Study: Marine Heatwaves Will Increase Climate's Effect on Fisheries

In a new study published in Science Advances on Friday, a team of researchers from University of British Columbia predict that extreme marine heatwaves could add to the impact that climate change is having on fisheries. 

The UBC Institute for the Oceans and Fisheries team created a model that incorporates extreme annual ocean temperatures within EEZ waters - where the majority of global fish catches occur - into existing projections for the impact of climate change on fish, fisheries and fishing communities. Based on a worst-case scenario, where CO2 emissions continue unabated, they predict that about three-quarters of all target fish species will see some decrease in biomass due to extremely hot years - on top of the projected declines due to long-term, decadal-scale climate trends. 

Some areas will be hit harder than others, the researchers found, including EEZs around South Asia, Southeast Asia and the Pacific Islands; along the Pacific coast of the Americas; and some countries in the West African region.

In British Columbia, sockeye salmon catches are expected to decrease by 26 per cent on average during each given high temperature event between 2000 and 2050. When combined with long-term losses due to climate change, when a temperature extreme occurs in the 2050s, the decrease in annual catch would be more than 50 per cent.

In Bangladesh, where fisheries-related sectors employ one-third of the country’s workforce, an extreme marine heat event is expected to cut two per cent — about one million — of the country’s fisheries jobs, in addition to the more than six million jobs that will be lost by 2050 due to long-term climate change.

The situation is similarly grim for Ecuador, where extreme high temperature events are projected to cut about 10 per cent - about $100 million - of the country’s fisheries revenue during affected years. This is top of the 25 per cent reduction expected by the mid-21st century due to long-term climate trends.

Some other fish stocks are projected to increase due to climate change and extreme heat events, but not enough to offset the losses. On a global scale, the impact of is expected to cost about three percent of global fishery revenue per year (on average) and about two percent of all fishery jobs. 

“These extreme annual temperatures will be an additional shock to an overloaded system,” said lead author Dr. William Cheung, professor and director of UBC’s Institute for the Oceans and Fisheries (IOF). "These temperature extremes are often difficult to predict in terms of when and where they occur, particularly in the hot spots with limited capacity to provide robust scientific predictions for their fisheries. We need to consider that unpredictability when we plan for adaptations to long-term climate change."

Potential adaptations include cutting catch quotas in years when fish stocks are suffering from extreme temperature events, or, in severe cases, closing affected fisheries so that stocks can rebuild. “We need to have mechanisms in place to deal with it,” said Cheung.