Warming of the oceans due to climate change will mean fewer productive fish species

Warming of the oceans due to climate change will mean fewer productive fish species to catch in the future, according to a new study. As temperatures warm, changing predator-prey interactions will prevent species from keeping up with conditions where they could thrive, the researchers found.

The U.S. National Science Foundation-funded results, published in the journal Proceedings of the Royal Society B, present a mixed picture of ocean health. "The impact of a warming ocean on marine ecosystems will be complex and difficult to predict," said Mike Sieracki, a program director in NSF's Division of Ocean Sciences. "This study helps us know what to look for as the ocean changes so we can best manage our resources."

Not only will large species and commercially important fisheries shift out of their historical ranges as climate warms, but they will likely not be as abundant even in their new geographic ranges. A cod fisher in the Atlantic, for example, might still find fish 200 years from now, but in significantly fewer numbers.

"While the species we fish today will be there tomorrow, they will not be there in the same abundance," said study coauthor Malin Pinsky of Rutgers University. "Overfishing becomes easier because the population growth rates are low. Warming coupled with food-web dynamics will be like putting marine biodiversity in a blender."

Previous studies of shifting habitat ranges focused on the direct impacts of climate change on individual species. While these "one-at-a-time" species projections offer insights into the composition of ocean communities in a warming world, they have largely failed to consider how food-web interactions will affect the pace of change, the researchers said.

The new study looked at trophic interactions -- the process of one species being nourished at the expense of another -- and other food-web dynamics to determine how climate change affects species' ranges.

Using sophisticated computer models, the researchers determined that predator-prey interactions are likely to cause many species, especially large predators, to shift their ranges more slowly than climate is changing.

"The model suggests that over the next 200 years of warming, species are going to continually reshuffle and be in the process of shifting their ranges," said lead author E.W. Tekwa at the University of British Columbia. "Even after 200 years, marine species will still be lagging behind temperature shifts. That’s particularly true for those at the top of the food web."