Fish­er­men, lend us your ear bones

Western Suburbs Weekly - - Workplace - By JON BAS­SETT

FISH skele­tons with in­ter­nal and sex or­gans at­tached are vi­tal to Depart­ment of Fish­eries pink snap­per re­searcher Brett Cirisa­fulli, who is mon­i­tor­ing the an­nual metropoli­tan spawn­ing of the prized species start­ing soon.

“But we want frames, or skele­tons, from the whole west coast to look at the ef­fect of cur­rent fish­ing pres­sures, chang­ing bag lim­its and sea­son clo­sures of Cock­burn and Warn­bro sounds, and new boat li­cence rules, which all have been in­tro­duced to man­age these stocks,” Mr Cirisa­fulli said.

Since 2010, the sounds’ spring-sum­mer breed­ing ag­gre­ga­tions of pink snap­per have been pro­tected with a fish­ing ban be­tween Oc­to­ber 1 and Jan­uary 31, and fish­ers are lim­ited to tak­ing two fish longer than 50cm at any other time.

The re­searchers use the skele­tons to col­lect fish ear bones, known as otoliths, in which tree trunk-like growth rings can be counted to find fishes’ ages.

The bones are chem­i­cally an­a­lysed to find out where the fish have lived, and while recre­ational and com­mer­cial fish­ers have al­ready do­nated about 300,000 fish ear bones from sev­eral species, the re­searchers still need about 500 just to de­ter­mine a range of ages in any fish pop­u­la­tion.

They have re­sorted to search­ing through skip bins for skele­tons in the past, but in the lab­o­ra­tory their work is de­tailed and spe­cialised.

“Each tiny ear bone is set in resin to stop it chip­ping, sliced thinly into a cross-sec­tion with a diamond cut­ter and placed un­der a mi­cro­scope, with the im­age pro­jected on to a com­puter screen,” Depart­ment of Fish­eries re­search ex­ec­u­tive di­rec­tor Rick Fletcher said.

Visit www.fish.wa.gov.au/frames, or call 9203 0111.

Fish ear bones are a key tool for pink snap­per re­searcher Brett Cirisa­fulli.

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