Study finds aquaculture production vulnerable to climate change

Unchecked global warming could reduce global aquaculture production by as much as 16 percent by 2090, a new study from the University of British Columbia Institute for the Oceans and Fisheries shows.

Marine aquaculture, or mariculture, could double its output by 2050, from a current 30 million metric tons (MT) per year live-weight to 74 million MT, but UBC’s researchers modeled that estimate against climate change scenarios and found climate change to be a more serious threat to the industry than expected.

“If we continue to burn fossil fuels at our current rate, the amount of seafood such as fish or mussels able to be farmed sustainably will increase by only eight percent by 2050, and decline by 16 percent by 2090,” Muhammed Oyinlola, a postdoctoral research fellow at Canada’s Institut National de la Recherche Scientifique and the study’s lead author, said.

In the face of depleting wild fish stocks, aquaculture has been held up as a possible solution for feeding a growing global population, which will total just short of 11 billion by the end of the century. However, the results of the study, published in Global Change Biology, show fish- and shellfish-farming production are surprisingly vulnerable to the effects climate change.

Projecting a scenario of current carbon emission rates, the study predicted salmon production would decrease globally by three percent by 2050, and by 14 percent by 2090. The projected impacts are mainly due to the direct ocean warming effects on farmed species and the indirect impacts of the changing availability of forage-fish supplies to produce fishmeal and fish oil for aquafeed. Shifting ocean currents and warming waters will significantly affect the distribution of fish stocks and altering the structure of ecosystems, the study found.

The study examined approximately 70 percent of the world's main production areas in 2015, focusing on exclusive economic zones, where most of the world's seafood farming occurs. The estimates it produced were based on United Nations’ scenarios from the best-case scenario (SSP1-1.9), in which countries manage to reduce fossil fuel use and cut greenhouse gas emissions, to the worst-case scenario (SSP5-8.5), in which no reductions are completed.

The researchers warn that only under a best-case scenario can aquaculture production increase to meet food security needs. Under the worst-case scenario, it found that more than 25 percent of aquaculture-producing nations are projected to lose between 40 percent and 90 percent of their current production potential by mid-century.

Countries most affected under a worst-case scenario trajectory include Norway, Myanmar, Bangladesh, the Netherlands, and China. Regions that produce more bivalves are expected to see fewer changes, as the impacts of climate change on species such as mussels, oysters and clams is likely to be smaller, the study found.

"This study highlights the need to diversify mariculture development from the current focus on fish,” University of British Columbia Institute for Oceans and Fisheries Professor and Director William Cheung said. “Climate-adapted mariculture would include species that are not dependent on fishmeal and fish oil, such as shellfish or algae, or those that can utilize non-fish-based feed. Farming these species generally helps to reduce exposure of seafood farming to climate hazards.”

The report suggests that substituting fishmeal and fish oil for plant-based foods such as soybeans could help to alleviate the effects of climate change for fish farms. The researchers found their projected model of a low-emissions scenario combined with the substitution of a quarter of the fishmeal and fish oil used in feed with soybeans increased projected production by 25 percent by 2050 and 31 percent by 2090. Under a scenario with no emissions reduction but the same substitution of fishmeal alternatives, the study found a projected increase in farmed seafood production of 15 percent by 2050 and four percent by 2090. Both scenarios showed even greater increases in production when vegetarian alternatives were substituted in half of the aquafeed.

"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 relying on one solution to solve all our seafood production problems.”

Photo courtesy of Nereus Program