also spelt idiotype.

idiotaxonomy = the taxonomic study of individuals, populations, species and higher taxa; traditional taxonomy.

idiothermous = homoiothermic (referring to organisms maintaining a constant internal temperature, usually above that of their environment. Some oceanic fishes attain temperatures above their surroundings due to muscular activity, control of a surficial vascular network and a small ratio of surface to volume, e.g. Thunnus).

idiotype = ideotype.

idler = the person on board a fishing vessel responsible for washing split fish before salting.

iex = abbreviation for ion exchange.

iff = a gaff (Kentish dialect).

iffing = using an iff; gaffing fish (Kentish dialect).

-iform (suffix) = 1) word ending anglicising the Latin word for an order, e.g. the perch order Perciformes may be referred to as perciform.

-iform (suffix) = 2) word ending indicating similarity, e.g. caniniform, resembling canines.

-iformes (suffix) = the formal ending of the Latin name of an order, e.g. Perciformes.

IFQ = abbreviation for individual fishing quota.

IGFA = the International Game Fish Association which records and maintains capture data on angled fishes.

IHN = abbreviation for infectious haematopoietic necrosis (an acute Rhabdovirus-group disease of salmonids transmitted by eggs in western North America, e.g. in chinook and sockeye salmon and rainbow trout. Particularly affects fish less than 5 cm long in water below 10°C).

ika-roa = the long fish in Maori legend that gave birth to all the stars in the Milky Way. Also called mang ō roa (long shark) or mangōroa i ata (long shark in the early dawn).

ike jime = "stab death", a spike or awl driven through the head to kill fish rapidly; especially favoured by Japanese consumers and adopted in the west as a humane method.

ikhthus = ichthus.

ikhthyes = a pair of large Syrian river fish who rescued Aphrodite and Eros when they were fleeing from the monster Typhoeus and were placed in the sky as the constellation Pisces. Alternatively the two gods disguised themselves as fish to escape the monster, or that the fish assisted in the birth of Aphrodite. Presumably the large river fish are Barbus esocinus, a large cyprinid of the Tigris-Euphrate basin.

iki-jime = ike jime.

Ikranoye = a village on the Volga River delta at the Caspian Sea, named for the caviar produced by the sturgeons fished there. See also Caviar.

ikura = salmon roe as served in a sushi restaurant.

ile = a fishing ground inside a main tidal current between two points where there is a counter current. Fishing maybe carried on irrespective of the tide, but in the main current, only at slack water (Caithness dialect).

ileophagous = eating detritus.

ileotrophic = bottom layer.

iliophagous = ileophagous.

iliotrophic = ileotrophic.

ill-willed = said of fish unwilling to bite (Scottish dialect).

illegitimate = in taxonomy, indicates use of a name not in accordance with the International Code of Zoological Nomenclature.

illicia = plural of illicium.

illicium (plural illicia) = a long, flexible spine on the dorsal median surface of the head usually with a modified tip or esca. Believed to be modified spine from the first dorsal fin and retractable in some species. Acts to lure prey close enough to be captured. Found in Lophiiformes.

im- (prefix) = not.

imbankment = embankment (1) a raised bank confining a river; 2) the act of making an embankment).

imbedded portion = the part of scale which is overlapped by other scales. It usually includes most of the lateral fields and all of the anterior field.

imbibition = uptake of water by non-active methods, e.g. swelling of fish eggs shortly after fertilisation.

imbricate = overlapping like shingles on a roof (with reference to scales). Sometimes used to indicate a complex pattern made up of small parts.

imitative flyfishing = matching the hatch (an angler's attempt to choose an artificial fly that resembles natural insects hatching and being fed on selectively by fish).

immaculate = spotless, without a pigmentation pattern; usually white or colourless.

immature = not ripe, not fully developed sexually.

immunology = the study of immunity, the chemical response to an infection, used to work out relationships between species based on similar responses.

imp = a length of hair twisted and forming part of a fishing line.

impaling gear = any apparatus which serves to stab and retain a fish, e.g. harpoon, spear.

impeller = an electrically driven propeller used in aquaria to push water through a pump or filter.

imperfect name = nomen imperfectum (an available name which when originally published met all mandatory requirements of the International Code of Zoological Nomenclature, i.e. met all criteria of availability but which contained some defect needing correction, such as names incorporating hyphens, diacritical marks or apostrophes, higher taxon names using an incorrectly formed stem).

imperforate = not pierced.

Imperial fluid ounce = 28.416 cm³. Abbreviated as fl oz_BI.

impounding net = various stationary or mobile net capturing fish by confinement, e.g. cast

impoundment = an enclosed body of water, of artificial construction and with variable environmental conditions, often turbid and with varying water levels. Used to retain water, sediment or wastes.

impression = the number of copies of a work produced at one time; an edition may have two or more impressions.

impressionistic fly = an artificial fly dressed to look exactly like a natural insect.

imprinting = the process by which salmon fry memorise their home stream to which they return to spawn as adults.

improved clinch knot = used for tying flies, lures, swivels and bait hooks or line to a reel spool. More secure than an ordinary clinch knot as it will not slip. Various websites have animated steps showing how to tie this knot.

improved end loop = a knot used for making loops in leaders or heavy lines. It is stronger than a perfection loop knot but thicker; used where a secure knot is more important than delicacy. Various websites have animated steps showing how to tie this knot.

in = in; used in nomenclature to indicate an author of a species contained within a larger work authored or edited by another person(s), e.g. Cuvier in Cuvier and Valenciennes indicates that the species was authored by Cuvier alone.

in adnot. = abbreviation for in adnotatio.

in adnotatio = in an annotation.

in bulk = fish piled in layers for curing, storage or shipment.

in copulo = in the act of mating.

in hospite = within the host.

in litt. = abbreviation for in litteris.

in litteris = in correspondence or communicated in writing. Used for an unpublished source of information. NOT in literature.

in press = used when citing a reference or information from a reference that is accepted for publication but has not yet appeared.

in situ = in the original or natural location.

in situ conservation = preserving habits and the species therein, cf. ex situ conservation.

in situ production = fish food produced within a culture system, e.g. algae and copepods.

in syn. = abbreviation for in synonymis.

in synonymis = in synonymy. Abbreviated as in syn.

in the round = fish delivered to a buyer intact, without being altered, cleaned or gutted.

in vitro = experiments or tests done in an artificial environment.

in vivo = experiments or tests done on living fish.

in- (prefix) = not.

in. = inch (2.54 cm).

in-line feeder = a type of feeder, q.v., in angling designed to run on the main fishing line. The line runs through a small tube along the length of the feeder and the feeder can be rigged to run free or locked in place.

in-line lead = a lead weight having a section of tubing running through it and extending out on both sides. This tube helps prevent snagging on weeds.

in-line spinner = in angling, any spinner or spoon mounted on a central shaft.

in-river run = the number of fish migrating up a river estimated by adding the spawner abundance, the number of naturally produced fish entering a hatchery (if present), and the in-river harvest.

in-season adjustments = regulatory changes that affect an ongoing fishery.

inactive = in angling, said of fish that are not feeding because of a major weather change, temperature change, lowered water level, etc.

inadmissable = used of a name or epithet which cannot be used within the provisions of the International Code of Zoological Nomenclature.

