A tiny fish ear bone could allow researchers to find out if restrictions on herring fishing are helping stocks recover along the Western Australia coast.
A report last December showed herring stocks had declined to the point that the overall catch needed to be reduced by 50 per cent in order for them to replenish.
Much to the disappointment of the fishing industry, that led the State Government to announce changes included the closure of a herring fishery off WA’s south coast and a reduction in the recreational bag limit from 30 to 12.
Dr Brett Molony, a Department of Fisheries supervising research scientist, said overfishing had meant most herring were not reproducing.
“A lot of fish were being captured before spawning in the West Coast and this was having an impact across the whole stock,” he said.
Now, the department is trying to find out if herring being caught under the new rules survived long enough to breed.
Senior research scientist David Fairclough said the answer to that question lay in a herring’s otolith, or ear bone.
“They grow throughout the lifetime of the fish. They deposit rings, much like the growth rings in a tree, and we can use those growth rings to work out how old a fish is,” Dr Fairclough said.
“We then use the ages of the fish in our stock assessments.”
The researchers are dissecting the fish, setting the otoliths in resin and slicing them open with a diamond cutter so they can be analysed under a microscope.
Dr Fairclough likened the research to a census of the fish, as it takes about 500 ear bones to find out the range of ages in a single school of fish.
“It’s a critical component of the data that we need to be able to assess the health of stocks. So, being able to work out how old a fish is, is a really important biological parameter we can use,” he said.
2015 ABC