Cod: Perhaps if we all stood back a bit?

Yellowfin tuna may sustain an industrial fishery indefinitely if managed by conventional models, but northern cod perhaps cannot. This may be a generality for tropical and cold-water fish. In their core habitat, yellowfin spawn continuously, year-round and from an early age, while northern cod mature only at middle-age and spawn only during a brief season. The resulting natural age structure of each species is well-adapted to the characteristic recruitment variability imposed by its habitat. Industrial fisheries managed by stock assessment models seem unavoidably to modify the age structure of cod so that very few spawning year-classes remain, though this does not seem to happen in yellowfin managed in a similar way. It is axiomatic that the natural age structure is that best fitted to the long-term survival of any species, and this fact implies that cold-water species exploited by an industrial fishery may be unable to sustain a viable population across periods when environmental stress is strong and recruitment weak: population collapses of cod and other cold-water fish under industrial fishing pressure may therefore be unavoidable. (C) 1998 Elsevier Science B.V. All rights reserved.