-inae (suffix) = the formal ending of the Latin name of a subfamily, e.g. Etheostomatinae in the family Percidae.

inappropriate name = a name that denotes a character, a quality, or an origin not possessed by the taxon bearing that name.

inarticulate = not jointed.

inasal = a broiled product made from sardines or herrings (Philippines).

inbreaker = a worker in their first season on a fishing boat, usually eligible only for a partial crew share for part of the first season and then working up to better pay (full crew share).

inbreeding depression = loss of vigour associated with repeated crosses between closely-related individuals.

inc. sed. = abbreviation for incertae sedis.

incertae sedis = of uncertain seat, meaning of uncertain taxonomic position or affinities.

inch = 2.54 cm. Abbreviated as in.

inchorn = the inner pocket or pouch of a fishing net (British dialect).

incidental allowance = a regulation allowing incidental catch in a fishery.

incidental catch = bycatch (fishes caught incidental to the target species; also called incidental catch or accidental catch. These fishes are usually of lesser value than the target species, and are often discarded. Some bycatch species are of commercial value and are retained for sale. The bycatch often consists of the juveniles of commercial species, and their loss has a deleterious impact on the overall yield obtained from a certain area. Also spelled by-catch). See also total catch.

incidental catch rate = the proportion of total catch which is incidental catch.

incidental harm = damage to individuals, stocks or populations of endangered or threatened species while fishing for commercial species. Usually permitted by licence where the harm is not considered critical to survival or recovery of the species.

incidental harvest = incidental catch.

incidental mention = the use of a name by an author who demonstrates no intention of adopting or introducing it, but merely mentions it without comment on its suitability; this mention does not fulfill the requirements of the International Code of Zoological Nomenclature.

incidental take = the catch of a threatened or endangered species that is incidental to, and not the purpose of, the carrying out of an otherwise lawful activity.

incipient = beginning to be apparent, e.g. larval structures during development.

incised = fin membranes deeply notched between the rays or spines.

incised channel = a stream that has cut its channel into the bed of a valley.

incisiform = compressed and wedge-shaped; said of teeth with a cutting edge resembling incisors of higher vertebrates, e.g. in Serrasalmus, the beak of Scaridae.

incisor = a flat shearing tooth with a fairly straight cutting edge, usually in the front of the mouth, e.g. Sargus, Charax (Sparidae).

incisura (plural incisuræ) = incisure.

incisuræ = plural of incisura.

incisure = a notch, fissure or cleft in a bone.

incl. = abbreviation for inclusus.

included = contained, e.g. the lower jaw is "included" when the upper jaw extends beyond and over it; the head length is included five times in the standard length when the length of the head can be stepped five times from the anteriormost point of the head to the base of the tail fin.

inclusus = included. Abbreviated incl.

incoming year class = the year class of fish recruited to the fishable stock.

incomplete cleavage = meroblastic cleavage (cell division in which sister cells are only partially separated from one another by cytokinesis).

incorrect original spelling = an original spelling that is incorrect under the provisions of the International Code of Zoological Nomenclature.

incorrect subsequent spelling = any change in the spelling of an available name other than a mandatory change or an emendation.

increment = the region between similar zones on an otolith or other structure used for ageing. In otoliths, a daily increment comprises a D- and an L-zone, an annual zone comprises an opaque and a translucent zone.

incremental zone = L-zone (that part of a microincrement of an otolith that is light in transmitted light or is an elevated region when acid-etched and seen with a scanning electron microscope. It has less organic matrix and more calcium carbonate than the D-zone, q.v.).

incubate = to hold eggs during development.

incubation = 1) the period of time from egg fertilization until hatching.

incubation = 2) the act or process of hatching.

incubation channel = a man-made channel in the streambed used for hatching fish eggs.

incubation period = incubation (1) the period of time from egg fertilization until hatching, as in a hatchery).

incubator = any apparatus for hatching fish eggs.

incus Weberi = intercalarium.

indented = emarginate.

indented key = a dichotomous key in which the first part of a couplet is followed by all subsequent couplets. Each subordinate couplet is indented to the right for reasons of clarity; not much used in ichthyology.

independent tributary = a stream flowing directly into the sea.

indeterminate = not defined, not definite, not classified.

indeterminate growth = growth that continues as long as the fish is alive. Body size and age are correlated and there is always a larger fish out there to be caught, unlike most other vertebrates that attain a maximum adult size. However, growth slows with age.

index fishing = sampling with standard gear to determine changes in proportion of individual age-classes or stocks within species, or ratios between species.

index of abundance = a relative measure of the abundance of a stock, e.g. a time series of catch per unit of effort data.

index of biotic integrity = the use of fish sampling data to indicate the overall health and integrity of a stream. Measures of fish species composition, trophic composition, reproductive behaviour and abundance and condition are used. Sites with high biotic integrity have relatively high numbers of total species. Abbreviated as IBI.

index species = indicator species.

India ink = a permanent and waterproof black ink often used in handwritten labels for museum specimens.

Indian cure salmon = brined strips of salmon hard smoked for about two weeks at 21-36°C.

Indian major carps = commercially important fishes of the family Cyprinidae, used in aquaculture, namely rohu (Labeo rohita), catla (Catla catla) and mrigal (Cirrhinus mrigal). See also Chinese major carps.

Indian minor carps = commercially important fishes of the family Cyprinidae, used in aquaculture but not as important as the Indian major carps, namely reba (Cirrhinus reba), bata (Labeo bata), calbasu (Labeo calbasu), white carp (Cirrhinus cirrhosus) and Cauvery carp (Labeo kontius).

Indian style salmon = Indian cure salmon.

Indiana blade = in angling, a type of spinner or spoon blade, oblong in shape and intermediate between a Colorado, q.v., and willowleaf, q.v., blade in action.

Indiana reel = a large diameter, narrow fishing reel with forked spokes around the ends of which the line is wound. The large diameter made for rapid retrieval and the narrow spool facilitated thumbing during the cast.

indication = published information that in the absence of a definition or description allows a name proposed before 1931 to be considered available or in the absence of an original designation (q.v.) determines the type-species of a nominal genus.

indicator = 1) a floating object placed on the leader or end of a fly line to track the movement of the line or to indicate a bite. Used with nymphs and a slack line, for example.

indicator = 2) biological indicator (a fish whose presence in a water body is indicative of certain environmental conditions).

indicator species = 1) a fish species whose status provides information on the overall condition of the ecosystem and of other species in that ecosystem; fish that are sensitive to environmental conditions and which can therefore be used to assess environmental quality.

indicator species = 2) a microorganism or a group of microorganisms, harmless themselves, but serving to indicate the presence of pathogens in fish food products. The harmless microorganisms are easier to detect than the pathogens.

indigenous = native to a particular area.

indigenous fishing = fishing undertaken by peoples native to an area.

indirect fishing = taking fish by means not involving usual methods such as nets, traps and hooks, e.g. removing fish from eagle nests, taken there by the bird to feed nestlings, in early nineteenth century Hungary; removing fish from pelican pouches by the Sumerians.

indirect methods = methods for stock assessment based on fishery-dependent data, e.g. catch and effort statistics, age structure of the catch.

