By targeting bigger fish, we are breeding populations of smaller and weaker fish
Darwin always winsIn nature, bigger, healthier, stronger individuals tend to have more offspring and thus there is a selection pressure in their favor. But humans can put other kinds of pressure on species, for instance by targeting bigger fish, actually reducing their chances of survival and reproduction compared to smaller and weaker individuals. This is what scientists at Bangor University seem to have found, showing in the Trinidadian guppy, a tropical fish, that there is a shift in the genetic make-up of harvested fish to smaller less fertile individuals within just a few generations.
"Our findings have major implications for the sustainability of harvested populations," said Prof Gary Carvalho, of Bangor University's School of Biological Sciences. "We would urge the scientific community, policy makers and managers to consider the capacity of harvested stocks to adapt to, and recover from, harvesting and predation."
They've also shown that undoing the damage to the DNA gene pool of a species, making it return to larger fish, will take 5-10 times longer than anticipated -- "if the DNA change can be reversed at all".
This means we have to rethink how we try to prevent over-fishing and become a lot more careful about how fisheries are affected by human activity.