"Much of what we now know about fish populations is not being accounted for in current fisheries management," said Berkeley, a research biologist at UCSC's Long Marine Laboratory.
Berkeley's research on West Coast rockfish, for example, shows that large, old females are far more important than younger fish in maintaining productive fisheries. The larvae produced by these "big, old, fat females" grow faster, resist starvation better, and are much more likely to survive than the offspring of younger fish. Unfortunately, older fish tend to disappear under current fisheries management practices--the old fish get caught and the younger fish never have a chance to grow old.
"Our research shows that you need to maintain older fish in the population because those are the most successful at reproducing. But normal fishing at what we now think of as safe levels will not maintain old fish in the population," Berkeley said.
The effects of fishing on the age structure of a population is particularly striking in the various species of rockfish, which are very long-lived fish. Many rockfish can live for 50 years or more, and some species can live well over 100 years.
Current fisheries management actually aims to reduce the number of old, slow-growing fish in the population, leaving more room and resources for younger, faster-growing fish. Most marine fish produce huge numbers of eggs and larvae
Contact: Tim Stephens
University of California - Santa Cruz