indirect reference = a clear statement that the description of a taxon for which a new name is given has been effectively published in an earlier work.

individual fishing quota = individual quota.

individual fishing share = individual quota.

individual non-transferable quota = allocation of total allowable catch to individual fishermen or companies but not as long-term rights because they are not tradable by their holders.

individual quota = a quota, e.g. a percentage, of a total allowable catch assigned to an individual, a vessel or a company, with the numbers of the latter limited too. A quota for a company and its fleet of vessels is usually called an enterprise allocation. Also called individual fishing quota and individual fishing share. This quota is supposed to give fishers a feeling of stock ownership by guaranteeing their share of the catch, eliminating competition in gear and effort to catch the biggest share of the catch. It therefore encourages conservation, cuts fishing costs, and fishing is directed to the best quality and prices. Results have been mixed as high grading (q.v.) may occur. Abbreviated as IQ or IFQ.

individual transferable quota = a fixed share of the catch assigned to each fisherman or vessel owner as a tradable right, one that can be sold or leased to others. This may make an operation more efficient as some fishers buy the quotas of others and fleets can be reduced or rationalised with less government interference. As above, results are mixed as wealthier fishers benefit and the owner-operator system is disadvantaged. Abbreviated as ITQ. Also called catch share.

individually quick frozen = fish, usually as fillets, that are rapidly frozen, in various sizes. Abbreviated as IQF.

indraft = an inward flow.

induced breeding = causing fish to reproduce in captivity.

induced spawning = laying of eggs by artificial stimulation, e.g. changes in the light regime, fertility cycle, salinity or temperature, osmotic shock, UV irradiation.

indulgence = a box placed beside the splitting table and constantly replenished with cod to be processed (Newfoundland).

industrial fishery = a fishery directed to the capture of fish for purposes other than food for humans, e.g. animal feed, fertiliser, oil. Occasionally used for fish meant to be canned or for fishing on a large scale for food. Removes many fish from the base of the food chain.

industry = the fishing industry includes both recreational, subsistence and commercial fishing, and the harvesting, processing, and marketing sectors.

-ine (suffix) = word ending anglicising the Latin word for subfamily, e.g. Etheostomatine.

ineditus = unpublished.

infauna = animals living in the soft bottom or substrate.

infection = bacteria, viruses and fungi invading and multiplying in the fish body. The infection may not be readily apparent. May refer to a specific infectious disease, cf. infestation.

infectious dropsy = an acute haemorrhagic viral infection of Cyprinidae, in particular of cultured Cyprinus carpio, usually appearing in spring. Symptoms include loss of coordination and equilibrium, popeyes, swollen belly, inflamed and swollen vent, and oedema and haemorrhages of various organs. Also called spring viraemia. See also bacterial haemorrhagic septicaemia.

infectious haematopoietic necrosis = an acute Rhabdovirus-group viral disease of salmonids transmitted from fish to fish and by eggs in western North America, e.g. in chinook and sockeye salmon and rainbow trout. The disease destroys the haemotopoietic tissues in the kidney and spleen. Fish become lethargic or hyperactive, dark in colour, develop popeyes, anaemia (pale gills) and a swollen belly, and produce faecal casts. Haemorrhages on the skin, viscera and fins occur. Particularly affects fish less than 5 cm long in water below 10°C with high mortality. Potentially dangerous to humans. Abbreviated as IHN. Also called sockeye salmon virus.

infectious pancreatic necrosis = a viral disease (Birnaviridae) particularly of juvenile salmonids, ususally in hatchery fish less than 5 cm long. Whirling, darkening, protruding eyes, abdominal distention and haemorrhages of the belly and fin bases, and mucoid faecal casts are external symptoms. Gelatinous material in the anterior intestine is indicative of this disease and hyalin degeneration of skeletal muscle occurs. Causes fatal infections of the pancreas.

infectious salmon anaemia = a viral disease of salmonids such as Atlantic salmon, sea-run brown trout and rainbow trout. The anaemia leaves fish open to other diseases and the kidneys may haemorrhage and the spleen swell. The disease is transmitted from fish to fish and from sea lice to fish. Abbreviated as ISA.

inferior = ventral, below. Used in reference to a mouth on the lower surface of the bead.

infestation = presence of parasites inside or on an organism, cf. infection.

infestation intensity = the number of parasites in relation to the number of fish.

infestation rate = the number of infested fish in relation to the number of fish examined.

infeudated = restricted; ecologically restricted to a niche or area.

inflated = swollen or expanded; said of anatomical structures.

inflated worm method = in angling, inserting an air bubble into a worm with a hypodermic needle.

inflow = flowing in.

influent = 1) flowing above the water table and losing water to it.

influent = 2) said of a lake having a single inflowing stream.

influent = 3) water that flows into sink holes, cavities and porous material and disappears into the ground.

influent stream = losing stream (a stream or a part of a stream that loses water to the groundwater).

influx = flowing in.

informosome = a molecule composed of RNA and protein found in the cytoplasm of eggs of fish and echinoderms and thought to be transmitted from the nucleus to the cytoplasm.

infra- (prefix) = below, beneath, sub, smaller.

infracaudal luminous gland = a long ventral median luminous gland in Myctophidae (ICG in illustration).

infraclavicle = a misnomer for the ectocoracoid (a paired dermal bone in Gasterosteiformes connected with the coracoid and extending posteriorly. Has also been applied to the element below the scapula and applied to the coracoid in Dipnoi), in fishes.

infradian rhythm = a biological rhythm with a periodicity longer than 28 hours or with a frequency less than one cycle per 24 hour, e.g. lunar and seasonal rhythms.

infrageneric = below the rank of genus.

infrahaline = fresh water having a salinity less than 0.5 parts per thousand.

infralittoral = 1) the depth zone of a lake with rooted vegetation.

infralittoral = 2) the upper subdivision of the marine sublittoral zone dominated by algae with a lower limit where light is about 1% of the surface level.

infralittoral = 3) the zone between low tide and 100 metres.

inframandibular = a very small bone between the outer side of the articular and the dentary in Umbra (Umbridae) and Stenodus (Salmonidae).

infraoral = below the mouth.

infraoral cusp = the tooth just below the mouth in lampreys (Petromyzontiformes).

infraoral lamina = the teeth just below the mouth in lampreys (Petromyzontiformes).

infraorobital = below the eye, suborbital.

infraorbital bone = one of a series of dermal bones generally below the eye. Name applied to the first six circumorbital bones: infraorbital 1 (lachrymal or preorbital), infraorbital 2 (jugal), infraorbital 3 (true postorbital), infraorbitals 4 and 5, and infraorbital 6 (dermosphenotic). Associated with the infraorbital lateral line. Suborbital bones, q.v., are recognised by some authors as a separate series, sometimes used as a synonym for infraorbital.

infraorbital canal = the cephalic lateral line canal (q.v.) extending from behind and below the eye to behind the upper lip. Abbreviated as IO.

infrapharyngobranchial dental plate = a tooth-bearing plate of dermal origin covering the upper surface of the fifth ceratobranchial. The plate may be divided into two parts with differing tooth types, e.g. in Merluccius. Also called lower pharyngeal bone.

infraspecies = within the species, below the species level. As used by various workers not of taxonomic status unless later elevated to species or subspecies.

infrasubspecific = of a category, taxon or name, of lower rank than the subspecies, and, as such, not subject to recognition by the International Code of Zoological Nomenclature, e.g. form, race, variety.

infraventral = one of a series of cartilaginous elements lying on the lower surface of the basiventrals below the vertebral centrum, which help enclose the haemal canal ventrally in Rajiformes.

infundibuliform = funnel-shaped.

infundibulum = a short stalk from the floor of the diencephalon to the pituitary in the brain.

infusorians = a general term for a variety of small aquatic organisms cultured and fed to small fish fry in aquaria. Vegetable matter, such as a crushed lettuce leaf, is left in a jar of water in a sunny spot. Once this jar of water becomes cloudy with infusorians, small quantities can be added to the aquarium.

ingesta = the total intake of food or energy through ingestion.

ingestion = taking in food, usually by swallowing.

ingroup = in a cladistic analysis, the set of taxa which are hypothesized to be more closely related to each other than any are to the outgroup, a monophyletic group (usually the one being studied).

inguinal process = axillary process (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).

