Ear bones no red her­ring

Western Suburbs Weekly - - Western Opinion - By JON BAS­SETT

RE­SEARCHERS want the ear bones from the com­plete skele­tons of fish to de­ter­mine the health of in­creas­ingly pres­sured her­ring stocks in WA.

“To find fish skele­tons and frames in the past we’ve had peo­ple go­ing through skip bins on wharves in the South-West in the dark with torches,” Depart­ment of Fish­eries se­nior re­search sci­en­tist Kim Smith said.

Do­nated skele­tons of pop­u­lar species, in­clud­ing her­ring, pink snap­per and dhu­fish, must have their in­ter­nal and sex or­gans if they are to be use­ful to the depart­ment’s Send Us Your Skele­tons pro­ject.

Dr Smith said re­search had in­di­cated that be­fore new mea­sures to pro­tect the species, up to 75 per cent of her­ring, which now have a daily bag limit of 12 fish, had been caught be­fore reach­ing ma­tu­rity and their first spawn­ing at about 3-4 years.

“It may be a com­bi­na­tion of over­fish­ing and en­vi­ron­men­tal fac­tors, in­clud­ing the higher wa­ter tem­per­a­tures we have been record­ing, be­cause you have to re­mem­ber her­ring are a tem­per­ate-wa­ter fish,” she said.

The do­nated skele­tons’ ear bones, known as otoliths, have tree trunk-like growth rings that can be counted to find fishes’ ages, and the bones are chem­i­cally an­a­lysed to find out where fish have lived.

Recre­ational and com­mer­cial fish­ers have al­ready do­nated about 300,000 fish ear bones from sev­eral species to the depart­ment but the re­searchers need about 500 ears from any species just to de­ter­mine a range of ages in any pop­u­la­tion.

Work on the ear bones in the lab­o­ra­tory 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 onto a com­puter screen,” Depart­ment of Fish­eries re­search ex­ec­u­tive di­rec­tor Rick Fletcher said.

Visit Send Us Your Skele­tons at www.fish.wa.gov.au/frames or call 9203 0111.

Her­ring re­searcher Kim Smith with a small catch.

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