Australian scientists are to hold a crisis meeting tomorrow in an attempt to discover why pilchards are dying in their millions off the country's coast. From Sydney on the east coast to Perth in the west, more than 3,000 miles of the Southern Ocean are littered with dead pilchards stricken by a mysterious disease.
The fish started dying off the coast of South Australia in late March. The disease spread west, then east to Bass Strait, above Tasmania, and finally north to reach the coast off Sydney three days ago. Fishermen have reported sailing through carpets of dead pilchards and watching others breaching the ocean surface, gasping for air and dying. No one knows what has caused the disaster, why only large pilchards are dying and why other fish species, including those that live off pilchards, have not succumbed. The coasts of Namibia and Peru are the only places where scientists can recall observing fish dying on a similar scale.
"It's unprecedented here," said George Cresswell, an oceanographer with the Commonwealth Scientific Industrial Research Organisation (CSIRO), Australia's leading research body. He belongs to a national task force of scientists from the CSIRO, universities and government departments which has been called to a crisis meeting tomorrow to discuss a phenomenon that threatens to wreck Australia's multi-million dollar pilchard industry.
Scientists know how the pilchards are dying. All of the fish examined have had serious swelling and damage to their gills, suggesting death from asphyxiation. "It's a bit like pleurisy," said Rick Fletcher, a senior research scientist with the Western Australian Department of Fisheries. A few weeks ago, he gathered evidence at Esperance, on the state's southern coast. "There were 30 to 40 dead pilchards every step I took," he said. At first, scientists thought that the deaths might have been caused by cold, nutrient-rich waters from the ocean depths bringing to the surface phytoplankton containing toxic algal blooms. But, while algal blooms were sighted near most of the kills, none were present in Tasmania, where the second wave of deaths occurred. Animal scientists have suggested a mystery virus. That does not explain why younger pilchards appear to have survived.
Teams of experts are now working along the waters just ahead of the death zones using satellite and aerial surveys to try to isolate possible oceanographic, climatic and other environmental causes. "It's spreading so fast that it defies logic," said Gustav Hallegraeff, a plant scientist of the University of Tasmania. "We're worried about the impact further up the food chain, on sharks, tuna, salmon and birds."