-ini = the ending of the name of a tribe.

initial phase = the first adult colour phase of a sexually dichromatic fish. Also called primary phase.

initium = the centre of origin of growth of the fin ray.

ink sac = the gland discharging into the cloaca of Lophotidae.

inkfish = not a fish but a cuttlefish.

inland fishery = a fishery in fresh or brackish water away from the sea coast.

inland sea = a large lake.

inland water = surface water existing inland including lakes, ponds, streams, rivers, natural or artificial watercourses and reservoirs, and coastal lagoons.

inlet = 1) an indentation in a shoreline, may be small or long and narrow.

inlet = 2) a short, narrow waterway connecting a bay or lagoon to a larger body of water.

inlet = 3) an entry point for water, e.g. a stream entering a lake.

inlet gorge = the deepest part of an inlet.

INM = abbreviation for a nautical mile (1.852 kilometres, 1.151 miles or 1 minute latitude of the great circle of the earth).

innate = inborn, inherited, e.g. innate behavior is that fixed element of behaviour which is inherited and not learned.

inner corner = corner or angle of pectoral fin close to the body.

inner ear = the auditory organ lying in the otic capsule, consisting of the semicircular canals, ampullae, utriculus, sacculus, lagena, sinus endolymphaticus and ductus endolymphaticus. Filled with and surrounded by perilymph (or seawater in forms with an endolymphatic duct), containing otoliths (sagitta, astericus and lapillus in teleostomes). Functions as a gravity receptor, acceleration detector and muscle tone regulator. Innervated by cranial nerve VIII.

inner net = lint (the inner net panel of a trammel net).

innominate bone = the pelvic fin bone in Gasterosteidae, sometimes a misnomer for the ectocoracoid. Also called pelvic bone, pelvic plate, posterior process, pubic bone and medial plate.

inophyllolide = a plant piscicide from the leaves and seeds of Calophyllum inophyllum (Guttiferae), used on the Malay Peninsula. Other piscicidal plant chemicals include callicarpone, huratoxin, ichthyothereol, juglone, justicidin, maingayic acid, rotenone, and vibsanine, all q.v.

input controls = management restrictions placed on the amount of effort input into a fishery, e.g. by restricting types and size of fishing gear and boats and the amount of fishing time.

input stuffing = a fishery uses various factors of production (called inputs) to produce a certain level of catch. Managers of the fishery may attempt to limit the catch by controlling certain inputs but not others. This may fail because fishing businesses substitute more of the uncontrolled inputs for the controlled inputs in an attempt to maintain their catch.

input substitution = input stuffing.

inquiline = lodger; an animal that lives habitually in the cavity or abode of some other species, causing no harm, e.g. Nomeus in the Portuguese man-of-war, Physalia; Fierasfer in the pearl oyster, Meleagrina; Paraclinus marmoratus in finger sponges; Gilbertidia sigalutes in sponges, and Carapus in sea cucumbers. But see also endoparasite.

inscale = one of a series of ratings at the lower end of a wicker trap in a river (Scottish dialect).

insectivore = a feeder on aquatic and terrestrial insects.

insert waggler = in angling, an insert tip pushed into a float. The insert tip is much thinner than the tip of a normal waggler float, q.v., and tips can be changed to allow for changing conditions.

insertion (fin) = the posterior end of a dorsal or anal fin. In paired fins the uppermost, anteriormost, or outermost end of the fin base or the end closest to the most highly developed ray in paired fins (insertion and origin are often used interchangeably in paired fins).

insertion (muscle) = end of a muscle attaching to a moving part. Opposite of origin.

inshore = in shallow waters near the shore; closer to land than the breaking waves.

inshore cod = cod migrating to, and taken in, inshore waters adjacent to the land (Newfoundland).

inshore fisherman = a worker in the inshore fishery.

inshore fishery = a fishery carried out near the shore in small, open boats and usually within territorial waters.

inshore waters = shallow waters at a small distance from the shore. Also called onshore or nearshore waters.

inshoring = the coming in of herrings towards the shore (Norfolk dialect).

inside door = the entrance to a cod trap, situated nearest to the land (Newfoundland).

inside stage = a shed on a fishing stage where split cod are salted and piled in Newfoundland.

instant fish = a commercial venture by the Wham-O Toy Company in the early 1960s. Members of the killifish family from Africa lay eggs in mud at the beginning of the dry season and these hatch when it rains. The idea was to sell mud or a mud substitute containing the eggs, adding water would result in "instant fish". However the idea was not commercially viable as not enough eggs were laid at a time but the eggs have been used in a limited way for educational purposes.

instantaneous count = a count of anglers or boats made quickly from an airplane, bridge, boat or other vantage point.

instantaneous mortality = the percentage of fish dying at any one time.

instantaneous rate of fishing mortality = used to describe the decrease in numbers of fish over time when fishing and natural mortality act concurrently (Nt = No * e^-Zt , where No is the initial number and Nt is the number of the remaining fish at the end of time t. Z is the instantaneous total mortality rate, usually composed of M + F, where M is the natural mortality rate and F is the mortality rate caused by the fishery). Abbreviated as F. Also called rate of fishing; instantaneous rate of fishing mortality, force of fishing mortality.

instantaneous rate of growth = a measure of the weight increase, the natural logarithm of the ratio of final weight to initial weight of a fish in a unit of time, usually a year. When applied collectively to all fish of a given age in a stock, the possibility of selective mortality must be considered (Ricker, 1975). Abbreviated as g or G. The formula is g = [Ln(Wt) - Ln(W0)]/(t1-t0) where Wt is the weight of the fish after t1 days and W0 is the initial weight.

instantaneous rate of mortality = the natural logarithm (with sign changed) of the survival rate. The ratio of number of deaths per unit of time to population abundance during that time, if all deceased fish were to be immediately replaced so that population does not change (Ricker, 1975). Abbreviated as Z. Also called coefficient of decrease.

instantaneous rate of natural increase = instantaneous rate of surplus production.

instantaneous rate of natural mortality = when natural and fishing mortality operate concurrently it is equal to the instantaneous total mortality rate, multiplied by the ratio of natural deaths to all deaths (Ricker, 1975). Abbreviated as M. Also called force of natural mortality.

