Types of Fish: Names, Main Groups and Common Species

Fish come in three main types: jawless fish, cartilaginous fish and bony fish. Wikipedia counts over 33,000 living species in total, more than every other vertebrate group, and almost all of them are bony fish.

• Jawless fish (about 118 species): hagfish and lampreys.
• Cartilaginous fish (over 1,100 species): sharks, rays and chimaeras.
• Bony fish (over 32,000 species): nearly every fish an angler or aquarium keeper meets. They split into the ray-finned fish, whose fins are webs of skin on thin rays, and the lobe-finned fish, now down to eight species: the two coelacanths and the lungfishes.

Inside the ray-finned fish, one branch dominates. The teleosts, which can push their jaws forward when they feed, make up about 96% of all fish species.

Wikipedia puts freshwater species at about 15,200, roughly half of all fish. In North America most fish an angler meets belong to a handful of families. Each name below links to a page with the marks that separate it from its look-alikes.

• Sunfish: bluegill, pumpkinseed, redear sunfish, black crappie, white crappie
• Black bass (also sunfish family): largemouth, smallmouth, spotted bass; see freshwater bass
• Catfish: channel, blue and flathead catfish, brown and yellow bullhead
• Perch family: walleye, sauger, yellow perch
• Pike: northern pike, muskellunge, chain pickerel
• Trout and char: rainbow, brown, brook and lake trout
• Ancient-looking fish: alligator gar, longnose gar, bowfin
• Temperate bass: striped bass, white bass
• Others: common carp, and from other continents the arapaima, peacock bass, snakehead and electric eel

About 14,800 species live in the sea, according to Wikipedia, and most of the variety is on coral and rocky reefs. The saltwater fish people ask about most fall into these groups:

• Drums and seatrout (inshore Atlantic and Gulf): red drum, black drum, spotted seatrout
• Flatfish: summer flounder
• Inshore gamefish: snook, sheepshead
• Reef fish: groupers, triggerfish, parrotfish, moray eels, clownfish, puffer fish
• Cold-water and open-ocean oddities: wolf eel, seahorses, mola mola

The North Carolina Division of Marine Fisheries keeps a common-name directory of about 70 coastal species, from almaco jack to swordfish, if you want a longer regional list.

Aquarium fish are a separate list again, chosen for colour, size and temperament rather than for food or sport. The ones people ask us about most:

• Betta, the Siamese fighting fish: freshwater, breathes air, males cannot share a tank
• Oscar: a large South American cichlid that needs a big tank
• Clownfish: saltwater, lives with sea anemones
• Puffer fish: kept by some aquarists; the page covers the tetrodotoxin risk

Common names are the main reason a fish list is hard to use. Wikipedia's list of fish by common name warns that one name can mean a single species, a whole genus or family, or several unrelated fish. A few examples from this site:

• Bass covers at least four unrelated families, from largemouth bass (a sunfish) to sea bass; see bass fish
• Chilean sea bass is not a bass at all but the Patagonian toothfish (Wikipedia)
• Wolf eel and electric eel are not true eels; see wolf eel and electric eel
• Peacock bass are South American cichlids, not bass; see peacock bass

The scientific name, two words in italics such as Lepomis macrochirus for the bluegill, is the only name that always points to one species. Every page on this site gives it.

The US Food and Drug Administration sorts commercially sold fish by mercury into three lists (page updated 5 March 2024, advice revised October 2021). It is the clearest public list of which fish to eat more or less often.

• Best choices, 2 to 3 servings a week: includes anchovy, black sea bass, catfish, cod, flounder, haddock, herring, freshwater and ocean perch, pollock, salmon, sardine, tilapia, freshwater trout and canned light tuna
• Good choices, 1 serving a week: includes bluefish, carp, Chilean sea bass, grouper, halibut, mahi mahi, rockfish, sheepshead, snapper, ocean striped bass and albacore tuna
• Choices to avoid: king mackerel, marlin, orange roughy, shark, swordfish, Gulf of Mexico tilefish and bigeye tuna

The serving counts are the FDA's advice for adults, including people who are pregnant or breastfeeding; one adult serving is 4 ounces. For fish that family or friends catch, the FDA says to check local advisories, and if there is none, to eat only one serving that week and no other fish.

To work out an unknown fish, go from the general to the specific:

• Water: fresh, salt or brackish cuts the list in half straight away
• Body shape: torpedo, deep and flat, long and snake-like, or flattened on one side like a flounder
• Fins: one dorsal fin or two, spines or soft rays, and whether there is a small fleshy adipose fin in front of the tail, which points to trout, salmon or catfish
• Mouth: how far the upper jaw reaches past the eye, and whether there are barbels
• Markings: bars, spots, stripes and ear-flap colour, which fade quickly once a fish is out of the water

Our guides to key features for identifying fish and identifying a fish from a photo take each step in turn. Or take a side-on photo, and the FishLens app will name the likely species.

Research and drafting for this page were assisted by AI and checked line by line against the sources listed below. Every number names the organisation it comes from; where sources disagree we say so rather than pick one silently. Rules and advisories change, so treat the dates given here as the date we checked. If you find an error, tell us and we will correct it.

Counts of all fish species differ by source because each uses its own cut-off and updates at its own pace:

• Wikipedia: over 33,000 living species
• FishBase: 36,700 species (version 06/2026)
• Eschmeyer's Catalog of Fishes (California Academy of Sciences): about 37,772 valid species, updated 21 September 2026

Eschmeyer's is the taxonomic reference that tracks every newly described species, so it runs highest. New species are still being named every year, which is why any 'all fish' figure needs a date next to it.

• FishBase: the largest free fish database, with 333,200 common names, 66,300 pictures and 68,500 references (version 06/2026). Best for looking up one species' size, range and biology
• Eschmeyer's Catalog of Fishes: the authority on scientific names; use it to check whether a name is still valid
• FishingBooker's fish list: an alphabetical index of about 800 angling species, from alligator gar to yellowtail amberjack, each linking to a fishing profile. It has no groupings by water type

This page groups the fish people search for most by type and habitat, with links to identification pages, which none of those three do.

The most numerous fish are not ones most people have seen. Bristlemouths of the genus Cyclothone are believed to be the most abundant fish genus, and the most abundant vertebrate genus, on Earth, with estimates of up to a quadrillion (10^15) individuals (Wikipedia). They are only 25 to 76 mm long and live 300 to 1,500 m deep, and they do not survive being brought to the surface, which is why so little is known about them.