"There are plenty of other fish in the sea," goes the old cliché. But are there? According to the International Union for Conservation of Nature's (IUCN) Red List of endangered species, 1,414 species of fish, or 5 percent of the world's known species, are at risk for extinction. While habitat loss and pollution are significant factors in the decline of these species, the greatest threat by far is overfishing.
So what if one of these endangered fish ends up on your hook? The best policy is to release them back into the water, but not before making a few observations. When did you encounter the fish? In what location? How many fish did you see and what size were they? Were they adult or juvenile? What activity did you observe (swimming, feeding)? You should provide this information, along with any photographs you might have taken, to local wildlife officials.
While it's difficult to determine which fish are the most endangered, the following list represents 10 endangered fish commonly harvested for food.
10: Atlantic Halibut
Found in the North Atlantic Ocean, the Atlantic halibut is the largest of the flat fish species. Boasting a 50-year lifespan, it can reach a length of 9 feet and weigh up to 1,000 pounds. 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 recover in the near future. This has prompted the United States to ban Atlantic halibut fishing in its coastal waters.
9: Beluga Sturgeon
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 can grow to 15 feet in length, weigh more than a ton and live to be 100 years old. Due to the popularity of their eggs, they're heavily overfished -- typically with gill nets. This particularly problematic because this species that doesn't reach sexual maturity until 20 or 25 years of age. 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 endangered, and the population is expected to continue its decline.
Gill nets are nets that sit like a fence on the ocean floor. When a fish that is tcoo big to swim through the net tries to swim back out, it gets caught by the gills.
8: Acadian Redfish
This species of North Atlantic fish grows to about 20 inches in length and can live as long as 50 years. Like other overfished species, the Acadian redfish is slow-growing and reaches reproductive age late -- at about eight or nine years old. Intensive trawling over the last 10 years has led to the smallest yields since commercial fishing of the species commenced in the 1930s. Worse, the Acadian redfish has been subject to pirate fishing, or fishing done in violation of environmental law. For these reasons, the IUCN lists the species as endangered.
Trawling is a fishing technique where a large, deep net is pulled behind a boat. Often this net drags on the ocean floor, stirring up sediment and altering seafloor habitat. The effects of trawling can actually be seen on satellite images taken from space.
7: Orange Roughy
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 Ocean. Its life expectancy is up to 149 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. Though the IUCN hasn't 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.
Bycatch are sea creatures caught unintentionally. This can either be ocean dwellers other than the desired species or juveniles of the desired species.
6: Winter Skate
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 a critically endangered rating from the IUCN.
5: Bocaccio Rockfish
Of the more than 70 species of rockfish living off the United States' west coast, the bocaccio rockfish is one of the most endangered. While this 3-foot fish reaches reproductive age sooner than many overfished species -- as early as four to five years -- its larvae have a very low survival rate. Changes in ocean currents and temperature since the 1970s mean that large numbers of bocaccio larvae live to become juveniles only once every 20 years. In response to their dwindling numbers, the United States closed several fisheries along the West Coast in 2002. But even without trawling in these areas, scientists believe it could take 100 years for bocaccio populations to recover. With such significant challenges to recovery, the IUCN has listed the species as critically endangered.
4: European Eel
Found primarily in the North Atlantic and the Baltic and Mediterranean Seas, European eel 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 4.5. 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. This has resulted in catastrophic overfishing of the European eel, and a critically endangered rating from IUCN.
3: Goliath Grouper
All species of grouper are endangered to some extent, but the Goliath Grouper is particularly threatened. Also known as the jewfish, it lives in the subtropical areas of the eastern Pacific (from Baja California to Peru) and the Atlantic (from North Carolina to Brazil). As the name suggests, it's a very large fish, growing to 7 feet in length in its 40-year life span. Overfishing of the Goliath grouper is a result of two main issues. First, it reproduces for only a short period of time, resulting in relatively few offspring compared to other species. Second, juveniles often become accidental bycatch in other fishing operations. What fish remain are targeted during spawning by hook-and-line fishing boats. Out of concern for the Goliath grouper's survival, the United States banned harvest of the species, and the IUCN rated them as critically endangered.
2: Maltese Ray
Historically, the Maltese ray populated the Mediterranean Sea in the coastal waters of Italy, Algeria, Malta and Tunisia. Today, its range is limited to the heavily-fished Strait of Sicily, a 90-mile-wide channel between Italy and Tunisia. Though little is known about this particular species, it likely displays characteristics similar to other rays: It grows slowly, matures late and produces few offspring. Commercial fishing vessels rarely target the Maltese ray. Rather, it is taken as bycatch in boats harvesting other species. Once they're caught, these unwanted fish are thrown back into the water, dead or dying. The decreasing population of this species and the slow response by regional governments to save it earned the Maltese ray a critically endangered rating from the IUCN.
1: Bluefin Tuna
Perhaps the most iconic of endangered fish, the 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 10 feet and weigh more than 1,400 pounds. This species' reputation as a fighter has made it a popular catch among recreational fisherman. 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. Chosen by the WWF (formerly known as the World Wildlife Fund) as the sixth most threatened species in the world, sea or land, the bluefin tuna is by all measures critically endangered.