Within seconds of being hauled onto the Shen Lain Cheng, a 79-foot tuna fishing boat from China, the crew’s most senior member, whose deeply wrinkled face conveys more than his 58 years, is plunging a T-handled spike between the glistening eyes of a 100-lb yellowfin tuna. The hope is that the swift death has minimized the release of lactic acid, which degrades the flesh meat and reduces the crew’s chances of earning a grade-A for this fish once it is offloaded back at port in Koror, Palau, a small island nation in the Pacific Ocean.
He quickly eviscerates the taut, silvery fish, pulling out an assembly of organs that look like something from another planet. He removes the heart and stomach – the scavenged parts that will likely go into tonight’s crew dinner – and tosses the rest of the guts overboard before flushing the carcass with running water, sewing up its gaping mouth, and placing it into the icy waters of the boat’s cold storage tank.
If the buyers back in Koror, who inspect and score the quality of each tuna’s meat, give it a high grade, this particular tuna could net around $2,800 wholesale in Japan, where it will be resold at great profit in a sushi restaurant.
It all looks like a typical day of tuna wrangling on the high seas, except that it’s not. Aboard are Lotus Vermeer, who manages the Pacific tuna program for The Nature Conservancy (TNC), a US-based environmental organization. Also aboard are Michael Musyl, principal scientist of the Pelagic Research Group in Hawaii and a shark expert, and Ivan Sesebo, a tuna fishery observer, who works for an auditor hired by the boat’s owner, Hong Kong-based Luen Thai Fishing Ventures, to ensure compliance with fishing regulations.
This trio is executing an experiment, funded by TNC’s Indo-Pacific Tuna Program, to test whether changing the designs of the hooks and other fishing practices could reduce the amount of bycatch – species that are unintentionally caught and often include sharks, turtles, reef fish and other threatened or endangered species – without also reducing the tuna catch, thereby keeping the business financially lucrative for fishing companies.
While many US fisheries have enacted rules meant to limit bycatch, what happens in Palau and other rich fishing grounds has a close connection to the diet of many Americans, because the US imports nearly 90% of seafood consumed.
A radical approach
Bycatch takes a financial toll on fishermen. Unwanted fish take up hooks on lines and require crew to spend time hauling and safely releasing the catch. Some fishermen keep bycatch illegally, cutting off fins to sell on the lucrative black market for shark fin soup. Some bycatch doesn’t survive, and its absence could upset the balance of a marine ecosystem already under threat from climate change and pollution.
However, asking commercial fishermen to experiment with new equipment, which may prove ineffective and costly, requires strong incentives.
TNC got creative to get itself onto an actual tuna boat, bopping along five degrees north of the equator and 133 degrees east of the prime meridian, in waters that the Western and Central Pacific Fisheries Commission (WCPFC) estimates generates 60% of the world’s tuna catch that amounts to a $7bn annual market.
Working with Palau’s government, TNC purchased the fishing rights and offered them to Shen Lain Cheng in return for an opportunity to carry out Vermeer’s experiment. They also tag sharks and other bycatch to track their movement after being released to see if they survive.
However, asking commercial fishermen to experiment with new equipment, which may prove ineffective and costly, requires strong incentives.
TNC got creative to get itself onto an actual tuna boat, bopping along five degrees north of the equator and 133 degrees east of the prime meridian, in waters that the Western and Central Pacific Fisheries Commission (WCPFC) estimates generates 60% of the world’s tuna catch that amounts to a $7bn annual market.
Working with Palau’s government, TNC purchased the fishing rights and offered them to Shen Lain Cheng in return for an opportunity to carry out Vermeer’s experiment. They also tag sharks and other bycatch to track their movement after being released to see if they survive.
Hooked on an idea
Studies have shown that switching from the traditional J-shaped hook to a circular hook, or using fish bait instead of squid bait, can reduce the likelihood of catching non-target species on tuna boats.
“Turtles tend to get hooked less often when the bait is a fish, which falls apart as they gum it, whereas with squid they have to chomp the whole thing,” Vermeer explains. “And if it does get hooked, the types of hooks we’re using, called circle hooks, tend to hook in the mouth, whereas an older type of hooks called J-hooks tend to hook turtles deeper, in the esophagus, which is associated with higher mortality.”
Research has so far failed to reveal a silver bullet combination that can minimize bycatch for any species. Until now, there have not been any trials designed to tease out the optimal type of hook and bait that would reduce bycatch of the most vulnerable species without also reducing a boat’s tuna haul for a specific fishery in a specific part of the ocean.
Luen Thai, like many boats fishing for sushi-grade tuna, uses the longline fishing technique, in which thousands of baited hooks are attached to a single, long line stretching up to 25 miles. The setup generates a significant amount of bycatch, though determining exactly how much is difficult for many reasons, including poor, incomplete or inaccurate reporting by many fisheries.
Still, data collected by the United Nations Fisheries and Agriculture Department indicates that tuna longlining produces an amount of bycatch second only to shrimp trawling, while another fishing technique called purse seining – in which schools of small tuna species (mostly for canning) are scooped up in massive nets – generates far less bycatch than longlining. A recent study in the science journal Aquatic Conservation found that bycatch from tuna longline fishing in Palau accounts for a third of all hooked species, so the potential for improvement in this fishery is significant.
Using circle hooks has also shown to reduce incidental hooking of stingrays. Other research has revealed that circle hooks and fish bait can actually lead to hooking more sharks. The truth is more complicated and nuanced, explains Eric Gilman, a professor at Hawaii Pacific University and a fishing industry consultant commissioned by TNC to help design the study on the circle hooks. Sharks migrate, so they reach certain age and size in different parts of the ocean, and those changes could make them more susceptible to being caught by circular hooks of particular sizes.
From there, scientists will be able to study data showing the ages and migration patterns of sharks in different pockets of the western and central Pacific and determine which hook sizes are best to use (and those to avoid) throughout the year. For the bait experiment, the hook variability will be removed, and the type of bait will be alternated between squid and fish to examine the link between bait and bycatch.