Caught by Accident: Global Hotspots of Unintended Catches

By Carl Safina and Rebecca Lewison

“Still alive, mon!” Trinidadian fisherman attempts to free a leatherback turtle tangled in his net. Photo: Carl Safina
“Still alive, mon!” Trinidadian fisherman attempts to free a leatherback turtle tangled in his net. Photo: Carl Safina

You might have heard that fishing gear accidentally catches sea animals that fishermen are not trying to catch. Certain nets set for mackerel and lines set for swordfish catch leatherback turtles; lines set for tuna catch sea turtles in some places, albatrosses in others. But what’s the big picture of who catches what where? No one could say—until now.

A team of scientists from Duke University Marine Lab and San Diego State University spent several years chasing down, assembling, and analyzing maddeningly scattered information of incidental catches in fisheries data worldwide. This research team put together a global picture of catches of seabirds, sea mammals, and sea turtles in three main types of fishing gear (gillnet, trawl and longline) in all oceans for many nations. We were part of the team, with Rebecca leading in assembling the final work. That study has just been published.

The scientific team found that there are ocean “hotspots,” areas where incidental catch is high across the board for all animals that we tallied; sea turtles, marine mammals and seabirds. The synthesis includes data for more than 50 different species of air-breathing marine animals. Based on existing data, the maps highlight hotspots of incidental marine mammal catches in the eastern Pacific and the Mediterranean, prevalent sea turtle incidental catch areas in the southwest Atlantic, eastern Pacific and Mediterranean oceans, and highest levels of seabird kill in fisheries in the southwest Atlantic and Southern Indian oceans.

But the global maps tell us more than species hotspots because the incidental catch picture isn’t just about individual species, caught by a single gear in a single place. It’s really about the current health and future of our oceans. By removing marine wildlife, we may be compromising the ability of ocean systems to function as we’ve known them.

The good news is that several strategies already exist to prevent unintended catch. For example, by varying the depth at which lines and nets are deployed, by using specially designed lures and hooks, and by employing excluder devices, and by ultrasonic sound-emitting “pingers” to alert marine animals to the presence of fishing gear, some fisheries have increased target catch and reduced unintended catch. Fishermen from many countries have also developed new fishing practices that have dramatically reduced unwanted catches. But these measures aren’t used everywhere. Promoting the use of strategies to reduce unintended catches is only part of the solution, according to the study’s authors. Community engagement is key in many poorly-regulated, small-scale fisheries.

As long as we have a fishing industry, we’re going to have to work to minimize non-target catch. Fishing nations need to work together to report and reduce unintended catches of unwanted sea animals. No single country can fix this.  We need to use the best-available science, fishing technology and innovative management strategies to link conservation action with sustaining human livelihoods and a commitment to protect the ocean environment.