A shift to harvesting crustaceans like shrimp and lobster is feeding a growing carbon footprint for the world's fisheries, according to new research from the University of B.C.
The study, published this week in the journal Nature Climate Change, found a 21-per-cent increase in greenhouse gas emissions per tonne of fish landed by the world's fishing fleets between 1990 and 2011.
"That wasn't really expected," said Robert Parker, the study's lead author and a postdoctoral fellow at UBC's Institute for the Oceans and Fisheries.
"We know that a lot of fisheries have been working to decrease their fuel consumption. It's a big cost to fisheries, so there's an economic incentive to do that."
A major source of this unexpected increase in emissions is a 60-per-cent increase in the lobster and shrimp caught in the 21 years covered by the study, according to Parker.
Compared to harvesting small schooling fish that live in the open ocean and can be easily scooped up in huge amounts, crustaceans are relatively solitary creatures.
That means shrimp and lobster operations require a lot more gas to bring in a good haul.
"You go out with traps and catch one or two lobsters here and there, so you're burning a lot of fuel on those trips and catching a much smaller catch," Parker explained.
The study is based on numbers compiled from databases that track fishing efforts and fuel use around the world.
The researchers found that fisheries produce about four per cent of the world's emissions from food production.
The fleets of five countries accounted for 49 per cent of fishing emissions in 2011: China, Indonesia, Vietnam, the United States and Japan. Canada's fishing industry emissions are pretty average, Parker said.
For anyone hoping to make new food choices to reduce their carbon footprint, eating certain types of fish can be a more environmentally friendly option than meat.
More than half of the world's fisheries produced fewer greenhouse gases than even the lower range estimates for emissions from beef, lamb and pork farming.
Small pelagic fish like herring, sardines and anchovies are especially good low-carbon options, according to the study. Peru's anchovy fleets emit just one kilogram of carbon dioxide for each kilogram of fish caught.
Crustaceans are another matter entirely.
"We estimate that a lot of lobster fisheries and shrimp fisheries have just as big of a carbon footprint as the big land culprits like beef and lamb," Parker said.
Australia's fleets, for example, tend to disproportionately harvest rock lobsters and prawns, and they emitted 5.2 kilograms of carbon dioxide for each kilogram of seafood — several times the average for more fuel-efficient countries.
But in the end, Parker says, eating vegetarian remains the best option for anyone concerned about cutting down on emissions.
"There's certainly some fisheries and some other animal protein sources like chicken that could fit in a low carbon diet, and there's some that certainly don't, like beef and lamb. But generally, eat plants if you want to have a low impact," he said.