Cod deaths stall comeback of fishery
Thursday, December 21, 2000 Globe and Mail
HALIFAX — As many as half of the young cod in the North Atlantic are dying in mysterious circumstances.
And the unexplained deaths of millions of young fish before they spawn have left the cod fishery in much of Eastern Canada at a standstill with only a few signs of a recovery eight years after full-scale commercial fishing was halted.
Federal fishery scientists are at a loss to explain the high natural mortality of cod in an area extending from east of Halifax north to the coast of Labrador. Natural causes normally kill off about 20 per cent of fish between the ages of three and four. But recent surveys by the federal Department of Fisheries and Oceans show that 40 per cent to 50 per cent of the young fish found the previous year are missing, and presumed to have died, Michael Sinclair, director of the Bedford Institute of Oceanography, said yesterday.
“It is quite an unusual phenomenon,” he said, adding that the high natural mortality has dashed hopes for a rapid recovery of the cod — a fish that only a decade ago was worth more than $700-million a year to the East Coast economy.
There is no shortage of theories about what could be killing the young fish. Some fishermen blame the burgeoning seal population, but there is no proof.
Initially, scientists believed cold water temperatures in the late 1980s and early 1990s had changed the ecosystem and reduced the cod stocks. But the waters have warmed in recent years and the cod continue to die.
There were reports of reduced amounts of traditional food such as plankton and krill, but those were also not substantiated.
There are also theories that the large adult cod protected small cod by feeding on herring and capelin that competed with young cod for plankton and other food. With heavy overfishing eliminating the large cod, the theory is that the herring and capelin schools have multiplied and are taking away food from the young cod.
Mr. Sinclair said DFO monitoring hasn’t shown any sign of disease in cod, although they appear to be smaller than they were before the moratoriums of cod fishing were announced in the early 1990s.
East Coast fishermen haven’t seen any indication that cod are dying young.
Jim Porter, a fisherman from Port de Grave, Nfld., said there have been no signs of dead young fish in the waters around northeastern Newfoundland.
Ransom Myers, a fisheries biologist at Dalhousie University in Halifax, said there was heavy overfishing in the years before the cod fishery was closed and the removal of large amounts of fish coupled with high natural mortality probably caused massive changes to the ocean ecosystem.