Winds of change cause fishery collapse
A change in seasonal wind patterns has caused the collapse of an important Australian fishery, according to new research.
The CSIRO study by Dr Ron Thresher from the Division of Marine Research shows that strong westerly winds have been moving steadily south, causing calmer conditions in areas which were previously very windy.
The gemfish fishery was worth about $12 million annually until it virtually disappeared in 1992.
"Basically we're not getting as many windy days any more," Dr Thresher said. He said the study showed a direct correlation between declining wind and the collapse of the fishery.
Climate change is one suspect in the wind shift, which has been going on for the past 70-80 years. Dr Thresher said there had been a poleward movement of winds, possibly caused by weather patterns at the equator expanding and pushing southward. Winds are estimated to have moved about 300km in the past 70 years.
Dr Thresher said a shift in wind patterns are known to affect fish, and also shellfish such as abalone, in several ways. Firstly it blows larval fish, which tend to stay near the surface, away from nursery feeding areas. Winds also affect water turbulance and the availability of nutrients moved up from deeper layers.
"We saw an abrupt decline in the 1988/89 wind strength, and at the same time the recruitment of larval fish was very bad," he said.
However, while the eastern coast fisheries have suffered, the species is unlikely to go extinct, as its range extends west across the entire Australian Bight and part way up the west coast of Australia.
While the wind appears to be the main culprit, Dr Thresher said a more robust population may have been able to withstand the pressure. "If the stock had been really healthy and not under fishing pressure, it could have survived this otherwise natural downturn.
"The fact that it has been heavily fished means the gemfish has less resilience to change," he said.