instantaneous rate of recruitment = number of fish that grow to catchable size per short interval of time, divided by the number of catchable fish already present at that time. Usually given on a yearly basis, i.e. the figure just described is divided by the fraction of a year represented by the short interval in question. This concept is used principally when the size of the vulnerable stock is not changing or is changing only slowly, since among fishes recruitment is not usually associated with stock size in the direct way in which mortality and growth are (Ricker, 1975). Abbreviated as z.

instantaneous rate of surplus production = equal to rate of growth plus rate of recruitment less rate of natural mortality - all in terms of weight and on an instantaneous basis. In a balanced or equilibrium fishery, this increment replaces what is removed by fishing, and rate of surplus production is numerically equal to rate of fishing (Ricker, 1975). Also called instantaneous rate of natural increase.

instantaneous rate of total mortality = the ratio of number of deaths per unit of time to population abundance during that time, if all deceased fish were to be immediately replaced so that population does not change. Also called coefficient of decrease.

instinct = the inherited, unlearned component of behavior.

instream cover = the layers of vegetation such as trees, shrubs, fallen limbs and overhanging vegetation, that are in the stream or immediately adjacent to the wetted channel.

instream use = uses of water within the stream channel, e.g. fish and other aquatic life, fisheries, recreation, navigation, and hydroelectric power production.

insular = 1) relating to, or characteristic of, or situated on an island.

insular = 2) isolated geographically.

insulin = a polypeptide, pancreatic hormone involved in sugar balance although in fish it is more probably involved in controlling protein metabolism.

intake = 1) a place where water is taken in.

intake = 2) the amount of water taken in by an intake.

integrated analysis = stock assessment methodologies that attempt to integrate multiple sources of data into a single estimation framework, e.g. total landings by fleet, size samples of landings, discard estimates, size samples of discards, standardized CPUE by fleet, fishery-independent surveys, and tagging records on movement, growth and recoveries.

integrated aquaculture = an aquaculture operation where many aspects are under its control, including such items as feed supplies and marketing at either end of the process of producing fish.

integrated fish farming = fish aquaculture with other organisms, e.g. ducks, pigs, poultry, and crops.

integrated management = a system where competing environmental, sociological and economic issues are considered together in order to optimise results for the community and ecosystem.

intensity = 1) effective fishing effort.

intensity = 2) fishing effort per unit area (must be proportional to fishing mortality through the relation F = q(f/A) where (f/A) is the fishing intensity and “q” the catchability coefficient).

intensity = 3) effectiveness of fishing.

intensive culture = an aquaculture system in a carefully controlled environment with a very high number of fish that depends on external inputs such as food, oxygen, and/or water exchange under optimal conditions. Most intensive culture systems are not sustainable in the medium or long term. Also called intensive farming.

intensive farming = intensive culture.

inter- (prefix) = between.

inter-annual = between years, in terms of comparing populations or events.

interaction = positive and negative associations between species that favour or inhibit mutual growth and evolution of populations. It may take the form of competition, predation, parasitism, commensalism or mutualism.

interactive feeding system = in aquaculture, a food release system triggered by detection of wastes or by monitoring fish behavioural responses.

interarcual cartilage = cartilage connecting the epibranchial bone of the first gill arch to the infrapharyngobranchial bone of the second gill arch.

interbasin transfer = the diversion of water from one drainage basin to one or more other drainage basins.

interbranchial septum = the tissue layer separating the two halves of the gill (hemibranchs). They extend to the exterior and are continuous with the skin in Elasmobranchii but are reduced in other fishes and do not project beyond the hemibranchs.

intercalar = a separate sesamoid bone, forming the posterior wall of the otic or auditory capsule, between the prootic, pterotic and the exoccipital and associated with the ventral process of the posttemporal. Also called opisthotic, q.v. and sometimes applied to the autopterotic. Absent in Siluridae and with a foramen for the glossopharyngeal nerve in Gadidae.

intercalare = an additional element in the vertebra.

intercalarium = 1) the third of the four Weberian ossicles, q.v., comprising an ascending process, an horizontal process where the interossicular ligaments attach connecting the scaphium, intercalarium and tripus), and a peg-like articular process with the second centrum.

intercalarium = 2) baseost (the distal radial or pterygiophore supporting the fin rays).

intercalary = intercalar.

intercalated = inserted, to insert among others, e.g. intercalated scales are extra scales added between the regular scales, after their formation.

intercentrum = with two pleurocentra, the two intercentra unite to form the centrum of a vertebra.

intercept survey = creel census (the estimation of anglers' catches, usually by a sampling program involving interviews and inspection of individual catches on a particular stream, lake or other area; a survey of the recreational fishery that quantifies the fish landings at public piers and docks).

interclavicle = urohyal (a flat, median, deep, endochondral bone below the ceratohyal; a tendon bone arising in the septum between the longitudinal muscles of the isthmus. Absent in such primitive fishes as Lepisosteus. Also called clidost, episternal and parahyoid).

intercleithral cartilage = one of the median cartilages lying between the ventral ends of the cleithra of Gobioidei. The ventral intercleithral cartilage is smaller and lies between the antero-ventral tips of the cleithra. The pelvic intercleithral cartilage lies between the postero-ventral tips of the cleithrum and the pelvic bone.

intercostal = between the ribs (arteries, veins, muscles).

intercostal artery = a series of arteries extending ventro-laterally from the dorsal aorta to serve the intercostal muscles and, as branches, the pectoral and pelvic appendages.

intercuale = a small muscle of the gill arches.

interdorsal = a cartilaginous structure between the basidorsals and the vertebral centra, which helps enclose the neural canal.

interdorsal ridge = a raised part of the body between the dorsal fins.

interested party = anyone or group having an interest in the fishery being managed, e.g. commercial, recreational, conservation, exploitation, artisanal, industrial, fisher, buyer, processor, trader, governments, general public, consumers, etc. A wider term than stakeholder.

interflow = the subsurface flow of groundwater between catchments or watersheds.

interglacial = a period during an ice age when glaciers retreated because of milder temperatures.

intergrade = the progeny of interbreeding of two or more subspecies of the same species.

interhaemal = an undesirable term for the anal fin ray supports. See radials or pterygiophores. Also spelled interhemal.

interhaemal bone = one of a series of bones found between the haemal vertebral spines and the anal fin pterygiophores, e.g. in Gempylidae and Trichiuridae.

interhemal = interhaemal.

interhyal = the deep, endochondral bone between the hyomandibular and symplectic bone and above the epihyal in the hyoid arch. Absent in Dipnoi. Also called stylohyal but not homologous with the stylohyal of Tetrapoda.

interlittoral = the marine zone between low tide and about 20 metres.

intermaxillary = premaxilla (one of the paired, superficial, usually toothed, dermal bones of the upper jaw, proximal or anterior to the maxillaries; in primitive Teleostomi they comprise the middle, in more advanced forms they may comprise the whole, of the oral edge of the upper jaw. Teeth may be present. In Diodontidae, the premaxillae are ankylosed and form a single bone. Absent in Chondrostei. In Holostei (Lepisoteus and Amia) the bone has two ossification centres and therefore is a double bone. Holostei and Teleostei have an ascending process anteriorly but these may not be homologous. Posterior to the ascending process in Teleostei there may be an articular and a postmaxillary process, and a posterior extension, the caudal process. Also called premaxillary, surmaxillary or bimaxillary).

