**6. Reproduction**

differ between the two strains in the spontaneous escape response [47], but after this first reaction, hatchery-reared juveniles stayed less time in association with the shelter than the wild animals. The same result has been found in the grass carp (*Ctenopharyngodon idella*); in the frame of restocking programs using hatchery-reared individuals, it is important to test the anti-predator behaviour. This behaviour was compared with that of wild-caught animals. The two groups exhibited a clear anti-predator behaviour; however, the hatcheryreared individuals showed lower aggregation and spent time in the risky areas and most of them were predated [48]. These variations between domesticated and wild strains in the display of the anti-predator behaviour are well documented in rainbow trout (*Oncorhynchus mykiss*). Comparisons between wild and hatchery population between clonal lines of rainbow trout derived from either wild and hatchery-reared populations identified several genes associated with behavioural variations between lines [49]. These genetic variations underlying anti-predator behaviours may be used in conservation programs for monitoring alleles

As behaviour is a phenotype corresponding to the plasticity of the responses of animal to the set of environmental conditions, it is interesting to understand how development can affect the behaviour of different genotypes. Now, the existence of transgenic species offers a good tool to study this problem. By comparing wild-type siblings and transgenic individuals, Sundström et al. [50] found that wild and transgenic animals behave in the manner under natural like conditions; but until now, there are not a sufficient number of studies to conclude that genetically modified organisms are not affected by the complexity of natural conditions.

Social behaviour is particularly developed in fishes, such as shoal [51], which is a part of the social life and is present in more than 25,000 species [52]. Shoal is important and ensures protection against a potential predator (a particular prey is undetectable in the group), but also it increases the foraging efficiency (the amount of food per individual is higher in groups than for solitary fishes whatever their diet). Shoal—defined as a group of individuals [51]—may be influenced by environmental factors, and domestication is one of these factors; reared conditions modify the fish environment. It limits the available space for fishes that could have for consequences a non-response of the fishes to environmental stimuli [53]; in reared conditions, food is distributed *ad libitum*, and such situation modifies the foraging behaviour limiting the exploration of the environment [54] and the predator avoidance [12, 32, 55]. In domesticated fishes, there is less variability of the age and size of the individuals, and so, the relations between fishes are modified and the results are counterbalanced; in some studies, they show that there is an increase of the aggressiveness between individuals [56, 57], and in other studies, they find that the aggressiveness is higher in domesticated populations [55, 58]. Growth

One of the most important components of the social relations between individuals is the agonistic behaviour. Comparisons between wild and reared fishes show that new agonistic behaviours do not appear due to domestication [61]; agonistic behaviours are the same for both wild-reared individuals. In general, agonistic behaviours appear for the competition for resources: prediction is that agonistic behaviours must be less numerous when the

in rearing situations is influenced by intra-specific competition [59, 60].

of loci affecting predation in natural populations.

**5. Social behaviour**

96 Animal Domestication

There is very few data on the influence of domestication or different lineages on the reproductive behaviour of fishes? This is the consequence that the reproductive behaviour in reared fishes received very little interest. It is the consequence that humans biased reproduction in reared fish populations; in fact, it is always handed by humans, and there is neither mate choice nor normal reproductive behavioural sequence. So, comparisons of reproductive behaviours between wild and reared fishes are based on behavioural differences between reared fishes that returned to natural environment and wild animals.

Studies focused on the choice of the spawn area; reared animals had more difficulties to find the good place to spawn with environmental features [76]. But the results are not so clear. Reared fishes may arrive earlier on the spawning zones than wild animals [77]. Fishes show different strategies with regard to their origin (wild or reared) [30, 78].

fish in more complex captive environments could create a more wild-like phenotype than

Effects of Domestication on Fish Behaviour http://dx.doi.org/10.5772/intechopen.78752 99

In this frame of animal personality, or coping style, an important effect of the domestication is the reduction of emotional reactivity or responsiveness to a fear-evoking stimulus [83]; the emotional reactivity of wild fishes is better than those of reared individuals [84]. The emotional reactivity of an animal is necessary for provoking a flight response when there is a potential danger; it could be linked to a survival response. It seems that after domestication, fishes lost very rapidly, in only one generation, the stress response. This change in behaviour is probably directly linked to physiological changes: in the rainbow trout, two different lineages were selected on the basis of their rate of cortisol as responsiveness to stress. Individuals, which showed a low rate of cortisol, had a lower response to stress; they developed a better foraging behaviour but had a bad response to a potential danger. These individuals were well adapted to the environmental conditions of fish farms, but not the natural environment [85]. This is a general problem; the selection by humans of particular lineages of fishes based on their potentiality of growth and development has an influence on other life traits especially on behavioural traits. In the sea bass, the repetitive application of stress elements (pursuit of the fishes with a net, luminous changes, application of predator lure) modifies the foraging habits of wild fishes but also of reared ones. This could be interpreted as a habituation to the situation, which

If the domestication process leads to a change in behavioural traits, empirical evidence for a difference in cognitive performance, however, is scarce. In the framework of animal personalities, differences in behaviour may arise during ontogeny through learning and bolder, and more aggressive animals (usually, the wild form) should learn faster. Such examples exist in vertebrates especially in mammals; by comparing wild cavies and domestic guinea pigs (*Cavia porcellus)* in behavioural tests. Domestic guinea pigs were less bold and aggressive than their wild congeners, but learnt an association faster [87]. Such studies exist also in fish but are scare, and now, results are not clearly established, leading an important field of research. For example, Klefoth et al. [88] tested two common genotypes of common carp, *Cyprinus carpio* L., differing in degree of domestication (a highly domesticated mirror carp and a less domesticated scaled carp) exposed to fishing. Domesticated mirror carp were more vulnerable to angling gear than scaled carp in both environments; these results were related to a bolder-foraging behaviour for the latter. Independently of genotype, fish become more difficult to catch, indicating learned hook avoidance, based on the boldness, so scaled carp get an advantage with a lower vulnerability to fishing. The study of Rodewald et al. [89] showed that after their release in natural environment, hatchery-reared salmon had a lower foraging rate than wild individuals. They showed that this difference was the consequence of higher abilities of learning the new environment and especially the presence of potential prey by the wild fish. Such studies should be initiated before the reintroduction of hatchery stock in the natural habitat, to ensure the

conventional rearing practices.

becomes less stressful [86].

**8. Learning-cognition**

success of the operation.

Most of the studies on the influence of domestication on the reproductive behaviour are done on salmonids because this is the group of species with the highest pressure for restocking the natural populations with hatchery-reared individuals, so it is absolutely necessary to evaluate their reproductive performances under natural environment. Coho Salmon (*Oncorhynchus kisutch*) produced by hatcheries have lower fitness in the wild than naturally produced salmon, but the factors underlying this difference remain an active area of research [71]. Neff et al. [79] used genetic parentage analysis of juveniles produced by experimentally mixed groups of wild and hatchery coho salmon to quantify male paternity. In all contexts, wild animals showed a higher paternity rate than hatchery-reared individuals.
