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To catch prized tuna and swordfish, fishing boats crisscross the world’s oceans casting miles-long lines with baited hooks into waters far offshore, an appealing lure to not only large fish but also seabirds looking for an easy meal. This practice, called longline fishing, accidentally drags to their deaths each year, contributing to the rapid decline of species.

It’s a significant problem with a relatively easy fix, conservation advocates say. Studies show that avian bycatch deaths drop by when vessels use well-known prevention tactics, including setting lines at night when birds aren’t feeding. While the vast majority of crews report doing exactly that, plummeting albatross populations suggest otherwise. That’s why seabird biologists paired up with data scientists at Global Fishing Watch, a nonprofit that tracks vessel location using information from satellite-synced transponders, to figure out what’s really happening on the water.

A team led by David Kroodsma, the group’s director of research, mapped out the movements of 300 boats from Japan and Taiwan—nations that have large longline fleets—in the southern Atlantic, Indian, and Pacific Oceans. They then used image-reading software and algorithms to categorize activities by each vessel’s direction and speed. From there, they extrapolated the time of day the lines were being cast and shared the intel with avian experts. “This is our first time seeing what’s happening on the boats. It’s quite exciting,” says Stephanie Prince, a biologist and project manager with Royal Society for the Protection of Birds’ Albatross Task Force.

The findings were more unnerving than she and Kroodsma expected. The analysis revealed that while 85 percent of vessels claimed they set lines at night, less than 15 percent did. Worse, most cast around dusk and dawn. Though data are limited, research shows these are key foraging times for seabirds in the area. For example, a recent study by Japan’s Fisheries Research Agency found the bycatch rate of 12 albatross (and three petrel) species started spiking the hour before sunrise.

The pattern spells ­particular trouble for species such as the , which breeds on South Georgia ­Island near Antarctica—an area frequented by Japanese and Taiwanese fleets. Prince saw the gruesome repercussions firsthand while doing fieldwork there. “Sometimes you’d find albatrosses with hooks through their faces,” she says.

While require boats in the area use two of three options to protect albatrosses—night ­setting, bird-­scaring streamers, or ­weighted lines—these mandates stop short of actual enforcement. As Kroodsma puts it, improved ­accountability is the first step to ensuring longline fishers actually take steps to protect seabirds. “The results from our study are discouraging but also encouraging,” he says. “We really need transparency, otherwise none of this stuff will work.”

In October, Prince to Australia, Indonesia, and the six other countries in the Commission for the Conservation of Southern Bluefin Tuna, which manages the region’s fishery. The Albatross Task Force hopes to work with the member nations to implement bird-friendly tactics on boats. Global Fishing Watch, meanwhile, plans to use its algorithm in other pelagic fisheries. Each satellite coordinate can reveal a story far from shore—one that could make a night-and-day difference for albatrosses.

This story originally ran in the Summer 2019 issue as “Hooked on the High Seas.” To receive our print magazine, become a member by .