Research by the University of British Columbia (UBC) has shown that fish stocks are more resilient to the effects of marine heatwaves than many previously thought, but this hardiness won’t save them from the effects of climate change.
Marine heatwaves are a period of abnormally high temperatures in certain areas of the ocean, which can last anywhere from a few days to almost two years, as was seen when “The Blob” warmed a large swath of the Pacific Ocean from late 2013 into 2015. Marine heat waves can have devastating effects, such as the bleaching of coral reefs and the growth of harmful algae blooms.
Based on data taken from 1993 to 2019 in both the Atlantic and Pacific Oceans, William Cheung, a professor at the University of British Columbia’s Institute for Oceans and Fisheries, has conducted research that he said shows the relationship between marine heatwaves and fish stocks is more complicated than was once thought.
“What we find, to our surprise, is that we didn’t find a statistically significant relationship between marine heatwaves and decreasing biomass. What that means is the effects are quite variable between species and different locations and time, as well,” said Cheung. “It also highlights that maybe we are still at a time where there is still some buffering capacity of the fish populations there.”
One conclusion Cheung has drawn from the UBC study is that from 1993 to 2019, marine heatwaves have become more and more common.
“In the last 15 years, there has been an increasing frequency and intensity of marine heatwaves,” said Cheung.
This trend, which the study said ties directly into global climate change, indicates that this rising frequency and intensity of marine heatwaves will only get worse with time. While fish stocks thus far have shown a surprising resistance to their effects, the study cautions that marine life, which has a lower tolerance to warming than life on land, will eventually begin to succumb to the longer and warmer heatwaves to come.
“The impacts are inconsistent, but by increasing the frequency, you increase the impacts,” said Cheung. “In a previous study I led, I used computer simulation models to provide theoretical expectations of how marine heatwaves would impact fish stocks around the world. It shows significant effects in very high-emission scenarios. That relates to my earlier point that there may still be some buffering capacity of the fish stocks to the heatwaves that we’ve seen. But, looking into the future, if we continue with climate change which will increase the frequency and intensity of marine heatwaves, particularly in high emissions scenarios, the effects will become more apparent.”
Cheung said that in the long term, humanity’s only course of action to mitigate these problems is to curb our greenhouse gas emissions. In the short term, he claimed there is a certainty that we will experience more recurrent and strong marine heat waves in the future.
Our only short-term solution, said Cheung, is to develop more robust management measures for fish stocks.
“Better monitoring of the occurrence of heatwaves, so that there could be some warning to both management authorities as well as sectors of people who are dependent on the species to respond to that. For example, reducing fishing mortality because of the potential of the predicted heatwave that may have impacts on the fish stocks,” said Cheung. “Ultimately, mitigation of climate change will be necessary. In the short term, adaptation can buy us some time before the effects of the mitigation can kick in.
