The world's reliance on farmed fish, such as the pictured trout, could be tested if climate change isn't addressed, according to a new study. File photo by Stephen Shaver/UPI | License Photo
Dec. 13 (UPI) -- Supplies of farmed seafood such as salmon and mussels are projected to drop 16% globally by 2090 if no action is taken to address climate change, a study published Monday by the journal Global Change Biology predicted.
If fossil fuels continue to be burned at their current rates, the amount of seafood able to be farmed sustainably will increase by 8% by 2050 before declining by 16% over the next 40 years, the data showed.
Conversely, in a low-emissions scenario in which action is taken to mitigate climate change, farmed seafood supplies could grow by about 17% by the mid-21st century and by about 33% by the end of the century, compared with the 2000s, the researchers said.
The findings are significant given that ocean-farmed seafood, or mariculture, is often seen as a potential solution to the problems of depleted stocks of wild fish and growing human demand, they said.
"This study highlights the need to diversify mariculture development from the current focus on fish," study co-author William Cheung said in a press release.
"Farming these species" -- including species that are not dependent on fishmeal and fish oil, such as shellfish or algae -- "helps to reduce exposure of seafood farming to climate hazards." said Cheung, director of the Institute for the Oceans and Fisheries at Canada's University of British Columbia.
Climate effects on mariculture include changes in the area of viable ocean in which to farm fish, as well as the stock of food used to feed them, the researchers said.
Fish farms tend to use fishmeal and fish oil, which are largely composed of smaller fish such as herring and anchovy, stocks which are also threatened by climate change.
The new computer model takes many factors into account, including changing ocean temperatures and the supply of fishmeal and fish oil, the researchers said.
For this analysis, they used the model to examine approximately 70% of the world's mariculture production as of 2015, focusing on Exclusive Economic Zones, where most of the global seafood farming occurs.
Climate change will affect mariculture production differently depending on where farms are in the world, and what they produce.
For example, the hardest-hit regions in their high-emissions scenario, including Norway, Myanmar, Bangladesh, the Netherlands and China, could see their mariculture production decline by as much as 90% by the end of the century compared with the early 2000s, the researchers said.
Under current carbon emission rates, finfish farming, such as salmon, is projected to decrease by 3% globally by 2050, and by 14% by 2090.
Bivalve farming, which includes mussels, oysters and clams, is projected to increase by 2050 and decrease by 2090 under both climate scenarios.
Substituting fishmeal and fish oil for plant-based foods such as soybeans could help alleviate the effects of climate change for fish farms, they said.
When one-quarter of the fish food was substituted with alternatives, under a low emissions scenario, mariculture production was projected to increase by 25% by 2050 and by 31% by 2090, the data showed.
However, with no change to current emissions, when one-quarter of the fish food was substituted with alternatives, mariculture production was projected to increase by 15% by 2050 and by 4% by 2090.
When half the food was substituted in both climate scenarios, these percentages increased, researchers said.
"Climate change affects everything, including aspects of seafood farming we've not previously considered," Cheung said.
"We need to act, and quickly, to mitigate climate change rather than rely on one solution to solve all our seafood production problems," he said.
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