Scientists say that cod and haddock are becoming smaller due toevolutionary pressure imposed by overfishing.
What happens is that only the smallest fish escape the netsthrough being able to squeeze through the mesh, and these runt fishreach sexual maturity earlier than normal and produce offspring thatare also runts, and so the cycle goes on.
Steven Murawski, chief of population dynamics at the US NationalMarine Fisheries in Woods Hole, Massachusetts said, “It isfascinating to think that humans are having this effect on fish.”
“It’s like eliminating people who are six feet tall. They’d becomerarer and rarer and you’d have only small people left.
“If you look at cod populations and other fisheries, they arematuring earlier, and the only common factor is overfishing.”
Forty years ago haddock spawned at three years of age or later,but now one-year-olds are spawning. Cod are spawning at a muchyounger age too.
“A number of people have talked about the possibility that this ishappening,” said Dr Colin Bannister, of DEFRA’s Fish ResearchLaboratory in Lowestoft, Suffolk. “It’s a controversial questionwhich we are hoping to answer with a major survey of codfishpopulations in the North Sea .
“It’s certainly conceivable that fishing may exert selectivepressure on stocks, but the jury is still out on whether or not thisis actually what is happening.”