intermaxillary gland = a gland lodged in a fossa formed mainly of dermal bones, situated wholly in front of the nasal capsules of Osteolepiformes.

intermediate fishing = removal of fish from an aquaculture facility to thin out excessive numbers so the remaining fish can grow more efficiently.

intermediate host = a fish in which a parasite passes a larval or non-reproductive phase.

intermediate mass = a very early blood rudiment located deep to the somites in the posterior trunk at a stage before the blood cells collect into the more prominent blood island.

intermediate spine = a paired ventral spine not of the pectoral or pelvic fins found in Early Devonian acanthodians (Gagnier and Wilson, 1996).

intermittent = said of a stream with interrupted flow or discontinuous flow. Opposite of perennial, q.v. Also said of lakes in karstic regions which drain every year.

intermittent spawning = spawning at intervals; see batch or fractional spawner.

intermuscular bone = a rib bone lying in the horizontal septum between the epaxial and hypaxial muscles or in the myocommata of the epaxials. See also myorhabdoi, epineurals, dorsal ribs.

internal bearer = internal fertilisation with females carrying embryos and/or young.

internal carotid artery = an artery originating at the junction of the first two aortic arches and supplying the anterior brain.

internal fertilisation = the deposition of sperm within the female by the male. Most fishes shed eggs and sperm to the outside so fertilisation is usually external.

internal filter = a filter for aquaria that is placed and functions inside the aquaria.

internal live bearer = an ecological group with several reproductive guilds (q.v.) where eggs are fertilised internally and young are born alive.

internal naris or nostril = a canal (opening) communicating between the nasal cavity and the mouth, thus providing access to the exterior; also called choana.

internal water = water on the landward side of the baseline of the territorial sea, e.g. river mouths, creeks, ports, harbors and canals.

internal yolk syncytial layer = the portion of the yolk syncytial layer that lies deep to the blastoderm during epiboly.

internarial = between the nostrils.

internarial flap = a ridge or ridges between the incurrent and excurrent nostrils. This may serve to divert a flow into the incurrent nostril and over the olfactory lamellae and out the excurrent nostril as the fish swims through the water or holds position in a current.

internasal = the area of the snout between the nostrils.

internasal gland = a gland in the endocranial cavity situated between the nasal capsules mainly in the internasal wall of Porolepiformes.

internasal pore = a pore between the nostrils, e.g. in certain Noturus (Ictaluridae).

internasal valve = a fleshy flap extending between the nostrils and partly covering the mouth of rays.

International Code of Zoological Nomenclature = the rules and recommendations adopted world-wide for zoological nomenclature. Adopted by the International Congresses of Zoology (more recently the International Union of Biological Sciences) and administered by the International Commission on Zoological Nomenclature. The most recent version of the Code is the Fourth Edition published in September 1999 and taking effect on January 1st 2000.

international food fisheries = those fisheries taking place beyond territorial waters and coastal zones of sea-girt nations.

International Zoological Congresses = the legislative bodies responsible for the rules of the International Code of Zoological Nomenclature and for authorization of the activities of the International Commission on Zoological Nomenclature.

interneural = slender, median, deep bones lying vertically at the juncture of the vertical and longitudinal myocommata above the vertebrae. Sometimes incorrectly applied to the dorsal fin ray supports properly called radials or pterygiophores.

interopercle = the paired dermal bone of the lower gill cover below the horizontal arm of the preopercle and in front of the subopercle. Connected to the mandible by a ligament. Absent in Lepisosteus and Siluridae.

interopercular bone = interopercle.

interoperculum = interopercle.

interorbital = between the eyes.

interorbital septum = a thin sheet of bone or cartilage lying vertically under the midline of the skull, separating the eyes.

interorbital space = the space on top of the head between the eyes. Measured at its narrowest point. Either the fleshy or the bony width may be measured. In the fleshy width no pressure is exerted by the dividers, in the bony width the dividers are squeezed to obtain the width of the bone.

interoparity = repeated reproduction, usually on an annual basis, in contrast to reproducing once and dying (semelparity).

interpelvic process = a fleshy process between the inner edges of the pelvic fins in some members of the Scombridae like tunas.

interpelvic space = the least distance between the bases of the pelvic fins.

interpolated name = a name placed within parentheses after a generic name to denote a subgenus, or after a genus-group name to denote an aggregate of species, or after a specific name to denote an aggregate of subspecies. Names used in this way are not counted as one of the names in a binomen or trinomen.

interpretotype = specimens interpreted by the originating author as belonging to the same taxon as the one proposed, i.e. authentic specimens or expertly-identified specimens.

interpterygiophore artery = an artery branching dorsally from the supraspinous artery, q.v., to serve each interpterygiophore muscle.

interradial = between the rays (or spines), e.g. interradial pigment is pigment on the membrane between the rays.

interradial membrane = the tissue between the fin rays or spines.

interradial window = a perforation in the membrane between the dorsal and anal fin rays and next to the body in Diretmus (Diretmidae).

interrenal gland = a yellowish endocrine gland producing corticosteroids, controlling water metabolism, stress and release of lymphocytes. Located between the kidneys (Elasmobranchii), or the heads of the kidney (Teleostomi).

intersexual = involving both sexes.

interspace = space between two parts, e.g. the gap between the two dorsal fins or between the pelvic fins, between parr marks in Salmonidae.

interspecific = between two or more species; a hybrid between two distinct species.

interspinal artery = a paired branch of the dorsal aorta or caudal artery which fuses and extends to the dorsal tip of each neural spine. This artery joins the supraspinous artery running antero-posteriorly at the dorsal tips of the neural arches.

interspinous bone = 1) dorsal pterygiophore; one of a series of bones forming the internal support for the dorsal and anal fins, called interspinous because they interdigitate with the neural spines of the vertebrae, for example.

interspinous bone = 2) interneural and interhaemal bones.

interspinous membrane = the membrane between fin spines.

interstadial = long intervals of desiccation between pluvial periods.

intersticine = living in small spaces, cavities or between and under rocks.

intertaxon = a hybrid between two taxa.

intertemporal = supratemporal-intertemporal (a dermal bone overlaying the pterotic (or autopterotic). Also called membranopterotic or dermopterotic).

intertidal = the shore exposed between high and low tides.

interventral = a cartilaginous element of the vertebral column which alternates with the basiventrals to enclose the haemal canal laterally.

intestinal arteries = branches of the coeliac artery that serve the enlarged proximal loop of the intestine and the intestinal diverticula (anterior intestinal artery) and the straight posterior terminal portion of the intestine (posterior intestinal artery).

intestine = often used for most of the gut of fishes as many lack a stomach, although strictly that stretch from the stomach, when present, to the cloacal aperture.

intestinal valve = a fold in the intestine which increases surface area for processing food without lengthening the intestine. Found in Elasmobranchii and Acipenseridae, for example. See also ring, scroll and spiral intestinal valves.

intestinal vein = delivers blood from the posterior intestine to the hepatic portal vein.

intra- (prefix) = within, inside.

