10 of the Most Endangered Fish Species in Our Oceans

Found in the New England/Mid-Atlantic region, the Atlantic halibut is the largest of the flat fish species. Boasting a 50-year lifespan, it can reach a length of 15 feet (4.5 meters) and weigh up to around 700 pounds (318 kilograms). But because this slow-growing fish doesn't become sexually mature until it's 10 to 14 years old, it's particularly susceptible to overfishing. While Atlantic halibut are normally caught with hooks-and-lines, they're often caught as bycatch in bottom trawl fisheries. The IUCN classifies them as endangered, and their numbers are not expected to recover in the near future. This has prompted the United States to manage Atlantic halibut fishing in its coastal waters. The Atlantic halibut stock is at a very low level, according to the National Oceanic and Atmospheric Administration.

While the beluga sturgeon is popular for its fillets, its eggs, known as "true caviar," are regarded as a delicacy. Native to the Caspian Sea, these ancient fish date back more than 200 million years , can grow to 24 feet (7 meters) in length, weigh more than 3,500 pounds (1,588 kilograms) and live to be 100 years old. Due to the popularity of their eggs, they're heavily overfished — typically with gill nets — which is a major threat to the species. This is particularly problematic because males reproduce for the first time at 10-15 years and females at 15-18 years, with an estimated generation length of 20-25 years.

In addition to fishing pressures, beluga sturgeon suffer from habitat reduction, having lost 90 percent of their historic spawning grounds over the past several decades. Because of these pressures, the IUCN classified the beluga sturgeon as critically endangered, and the population is expected to continue its decline. Statistics show that in 1992, 573 tons (520 metric tons) of beluga were caught while in 2007, 36 tons (33 metric tons) were caught, which is a 93 percent decline in catch. In 2020, 7,000 farm-raised baby sturgeon were released into the Danube River to help reverse this population decline, the World Wildlife Fund reported.

The Southern bluefin tuna is found in the Atlantic, Indian and Pacific oceans. They can grow up to 8 feet (2.4 meters) in length, weigh up to 573 pounds (260 kilograms) and live up to at least 40 years old. The IUCN classified the southern bluefin tuna as critically endangered, because the estimated spawning stock biomass declined approximately 85 percent between 1973 and 2009. This species has been intensively fished since the 1950s, thanks to the worldwide popularity of sushi. The population is estimated to sink below 500 mature individuals in 100 years if the current exploitation of the fish continues.

Also known as the "slimehead," the orange roughy has a wide-ranging habitat that includes the coasts of New Zealand, Australia, Namibia and the northeast Atlantic and Indo-Pacific Oceans. Its life expectancy can be over 140 years, and it reaches sexual maturation age between 20 and 32 years, making it the epitome of a species inherently vulnerable to overfishing. The pressure of overfishing is amplified by fishermen's tendency to trawl for orange roughy when the fish congregate to feed and breed. The resulting catches wipe out generations. Orange roughy is sold skinned and filleted, fresh or frozen and are seen as a delicacy in U.S. restaurants. Though the IUCN hasn't formally reviewed this species to determine if it is endangered, a number of other organizations have recognized the significant decline in its numbers after only 25 years of commercial harvesting. They can grow up to 2.5 feet (76 centimeters) in length and weigh up to 15 pounds (6.8 kilograms).

The Nassau grouper is found in the tropical and subtropical waters of the western North Atlantic. The fish can grow up to 4 feet (1.2 meters) long, weigh up to 55 pounds (25 kilograms) and live up to 29 years old. The Nassau grouper is highly valued by commercial and recreational fisheries, which meant heavy fishing on spawning aggregations, which has caused severe declines in most countries. More than 30 of the known 50 aggregations across its range have disappeared. This used to be a very common fish to catch off the U.S. shores but has now been banned from harvesting in the U.S. due to low stocks. This devastating decline has earned the Nassau grouper a critically endangered rating from the IUCN.

The red handfish was once found in eastern Tasmania, but now it only exists in two small subpopulations in the Frederick Henry Bay in Australia. The IUCN classified the red handfish as critically endangered, with only about 100 mature individuals left. Threats to this species include loss of spawning substrate, habitat loss and degradation, water pollution and siltation and increasing densities of native sea urchins, according to the IUCN. They are also bright red to light pink/brown and are less than 4 inches (10 centimeters) in length, which makes them difficult to find.

Found primarily in the North Atlantic and the Baltic and Mediterranean Seas, European eels face a unique set of survival challenges. They have a fascinating development cycle, which begins with their birth out at sea and continues in freshwater streams thousands of miles inland, where they can grow to a length of 5 feet (1.5 meters). When they reach sexual maturity, at anywhere from 6 to 30 years of age, they return to the sea to spawn. If their route to the sea is blocked, they return to freshwater and can live for 50 years. But if they make it back to salt water and reproduce, they die. Because of this unusual life cycle, any eel that is caught at sea is a juvenile that has not yet had a chance to spawn. Other threats to this species include climate change, habitat loss/degradation, invasive species, parasitism, pollution, predation and unsustainable exploitation. This has resulted in catastrophic overfishing of the European eel, and a critically endangered rating from IUCN.

The winter skate is a fascinating species known to deter predators and stun prey with a quick jolt of electricity. Most are found in the northwest Atlantic Ocean, from the Gulf of St. Lawrence in Canada to North Carolina in the United States. Once thought to be a "trash fish," the winter skate is now harvested and processed into fishmeal and lobster bait, and is even marketed for human consumption. Increased trawling for the species has resulted in the accidental capture of juveniles, which are easily mistaken for smaller, more abundant species. This has led to a staggering population decline among winter skate, which are slow to reach sexual maturity and have few offspring. Experts blame these factors for a 90 percent reduction in mature individuals since the 1970s. This devastating decline has earned the winter skate an endangered rating from the IUCN.

The Chinese sturgeon was historically found in southwestern Korea, western Kyushu, Japan and in China (Yellow, Yangtze, Pearl, Mingjiang and Qingtang rivers). However, it is now only found in the Yangtze and Pearl rivers and the East and South China Sea. They have survived for more than 140 million years, but their days seem to be numbered now. This species has been historically overfished and the construction of the Gezhouba dam in 1981 blocked the migration routes of the Chinese sturgeon, which made it impossible for it to reach its spawning sites. Currently, there is just one remaining spawning ground, below the Gezhouba dam. Therefore, the IUCN rated them as critically endangered. This very large fish can weigh up to 990 pounds (450 kilograms), grow up to 16 feet (4.8 meters) and live at least 35 years. The Chinese government did try to repopulate the Yangtze with 9 million sturgeon between 1983 and 2007, but without any way to enable the fish to reproduce, populations did not increase. Currently the annual rate of reproduction is estimated at between 4.5 percent and zero.

Perhaps the most iconic of endangered fish, the Atlantic bluefin tuna occupies most of the northern Atlantic Ocean. One of the fastest fish in the sea, this species can grow to a length of 15 feet (4.6 meters) and weigh more than 2,000 pounds (907 kilograms). This species' reputation as a fighter has made it a popular catch among recreational fishermen. And at a going rate of up to $100,000 per fish, it's highly prized by commercial fisherman as well. Bluefin tuna are heavily overfished, and most experts agree that without prompt intervention, the slow-growing, slow-maturing species will become extinct. International regulation is tricky, however, since the bluefin tuna is known to migrate thousands of miles across the ocean. And so far, efforts to control harvests have largely failed. The Atlantic bluefin tuna is by all measures endangered by the IUCN, since both the Eastern and Western Atlantic stocks have declined at least 51 percent since 1970.