NET BEN­E­FITS FOR FISH­ERIES ARE ALSO NOT WELL UN­DER­STOOD

Scuba Diver Australasia - - Feature: The Ups And Downs Of Marine Protected Are - www.mongabay.com

In the­ory, MPAs, par­tic­u­larly those that are closed off to all or most fish­ing, can al­low over­fished species to ma­ture undis­turbed and pro­duce more off­spring. The off­spring can then swim over the in­vis­i­ble bound­aries to ad­ja­cent fished ar­eas and pro­vide big­ger catches and more money for fish­ers. In­deed, as men­tioned, a good body of re­search sug­gests that species tar­geted by fish­ers of­ten do re­spond well to pro­tec­tion. But do more and larger fish in­side a pro­tected area re­ally mean higher catches out­side its bound­aries?

One sys­tem­atic re­view pub­lished in 2016 found ev­i­dence of spillover in 80 per­cent of its stud­ies. But the re­searchers added a caveat: “[Twenty] per­cent of re­main­ing stud­ies that failed to pro­vide any ev­i­dence of spillover is likely to be un­der­es­ti­mated …be­cause of pub­li­ca­tion bias in ecol­ogy, and specif­i­cally in ma­rine pro­tected area sci­ence,” where pos­i­tive re­sults are favoured, they wrote.

But even if there is some spillover, is it enough to com­pen­sate for re­duced fish­ing ar­eas with in­creased fish­ing pres­sure and thus pro­vide a net ben­e­fit to fish­ers?

Mongabay’s re­view cap­tured only one em­pir­i­cal study that looked at this, bear­ing in mind that their re­view and search terms were not ex­haus­tive. This study, pub­lished in 2001, found that the biomass of five com­mer­cially im­por­tant fish fam­i­lies in­creased both in­side and out­side ma­rine re­serves in the Caribbean is­land of St. Lu­cia within three years of estab­lish­ment. More­over, the fish catch in­creased sub­stan­tially – by be­tween

46 and 90 per­cent, de­pend­ing on the type of traps the fish­ers used.

The re­sults of this sin­gle study can­not be gen­er­alised, of course, and ex­perts have noted that while there are some em­pir­i­cal stud­ies look­ing at how MPAs af­fect fish­eries, most of them are not rig­or­ous and their con­clu­sions are mixed.

For ex­am­ple, a 2013 study found that fish­ers who worked near the Goukamma MPA in South

Africa saw a nearly steady in­crease in the catch of com­mer­cially im­por­tant Ro­man seabream

(Chrysoble­phus lat­i­ceps) over the 10 years since the park’s estab­lish­ment in 1990.

By con­trast, in a 2000 study from Kenya, re­searchers found that while the cre­ation of a no-take MPA had led to some spillover, the fish catch was lower than it was be­fore the park’s cre­ation halved the avail­able fish­ing area. Sim­i­lar re­sults were found in Aus­tralia’s Great Barrier Reef.

Most pos­i­tive ex­am­ples come from MPAs that are ei­ther very small (so the fish­ers lose only a small amount of their pre­vi­ous fish­ing area), or from parks lo­cated in ar­eas where fish stocks are se­verely over­ex­ploited, said the Univer­sity of Wash­ing­ton’s Ray Hil­born.

Halpern agreed that the ben­e­fits of MPAs on fish­eries are very con­text-de­pen­dent and tra­di­tional man­age­ment tech­niques, such as sea­sonal fish­ing clo­sures or re­stric­tions on cer­tain kinds of fish­ing equip­ment, some­times come out ahead.

“In de­vel­oped coun­tries and large stocks, tra­di­tional fish­eries man­age­ment has been very ef­fec­tive, es­pe­cially more re­cently,” he said. “In de­vel­op­ing na­tions and highly di­verse fish­eries – as is the case with many co­ral reef fish­eries in trop­i­cal coun­tries – tra­di­tional fish­eries man­age­ment has not been as ef­fec­tive and ma­rine pro­tected ar­eas are of­ten a much more ef­fec­tive and vi­able strat­egy. But there are many coun­terex­am­ples and other is­sues in play – in other words, con­text mat­ters.”

“Over­all, I am sat­is­fied with the re­search that is be­ing done to see the eco­log­i­cal ef­fec­tive­ness of ma­rine pro­tected ar­eas. I think it’s use­ful to keep study­ing that – how things change with time and pro­tec­tion,” Ban said. “But I do think we need a lot of em­pha­sis on the hu­man el­e­ment: to what ex­tent ma­rine pro­tected ar­eas af­fect hu­man well-be­ing for coastal com­mu­ni­ties that rely on the oceans for their liveli­hoods.”

Over­all, I am sat­is­fied with the re­search that is be­ing done to see the eco­log­i­cal ef­fec­tive­ness of ma­rine pro­tected ar­eas. I think it’s use­ful to keep study­ing that how things – change with time and pro­tec­tion Natalie Ban

ABOVE A fish­er­men cast­ing his net

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