intracranial joint = the joint between two divisions of the Crossopterygian braincase. It may help in the consumption of large prey by suction in coelacanths.

intradentary = coronoid (a paired dermal bone bearing teeth located on the upper edge of Meckel's cartilage. One pair is found in Acipenseridae and two pairs in Amia and Lepisosteus. Also called presplenial, splenial and prearticular).

intrageneric = within the same genus; among members of the same genus.

intrasexual = involving only one of the sexes.

intraspecific = within a species.

intraorbital = an ossification of the anteroventral portion of the membrane in the orbital cavity confined to certain genera of Eleotridae.

intraspecific = within a species; among members of the same species.

intrinsic = gas bladder muscles with both ends inserting on the gas bladder, as opposed to extrinsic.

intrinsic growth rate = how much a population can grow between successive time periods when not slowed down by competition. Often estimated with production models and plays an important role in evaluating the sustainability of different harvest levels and the capacity to recover after depletion. Abbreviated as r.

intrinsic quality = the quality of the fish at the time of capture. Includes species, size, condition, composition, fat content, damage, parasites, pathogens, taints, toxins and contaminants.

intrinsic rate of increase = the change in the amount of harvestable stock estimated by recruitment increases plus growth minus natural mortality.

intrinsic sonic muscles = striated muscles of the gas bladder wall, used in sound production by contraction, e.g. Porichthys notatus (Batrachoididae). See also extrinsic sonic muscles.

intro- (prefix) = inward.

introduced = any species accidentally or deliberately moved and released outside its natural range. When not established these are alien species, included under the term introduced.

introgression = the spread of inherited characters between species by hybridisation.

introgressive hybridization = the spread of inherited characters of one species to another species through hybridization.

intromittent fertilisation = internal fertilisation where the male deposits sperm in the female using a specialised structure such as the gonopodium.

invalid = any name (available or unavailable) for a given taxon other than the valid name; a nomenclatural act not valid under the International Code of Zoological Nomenclature.

invalidation = the action of making a name invalid. May be brought about by suppression by the International Commission on Zoological Nomenclature.

invasive species = fish that damage the ecosystem into which they are introduced. See also alien.

invecked - misspelling of invected.

invected = having a border or edge comprised of semicircles, distally convex, e.g. the frilly lip margin of some fishes such as the cyprinid Garra. Opposite of engrailed.

inventory = a collection of data on natural resources and their properties.

invertebrate drift = aquatic and terrestrial invertebrates that float with the current and are often fed on by fishes.

invertivore = feeding on invertebrates other than insects.

investing bone = membrane bone (a bone which arises directly from connective tissue membranes without cartilaginous precursors. Includes dermal bones, as opposed to cartilage ones. Membrane bones are thin, laminar and located near the surface of the body. When the connective mesenchyme transforms into bone it does not differ histologically from bone which arose from cartilage. Also called achondral bone and covering bone).

inviolate name = nomen inviolatum (an inviolate name, all available names not subject to any sort of alteration from their originally published form, i.e. they were correct as originally published and need no correction or emendation).

invisible fish = an advertising stunt where a bowl of water was placed in the window of a store with a sign saying it contained an invisible fish. The idea was to attract customers. Sometimes a concealed fan produced ripples on the water. Apparently crowds gathered claiming they could see the fish. Also called Brazilian invisible fish.

involution = deep cell movement at the blastoderm margin in which the deep cell layer folds inwards and back on itself producing the germ ring and its two primary layers, the epiblast and hypoblast.

IO = abbreviation for infraorbital canal.

iodofor = a chemical used to disinfect eggs.

iodoform odour = a slightly irritating odour similar to iodoform found in some fish, typically confined to certain fishing grounds and seasons.

ion exchange = a process used in aquaria to treat the water, softening it or removing pollutants. An ion-exchange unit uses resins to alter water chemistry, conditioning tap water before use in an aquarium, removing nitrites, de-ionising and softening water. Different resin units are required for different chemical alterations.

ionic regulation = in freshwater fishes enabled by copious dilute urine and taking up salt; in marine fishes by drinking large quantities, producing small amounts of concentrated urine and excreting sodium salts.

ionic strength= relating to the mineral requirements in water for supporting the health of fishes residing in that water.

ionocyte = chloride secreting cell (a cell in the gills, especially along the bases of the secondary gill lamellae and the pseudobranchs when present, which excrete chloride, potassium and sodium ions in marine fishes. These cells maintain the osmotic balance from the loss of water via the gills and the necessity of drinking sea water).

IP = abbreviation for initial phase in diandric fishes (possessing two different types of males, a large, brightly-coloured and aggressive terminal phase (TP) and a smaller, drab and relatively non-aggressive initial phase (IP), e.g. in Thalassoma lunare (Labridae). The TP has priority access to food and spawning females. On the death or removal of a TP, the first-ranking IP becomes the next TP (after first checking the reef thoroughly to make sure the TP is gone)).

ipogean = the subterranean environment inhabited by "cave" fishes. See also hypogean and epigean.

ipsilateral = same side. Opposite of contralateral.

IQ = abbreviation for individual quota.

iqf = abbreviation for individually quick frozen.

iridescent = having rainbow colours; shown by many fishes in life, rapidly fading on death.

iridocyte = a crystal of guanine in the dermis of fishes, a layer of which produces reflective silvery white or iridescent tones typical of fishes. Also called iridiophore.

iridiophore = iridocyte.

iris = the heavily pigmented anterior part of the choroid layer, q.v., lying just internal to the cornea in the fish eyeball.

Irish trawl = a long-winged trawl with outriggers of wood or bamboo stepped on board the boat spread the wings apart.

iron chink = a machine used in canneries to remove the head, fins and guts of fish (derogatory, brought in to replace Chinese workers who cleaned Pacific salmon before canning). Also called Smith Butchering Machine after A. E. Smith of Bellingham, Washington who invented it.

iron fish = a comic book vessel shaped like a torpedo and also capable of flight.

irradiation = exposure of fish to ionising radiation from radioactive isotopes or an electron source. At 150,000-450,000 rads, over 90% of spoilage bacteria are killed and shelf life of fish is extended by about two weeks.

irrigation = watering of land artificially, often affecting fish populations as water is abstracted from rivers.

ISA = infectious salmon anaemia.

