Fishing study suggests strategy change

SAN DIEGO, Oct. 18 (UPI) -- U.S. scientists are questioning a common fishing strategy of catching older, larger fish and leaving younger and fitter generations alive.

George Sugihara and colleagues at the University of California-San Diego say the strategy might make the remaining fish more vulnerable to environmental change.

The researchers reached their conclusions after studying results of the California Cooperative Oceanic Fisheries Investigation, a unique 50-year survey that enabled them to compare the abundance of exploited and non-exploited species in the same ocean.

They found overfishing decreases the total abundance of species but increases the variation in abundance over time. That is, the numbers of exploited fish are more likely to go up and down. The team believes the effect is probably caused by the practice of catching older, bigger fish, which destabilizes the rest of the population.

The scientists say their study's results have strong implications for fisheries management and suggest that, to avoid collapse, fisheries must be managed not only to sustain the total biomass but also to maintain the heterogeneous age structure of the population.

The study is detailed in the current issue of the journal Nature.