As new techniques make fish farming more efficient, farmed fish become competitive with captured fish in the marketplace. Already the salmon, shrimp, catfish, tilapia, and trout sold in supermarkets are frequently obtained from farms rather than fishing boats. Workers test the readiness of a salmon's eggs at a commercial fish farm near Schelt, British Columbia, Canada. The growth of the aquaculture industry could bring important environmental and other benefits. By providing an alternative source of fish, aquaculture could help ease current unsustainable pressures that threaten the collapse of wild fish populations.
Aquaculture can be a clean form of economic development.
Raising seaweed or filter-feeding shellfish, such as clams and oysters, can actually improve water quality since these organisms feed by cleansing water of nutrients. Several New England states have encouraged growth of their aquaculture industries as a way of providing jobs for fishermen left jobless by the crashes of wild fish stocks in the region. If aquaculture facilities are developed with little thought to environmental protection and the needs of local communities, however, they can also have considerable drawbacks. Fish feces and uneaten fish food from ocean netpens or other enclosures with large numbers of fish can cause significant water pollution. Over time, these materials can accumulate in the sediments on bay bottoms and result in the release of gases such as ammonia and hydrogen sulfide, which are toxic to fish.