The fishing mantra of harvesting the largest individuals from a fish population introduces genetic changes that harm the overall fish population, a new University of California study has found. The researchers say that removing the large fish over several generations causes the remaining fish in the population to become progressively smaller, have fewer and smaller eggs with lower survival and growth, and have lower feeding rates.
According to study leader Matthew R. Walsh, the study was the first to simulate the evolutionary impacts of harvesting in a laboratory setting. “We have shown for the first time that many traits correlated with fish body-size may be evolving in response to intense fishing pressure,” he explained.
The study, appearing in the journal Ecology Letters, focused on the Atlantic silverside, a commercially harvested fish found along the east coast of North America. The researchers conducted harvesting experiments over five generations, selecting out the largest individuals from each generation and evaluating multiple traits, such as body size and the number of eggs.