Fish words
147 terms. The words of fish biology, fishing and fishkeeping, in plain language.
A
- Adipose fin
- A small fleshy fin without rays on the back near the tail, found in salmon, trout, catfish and characins.
- Anadromous
- Living mostly in the sea but swimming up rivers to spawn, as salmon, hilsa, shad and many sturgeons do.
- Anal fin
- The single fin on the underside behind the vent, which steadies a fish from below.
- Angling
- Fishing with a rod, line and hook, for food or for sport; fly fishing uses a light, feathered lure cast on a heavy line.
- Antifreeze proteins
- Molecules in the blood of polar fish that stop ice crystals from growing, letting them live in water below zero.
- Apex predator
- A hunter at the top of its food chain with few or no natural enemies as an adult, such as the great white shark.
- Aquaculture
- Raising fish, shellfish and water plants in ponds, tanks or cages; it now supplies more than half of aquatic animals eaten.
- Aquarium
- A tank of water in which fish and other water life are kept, at home or in a public aquarium.
B
- Bait ball
- A tight sphere that sardines or anchovies form when attacked from all sides by predators.
- Barbel
- A fleshy whisker near the mouth, covered in taste buds, that catfish, carps and cod use to find food.
- Benthic
- Living on or in the bottom of the sea, a lake or a river, as flatfish, rays, gobies and many catfish do.
- Biofluorescence
- Absorbing blue light and glowing back in green, red or orange, seen in many sharks, eels and reef fish.
- Bioluminescence
- Making light by a chemical reaction, which most deep-sea fish do to hunt, hide or signal in the dark.
- Biotope aquarium
- A tank set up to copy one natural habitat, with only the fish, plants and water of that place.
- Blue Revolution
- India's name for the drive to raise fish production through farming, hatcheries, harbours and cold chains.
- Body shape
- How a fish's outline fits its life: torpedo-shaped for speed, flattened side to side for reefs, flat top to bottom for the sea floor.
- Bony fish
- Fish with skeletons of bone: the ray-finned and lobe-finned fish, which make up almost all living fish species.
- Brackish-water farming
- Raising fish and shrimp in coastal ponds and lagoons where sea water mixes with fresh, such as the bheris of Bengal.
- Bycatch
- Fish and other animals caught by accident while fishing for something else, often thrown back dead.
C
- Camouflage and mimicry
- Looking like something else, such as sand, weed or a more dangerous fish, to hide from predators or prey.
- Cartilaginous fish
- Sharks, rays, skates and chimaeras, whose skeletons are made of cartilage rather than bone.
- Catadromous
- Living in fresh water but going down to the sea to spawn, as freshwater eels do.
- Catch and release
- Returning a caught fish alive to the water, common in sport fishing for mahseer, salmon, bass and billfish.
- Caudal fin
- The tail fin, which drives most fish forwards with side-to-side strokes.
- Cave fish
- Fish that live their whole lives in underground water and have often lost their eyes and colour.
- Caviar
- The salted roe of sturgeon, once mainly from the wild beluga and other sturgeons of the Caspian Sea, now mostly farmed.
- Ciguatera
- Food poisoning from eating reef fish that have built up toxins from tiny algae living on corals.
- CITES
- The treaty that controls international trade in threatened wildlife, including sharks, rays, sturgeon, eels and seahorses.
- Cleaner fish
- Small fish that eat parasites and dead skin off larger fish, which visit their cleaning stations on the reef.
- Closed season
- A period when fishing is banned, often timed to spawning; India bans mechanised sea fishing for 61 days each monsoon.
- Cold-blooded
- Most fish take on the temperature of the water around them, so their activity rises and falls with it.
- Composite fish culture
- Stocking several carp species in one pond so that each feeds at a different level, making full use of the pond's food.
- Coral bleaching
- When heat stress makes corals expel the algae that feed and colour them, leaving them white and starving.
- Coral reef
- A ridge built by colonies of tiny coral animals in warm, clear, shallow seas, home to about a quarter of marine fish species.
- Countershading
- Being dark on the back and pale on the belly, which hides a fish from predators looking down or up.
- Cryptic species
- Two or more species that look so alike they were long taken for one, often told apart only by DNA.
