Can Breaking Down Ethnic Barriers in a Tuna Fishery Prevent Accidental Shark Deaths?

From the mouths of sharks: Humans, please diversify your social circles.

August 03, 2016
A thresher shark Klaus Stiefel/Flickr

When Hawaiian fishermen pull up their anchors and go to work each morning, they don’t thread a worm onto a hook and cast it into the sea. Instead, they unfurl thousands of hooks attached to the same line. These longlines can stretch out for miles, like the barbed tentacles of some great sea beast, indiscriminately snaring any creature with a mouth big enough to bite down on the bait.

Sometimes the lines hit home, hooking a large tuna or swordfish. But all too often they capture other creatures, such as sharks. Shark finning is illegal in these waters, and bringing a whole one to shore isn’t worth the space on the boat. Sharks can also damage fishing equipment and, if still alive, potentially injure whoever tries to unhook them. And obviously, every minute spent repairing line or removing sharks is a minute not spent catching fish that can be sold for profit.

Interestingly, a new study on the Hawaiian tuna fishery has found a correlation between lower shark catches and the social lives of the fishers hauling up the longlines. And as often happens with humans, those social circles have particular ethnic identities. The workforce mostly comprises white, Vietnamese-, and Korean-Americans who usually belong to a fishing network made up of others of the same background. Out of the 159 fishers interviewed for the study (basically all of them), only six worked in a fishing network that didn’t coincide with their ethnic identity.

Turns out, the majority white network brings up slightly fewer sharks per 1,000 hooks a year than the Vietnamese- and Korean-American groups. Now, nobody is proposing that being of European descent makes you a better fisherman. Rather, the researchers think the difference lies somewhere within the network and how the tendency to socialize within one’s group reinforces each network’s fishing behavior, for better or for worse. It’s what sociologists call homophily.

“Our most important finding suggested that it wasn’t ethnicity that was most important for determining rates of shark bycatch at all,” says lead author Michele Barnes, an environmental social scientist at the University of Hawaii and James Cook University. “It was all who fishers were sharing information with—it was their social network.” So, according to the research, published in June in the Proceedings of the National Academy of Sciences, it’s not what you are but whom you’re interacting with that seems to matter most.

You see, those fishermen like to talk. And it turns out the stories they share with one another can contain valuable information. The fishers Barnes interviewed said they gab about what baits are working and where, about lunar and seasonal patterns, and about the locations of particularly sharky waters.

The difference between the networks’ bycatch rates are small but statistically significant; given the thousands of hooks the fishery sends into the sea each year, those shark bodies really start to add up. If everyone fished like the most efficient network, the researchers estimate that over the course of five years, about 46,000 sharks would be spared the experience of a hook in the mouth or death.

“Bycatch is a major threat to shark populations, particularly for those that are already in decline and those with high extinction risk,” says Austin Gallagher, a conservation biologist who has studied how being snagged by a hook or net affects sharks. Unfortunately, many of the sharks most often caught by the Hawaiian longline industry fit this bill. These include blue sharks (near threatened), bigeye threshers (vulnerable), shortfin makos (vulnerable), oceanic whitetips (vulnerable), silky sharks (near threatened), and crocodile sharks (near threatened).

So what is the European-American network doing differently? Surely the other networks and shark conservationists would like to know. “We are just as curious as you are,” Barnes says. The model her team used accounted for multiple variables—vessel length, number of hooks, set location, soak time, temperature, bait, season, moon phase, and technology used—to see what the advantage might be. Nothing stood out, though Barnes hopes a follow-up study may yield more insights.

In the meantime, the team hopes to shake up the cliques through informal community events and workshops. After all, the fishermen may not even realize that their methods might differ, and perhaps when presented with her findings, they’ll get talking—though it might take a while before truly robust communication evolves among the networks. Ethnicities aside, these men are also rivals. Plus, as every high-school freshman knows, making new friends can be scary. But even if the secret to snagging fewer makos and threshers remains a mystery, the study provides an interesting glimpse into how human psychology can affect the world around us—and what good may come if we all just work together and, once in a while, swap some fish stories.


onEarth provides reporting and analysis about environmental science, policy, and culture. All opinions expressed are those of the authors and do not necessarily reflect the policies or positions of NRDC. Learn more or follow us on Facebook and Twitter.

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