Types of Fish in the Ocean: Groups, Zones and Examples

Ocean fish fall into three big groups: jawless fish (hagfish and lampreys), cartilaginous fish (sharks, rays and chimaeras) and bony fish, which are by far the largest group (Wikipedia). Within those groups, the most useful way to sort ocean fish is by where they live, because habitat shapes body form: reef fish are deep-bodied and colourful, open-ocean fish are streamlined, and deep-sea fish are small, dark and often glow.

Wikipedia's Freshwater fish article puts 41.24% of known fish species in fresh water, so most of the rest are marine or move between salt and fresh water. For the difference in how they live, see freshwater versus saltwater fish.

Reefs hold the most colourful ocean fish. Examples from Oceana's ocean fish list: blue tang, queen angelfish, French angelfish, queen parrotfish, bluehead wrasse, common clownfish, threespot damselfish, banded butterflyfish, clown triggerfish and red lionfish.

Our pages on reef fish: saltwater angelfish, parrotfish, surgeonfish and tangs, clownfish, butterflyfish, triggerfish, grouper and moray eel.

Pelagic fish live in open water, away from the bottom and the shore. Wikipedia says this environment holds 11% of known fish species and splits them in two:

• Forage fish: small filter feeders such as herrings, sardines, anchovies and menhaden.
• Predators: tuna, billfish, sharks, king mackerel, barracuda, swordfish and marlin.

Oceana's list adds sailfish, wahoo, common dolphinfish (mahi-mahi), skipjack and yellowfin tuna, tropical two-wing flyingfish and the ocean sunfish. The epipelagic or sunlit zone runs from the surface to 200 m (Wikipedia).

Below the sunlit layer the fish change completely. Wikipedia gives these zones and examples:

• Mesopelagic, 200 to 1,000 m: lanternfish, sabertooth fish and barreleye. Lanternfish account for as much as 65% of all deep-sea fish biomass.
• Bathypelagic, 1,000 m to the seafloor: anglerfish, bristlemouths, fangtooth and viperfish.

Oceana's list includes the deep sea anglerfish, flashlight fish, blobfish, oarfish, orange roughy and tan bristlemouth. For the anglerfish's shallow-water relatives, see frogfish.

Demersal fish live on or near the seafloor (Wikipedia). Many of the most important food fish are in this group. NOAA Fisheries' New England and Mid-Atlantic page, which says the agency manages 42 commercial and recreational fish and shellfish in that region, features Atlantic cod, haddock and Atlantic halibut alongside open-water Atlantic mackerel, Atlantic herring, bluefish and bluefin tuna. Oceana's list adds Pacific halibut, peacock flounder, stonefish, black scorpionfish and Atlantic wolffish.

Our bottom-fish pages: flatfish, sea robin, sculpin, toadfish, catshark and wolf eel.

Some ocean fish are also river fish at another stage of life. Wikipedia calls fish that breed in fresh water but spend most of their adult life at sea anadromous: salmon, some trout and sea lamprey. Fish that are born at sea and live much of their adult life in fresh water are catadromous, with eels the main example. Oceana's ocean list includes four salmon (Atlantic, chinook, sockeye and pink) and the beluga sturgeon. See American eel and beluga sturgeon.

Most common: probably a fish most people have never seen. Wikipedia says the bristlemouth genus Cyclothone is thought to be one of the most abundant vertebrate genera in the world, with an estimated population of hundreds of trillions to quadrillions. They are small, typically around 7.5 cm, and usually live deeper than 1,000 feet.

Most caught: Wikipedia calls the Peruvian anchoveta the most heavily exploited fish in world history, with a peak catch of 13.1 million tonnes in 1971 and 3.14 to 8.32 million tonnes a year from 2010 to 2021. By 2023 its catch had fallen below Alaska pollock and skipjack tuna, the two other giants of wild fisheries.

A few quick checks narrow it down before you look at species:

• Skeleton type: five to seven separate gill slits (on the sides in sharks, underneath in rays) and no gill cover means a cartilaginous fish; one gill cover on each side means a bony fish. Our cartilaginous fish page explains the differences.
• Body shape: a fish lying flat on one side with both eyes on the upper side is a flatfish.
• Where you were: reef, pier, surf or offshore narrows the list more than colour does.

Then photograph the whole fish from the side. FishLens identifies ocean fish from a photo, and our photo guide shows which angles help. Check local size and bag limits before you keep any fish.

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, and where sources disagree we say so instead of picking one silently. Prices and rules are given with the date we checked them; they change, so confirm before you rely on them. If you find an error, tell us and we will correct it.