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SpeciesScientists Discover Mysterious New Fish in the Red Sea – and Have Never Seen It AgainOceanEye to eye with Britain's hidden sharks at SharkAdemy - OceanographicRiversIn October, biologists surveying a New York harbor for invasive fish pulled up a bright yellow one. It wasn't an invasive species at allOceanShedd Aquarium Sends Shark Eggs to Bolster Wild PopulationsSpeciesA rare fish has been found in Lake Ontario, North America, whose entire body is golden. It is a nati..OceanThe Great Sea Reef Is Fiji’s Wildest Dive, and a New Frontier for ConservationOceanEckerd College professor contributes to designating Biscayne Bay an Important Shark and Ray AreaSpeciesRio Verde Grande Survey Identifies Fifty-Three Fish Species Facing Flow ReductionsFisheriesAdams River Salmon Run in Thompson-NicolaIndiaHilsa production dropped 26% in five years, fisheries minister tells parliamentSpeciesScientists Discover Mysterious New Fish in the Red Sea – and Have Never Seen It AgainOceanEye to eye with Britain's hidden sharks at SharkAdemy - OceanographicRiversIn October, biologists surveying a New York harbor for invasive fish pulled up a bright yellow one. It wasn't an invasive species at allOceanShedd Aquarium Sends Shark Eggs to Bolster Wild PopulationsSpeciesA rare fish has been found in Lake Ontario, North America, whose entire body is golden. It is a nati..OceanThe Great Sea Reef Is Fiji’s Wildest Dive, and a New Frontier for ConservationOceanEckerd College professor contributes to designating Biscayne Bay an Important Shark and Ray AreaSpeciesRio Verde Grande Survey Identifies Fifty-Three Fish Species Facing Flow ReductionsFisheriesAdams River Salmon Run in Thompson-NicolaIndiaHilsa production dropped 26% in five years, fisheries minister tells parliament
EveryFish

Between sea and river

Fish that migrate between salt and fresh water to breed, like salmon and hilsa. 36 fish on EveryFish so far.

Some fish move between the sea and fresh water to breed. Anadromous fish, such as salmon, hilsa, shad, many sturgeons and the sea lamprey, grow at sea and swim up rivers to spawn. Catadromous fish, such as freshwater eels, do the opposite, living in rivers and travelling to the sea to spawn. These journeys can run to thousands of kilometres and link the ocean to the heart of the continents.

Journeys between waters

Pacific salmon return to the stream where they hatched, often finding it by smell, after years at sea. The hilsa enters the rivers of Bengal in the monsoon, and its run sets the fishing season in Bangladesh and West Bengal. European eels cross the Atlantic to the Sargasso Sea to spawn. Each of these fish has to rebuild its body's salt balance as it moves between salt and fresh water, a change controlled by hormones.

Blocked rivers

Migratory fish need open rivers. Dams, barrages and weirs block their way, and the Living Planet Index for migratory freshwater fish found an average fall of 76 per cent in monitored populations between 1970 and 2016. The Farakka Barrage cut the hilsa run up the Ganges, and dams on the Volga cut sturgeon from their spawning grounds. Fish ladders and lifts help some species, and removing old dams, as on the Elwha River in the United States, has let salmon return.

Famous between sea and river fish

Sockeye salmonThe great runs of AlaskaSea lampreyA jawless fish that spawns in rivers

Still to be written: Ilish, Atlantic salmon, European eel, Japanese eel, American shad, Beluga (sturgeon).

Further reading

GroupSharkRayCarpCatfishSalmonidHerringCodTunaPerch-likeCichlidReef fishEelFlatfishLivebearerAncientOther
UseFood fishFarmedAquarium fishSport fishingCulture and faithVenomous or dangerousInvasiveScience and research
OrderBest knownA to ZOldest firstNewest firstBy size
🇮🇳 India and 4 moreRohu A large silver carp from South Asian rivers, farmed for food and prized as a game fish.Carp · Rivers and lakes 🇵🇭 Philippines and 4 moreMilkfish The sole living species of the family Chanidae, found across the Indo-Pacific.Other · Coasts and shelves 🇷🇺 RussiaSterlet A small Eurasian sturgeon found in rivers flowing to the Black, Azov, and Caspian seas.Ancient · Rivers and lakes · 1758 🇺🇸 United StatesShovelnose sturgeon Smallest North American freshwater sturgeon, known for its shovel-shaped snout and caviar production.Ancient · Rivers and lakes · 1820 🇺🇬 Uganda and 2 moreSilver cyprinid A small pelagic fish from Lake Victoria that supports regional food security.Other · Rivers and lakes 🇧🇷 Brazil and 3 moreTambaqui A large freshwater fish from South America known for its heavy body and seed-eating habits.Other · Rivers and lakes WorldSnakehead Elongated freshwater predators with air-breathing organs found in Asia and Africa.Other · Rivers and lakes 🇧🇷 Brazil and 1 moreArapaima Large freshwater fish from the Amazon basin known for its size and air-breathing ability.Ancient · Rivers and lakes Southeast AsiaGiant snakehead A large freshwater predator from Southeast Asia known for air breathing and invasive potential.Other · Rivers and lakes 🇨🇳 China and 3 moreAsian swamp eel A freshwater, air-breathing fish native to Asia and introduced elsewhere.Eel · Rivers and lakes 🇧🇷 Brazil and 1 moreRed-bellied Pacu A large South American freshwater fish related to piranhas, farmed for food and kept in aquariums.Other · Rivers and lakes

Photo credits on this page

The small pictures above come from Wikimedia Commons under free licences. Some are cropped to fit.

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