Fishermen, lend us your ear bones
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.