Passage V

Aquaculture: A Solution or a Problem?

Overfishing has depleted much of the world’s naturally occurring supply of edible aquatic creatures. Despite a growing recognition of this ecological threat, demands for seafood continues to rise. The United States alone consumed around six million metric tons of seafood in 2000, and that figure is expected to increase to over eight million by 2025. Aquaculture—commercially raising fish, shellfish, and other aquatic organisms in tanks or enclosures, is one way to reduce people’s dependence on wild-caught creatures, but it has its own drawbacks.

By increasing the supply of seafood and avoiding the high transportation costs associated with ocean-based fishing, aquaculture helps keep prices low for consumers.(63)Freshness is also a benefit, commercially raised fish can reach market more quickly than ocean-caught fish. Relying less on wild-caught fish, aquaculture supporters say, this is also an ecologically sound approach to helping threatened natural populations recover.

The ecological impact of aquaculture depends on which species are raised and what method is used. Mussels and oysters (68) can benefit the coastal environments in which they’re raised. On the other hand, farmed salmon, typically raised in netted ocean pens, quickly pass diseases, which make salmon ill, in the pens’ crowded conditions. When salmon escape the nets, the diseases they carry can infect wild populations. Salmon also produce massive quantities of waste. If untreated, that waste can contaminate the land or water where it’s deposited.

Many ecological experts believe that the safest place for aquaculture is far from a natural body of water. Catfish produce little waste, and raising them in inland pens has a fairly small environmental impact. By contrast, shrimp create much more waste, and farms can yield 100,000 kilograms of shrimp per hectare yearly. To combat some of the problems associated with aquaculture, by the way, scientists and aquaculturists are developing better waste-removal processes as well as hard-walled pen systems designed to keep them separate.