When World War II broke out in 1939, it triggered an unintended fisheries experiment in the North Sea. Fishing vessels stayed away from fear of being blown up by naval minefields and aerial attacks, ships were requisitioned for war, and sailors drafted. With most fishing paused for the next six years, the North Sea, spanning 575,000 square kilometres, or 222,000 square miles, was turned into an accidental marine protected area, researchers wrote in a study published in 2010. The results of the experiment were revealing: previously overexploited fish, such as cod, haddock and whiting, rapidly replenished, their sizes increased, and their catch, immediately after the war, shot up.
Today, there’s another unprecedented fishing pause at play in the oceans.
To curtail the COVID-19 pandemic, countries around the world have constrained people’s movements, which has taken a toll on marine fisheries. Supply chains fragmented, markets closed, fish imports declined, sales dwindled and fewer fishing vessels are reportedly out at sea. For fishing communities and the industry as a whole, this is an exceptional crisis. But could the fishing slowdown give marine life a chance to recover?
This isn’t yet easy to answer with certainty, experts say. To figure out the impacts on fish stocks, experts rely on two kinds of information: the fishing effort, such as the number of hours or days fished or the size of gear used; and the fish catch, such as the amount and size of fish caught. With staff from government agencies, nonprofits and research institutes limiting their movements, field data collection is on pause.
Satellites, however, continue to provide some early clues, especially on who’s fishing where.
Researchers at Global Fishing Watch (GFW), which tracks near-real-time positions of fishing vessels through their onboard automatic identification system (AIS), for example, have observed that between Jan. 1 and April 28, fishing activity around the world, primarily of large industrial vessels, went down by 6.5% compared to the average activity over the last two years. Since March 11, when the World Health Organization declared COVID-19 a pandemic, fishing activity has been down by nearly 10% compared to the 2018-2019 average, according to a recent analysis by GFW.
Zooming in on China, where the COVID-19 outbreak first began and whose fishing fleets form the major chunk of known vessels in GFW’s database, researchers found some distinct patterns linked to the country’s lockdown. Every year, fishing activity in China’s exclusive economic zone (EEZ) goes down around Lunar New Year, which falls in January or February depending on the lunar calendar. After the holiday, fishers head to sea once again.
This year, too, Chinese fleets reduced their activity as the Lunar New Year approached on Jan. 25. But with the country initiating a lockdown in Wuhan on Jan. 23, fishing activity remained low for several weeks instead of climbing steeply after the New Year as it usually does. Between the Lunar New Year and early April, cumulative fishing activity in China’s EEZ had fallen by nearly 40% compared to the average of previous two years for the same time period, GFW’s analysis found, with approximately 1.2 million fewer fishing hours.
The fishing slowdown could have some positive effects on fish stocks, said David Kroodsma, GFW’s director of research and innovation. However, the impacts are unlikely to be dramatic, given China’s usual fishing patterns, he said.
Every summer since 1995, most fishing in China is banned for three to four-and-a-half months beginning in May. Some studies suggest that the ban has increased numbers and sizes of certain fish species, but its long-term benefits remain limited. This is partly because the ban doesn’t cover breeding periods of many commercial species, and fishing after the ban lifts becomes more intense and widespread. In fact, despite the yearly moratorium, continued overfishing has caused the country’s marine fish stocks to decline and spawning grounds to degrade, studies suggest. Whether a few more weeks without fishing, courtesy of COVID-19, could improve overall fish stocks remains to be seen.
It’s going to be an interesting experiment because a number of us have been suggesting that China needs to have another closed period to reduce their overall fishing pressure, said Ray Hilborn, a fisheries scientist and professor at the University of Washington’s School of Aquatic and Fishery Sciences.
2020 Copyright Conservation news