C O N S E R VAT I O N

Marlin - - CONTENTS - BY JA­SON SCHRATWIESER, CON­SER­VA­TION DI­REC­TOR, IGFA

Open-ocean oa­sis or quag­mire?

As beau­ti­ful as it is, the open ocean is a bar­ren place that is largely de­void of struc­ture, and any piece of float­ing de­bris — big or small, nat­u­ral or man­made — is, at times, ca­pa­ble of at­tract­ing a stag­ger­ing di­ver­sity of ma­rine crit­ters.

For this rea­son, fish and an­glers alike are drawn to weed lines, cargo pal­lets, and every con­ceiv­able man­ner of flot­sam and jet­sam. And for cen­turies, in­dus­tri­ous hu­mans have been con­struct­ing fish ag­gre­gat­ing de­vices to con­cen­trate and har­vest fish. As early as the 17th cen­tury, Mediter­ranean an­glers con­structed FADs that were an­chored to the seafloor in rel­a­tively shal­low wa­ter. To­day, moored FADs can be de­ployed in depths of more than 2,000 me­ters, and over the past sev­eral decades, free-float­ing or drift FADs have col­o­nized the open ocean.

Com­mer­cial fish­er­men de­ploy the vast ma­jor­ity of FADs, and it is es­ti­mated that more than 120,000 drift FADs were de­ployed in 2013 alone. The purse seine FAD fish­ery has be­come a global is­sue be­cause it leads to the over­har­vest of ju­ve­nile yel­lowfin and big­eye tuna that con­gre­gate in large num­bers around FADs.

Recre­ational bill­fish an­glers are also big into the FAD game now. In the past sev­eral decades or so, FAD-as­so­ci­ated bill­fish hot spots have popped up in places like Costa Rica, the Do­mini­can Repub­lic and oth­ers that are re­port­ing amaz­ing num­bers of mar­lin raised and caught. The so­cial im­pli­ca­tions of these fish­eries have been a com­mon topic of late. Some equate fish­ing around FADs to shoot­ing fish in a bar­rel, while oth­ers con­tend that FADs have the abil­ity to greatly shorten the learn­ing curve for both an­glers and crew.

Whether or not you like to fish around FADs, they can have some neg­a­tive im­pli­ca­tions on recre­ational bill­fish fish­eries. A re­port writ­ten for the FAO by bill­fish ex­perts at the Univer­sity of Florida work­ing on a re­gional bill­fish con­ser­va­tion and man­age­ment project in the Caribbean in­di­cates that recre­ational and com­mer­cial bill­fish catches made in as­so­ci­a­tion with FADs mud­dle catch-per-unit ef­fort in­dices, which are used by sci­en­tists to es­ti­mate bill­fish abun­dance. The prob­lem is that FADs have the abil­ity to ac­cu­mu­late bill­fish biomass in­de­pen­dently of true stock abun­dance. That is, catch rates as­so­ci­ated with FADs can re­main sta­ble, or even be­come el­e­vated, as true stock abun­dance ac­tu­ally de­creases. In this “il­lu­sion of plenty,” un­nat­u­ral den­si­ties of bill­fish are mis­taken for a healthy stock, which can lead to im­proper man­age­ment.

Moored FADs are widely used in the Caribbean by fish­er­men tar­get­ing tuna, mahimahi and other pelagic species. Un­for­tu­nately, they also in­cur high lev­els of bill­fish by­catch. In the FAD fish­ery off Mar­tinique, bill­fish ac­count for up­wards of 51 per­cent of fish com­mer­cially landed, and it’s es­ti­mated that the ma­jor­ity of blue mar­lin landed in the east­ern Caribbean comes from FAD-as­so­ci­ated fish­eries.

FADs in the Caribbean have also sparked a bit of a turf war in some ar­eas: Heated dis­putes, some­times ap­proach­ing phys­i­cal­ity, have erupted over who has the right to fish a given FAD. Mar­lin hi­jack­ings are also be­com­ing more com­mon­place, where dis­grun­tled com­mer­cial an­glers “com­man­deer” bill­fish that are be­ing fought or re­leased by recre­ational an­glers.

So, like ’em or not, there’s more at stake with FADs than whether you con­sider them sport­ing. Even well-in­ten­tioned FADs de­ployed by an­glers for catc­hand-re­lease pur­poses can be found by com­mer­cial fish­er­men who don’t have a mar­lin’s best in­ter­ests in mind. In the end, global bill­fish pop­u­la­tions are not far­ing too well in most places, so it doesn’t make sense to de­ploy FADs in coun­tries where they can be com­mer­cially ex­ploited and where reg­u­la­tory frame­works can’t pre­vent FADs from ex­ac­er­bat­ing the over­fish­ing that’s al­ready oc­cur­ring.

ABOUT THE AU­THOR JA­SON SCHRATWIESER HAS A MAS­TER’S IN MA­RINE ECOL­OGY AND HAS WORKED ON FISH­ERIES IS­SUES FOR 16 YEARS.

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