In a report scientists reveals that hunting, commercial fishing and some conservation regulations, like minimum size limits on fish, may all work against species health. This increases the rate of evolutionary change in plants and animals. Researchers reported several years ago that after decades of heavy fishing, Atlantic cod had evolved to reproduce at younger ages and smaller sizes.
Scientists studied 29 species — mostly fish, but also a few animals and plants like bighorn sheep and ginseng —found that rates of evolutionary change were three times higher in species subject to “harvest selection” than in other species. The researchers said that the data they analyzed suggested that size at reproductive maturity in the species under pressure had shrunk in 30 years or so by 20 percent, and that organisms were reaching reproductive age about 25 percent sooner.
Chris Darimont, a postdoctoral fellow in environmental studies at the University of California, Santa Cruz, who led the work, said that the fish they studied that are reproducing earlier on average have far, far, far fewer eggs than those who wait an additional year and grow a few more centimeters. He also said that the it was unknown whether traits would change back if harvesting were reduced, or how long that might take. Some fisheries scientists have said their studies of fish stock had not shown a correlation between fishing intensity and growth rates.
Daniel Pauly, who directs the Fisheries Center at the University of British Columbia, said the new findings make sense saying after decades of heavy fishing, the size of the typical adult fish had shrunk to about 10 centimeters from about 15 centimeters.
