Global warming proves a good thing for scallops ... for now

A little ocean warming is proving to be a good thing for scallops in British waters, scientists have found — but continued warming could reverse that benefit.

According to a study published in the journal Marine Biology, warmer oceans around the UK have led to increased stocks of the great scallop Pecten maximus and a boost for a £30m industry. However, researchers warn that further rises in water temperatures could have the opposite effect on scallops, meaning these fisheries must be better managed to protect sensitive seabed habitats.

The findings stem from an analysis of 20 years of data by scientists at Bangor University and the Universities of York and Liverpool.

“It’s great to provide some good news about one of our fisheries for a change,” said Bryce Beukers-Stewart, a researcher with the University of York’s environment department. “However, scallop fisheries are difficult to manage and have a history of boom and bust around the world.”

He continued, “We must ensure this valuable resource is fished in a way that maximises yields and reproduction to ensure healthy stocks in the future.”

“Temperature can be a strong driver of growth and reproduction in scallops, and this was expressed across almost two decades of ocean warming,” added Samuel Shephard, who led the analysis and is now at the Galway-Mayo Institute of Technology. “It was disconcerting to see first-hand how climate change may affect important fisheries.”

The study focused on the scallop fishery around the Isle of Man, which has been surveyed since 1990. It found that numbers of young scallops each year were, on average, positively related to water temperature in the spring when they were spawned. The gonads of adult scallops were also larger, indicating higher egg production, in warmer years.

While the research suggests that climate change is helping support scallop populations they face other pressures, including dredging on sensitive seabed habitats.

“The scallop industry in the UK has the potential to be even more valuable in the future, but this will only happen if European and national legislation is introduced to control effort and to deal with the issue of latent capacity in the fleet,” said Mike Kaiser, from the School of Ocean Science at Bangor University. “These climate-related benefits could easily be erased by an uncontrolled increase in landings and fishing activity.”

A continued growth in ocean temperatures and greenhouse gas emissions, raising the acidity levels of the water, could also eventually affect the ability of scallops to form proper shells and cause widespread mortality.