Isaac-Kidd midwater trawl = a trawl designed for catching small organisms, including fish, at great depth. Used by researchers.

isabelline = a dirty yellowish-grey colour, often included in dictionaries since it is purportedly based on Isabella, Archduchess of Austria, who refused to wash her underwear until her husband took Ostend. This he did but the siege lasted three years from 1601. When he finally succeeded, the garments were this colour. The word may in fact be from the Arabic izah for lion, thus “lion-coloured”.

isallotherm = a map line connecting all points having the same temperature variation within a given time period.

ischiopubic bar = a straight and horiontal bar in cartilaginous fishes forming the pelvic girdle. The pelvic fins articulate at the acetabular surfaces. An iliac process extends from each end of the bar. In Elasmobranchii both halves of the pelvic girdle are fused into a single ventral puboischiadic bar.

ischiopubic cartilage = ischiopubic bar.

ischiopterygia = plural of ischiopterygium.

ischiopterygium (plural ischiopterygia) = pelvic fin (the paired fin which is located posterior, ventral or anterior to the pectoral fins (abdominal, thoracic or jugular in position). It functions to steer, brake and propel the fish and acts as a keel. In the pelvic fin ray count usually all the rays are counted except a small ray preceding the first ray and usually bound so closely to it so as to require dissection to be seen. In some fishes with reduced pelvics, the spine and the first ray may be bound together by a membrane and appear as one; both are counted, e.g. in Cottidae. Abbreviated as P2 or V).

isinglass = the glutinous or gelatin-like fluid prepared from the collagen of the outer layer of gas bladders of sturgeons or other fishes. Used in clarifying wines and beers, for jams and jellies, in printing inks and as an adhesive cement.

island wake = upwelling of deep waters through the meeting of ocean currents with an island.

islet = small island.

islets of Langerhan(s) = the endocrine part of the pancreas producing hormones and, in particular, insulin. Also called pancreatic islets.

iso- (prefix) = equal, same.

isoamphicoelous = vertebral centra in which the restriction or narrowing lateral view is in the middle of the centrum, rather than anteriorly, e.g. in Cryptacanthodidae.

isobar = a map line connecting all points having the same barometric pressure.

isobath = a map line connecting all points having the same depth; bathymetric contour.

isobathytherm = a map line connecting all points having the same depth and temperature.

isobatic = said of a symmetrically forked caudal fin.

isobenth = a map line connecting all points having the same biomass.

isocercal = diphycercal (an internally and externally symmetrical tail fin. May be secondarily acquired from the homocercal condition by loss of the real caudal fin and the gaining of a new one from dorsal and anal elements, e.g. in Gadidae).

isocheim = a map line connecting all points having the same mean winter temperature or coldest winter month.

isochrone = a map line connecting all points having the same time of travel for contaminants to move through the saturated zone and reach a well.

isocon = a map line connecting all points having an equal concentration per unit area and time, e.g. salinity.

isodeme = a map line connecting all points having the same population density.

isodont = having teeth all of the same type, the usual condition in fishes.

isoflor = a map line connecting all points having the same number of species.

isogene = a map line connecting all points having same gene frequency.

isogeotherm = a map line connecting all points having same mean temperature on the earth's surface.

isogram = a map line connecting all points having the same anything. Also called isoline.

isohaline = a map line connecting all points having the same salinity.

isohel = a map line connecting all points having the same sunshine.

isohume = a map line connecting all points having the same relative humidity.

isohydric = a map line connecting all points having same pH.

isohyet = a map line connecting all points having the same rainfall.

isolated fish = a location in angling where fish are separated from open water, e.g. by a fallen tree, or in a cove.

isolation facility = part of an aquaculture facility used to prevent the introduction of disease or parasites, e.g. to maintain eggs from wild fish separate from those from hatchery stock.

isolecithal = eggs having little yolk evenly distributed throughout the egg, e.g. eggs of Petromyzontidae, Acipenseridae, Amiidae, Lepisosteidae. Also called homolecithal.

isoline = a map line connecting all points having the same anything. Also called isogram.

isolume = a map line connecting all points having same light intensity.

isometric growth = growth that occurs at the same rate for all parts of an organism so that its shape is consistent throughout development. See alos allometric growth.

isoneph = a map line connecting all points having the same cloudiness.

isonome = a map line connecting all points having same abundance of a species.

isonym = one of two or more names based on the same nomenclatural type.

isopag = a map line connecting all points having same number of days per annum during which ice is present.

isoparatype = a duplicate of a paratype.

isopectic = a map line connecting all points where ice begins to form at the same time of the winter.

isopedine = an inner layer of compact lamellar bone found in the plates and scales of ostracoderms and placoderms and in ganoid scales of teleosts.

isophagy = predatory activity selective on prey items but not restricted to a single one.

isophene = a map line connecting all points having the same phenotype or variant.

isophot = a map line connecting all points having the same incident radiation.

isopiptesis = a map line connecting all points having the same arrival date of a migratory species.

isopleth = a map or graph line connecting all points of the same numerical value. Commonly used in determining yield-per-recruit. Also called isorithm.

isopract = a map line connecting all points having the same expression of a given factor.

isopropyl alcohol (isopropanol) = used in some collections to preserve fish, usually at a concentration of 50% or 55%. Less inflammable than ethanol (ethyl alcohol) and not subject to stringent controls but may clear tissues and decalcify bones.

isopycnic = an isopleth of density. Constant or uniform in density.

isorithm = a map or graph line connecting all points of the same numerical value. Commonly used in determining yield-per-recruit. Also called isopleth.

isosmotic = pertaining to solutions that exert the same osmotic pressure.

isospondylous = referring to fishes having vertebrae behind the skull similar in form to the rest. Contrasts with Ostariophysans which have the anterior vertebrae modified into a Weberian apparatus.

isostatic = pertaining to the rise in land level after the melting of glaciers whose weight had depressed the land level.

isosyntype = a duplicate of a syntype not mentioned at the time of valid publication of a name.

isotac = a map line connecting all points having the same melting time of ice in the spring.

isotach = a map line connecting all points having the same wind speeds.

isothere = a map line connecting all points having the same mean summer temperature or warmest month.

isotherm = a map line connecting all points having the same temperature.

isothermobath = a map line connecting all points having the same temperature at a given depth of ocean.

isotonic = having a concentration equal to that of the environment.

isotype = 1) a type described from two species of the same genus.

isotype = 2) a form occurring in a variety of localities.

isotype = 3) a duplicate of a holotype from the single collection that contained the holotype.

isovel = a map line connecting all points having the same velocity of water flow.

isozoic = having a similar fauna.

isthmal = of the isthmus, e.g. isthmal photophore of the paralepidid Lestidium bigelowi.

isthmus = strip of flesh lying between the gills on the underside of the head.

Italian = a grade of dried and salted cod prepared for the Mediterranean market, especially that of Italy (Newfoundland).

iteroparity = the condition of producing offspring in successive years or seasonal batches, as is the case in most fishes, cf. semelparous.

iteroparous = adjective for iteroparity.

ITQ = individual transferable quota (assigning a fixed share of the catch to each fisherman as a tradable right, one that can be sold or leased to others).

IUCN = International Union for Conservation of Nature and Natural Resources.

IUCN Criteria = criteria developed to assess the threatened status of species using numerical measures of populations, their levels, range, decline, etc.

IUU = abbreviation for illegal, unregulated and unreported fishing vessels.

IV = a row of ventral photophores running from the anterior end of the isthmus to the origin of the pelvic fin.

Ivlev's electivity index = electivity index (an index (E) showing the degree of choice a predator shows in its feeding behaviour, e.g. of a predator on plankton; E is derived from r_i - p_i / r_i + p_i where r_i is percent composition of plankter i in the gut contents and p_i is percent composition of plankter i in the plankton sample. Values for E range from -1 to +1 with -1 meaning complete avoidance, 0 meaning no active selection, and +1 meaning complete selection).

Izaak Walton = 1593-1683, author of "The Compleat Angler", first published in 1653 and the classical work on angling. A fifth edition in 1676 with Charles Cotton added material on fly-fishing.

© Brian W. Coad (www.briancoad.com)

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