- Cycloid and ctenoid scales
- The two main scale types of bony fish: smooth-edged cycloid scales and comb-edged ctenoid scales.
D
- Deep sea
- The cold, dark ocean below about 1,000 metres, down to the trenches, where fish live under huge pressure.
- Demersal
- Living near the bottom, though not always on it, as cod, haddock, croakers and snappers do.
- Diadromous
- The general word for fish that move between fresh and salt water during their lives.
- Diel vertical migration
- The daily movement of fish and plankton from the deep sea up to the surface at night and back down at dawn.
- Dorsal fin
- The fin on a fish's back, which keeps it upright and stops it rolling as it swims.
- Dried and cured fish
- Fish preserved by drying, salting, smoking or fermenting, from Bengali shutki and dried bombil to Norway's stockfish.
E
- Egg-laying fish
- Most fish lay eggs that hatch outside the body, either scattered in the water or laid on plants, rocks or nests.
- Elasmobranch
- A shark, ray or skate: the main branch of the cartilaginous fish, with five to seven gill slits on each side.
- Electric organ
- Muscle turned into living batteries, used by electric eels, torpedo rays and knifefish to stun prey or sense their surroundings.
- Electroreception
- The ability to sense weak electric fields, which sharks and rays use to find prey hidden in sand.
- Endemic species
- A species found naturally in only one place, such as one lake, one river system or one island.
- Environmental DNA
- Traces of DNA that fish shed into water, which scientists collect and read to learn which species live there.
- Eschmeyer's Catalog of Fishes
- The authoritative database of fish names, kept by the California Academy of Sciences, that records every valid species and genus.
- Estuary
- The place where a river meets the sea, where fresh and salt water mix, rich in food and young fish.
- Euryhaline
- Able to live in a wide range of saltiness, from fresh water to the sea; stenohaline fish tolerate only a narrow range.
- Eye migration in flatfish
- As a young sole or plaice grows, one eye moves across the head so that both end up on the upper side.
F
- Filter feeding
- Feeding by straining tiny plankton from the water, as whale sharks, manta rays, sardines and silver carp do.
- Fin rays and spines
- The thin bony rods that hold a fin open; soft rays are jointed and flexible, spines are stiff and often sharp.
- Fingerling
- A young fish about the length of a finger, the size at which farms stock ponds and hatcheries release fish into rivers.
- Fish aggregating device
- A floating or anchored object that attracts open-sea fish, used to make tuna easier to find and catch.
- Fish ladder
- A channel of steps or pools built beside a dam or weir so that migrating fish can swim past it.
- Fish larva
- The tiny early stage of a fish after hatching, often transparent and very unlike the adult.
- Fish tagging
- Fixing a marker or electronic tag to a fish to follow where it goes, how deep it dives and how fast it grows.
- FishBase
- A free global online database of fish species, with facts on their names, size, range, biology and uses.
- Fishing quota
- A limit on how much of a fish species may be caught in a year, often shared out among countries or boats.
- Food web and trophic level
- The web of who eats whom; a fish's trophic level is how many steps it sits above plants and algae.
- Fry
- A young fish that has used up its yolk and started feeding itself; in Indian fish farming, the stage after spawn.
G
- Ganoid scales
- Thick, diamond-shaped scales with a glassy coat called ganoine, worn as armour by gars and bichirs.
- Ghost nets
- Lost or abandoned fishing nets and traps that keep catching fish and other animals for years.
- Gill rakers
- Bony or comb-like points on the inside of the gill arches that keep food in and, in filter feeders, strain plankton.
- Gillnet
- A wall of fine net that fish swim into and are caught by the gills; the mesh size decides the size of fish caught.
- Gills
- The feathery organs behind the head where a fish takes oxygen from water and gives off carbon dioxide.
- Gonopodium
- A male livebearer's anal fin reshaped into a rod that passes sperm into the female.
H
- Hatchery
- A place where fish are bred and their eggs hatched and young raised, to stock farms or rivers.
- Heterocercal tail
- A tail with a longer upper lobe that holds the end of the backbone, as in sharks and sturgeons.
- Holotype
- The single preserved specimen that a species name is based on, kept in a museum as the reference.
