Magi Mike's Blog

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Canadian Commercial Fishery Research Supports Evolution

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Charles Darwin’s theory of natural selection has often been misrepresented over the years. Many people, especially Christians and self serving capitalists, think that “survival of the fittest” means only the biggest, meanest and strongest survive. But when survival favors the smallest, as in periods of famine, and when food is scarce, as it is on small islands, then smallness becomes a necessity for survival. Smaller animals survive when larger ones would starve.

David Coltman from the University of Alberta in 2003 found that trophy hunters were driving down the horn size of bighorn sheep. The report was published in the prestigious scientific journal Nature. By hunters killing rams with large horns before they reached their breeding peak, the sheep were evolving with smaller horns. Reduced horn size was an evolutionary response by the sheep to excessive “predation” by hunters who sought out the animals with trophy horns.

What you would normally expect for bighorn sheep is those that have the largest size and largest horns are those supposed to have the strongest reproductive quality, but we remove them from the population before they have a chance to pass those genes on from one generation to the next. As a result, it’s the other sheep that are reproducing.

Sean Rogers, a University of Calgary evolutionary biologist

Turning to a different situation, Rogers is exploring whether the desire to have the plumpest, flakiest whitefish fillets on dinner plates may be similarly gutting the evolution of the species in a northern Alberta lake and threatening the million dollar whitefish industry. The Alberta whitefish industry is worth an estimated $1 million annually in the province and $18 million nationwide. But the Winnipeg Free Press reports that commercial fishery at Lesser Slave Lake has seen severe fluctuations in fish populations over time, and, Between 1965 and 1972, the fishery was actually shut down.

Nets used by the commercial whitefish industry on Lesser Slave Lake have always been designed to catch the biggest and best fish. It means the smaller fish are more likely to reproduce by falling through the holes in the nets. Historical data shows a shift in the genes of the fish. It is the genes of the small whitefish that are being passed on.

Instead of the bigger and best surviving, those were the ones we were actually removing from the population and consequently we elicited this selection response in the fish population. What you see from fishing with the gill nets was the average size for lake whitefish declining.

Sean Rogers

Rogers’s molecular ecology lab has initiated a study to dig deeper into what’s happening, looking at fish scale samples collected by the government over the last 30 years. The DNA from the samples will allow researchers to determine how the fishery has evolved over time.


Written by mikemagee

2 May, 2010 at 11:57 pm

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