774 articles
Noodling
Noodling, also called hogging or hand fishing, is catching catfish bare-handed by reaching into underwater holes and letting the fish bite; legal in about 17 mostly Southern and Midwestern U.S. states, banned elsewhere.
Northern pike
Northern pike (Esox lucius, jackfish) is a large holarctic freshwater ambush predator prized as sport and commercial fish, invasive in 38 of 50 U.S. states and southcentral Alaska, where suppression removed nearly 40,000 pike from 2010 to 2020.
Northern red snapper
Northern red snapper (Lutjanus campechanus), also called American red snapper or pargo colorado, a western Atlantic reef fish of family Lutjanidae; long-lived (to 57 years), 30-620 ft deep, managed under Gulf and South Atlantic rebuilding plans.
Northern snakehead (乌鳢)
Northern snakehead (乌鳢, Channa argus), an air-breathing freshwater fish native to China, Siberia, and Korea; invasive in the U.S. since 2002, regulated under the Lacey Act, often confused with the native bowfin.
Notopterus notopterus
Notopterus notopterus, the bronze featherback or Asiatic knifefish, sole species of Notopterus (Notopteridae), a 60 cm Asian freshwater food fish distinguished from Chitala by plain coloration, well-developed pelvic fins, and large genetic divergence.
Nototheniidae
Nototheniidae, the notothens, is the largest family of Antarctic notothenioid fishes, dominant in the Southern Ocean, bearing trypsinogen-derived antifreeze glycoproteins and including Notothenia and Dissostichus.
Nurse shark
Nurse shark (Ginglymostoma cirratum), Atlantic nurse shark: a suction-feeding, bottom-dwelling carpet shark from Cape Hatteras to Brazil; IUCN Vulnerable, biennial female reproduction, distinct from the grey nurse shark (Carcharias taurus).
Oarfish
Oarfish (Regalecus glesne, king of herrings, doomsday fish): the longest bony fish, a ribbon-shaped deep-sea lampriform reaching 8 m and 272 kg, circumglobal in tropical and temperate seas, feeding on krill by suction.
Ocean sunfish
Ocean sunfish (Mola mola, common mola), a large pelagic Molidae fish of temperate and tropical seas; second-largest bony fish, generalist jellyfish-inclusive feeder, IUCN vulnerable, declining over 10% per decade; heaviest weighed specimen belongs to Mola alexandrini.
Oceanic whitetip shark
Oceanic whitetip shark (Carcharhinus longimanus), large pelagic tropical shark with white-tipped fins. Once abundant, now Critically Endangered; ESA threatened since 2018 and first shark on CITES Appendix I (2025).
Odontesthes bonariensis
Odontesthes bonariensis, the pejerrey or Argentinian silverside, is an Atherinopsidae fish of the Río de la Plata basin, key in Argentine fisheries, with temperature-dependent sex determination and aquaculture since 1904.
Oily fish
Oily fish (fatty fish): fish with fat in the flesh, such as salmon, mackerel, herring, sardines, and trout; richest food source of EPA/DHA omega-3s and vitamin D, with recommended weekly intakes and mercury limits.
Oncorhynchus masou (マス)
Oncorhynchus masou (マス), masu or cherry salmon, an anadromous Pacific salmon native only to the western Pacific (Kamchatka to Japan, Korea, China, Russia); IUCN Least Concern, subspecies ishikawae Endangered, formosanus landlocked in Taiwan.
Opah
Opah, or moonfish (Lampris spp.), is a large deep-bodied pelagic fish and the only known fully warm-blooded fish, heating its body via pectoral fin flapping and gill heat exchangers; a five-species complex caught as bycatch in tuna and swordfish fisheries.
Ophidiiformes
Ophidiiformes is an order of teleost fishes comprising the cusk eels, pearlfishes, brotulas, and relatives: almost exclusively marine bottom fishes with a worldwide tropical and temperate distribution.
Oranda
The oranda, also known as the Oranda goldfish (高头), is a fancy goldfish variety with a raspberry-like head growth called the wen and a long, flowing double tail.
Orange roughy
Orange roughy (Hoplostethus atlanticus, slimehead) is a deep-sea trachichthyid fish living 700-1,400 m, reaching 120-150 years and maturing at 27-32; heavily overfished after 1980s boom, now quota-managed in Australia and New Zealand.
Oreochromis mossambicus
Oreochromis mossambicus, the Mozambique tilapia (Mozambique mouthbrooder), is a southern African cichlid fish described by Peters in 1852; a hardy, euryhaline maternal mouthbrooder farmed widely in Southern Africa and listed among the IUCN's 100 worst invasive species.
Oreochromis niloticus
Oreochromis niloticus, the Nile tilapia, an African cichlid farmed in over 100 countries; Africa produced 1,287,053 mt in 2019, but cage escapes threaten native Oreochromis species.
Oreochromis spp
Oreochromis (blue tilapias) is a genus of about three dozen African maternal-mouthbrooding cichlids erected by Günther in 1889; it includes Nile tilapia (O. niloticus), a leading farmed fish, and several Critically Endangered species.
Oscar (fish)
Oscar (Astronotus ocellatus), also velvet cichlid, a large South American cichlid from the Amazon and Orinoco basins, popular in aquariums and established in Florida, Hawaii, Puerto Rico, Guam, and Australia.
Osmerus eperlanus
Osmerus eperlanus, the European smelt (sparling), is a small anadromous osmerid fish from the White Sea to the Gironde estuary, with landlocked lake populations; spawns February to May, reaches 45 cm, IUCN least concern but ICES data deficient.
Osmerus mordax
Osmerus mordax, the rainbow smelt, is a small anadromous or landlocked Osmeridae fish of northeastern North America, introduced widely as forage, commercially harvested, with endangered Lake Utopia populations.
Osphronemus goramy
Osphronemus goramy, the giant gourami (ikan gurami), is a large Southeast Asian labyrinth fish, up to 70 cm SL, farmed for food, an obligate air-breather building plant-fiber nests, IUCN Least Concern.
Osteichthyes
Osteichthyes, the bony fishes, is the vertebrate group with a bony endoskeleton, split into ray-finned Actinopterygii (over 28,000 species, about 44% of vertebrates) and lobe-finned Sarcopterygii, arising in the Late Silurian and including tetrapod descendants cladistically.
Osteoglossidae
Osteoglossidae, the bony-tongue fish family (arowanas, arapaimas, Heterotis) of Osteoglossiformes; freshwater fishes of South America, Africa, Asia, and Australia with a toothed tongue-and-parasphenoid bite.
Otolithes ruber
Otolithes ruber, the tigertooth croaker (basionym Johnius ruber), is a Sciaenidae fish of the Indo-West Pacific, up to 90 cm and 7 kg, commercially fished; IUCN Least Concern but Makran coast and Indian stocks overfished.
Oxyeleotris marmorata
Oxyeleotris marmorata, the marbled goby (Soon Hock, Ketutu), is a large Southeast Asian freshwater sleeper (Eleotridae) described by Bleeker in 1852, a high-priced food fish farmed in aquaculture and listed IUCN Least Concern.
Oyster toadfish
The oyster toadfish (Opsanus tau) is a bottom-dwelling fish of the western Atlantic coast of the United States, living in oyster reefs and known for the male's foghorn-like boatwhistle mating call.
Pacific sleeper shark
Pacific sleeper shark (Somniosus pacificus), a large deep-water North Pacific sleeper shark reaching 7 m, sister species of the Greenland shark; slow-swimming, Near Threatened, bycatch-caught, olfactory-driven predator of fish, squid, and marine mammals.