Nav: Home

Models may help reduce bycatch from longline fishing

August 08, 2018

DURHAM, N.C. -- Hundreds of thousands of sharks, sea birds and other marine species are accidentally killed each year after they become snagged or entangled in longline fishing gear.

New models developed by a Duke University-led team may help reduce this threat by giving regulatory agencies a powerful new tool to predict the month-by-month movements of longline fishing fleets on the high seas. The predictions should help determine where and when the boats will enter waters where by-catch risks are greatest.

"By comparing our models with data showing where by-catch species are likely to be each month, ship captains, national agencies and regional fisheries management organizations can pinpoint potential hotspots they may want to temporarily avoid or place off-limits," said Guillermo Ortuño Crespo, a doctoral candidate in the Marine Geospatial Ecology Lab at Duke's Nicholas School of the Environment.

"This represents a movement away from a reactive approach to fisheries management -- where we only know about problems as or after they occur -- to a more proactive approach that helps us stay one step ahead of the game," he said.

Ortuño Crespo and his colleagues describe their new models in a peer-reviewed paper August 8 in Science Advances.

To devise the models, they collaborated with Global Fishing Watch to collect geospatial information from individual boats' automatic identification system (AIS) signals. AIS data shows the movements and distribution of longline fishing fleets operating in the high seas in 2015 and 2016.

Then they statistically correlated each ship's fishing efforts to 14 environmental variables -- such as sea surface temperatures or distance to the nearest seamount -- that influence a region's seasonal suitability as a habitat for species targeted by longliners. This allowed them to create highly accurate models that predict where the fishing fleets will be each month of the year.

The new models track data for fleets from Japan, South Korea, Taiwan, China and Spain, which accounts for most of the longline fishing currently taking place in the open ocean beyond national jurisdictions. Future models could include fleets from other nations and offer expanded functionality that will allow regulatory agencies to view the data within a global context or break it down by individual nation, region or fleet.

"If we can provide this level of information, it becomes a highly practical management tool for the agencies charged with managing fishing on the high seas," Ortuño Crespo said.

In longline fishing, hundreds or even thousands of individual fishing lines with baited hooks are hung off a main line that can extend for miles across the sea. Fishermen typically use longline gear to catch swordfish, tuna and other commercially valuable fish that live in the upper depths of the open sea, but the bait also attracts non-targeted marine species such as sharks and sea birds, which get snagged on the hooks or entangled in the lines.

"Blue sharks, mako sharks, oceanic whitetip sharks, thresher sharks and silky sharks are among the species most frequently killed by longlines, and some of them are listed as species of concern on the IUCN Red List of Threatened Species," Ortuño Crespo said. "The industry has made great strides in developing safer gear, but hundreds of thousands of animals are still being killed each year."

Getting the new models into the hands of regulators, industry leaders and policymakers is critical, and time is of the essence, said Patrick N. Halpin, professor of marine geospatial ecology at Duke and a co-author of the study

"Climate change and fishing pressures are the two main drivers of ecological impacts in the open ocean, and there is a possibility that neither of them will be part of United Nations negotiations this September on protecting marine biodiversity beyond national jurisdictions," Halpin said. "Some countries, especially those that do a lot of deep-sea fishing, do not want to include fisheries in the discussions. We hope our findings will help change their attitudes."
-end-
Ortuño Crespo and Halpin conducted the new study with Daniel C. Dunn of Duke; Gabriel Reygondeau and William Cheung of the Nippon Foundation Nereus Program and Changing Ocean Research Unit at the University of British Columbia; Kristina Boerder and Boris Worm of Dalhousie University, and Derek P. Tittensor of Dalhousie and the United Nations Environment Programme's World Conservation Monitoring Centre.

Funding came from the Nippon Foundation Nereus Program and from a Google Earth Research Award.

CITATION: "The Environmental Niche of the Global High Seas Pelagic Longline Fleet," Guillermo Ortuño Crespo, Daniel C. Dunn, Gabriel Reygondeau, Kristina Boerder, Boris Worm, William Cheung, Derek P. Tittsensor and Patrick N. Halpin; Science Advances, August 8, 2018. DOI: 10.1126/sciadv.aat3681

Duke University

Related Sharks Articles:

The private lives of sharks
White sharks are top predators in the marine environment, but unlike their terrestrial counterparts, very little is known about their predatory activity underwater, with current knowledge limited to surface predation events.
Basking sharks exhibit different diving behavior depending on the season
Tracking the world's second-largest shark species has revealed that it moves to different depths depending on the time of year.
These sharks use unique molecules to glow green
In the depths of the sea, certain shark species transform the ocean's blue light into a bright green color that only other sharks can see -- but how they biofluoresce has previously been unclear.
Blue sharks use eddies for fast track to food
Blue sharks use large, swirling ocean currents, known as eddies, to fast-track their way down to feed in the ocean twilight zone.
Hundreds of sharks and rays tangled in plastic
Hundreds of sharks and rays have become tangled in plastic waste in the world's oceans, new research shows.
Baby tiger sharks eat songbirds
Tiger sharks have a reputation for being the 'garbage cans of the sea' -- they'll eat just about anything, from dolphins and sea turtles to rubber tires.
Sand tiger sharks return to shipwrecks off N.C. coast
A study co-led by Duke University reveals shipwrecks off North Carolina's coast are important habitats for sand tiger sharks, whose population plummeted in the 1980 and 1990s.
Sharks more vulnerable than originally thought, new research shows
New study reveals in excess of 2.5 million sharks are caught annually in the South West Indian Ocean - 73% more than officially reported.
Tunas, sharks and ships at sea
Researchers combine maps of marine predator habitats with satellite tracks of fishing fleets to identify regions where they overlap -- a step toward more effective wildlife management on the high seas.
The speedy secrets of mako sharks -- 'cheetahs of the ocean'
To investigate how shortfin mako sharks achieve their impressive speeds, researchers tested real sharkskin samples, using digital particle image velocimetry.
More Sharks News and Sharks Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Rethinking Anger
Anger is universal and complex: it can be quiet, festering, justified, vengeful, and destructive. This hour, TED speakers explore the many sides of anger, why we need it, and who's allowed to feel it. Guests include psychologists Ryan Martin and Russell Kolts, writer Soraya Chemaly, former talk radio host Lisa Fritsch, and business professor Dan Moshavi.
Now Playing: Science for the People

#538 Nobels and Astrophysics
This week we start with this year's physics Nobel Prize awarded to Jim Peebles, Michel Mayor, and Didier Queloz and finish with a discussion of the Nobel Prizes as a way to award and highlight important science. Are they still relevant? When science breakthroughs are built on the backs of hundreds -- and sometimes thousands -- of people's hard work, how do you pick just three to highlight? Join host Rachelle Saunders and astrophysicist, author, and science communicator Ethan Siegel for their chat about astrophysics and Nobel Prizes.