Principles of Genetics and Breeding

14.1.1 Domestication in fishes

According to Clutton-Brock (1999) a domestic animal can be defined as “one that has been bred in captivity for purposes of economic profit to a human community that maintains total control over its breeding, organization of territory, and food supply”.

Genetically domestication is change in the quantity, variety, or combination of alleles within a captive population or between the founder captive population, the derivative broodstock, and the source or donor population.

The basic process behind domestication is natural selection.

Most of the domestications happened as early as the Neolithic ( c . 14000 years ago). In a truly domesticated organism,

(a) the individual is valued and kept for a specific purpose,

(b) its breeding is subject to human control,

(c) its behaviour is different from that of the wild ancestor,

(d) its morphology and physiology exhibit variations never seen in the wild, and

(e) some individuals at least would not survive without human protection.

• The best known examples of domestication are the transformations of wolves into breeds of dog, aurochs into cattle, guanaco into llama and alpaca, wild boar into domestic swine, wild horse into domestic horses, and red jungle fowl into domestic chickens. All domesticated animals depend for their day-today survival upon their owners.
• For a fish to be a true domesticate, criteria (d) and (e) above must apply. Some of these variants in colour and form would not survive without human protection. The original criterion of economic profit may only partially apply to domesticates when kept as pets.
• Use of established, high performance domestic strains is the first step in applying genetic principles to improved aquaculture management. Strain variation is also important, since there is a strain effect on other genetic enhancement approaches, such as intraspecific cross breeding, inter specific hybridization, sex control and genetic engineering.

Clutton-Brock (1999) believes ‘that animals bred under domestication evolve into new species as a result of reproductive isolation from their wild progenitors’. Domesticated animals released into the wild to fend for themselves usually perform poorly and, while some revert to resemble their wild ancestors in time, the process is nearly always incomplete. All such feral forms remain poor facsimiles of their progenitors (Livingston, 1994).