Ear bones no red herring
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.