Principles of Genetics and Breeding

14.1.2 Domestication of fishes

Domestication of fishes

Fishes were domesticated much later than many other animals and plants around 10500 years ago (Diamond, 2002).

Domestication consists of the transfer of an organism from its natural to a captive environment and its genetic adaptation to the new environment.

It requires reproduction of the transferred organism in the captive environment and reproductive isolation from wild populations.

Natural selection both in the wild and under domestication is for maximum reproductive fitness in that environment, but the component traits on which natural selection operates differ in these environments.

Under domestication, tolerance to captive environment diseases and crowding are expected to increase.

Domesticated animals possess the ability to survive and reproduce on diets different from “natural” food.

Behavioral traits, such as the ability to escape from predators and avoid man may be lessened in domestication. Conscious efforts of artificial selection are not required, but some selection is likely to be practiced during domestication by a nonrandom choice of individuals picked out from reproducing the next generation.

Criteria of artificial selection are likely to include traits such as growth rate, survival, body conformation, meat quality, and ease of handling. It follows that the intensity of domestication and the resulting genetic changes are a function of the differences between natural and captive environments, the number of generations of domestication, as well as heritabilities and phenotypic variances of the traits involved. Domestication from different wild stocks or under different agricultural managements is expected to result in the production of different domesticated stocks.

Following these generalities, let us now consider the domestication of different fish in aquaculture (Table 1).

Table 1.Domestication of different fish species in aquaculture

Species	Comments
Common carp	Most intensively domesticated of all fish, through adaptation to different aquaculture managements. Groups isolated: 1. Chinese (Big Belly) carp. Semi-domesticated since brood stock continuously augmented by fish from the wild. 2.European breeds. E.g., Aischgrund, Galician, Ukrainian. 3. Ornamental carp (Koi), domesticated in Japan.
Catfish	Mainly channel catfish. Large amount of domesticated strains, but domestication for relatively small number of generations. Source: Red River, Oklahoma. Some domestication in blue and white catfish and various bullheads.
Tilapias	Mainly O. mossambicus, O. niloticus and O. aureus. Transfer of samples from areas of endemic occurrence, cultivation and reproduction in non endemic areas, mainly South–east Asia. Number of individuals in transferred samples often small, probably leading to some inbreeding.
Trout and salmon	Rainbow trout most highly domesticated. Large number of strains domesticated at different hatcheries. Source: McCloud River, California. Other species domesticated include brook trout, brown trout, lake trout, cutthroat trout. Beginning of domestication in Atlantic salmon. Establishment of strains by sampling natural populations from different river systems and their reproduction in captivity.
Chinese carps	Include silver carp, bighead carp, grass carp, mud carp, black carp. Some transferred from China to other countries. Small number of generations of induced breeding in captivity.
Indian carps	Include catla, rohu, mrigal. Some induced spawning in captivity. Selection of brood stock possibly not isolating faster growing fish.
Ornamental fish	Mainly goldfish. Highly domesticated, isolating strains with different colours and body shapes.

Domestication occurs even without directed selection by the fish culturist. Domestication effects can be observed in some fish within as few as one to two generations after removal from the natural environment.