Fish and sustainability


December 13, 2012

Why Eating Fish is Not a Good Alternative to Eating Other Animals

Oceans are being depleted

Wild fish stocks are in serious decline. Humans have become increasingly effective at tracking down schools of fish using sophisticated sonar and satellite technologies. Capture methods include drag nets that rake the ocean floor, longlining – using miles of baited hooks, and dynamiting coral reefs to scare fish into nets.

turtleNets reel in a great number of non-targeted species including seabirds, turtles, seals and dolphins. Biologists calculate that around 27 million tonnes of fish are wasted per year because they are the wrong kind or size. Marine mammals frequently get tangled in fishing gear — a problem that kills 1,000 whales, dolphins and porpoises around the world every day (CP June 16, 2003). Shrimp boats that drag the bottom are the most wasteful, scooping up 10 kilograms of other marine life for every one kilogram of shrimp.

A recent global study, published in the international journal Nature in May 2003, concludes that 90 percent of all large fishes have disappeared from the world’s oceans in the past half century.

“There is nowhere left in the ocean not overfished,” says Ransom Myers, a fisheries biologist at Dalhousie University in Halifax and lead author of the study. Reversing the decline, he suggested, would require cutting back fishing by as much as 60 percent.

Decades of overfishing caused the huge cod fishery off the east coast of Canada to collapse in 1993. Even with heavy management, populations show no sign of rebuilding. Atlantic Halibut also crashed in the 20th century due to overfishing and remain depleted today. Tuna is another example. Exploited heavily for decades, the West Atlantic Bluefin Tuna population is critically endangered, and the East Atlantic population is endangered. Tuna longline fisheries also catch high numbers of finfish, sea turtles, and marine mammals.

High energy costs

The high price of seafood reflects the enormous energy and transportation costs that go in to catching what is otherwise a free resource. Fleets of trawlers need to be built, maintained and fuelled. Ocean fish are generally transported refrigerated or frozen over great distances before ending up in our local supermarkets.

Farmed fish

Aquaculture (farmed fish) has been growing in popularity, making up for the decline in wild fish stocks.

But as is the case for intensive livestock operations, fish farms require large amounts of feed and chemicals. Disease and pollution often spill out from the submerged floating cages located along shorelines. Disease pathogens spread easily among the high densities of fish, and concentrated fecal wastes and drugs can contaminate adjacent waters. Fish that escape from the cages can spread disease and inbreeding to wild stocks. At least 140 distinct salmon stocks in British Columbia are already extinct.

Shrimp farms in Asia and India displace mangrove forest. The lost of this critical buffer was one of the main reasons the 2004 tsunami caused so much damage. See Shrimp and tsunamis.

More information

Fish’s dark side – pollutants, toxins and heavy metals 
Many consume fish thinking it is healthy or at worst a relatively harmless indulgence. They couldn’t be more wrong!

Fish oil and omega-3s
A new study published in the Canadian Medical Association Journal casts doubt on the health benefits of fish oil.

SeaChoice has a list of fish to avoid for Canada. These are the ones most overfished or involve environmentally damaging fishing methods. They also list fish that are relatively abundant, but these will also likely come under pressure if demand for fish remains high. For other countries see

The State of World Fisheries and Aquaculture (SOFIA)
This comprehensive, objective and global view of fisheries and aquaculture is published every two years by the Fisheries Department of the Food and Agriculture Organization of the United Nations (FAO)

A Heavy Toll
New York Times (free registration required) has an excellent multimedia feature that shows images and movies on the effect of bottom trawling and overfishing on the world’s oceans and fish populations.

Along the Pacific coast of Canada, fish farming is polluting the environment and seriously threatening the integrity of wild stocks. The David Suzuki Foundation studies salmon farming and shellfish farming, and their effects on marine environments.

Filed under: Sustainability