Our Ethnic Segregation Is Killing Sharks

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A study of social networks in a Hawaiian tuna fishery suggest that ethnic barriers hamper the spread of shark-saving practices.

By Nathan Collins


(Photo: Conal Gallagher/Flickr)

Reducing racial and ethnic segregation has some clear societal benefits, and it’s a pretty reasonable goal in and of itself. But according to a new study, breaking down barriers between ethnic groups could also do a lot to improve environmental sustainability, at least in tuna fishing communities in Hawaii.

The tuna industry is well known for being less than kind to sea life, primarily because of what’s called bycatch, where vast nets or “longlines”— lines that comprise hundreds of individual fishing hooks—unintentionally catch sea turtles, sharks, and other animals. But a surprising amount of that bycatch, including perhaps 46,000 sharks between 2008 and 2012, might have been prevented had there been better communication between ethnically divided groups of fishers in Hawaii, James Cook University research fellow Michele Barnes and his colleagues report today in Proceedings of the National Academy of Sciences.

The researchers began their study by interviewing 145 fishers who either owned or captained one of the fishery’s 121 boats, which bring in between $65 and $94 million each year. Those interviews revealed social networks that broke down on sharply ethnic lines. Three main groups are represented—Vietnamese Americans, European Americans, and Korean Americans—and contacts between those groups is generally quite limited. Only six fishers, the team found, had a majority of contacts outside their ethnic group, and only one had an equal number of contacts within and without his group.

Breaking down barriers between ethnic groups could also do a lot to improve environmental sustainability.

What’s more, there were substantial differences in the shark bycatch among the three main groups—after controlling for when and where the three groups tended to fish and how big their boats were, white fishers tended to catch fewer sharks than the other two groups. That, Barnes and his colleagues argue, hints that if fishers shared more information across ethnic boundaries about how to avoid sharks, more sharks could be saved without affecting tuna catches. (Incidentally, it’s not entirely clear why white fishers are catching fewer sharks, but interviews suggested that they may communicate more about shark sitings and cooperate to avoid catching sharks.)

Further evidence comes from the seven atypical fishers who had contacts across ethnic groups. Two in particular were of interest, one a European American with closer ties to Korean-American fishers, and another a Korean American with closer ties to European Americans. The former had a shark bycatch rate very close to the overall rate for Korean Americans, and the latter had a rate very close to the overall rate for European Americans.

“In other words, our results suggest that social affiliations are indeed tied to fishing behaviors that can have a direct impact on ecosystems,” the authors write. “If there were more ties across ethnic groups and fishers chose to act on the information accessed through those ties—specifically, how European American fishers manage to encounter and trap fewer sharks—interactions with ∼46,339 sharks might have been avoided, representing an estimated 12% annual reduction in overall shark bycatch in Hawaii’s longline tuna fishery alone.”