How climate change affects fish

Commercially important fish species will leave their historic range and large marine species such as cod will migrate to new areas. However, even in these new areas, their numbers will decrease significantly.

The stark assessment stems from a new study for which a team of researchers developed a computer model to predict how prey and predator species will interact in certain thermal niches and changing food webs exposed to warmer temperatures.

Their findings suggest that “although the species of fish we catch today will be there tomorrow, they will not be there in the same abundance. In such a setting, overfishing becomes easier because population growth rates are low,” said Malin Pinsky, associate professor in the Department of Ecology, Evolution and Natural Resources at Rutgers University.

“Heating with the dynamics of the food web will be like putting marine biodiversity in a blender” with unintended consequences, adds the scientist.


study the food web

The scientists used their computer model to examine trophic interactions, in which one species grows at the expense of another, and other food web dynamics to determine how climate change will affect the historic ranges of species. Predator-prey interactions cause many species, especially top predators, to change their range more slowly than climate.

“The model suggests that over the next 200 years of warming, species will continually reorganize and shift their ranges,” says EW Tekwa, a University of British Columbia scientist who was part of of the team. “Even after 200 years, marine species will still lag behind temperature changes, and this is especially true for those at the top of the food chain.”

Faced with warming water temperatures, millions of species are heading towards the poles with their cooler waters in a dramatic reorganization of life in the oceans. However, it is not yet fully understood how changing movements of prey and predators will affect food web dynamics.

This gap in our knowledge is what this new research attempted to fill using a specially designed “spatially explicit” food web model, which included differences between species such as their metabolism, body size and their optimum temperature ranges.

Fish species with different destinations

Even in the face of a changing climate, scientists have found that species will be hampered in their ability to respond quickly to rising temperatures due to their reliance on dynamic trophic interactions. Top predators will especially stay longer in their historical ranges as new food sources from other ranges will arrive in their traditional ranges evacuated by their previous prey.

The effects of these changing dynamics across ranges could have unintended consequences for fisheries around the world, further depleting fish stocks already under pressure.

“That momentum won’t just be in one place but on a global scale,” Pinsky points out. “That doesn’t bode well for marine life, and it’s not a widely recognized effect.”

By Daniel T. Cross. Articles in English

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