Blue Acres

Aquaculture, or "fish farming," has become the fastest growing supplier of fish worldwide--so fast that environmental effects are spiraling out of control. In this form of agriculture, seafood is cultivated in a more-or-less controlled environment, such as ponds or tanks. By adjusting the feed, farmers can affect fattiness, flavor, color, and nutritional quality. Increasing the fat content of the feed, for example, produces salmon that's more difficult to overcook.

Farmed fish are often reared with the use of antibiotics, hormones, disinfectants, anesthetics and/or pesticides. Formaldehyde (Formalin) is one of five aquaculture drugs approved by the Food & Drug Administration (FDA), and is used to kill fungi and parasites. FDA specifies withdrawal periods to allow such drugs to pass out of fish before they are sold. But it is the farmer's responsibility to comply; FDA does very little residue testing.

Nor does FDA mandate testing of water sources for farmed fish. Wells and springs, less frequently contaminated by PCBs, mercury, dioxins, and pesticides like chlordane and DDT--all of which accumulate in animal fat--are the best freshwater sources for raising fish. Coastal aquaculture, called mariculture, utilizes bays or the open ocean, where there is more risk of water pollution. In general, low-fat species and younger, smaller fish will have accumulated fewer contaminants.

Environmental Defense reports that now about one-quarter of all fish consumed around the globe is farm-raised. Americans are most likely to see farmed shrimp and salmon at their market.

Shrimp: America's #2 Seafood Choice

Up to one-half of all shrimp consumed today are farm-raised. Some are farmed domestically, in Texas, but most come from places like Thailand and Ecuador, where the shrimp are grown in coastal "ponds"--usually former mangrove forests or rice paddies.

Shrimp farmers clearcut coastal wetlands and rely on massive amounts of water, destroying native fishing economies in the process. Some Asian countries have been able to boost production from 4,000 shrimp per acre to 121,000 by using drugs and fish feed, which are discharged along with waste into surrounding ecosystems. "Coastal wetlands are essential nurseries for wild fisheries, and their destruction directly undermines marine fishing," write the authors of Worldwatch Institute's 1995 State of the World report.

Closed-cycle systems, located in warehouses where water is pumped in from underground aquifers, avoid such depletion and drainage, but are not the norm. Kate Cissna, co-director of Mangrove Action Project (MAP), says that probably the biggest issue with shrimp aquaculture "is that it takes a common resource base away from communities and privatizes it for the unsustainable use of a few individuals." Shrimp farming is a boom and bust industry, where shrimp farmers can easily get a return on their investment in two years. But when farms are hit by disease (a common occurrence in factory livestock farming, where animals are confined in small areas), the farmers will abandon the area, leaving behind denuded land and polluted waters.

Thailand's fisheries department now has a policy in place prohibiting the removal of mangroves to build shrimp farms. But Alfredo Quarto, co-director of MAP, is skeptical, saying, "Since ... Thailand has passed earlier regulatory legislation addressing mangrove forest loss [several] times in the last decade, we must be cautious in assuming that this time around, the regulations will be enforced."

The Growth of Salmon

Since 1990, U.S. per capita consumption of salmon has grown faster than any other seafood, with most of the increase accounted for by farmed imports from Chile and Canada. If it's labeled Atlantic salmon, you can be almost positive it's farmed, says Michael Weber, author of an upcoming report on salmon aquaculture for the Consultative Group on Biological Diversity. Other varieties, like King (or Chinook), Coho (or Silver), and Pacific salmon, are usually wild, unless it's the winter off-season.

Dr. Sylvia Earle, marine biologist and author of Seachange, calls the sea mostly a "fish-eat-fish world." Aquaculture of carnivores, such as salmon, shrimp and trout, takes food from the mouths of wild fish and decimates the lower food chain. Much marine catch goes to meet the increasing demand for farmed-fish feed. Three to five pounds of fish, processed into pellets, produce one pound of farmed salmon, for example.

Farmed salmon harm biological diversity by escaping from their enclosures and breeding with fish in the wild. Today, ever-greater numbers of seemingly wild fish have lost their genetic distinctiveness due to reproduction with escapees. Wild fish may also contract diseases from infected farm-raised fish. Salmon aquaculture has been outlawed in Alaska in part to preserve wild salmon stocks.

Standards for the Future

"Aquaculture serves as a distraction from facing the limits of marine fisheries," the authors of State of the World write, hypothesizing that policymakers may continue to allow the mistreatment of the oceans by facilitating the expansion of fish farming. Nothing should replace the rehabilitation of marine and freshwater fisheries and maintaining access to coastal zones for small-scale fishermen.

Aquaculture may help us meet increasing global demand for food fish if farmers make commitments to sustainability by:

+ Avoiding the use of drugs and chemicals
+ Using marginal lands, not sensitive waters or coastal wetlands
+ Utilizing barriers so that fish and shrimp cannot escape
+ Diverting waste from ponds to farmland for fertilization
+ Raising more herbivorous fish, such as catfish and tilapia (also called Nile perch)