Dol­phins take ‘risks for cheap meal’

Pilbara News - - News - Tay­lar Amonini

Pil­bara dol­phins are prov­ing they are smart lit­tle risk-tak­ers as new re­search shows a small sec­tion of the off­shore mam­mals’ pop­u­la­tion are fol­low­ing fish­ing trawlers for an easy feed.

The Univer­sity of West­ern Aus­tralia’s Dr Si­mon Allen, who com­pleted the re­search as part of his PhD, said some dol­phins were faith­ful, fol­low­ing fish­ing trawlers over days, weeks and years.

“Pre­vi­ous stud­ies have shown that 20-50 dol­phins are ac­ci­den­tally caught in this fish­ery ev­ery year, and that this pop­u­la­tion is iso­lated from coastal bot­tlenose dol­phin pop­u­la­tions,” he said.

“Large num­bers of dol­phins are seen fol­low­ing trawlers, lead­ing to the im­pres­sion that the pop­u­la­tion is large, but this re­search shows that the same dol­phins stay with trawlers and that this can oc­cur again and again over sev­eral years.

“With a smaller dol­phin pop­u­la­tion than ex­pected, th­ese new find­ings should be used to as­sess the pop­u­la­tion’s con­ser­va­tion sta­tus.”

Ac­cord­ing to con­ser­va­tion ex­perts, the new re­search could in­form fish­eries and wildlife man­age­ment agen­cies as­sess­ing the im­pact of fish­eries-re­lated mor­tal­ity on dol­phins and other pro­tected and en­dan­gered species.

The pop­u­la­tion size es­ti­mate, based on an aerial sur­vey, sug­gests be­tween 2000 and 5000 bot­tlenose dol­phins use the area trawled by the com­mer­cial fish­ery off WA’s Pil­bara coast.

Boat-based re­search also in­di­cated some dol­phins re­peat­edly fol­lowed the trawlers around dayin, day-out, feed­ing on in­jured or dis­carded fish.

“The ten­dency for the dol­phins to ex­ploit the trawlers as a risky but ef­fi­cient means of scor­ing a meal on a re­peated ba­sis is prob­lem­atic for fish­eries man­age­ment, as dol­phin for­ag­ing tra­di­tions tend to be handed down from one gen­er­a­tion to the next,” Dr Allen said.

“As long as the trawlers are fish­ing, the dol­phins will be there, tak­ing big risks for a cheap meal.”

Pro­fes­sor Neil Lon­er­a­gan, se­nior au­thor and pro­fes­sor of ma­rine ecol­ogy and con­ser­va­tion at Mur­doch Univer­sity, said the data was pre­lim­i­nary, but crit­i­cal.

“This re­search pro­vides the much-needed ba­sis for as­sess­ment of the level of im­pact that dol­phin cap­ture has on the pop­u­la­tion,” he said.

Pic­ture: Si­mon Allen/MUCRU

Bot­tlenose dol­phins in Shark Bay.

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