- Hypoxia
- Water with too little dissolved oxygen for most fish, often caused by pollution or warm, still conditions.
I
- Ichthyology
- The scientific study of fish, from their anatomy, behaviour and evolution to their naming and conservation.
- Indian major carps
- Catla, rohu and mrigal, the three native river carps that are the backbone of fish farming in India and Bangladesh.
- Induced breeding
- Making farmed fish spawn by injecting hormones; India's first success with carps, in 1957, freed farmers from river-caught seed.
- Invasive species
- A fish moved by people outside its natural range that spreads and harms native wildlife or people's livelihoods.
- IUCN Red List
- The world's main list of how close species are to extinction, kept by the International Union for Conservation of Nature.
- IUU fishing
- Illegal, unreported and unregulated fishing, which undermines rules meant to keep fish stocks healthy.
J
- Jawless fish
- Lampreys and hagfish, the only living fish without jaws, survivors of the earliest branch of fish.
L
- Labyrinth organ
- A folded chamber above the gills that lets bettas, gouramis and climbing perch breathe air from the surface.
- Lateral line
- A line of sense organs along each side of a fish that feels movement and pressure changes in the water.
- Lifespan of fish
- How long fish live varies hugely, from a few weeks for some gobies to around 400 years for the Greenland shark.
- Livebearing
- Giving birth to live young rather than laying eggs, as guppies, mollies and many sharks do.
- Living fossil
- A popular name for a living species that looks much like its relatives in very old fossils, such as the coelacanth.
- Lobe-finned fish
- Fish with fleshy, bony fins like stumpy limbs: the coelacanths and lungfish, close relatives of the first land animals.
- Longline
- A main fishing line, sometimes tens of kilometres long, with thousands of baited hooks on short side lines.
- Lungs in fish
- Lungfish and bichirs have true lungs; African lungfish can survive dry seasons buried in mud.
M
- Mangrove
- Salt-tolerant trees of tropical coasts whose tangled roots shelter young fish, crabs and prawns.
- Mariculture
- Farming fish and shellfish in the sea, often in floating net cages, as with salmon in Norway or cobia in India.
- Marine protected area
- A part of the sea where fishing and other uses are limited or banned so that fish and habitats can recover.
- Maximum sustainable yield
- The largest catch that can be taken from a fish stock year after year without shrinking it.
- Milt
- The fluid of sperm that male fish release over the eggs during spawning; also eaten as soft roe.
- Model organism
- A species studied in depth in laboratories to answer general questions in biology, such as the zebrafish and medaka.
- Mouthbrooding
- Carrying eggs and young in the mouth to protect them, as many cichlids, arowanas and cardinalfish do.
N
- Nitrogen cycle (aquarium)
- The process by which bacteria in a filter turn toxic fish waste, ammonia, into nitrite and then into much safer nitrate.
O
- Operculum
- The bony flap that covers and protects the gills of a bony fish.
- Osmoregulation
- How a fish keeps the right balance of salt and water in its body, whether it lives in fresh or salt water.
- Otolith
- A small stone of calcium carbonate in a fish's inner ear, used for balance and hearing, and by scientists to age fish.
- Overfishing
- Catching fish faster than they can breed and grow, so that a stock shrinks below the level that gives the best long-term catch.
P
- Parental care in fish
- Guarding eggs and young: building nests, fanning eggs, carrying them in the mouth or on the body.
- Pectoral fin
- The paired fins just behind the gills, used for steering, braking and, in some fish, walking or gliding.
- Pelagic
- Living in open water away from the bottom, as tuna, sardines, mackerel and flying fish do.
- Pelvic fin
- The paired fins on the belly, matching the hind legs of land animals, used for balance and steering.
- Pharyngeal teeth
- Teeth in the throat, behind the gills' arches, that carps and cichlids use to crush and grind food.
- Photophore
- A light-making organ in the skin of lanternfish, hatchetfish and many other deep-sea fish.
- Placoid scales
- The tiny tooth-like scales of sharks and rays, each with a core of dentine and a hard enamel-like cap.
- Plankton
- Tiny plants and animals that drift in the water and feed most fish, at least when they are young.
- Plant-eating fish
- Fish that eat algae and plants, such as parrotfish, surgeonfish and grass carp, which keep reefs and ponds clear.
