Vince McDonagh

BY VINCE MCDONAGH

Feeling the heat

Warming oceans represent a clear and present danger for fi shing and fi sh farming, a new report concludes

GLOBAL warming poses a bigger threat to the future growth of aquaculture than many realise, a new study suggests, with salmon and mussels par� cularly at risk.

The University of Bri� sh Columbia (UBC), close to Canada’s main salmon ac� vity and the world’s largest ocean, has completed a major research project that shows that fi sh farms are not immune to the impact of climate change.

The poten� al consequences are seriously worrying. Sea warming is already being blamed for the increase in salmon lice and diseases such as infec� ous salmon anaemia (ISA), but the UBC study says that if no ac� on is taken to mi� gate climate change the supply of salmon and mussels could drop by 16% globally over the next 70 years.

The researchers from the UBC’s research unit, known as the Ins� tute for the Oceans and Fisheries (IOF), used a complex model incorpora� ng extreme annual ocean temperatures in exclusive economic zones, where the majority of global fi sh catches occur, into climate-related projec� ons for fi sh, fi sheries and their dependent human communi� es.

Above: Muhammed Oyinlola Left: Glacier mel� ng Opposite: Bangladesh fi shing boat

Ocean-farmed seafood or mariculture is o� en seen as a solu� on to the problems of depleted stocks of wild fi sh and growing human demand. It is expected to grow substan� ally in the coming years, says Dr Muhammed Oyinlola, the report’s lead author.

But Dr Oyinlola, who is a postdoctoral research fellow at the Ins� tute for the Oceans and Fisheries, warns the industry is as vulnerable to the eff ects of climate change as any other, adding: “If we con� nue to burn fossil fuels at our current rate, the amount of seafood such as fi sh or mussels able to be farmed sustainably will increase by only 8% by 2050, and decline by 16% by 2090.”

But there is also an upside. The study says in a “low emissions” scenario, where ac� on is taken to mi� gate climate change, mariculture is projected to grow by about 17% by the mid-21st century, and by about 33% per cent by the end of the century, rela� ve to the present � me.

The model takes into account many factors, including changing ocean temperatures, suitable mariculture areas in the future, and the supply of fi shmeal and fi sh oil. It examined approximately 70% of the world’s mariculture produc� on as of 2015, focusing on exclusive economic zones.

Climate change will aff ect mariculture produc� on diff erently depending on where farms are in the world and what they produce, says Dr Oyinlola.

The hardest-hit regions iden� fi ed in the high-emissions scenario are Norway and the Netherlands (and, presumably, Scotland and the Faroe Islands because of their proximity to Norway) along with warm climate countries such as Myanmar, Bangladesh and China. These could all see their aquaculture produc� on decline by as much as 40% to 90%.

The report also maintains that the climate eff ects on aquaculture include changes in the area of viable ocean in which fi sh can be farmed, as well as in the stock of food used to feed them. Fish farms tend to use fi shmeal and fi sh oil, which are largely composed of smaller fi sh such as herring and anchovy – stocks that are also threatened by climate change.

“Some regions produce more bivalves, such as mussels, oysters and clams, and in these regions the impact is smaller,” Dr Oyinlola says. “In regions that produce more fi nfi sh, such as salmon, the impact will be high due to reduc� on in the supply of fi shmeal and fi sh oil.”

Under current carbon emission rates, fi nfi sh farming, includings salmon, is projected to decrease globally by 3% by 2050, and 14% by 2090. Bivalve farming is projected to increase by 2050 and decrease by 2090 under both climate scenarios.

The study also found that subs� tu� ng plant-based foods such as soybeans for fi shmeal and fi sh oil could help alleviate the impact of climate change from fi sh farming opera� ons.

When a quarter of the fi sh food was subs� tuted with alterna� ves, under a low-emissions scenario, mariculture produc� on was projected to increase by 25% by 2050 and 31% by 2090.

With no change to current emissions, when a quarter of the fi sh food was subs� tuted with alterna� ves, mariculture produc� on was projected to increase by 15% by 2050 and 4% by 2090. When half the food was subs� tuted in both climate scenarios, these percentages increased.

“This study highlights the need to diversify mariculture development from the current focus on fi sh,” says senior author Dr William Cheung, IOF professor and director.

Climate-adapted mariculture would include species that are not dependent on fi shmeal and fi sh oil, such as shellfi sh or algae, or those that can u� lise non-fi sh-based feed. The report says: “Farming these species generally helps to reduce exposure of seafood farming to climate hazards.”

While there is enthusiasm about ocean mariculture helping to increase the produc� on of seafood, the study shows that if humans don’t address climate change, such enthusiasm will be tempered, says Dr Cheung.

He concludes: “Climate change aff ects everything, including aspects of seafood farming we’ve not previously considered. We need to act, and quickly, to mi� gate climate change rather than rely on one solu� on to solve all our seafood produc� on problems.” FF

“This study highlights the need to diversify mariculture development”