Marine fish farms, according to new research, are not climate change safety nets.

A new UBC study suggests that the global supply of farmed seafood such as salmon and mussels is expected to plummet by 16 percent by 2090 if no action is made to counteract climate change.

Ocean-farmed seafood, also known as mariculture, is usually regarded as a panacea for the issues of declining wild fish stocks and rising human demand, and it is predicted to expand significantly in the future years.

However, the new modeling study shows that the industry is just as vulnerable to climate change as any other.

“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 per cent by 2050, and decline by 16 per cent by 2090,” said lead author Dr. Muhammed Oyinlola.

In a low-emissions scenario in which action is done to combat climate change, mariculture is expected to rise by about 17 percent by the mid-twentieth century and by about 33 percent by the end of the century, compared to the 2000s.

Many aspects are considered in the model, including changing ocean temperatures, future potential mariculture regions, and the supply of fishmeal and fish oil. It looked at about 70 percent of the world’s mariculture production in 2015, focused on Exclusive Economic Zones, which are where the majority of the world’s seafood farming takes place.

According to Dr. Oyinlola, climate change will effect mariculture productivity differently depending on where farms are located and what they produce. In the high-emissions scenario, the hardest-hit regions—Norway, Myanmar, Bangladesh, the Netherlands, and China—mainland mariculture production might drop by 40 to 90 percent.

Changes in the area of usable ocean in which to grow fish, as well as the supply of food needed to feed them, are all climate-related affects on mariculture. Fishmeal and fish oil, which are mostly made of smaller fish such as herring and anchovy – populations that are similarly endangered by climate change – are commonly used in fish farms.

“Some regions produce more bivalves, such as mussels, oysters and clams, and in these regions, the impact is smaller,” added Dr. Oyinlola.

“In regions that produce more finfish, such as salmon, the impact will be high due to reduction in the supply of fishmeal and fish oil.”

Finfish farming, such as salmon farming, is expected to decrease globally by 3 percent by 2050, and by 14 percent by 2090, based on current carbon emission rates. Under both climate scenarios, bivalve farming is expected to increase by 2050 and decrease by 2090.

According to Dr. Oyinlola, countries whose mariculture is mostly used for finfish production, such as Norway, Iceland, Finland, Chile, and Bangladesh, will be hit the worst, whilst regions that produce more bivalves will be more stable, or in Canada’s case, will increase.

The study also discovered that replacing fishmeal and fish oil with plant-based diets like soybeans could help fish farms cope with the consequences of climate change.

Under a low-emissions scenario, when a quarter of fish food is replaced with alternatives, mariculture production is expected to increase by 25 percent by 2050 and 31 percent by 2090.

When a quarter of the fish food was replaced with alternatives, mariculture production was anticipated to increase by 15 percent by 2050 and 4 percent by 2090, with no change in current emissions. These percentages increased when half of the food was swapped in both climate scenarios.

“This study highlights the need to diversify mariculture development from the current focus on fish,” said Dr. William Cheung, senior author.

Species that are not dependent on fishmeal and fish oil, such as shellfish or algae, or those that can use non-fish-based diet, would be considered climate-adapted mariculture.

“Farming these species generally helps to reduce exposure of seafood farming to climate hazards.”

While there is enthusiasm for ocean mariculture as a means of increasing seafood output, the study suggests that such enthusiasm will be muted if humans do not address climate change, according to Dr. Cheung.

“Climate change affects everything, including aspects of seafood farming we’ve not previously considered. We need to act, and quickly, to mitigate climate change rather than rely on one solution to solve all our seafood production problems.”

Source: 10.1111/gcb.15991

Image Credit: Getty

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