- Polar fish
- Fish of the Arctic and Southern Oceans, adapted to water near minus 2 degrees Celsius.
- Pole and line
- Catching tuna one at a time with poles and hooks as a school feeds at the surface, with very little bycatch.
- Potamodromous
- Migrating within fresh water, between parts of a river or between a lake and its rivers, as mahseer and many carps do.
- Public aquarium
- A large aquarium open to visitors, often also a research and conservation centre.
- Purse seine
- A long wall of net set around a school of fish and drawn shut at the bottom like a drawstring purse.
R
- Ray-finned fish
- Fish whose fins are webs of skin held up by thin bony rays, the group that includes about 99 per cent of fish species.
- Recirculating aquaculture system
- A closed tank farm that cleans and reuses its water, letting fish be raised indoors with little water and space.
- Redd
- A shallow nest a female salmon or trout digs in river gravel with her tail to lay her eggs.
- Roe
- The mass of eggs inside a female fish, eaten in many cuisines, from Bengali ilish roe to caviar.
S
- Scales
- Thin plates of bone and enamel-like tissue that overlap like roof tiles to protect a fish's skin.
- Schooling
- Swimming in a tight, coordinated group, which helps fish avoid predators, find food and save energy.
- Selective breeding
- Breeding fish for chosen traits over many generations, which gave us fancy goldfish, koi, show guppies and bettas.
- Sex change in fish
- Some fish change sex during their lives: clownfish from male to female, many groupers and wrasses from female to male.
- Sexual dimorphism
- Differences in size, shape or colour between males and females of the same species.
- Shoal and school
- A shoal is any group of fish that stay together; a school is a shoal swimming in step, all facing the same way.
- Slime coat
- The layer of mucus over a fish's skin that cuts drag and keeps out parasites and germs.
- Small-scale fishing
- Fishing by individuals, families and villages from small boats or the shore, which employs most of the world's fishers.
- Smolt
- A young salmon that has turned silver and is ready to leave its home river for the sea.
- Spawning
- The release of eggs and sperm, usually into the water, for fish to breed.
- Species
- A group of living things that can breed with each other and are distinct from other such groups; about 36,000 fish species are known.
- Species flock
- Many closely related species that evolved from a few ancestors in one place, like the cichlids of the African Great Lakes.
- Spiracle
- A small opening behind the eye of rays, skates and many sharks that lets them draw in water while resting on the bottom.
- Stock assessment
- A scientific estimate of how many fish of one species are in an area, how fast they grow and how hard they are fished.
- Surimi
- A paste of minced, washed fish flesh shaped into products such as kamaboko and imitation crab sticks.
- Swim bladder
- A gas-filled sac inside many bony fish that lets them float at a chosen depth without swimming.
- Symbiosis
- A close relationship between two species living together, such as the clownfish and its sea anemone.
T
- Taxonomy and scientific names
- The naming of species with a two-part Latin name, such as Tenualosa ilisha for the hilsa, followed by who named it and when.
- Teleost
- The huge group of modern bony fish with a movable upper jaw and a symmetrical tail, about 96 per cent of all fish species.
- Tetrodotoxin
- A strong nerve poison found in pufferfish, which is why fugu in Japan may only be prepared by licensed chefs.
- Trawling
- Towing a large cone-shaped net behind a boat, either along the sea floor or through open water.
- Twilight zone
- The dim layer of the ocean from about 200 to 1,000 metres deep, home to lanternfish and bristlemouths.
U
- Upwelling
- Cold, nutrient-rich water rising from the deep to the surface, feeding plankton and some of the world's biggest fisheries.
V
- Venomous fish
- Fish that inject venom through spines or teeth, such as stonefish, lionfish, stingrays and some catfish.
W
- Warm-bodied fish
- Tuna, some sharks and swordfish keep parts of their body warmer than the water, which gives them speed and range.
- Warming seas and fish
- As water warms, many fish shift towards the poles or deeper water, and some stocks shrink.
- Weberian apparatus
- A chain of small bones linking the swim bladder to the inner ear, which gives carps, catfish and tetras sharp hearing.
- White spot disease
- A common fish disease caused by a parasite that shows as tiny white dots on the skin and fins.