Vegetarian Fish Might Save the Planet

If eating meat in place of other proteins hogs natural resources and spews an overabundance of greenhouse gases into the atmosphere, wouldnt fish be a climate-friendlier menu selection? Asked Janet Raloff in a Science News report.

Usually, but not always. Or so panelists pointed out this morning at the American Association for the Advancement of Science annual meeting, in Chicago. Focusing on salmon, they showed that fish consumptions carbon footprint depends on what a fish has eaten, how it has been caught and stored, and how its transported to market.

According to Science News, there were some real eye openers within these assessments.

Peter Tyedmers of Dalhousie University in Halifax, Nova Scotia, focused on greenhouse gas aka GHG assessments of fish production downstream of food-processing plants. In other words, how fish are reared and caught.

He started by focusing on the big North Atlantic and Chilean sources in Norway, Scotland, Canada and Chile. For every tonne of fish harvested, there is a substantial GHG cost measured in terms of the amount of carbon dioxide that would produce equivalent warming.

For production of Norwegian fish its 1,750 kilograms of CO2 equivalents, 2,250 kg for Chilean salmon, 2,500 kg for the Canadian fish, and 3,300 kg for Scottish farmed stock.

The difference in the warming potential largely traces to what the finned populations have been fed, Tyedmers explains. Scottish farmers feed their salmon the highest proportion of fish meal almost 70 percent, on average. Those fishy diets account for 85 percent of the greenhouse-gas emissions associated producing Scottish salmon, his team calculated. Elsewhere, fish farming operations tend to substitute plant-based meals and oil or meat byproducts for a share of that fish meal.

Not surprisingly, the higher the proportion of plant sources in a farmed fishs diet, the lower the climate impacts associated with its rearing.