Many species of fish spawn in the Gulf of Mexico in early summer, and the BP Deepwater Horizon disaster threatens to decimate already vulnerable populations of Atlantic fish.
Female bluefin tuna instinctively return to areas of the gulf to lay their eggs every year. Yet these breeding grounds have been fouled by oil, and any oiled fish eggs or larvae have little or no chance of survival. The bluefin has already been severely overfished, but international efforts of protection have been stymied by high demand. Bluefin tuna are prized for their meat, and an individual fish can fetch hundreds of thousands of dollars in Japanese fish markets.
And the bluefin is not the only fish threatened by the April 20 explosion of the Deepwater Horizon rig. It’s more important than ever for seafood lovers to think carefully about where their fish are coming from in the wake of the spill.
Consumers first have to answer the basic question of whether a fish in the supermarket comes from a farm or whether it was caught in the wild. Although whether domesticated or wild fish are better for the environment depends on the species, and both sources of seafood can have serious ecological implications.
Aquaculture, or raising fish for food, can be practiced sustainably. Shellfish such as oysters have been farmed since Roman times, and shellfish farming can actually benefit the surrounding environment since shellfish filter seawater. But environmental standards vary by country and do not always prevent aquaculture from harming marine ecosystems. Shrimp farming in coastal ponds in tropical countries such as Thailand and Ecuador, for example, has led to widespread destruction of mangrove forests, which long protected ecosystems and human inhabitants from tropical storms and erosion.
Raising fish in open-net pens in the ocean or in lakes is the most destructive form of aquaculture. A cube of netting encloses the fish, but the fish’s feces and uneaten food can float into the rest of the ecosystem. Diseases and parasites are rampant in these pens because of crowding, and fish can spread these to wild fish if they escape. Escaped fish themselves can also compete with or prey on native fish. African tilapia, escaped from fish farms, have become an invasive species in many parts of the world.
Tilapia are a promising choice for aquaculture if properly contained. U.S. farmed tilapia, along with catfish, are raised in an environmentally responsible manner on a mostly vegetarian diet, according to the Monterey Bay Aquarium’s species-by-species report on seafood sustainability. Farmed salmon, on the other hand, consume three times their weight in fish feed made from processed wild fish such as sardines or menhaden, and tuna eat 15 times their weight, making these species poor choices for sustainable farming.
Wild-caught fish can have problems of their own, depending on how they were caught. Bycatch, the term for other species caught and killed in fishing nets, can include vulnerable species such as turtles, seabirds, and marine mammals. And bottom trawling for fish such as flounder can damage the sea floor.
It’s important to stay away from wild-caught fish if the species’ wild population is dwindling. Alaskan wild-caught salmon and halibut stocks are safe, thanks in large part to the state’s management of its fisheries. When in doubt, do some research.
The Marine Stewardship Council certifies fisheries for the sustainability of their operations and their chain of supply. The organization has been criticized because its standards are not consistently enforced, but its label along with the Monterey Bay Aquarium’s report should provide consumers a good start. The best approach is to support local fishermen who can talk about their fishing practices in person, but for people living inland this may not be an option.
Sustainable salmon aquaculture in onshore, closed-tank systems has succeeded in the United States, creating an alternative to threatened wild fish. And bluefin tuna ranching can perhaps relieve pressure on wild stocks. Bluefin ranching has in the past meant capturing juveniles from the wild before they have a chance to breed, but bluefin can now be bred in captivity, with the potential to create a supply of tuna meat wholly separate from the wild bluefin. Bluefin ranching still faces environmental and technological obstacles, but it may be the best hope for the species without a determined international effort to halt bluefin fishing.