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.

Global fishing activity (hours) through April 28th, 2020, relative to the previous two-year average, displayed for the periods before and after the March 11th WHO declaration of the COVID-19 pandemic. Click to enlarge. Image courtesy of Global Fishing Watch.

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.

Fishing activity in China’s exclusive economic zone for 2018-2020 is plotted relative to the date of Chinese New Year in each year. In 2020, the holiday occurred on January 25. The steep drops seen in 2018 and 2019 correspond with the start of the annual fishing moratorium. Click to enlarge. Image courtesy of Global Fishing Watch.

In India, too, restrictions due to COVID-19 have added more no-fishing days to the country’s calendar. Every year, the country executes a two-month annual fishing ban that starts in April on the east coast and June on the west coast. But this year, a 21-day nationwide total lockdown, announced on March 24, led to an extension of the ban that fishers weren’t ready for. “On the east coast, they’ve lost about 20 days of active fishing that otherwise would be there,” because of the pandemic, said Yugraj Yadava, director of the Bay of Bengal Programme Inter-Governmental Organisation in Chennai, India. “So, fish catch will definitely be down.”

Similarly, in European countries like Italy, Spain and France, the pandemic led to weekly fishing activity within the countries’ EEZs dropping by up to 50% between March and April relative to the previous two-year average, according to GFW.

How marine life will respond to this sudden removal of fishing pressure, though, depends on several factors, experts say. These include the species’ life history traits, whether the species breed during these months, and how heavily they are usually fished. For example, studies on the impacts of marine reserves, where fishing is banned, show that slow-growing, long-lived species like cod take a long time to recover. Fast-growing, short-lived species like scallops respond more quickly. Similarly, overexploited species could rebound when fishing, the main cause of their decline, is removed.

“If your harvest each year is small, and you fish a little bit less, it’s not going to make much difference,” Hilborn said. “But in places like China, India or Southeast Asia, where a net is passing over every square meter of ground several times a year, there could be much more of a result.”

How long fishing restrictions will last is still unclear. But in countries like the Philippines, where most fishing grounds are heavily overfished, short lockdowns may not affect fish much, even if fishing is significantly reduced, said Jonathan Anticamara, a professor at the University of the Philippines. “Considering the life history of most targeted fish, they would require more than a month to increase their populations,” he said.

Even if marine species start recovering during the lockdown period, the benefits may not last very long.

“The good effects will be limited if fishing pressure builds up again soon,” said Daniel Pauly, a marine biologist and principal investigator with the Sea Around Us project at the University of British Columbia. “And yes, there will be a surge of fishing because it will be more profitable for a very short time.”

The COVID-19 outbreak could have other unintended consequences. For example, consumers are purchasing more non-perishable foods to stock up their pantries, which has increased demand for canned products like tuna and herring, said John Tanzer, WWF International’s oceans practice leader. This could increase the risk of overfishing in already poorly managed fisheries, he added.

Some conservation groups have another worry: with the movement of people involved in patrolling, at-sea observations, and surveillance at sea and ports restricted along with everybody else, they say that illegal, unreported and unregulated fishing (IUU) could increase. While estimates of IUU remain uncertain, studies suggest that it accounts for tens of billions of dollars’ worth of fish catch annually.

COVID-19 lockdowns and quarantines forced marine conservation group Sea Shepherd to suspend its patrols in Mexico’s upper Gulf of California, for instance, which is home to the last remaining critically endangered vaquita porpoise (Phocoena sinus). The vaquita is down to fewer than 19 individuals, because it frequently becomes tangled in illegal gill nets set to catch totoaba fish (Totoaba macdonaldi), another critically endangered species.

In the Philippines, conservation NGO Oceana reported that between March 22 and 28, more than 500 possibly commercial fishing operators were detected in waters meant only for small boats. In some areas, these vessels were detected more often than the weekly average detections last year.

At-sea observers, meant to monitor fishing activities and keep fisheries more transparent, have been temporarily suspended in several places to reduce the risk of the virus spreading between people. For example, in parts of the Pacific Ocean, purse seiner tuna boats no longer require 100% observer coverage, which some experts worry could lead to an increase in illegal fishing.

Whether IUU will actually increase, though, is tough to estimate, given the clandestine nature of illegal fishing and the difficulty of detecting it. “My opinion is that the [COVID-19] risk will have very small impacts on the magnitude of IUU in many areas because the illegal nature of the business will probably be just maintained,” Anticamara said.

At this point, experts can only make educated guesses about how reduced legal fishing could affect marine life. The actual extent of COVID-19 impacts — dependent on data collected at sea, on shore, at markets, and from satellite monitoring — will likely emerge only after several months or years. “You can expect lots of scientific papers on this topic later this year or next year,” Pauly said.

Unlike during World War II, decreased fishing due to the coronavirus outbreak looks short-term for now. “But the reduction of fishing is more widespread — I don’t know how that will affect fish stocks,” Hilborn said.

Overall, the COVID-19 pandemic has created huge disruptions within the fishing industry. At the same time, it’s presented a unique, unintentional opportunity to study how marine life reacts to a break from fishing.

“While we are concerned about the impacts on people, we also see [the COVID-19 pandemic] as a time to learn more about the fisheries,” Tim McClanahan, senior conservation zoologist at the New York-based NGO Wildlife Conservation Society, told Mongabay. “These types of unplanned changes in human behavior are very insightful into the impacts that we have on fisheries and can lead to better understanding and hopefully improved management in the future.”

Banner image: Fishing boats of small-scale fishers in Tamil Nadu, India. Image by Shreya Dasgupta.


Beare, D., Hölker, F., Engelhard, G. H., McKenzie, E., & Reid, D. G. (2010). An unintended experiment in fisheries science: A marine area protected by war results in Mexican waves in fish numbers-at-age. Naturwissenschaften97(9), 797-808.  doi:10.1007/s00114-010-0696-5

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