Global fish stocks have been migrating towards cooler, 
deeper waters for the past four decades due to climate 
change. Now, University of British Columbia (UBC) 
scientists have used the temperature preferences of fish 
and other marine species as “thermometer” to assess the 
effects of climate change on oceans across the globe 
between 1970 and 2006.

The researchers gathered data on the distribution of 990 
marine fish and invertebrates and had their findings 
published in Nature.

The UBC scientists discovered that, except in the tropics, 
global fisheries catches were increasingly driven by warm-
water species and saw fewer cool-water species, which 
resulted from so many fish stocks moving toward the poles 
to escape warming waters. This has thereby impacted the 
mix of fish species caught by fishers’ nets as well, as 
most ecosystems slowly shifted to include more warm-water 
species.

“One way for marine animals to respond to ocean warming is 
by moving to cooler regions,” said the study’s lead author 
William Cheung, an assistant professor at UBC’s Fisheries 
Centre. “As a result, places like New England on the 
northeast coast of the US saw new species typically found 
in warmer waters, closer to the tropics.”

In turn, this has meant that in the tropics, fishers have 
seen fewer marine species and poorer catches, issues with 
potentially very serious repercussions for food security, 
he said. Species from warmer waters have been replacing 
those traditionally caught in many fisheries across the 
globe since 1970 if not earlier.

Additional negative impacts from these changing fisheries 
could include loss of traditional fisheries, decreases in 
profits and jobs, conflicts over new fisheries that emerge 
because of distribution shifts and food security concerns, 
particularly in developing countries near the tropics.

“We’ve been talking about climate change as if it’s 
something that’s going to happen in the distant future – 
our study shows that it has been affecting our fisheries 
and oceans for decades,” said Daniel Pauly, principal 
investigator with UBC’s Sea Around Us Project and the 
study’s co-author. “These global changes have implications 
for everyone in every part of the planet.”