Principles of Genetics and Breeding

13.1.12.1. Random Mating

Nonrandom mating in fish hatcheries is generally undesirable, not because fish breed randomly in nature but, because nonrandom mating in a facility is due to influences most likely different from those occurring in nature.

Consequently, genetic diversity of hatchery fish may be lost with a potential for reduced fitness when stocked in a different environment. Since, in most cases, hatchery managers do not know the details of reproductive behavior in nature, attempting to mimic the unknown is likely to be off the mark, thus, creating high risk of genetic hazards occurring, perhaps resulting in disruption of naturally evolved breeding behaviours and reduced fitness.

The success of a random mating strategy in meeting both production and genetics goals in a captive broodstock programme hinges on two major requirements.

• First, a very large population of mature broodfish, perhaps on the order of 2,000 adults is necessary.
• Second, the hatchery manager must be able to sample individuals in a random, unbiased manner when selecting broodfish to spawn.