Principles of Genetics and Breeding

10.1.12 Genetic drift

In carp hatchery few brood stocks are used for breeding at a time, which leads to genetic drift.

• It is a phenomenon that leads to a random changes in the gene frequency in a founder population, which may not carry some alleles due to sampling error.
• Sampling that result in these changes can be natural such as escapes or mortality due to poor water quality, or man-made such as transfers or culling.
• Genetic drift leads to loss or fixation of alleles within populations.
• The loss of alleles reduces genetic variance in the hatchery population.
• The effects of genetic drift can be devastating. Genetic drift can irreversibly alter gene frequencies and eliminates alleles, which can decrease a populations ability to survive or to adapt to an altered environment, and it can preclude future selection.
• Allendorf and Phelps (1980) first addressed this problem of hatchery practices leading to genetic drift in Cutthroat trout Oncorhnchus clarki (Wallbum). They showed the loss of alleles due to genetic drift by comparing the allelic frequencies in hatchery and their wild relatives.
• The effect that genetic drift can have on a population’s gene pool can make management goals impossible to achieve.
• Genetic drift makes a population unfit for selective breeding as occurred in case of Tilapia nilotica.
• It was also found that genetic drift led to the extinction of certain strain of channel catfish (Tave,1991). The loss of alleles via genetic drift has two effects.