Environmental effects on behavioural development consequences for fitness of captive‐reared fishes in the wild

Abstract

Why do captive-reared fishes generally have lower fitness in natural environments than wild conspecifics, even when the hatchery fishes are derived from wild parents from the local population? A thorough understanding of this question is the key to design artificial rearing environments that optimize post-release performance, as well as to recognize the limitations of what can be achieved by modifying hatchery rearing methods. Fishes are generally very plastic in their development and through gene-environment interactions, epigenetic and maternal effects their phenotypes will develop differently depending on their rearing environment. This suggests that there is scope for modifying conventional rearing environments to better prepare fishes for release into the wild. The complexity of the natural environment is impossible to mimic in full-scale rearing facilities. So, in reality, the challenge is to identify key modifications of the artificial rearing environment that are practically and economically feasible and that efficiently promote development towards a more wild-like phenotype. Do such key modifications really exist? Here, attempts to use physical enrichment and density reduction to improve the performance of hatchery fishes are discussed and evaluated. These manipulations show potential to increase the fitness of hatchery fishes released into natural environments, but the success is strongly dependent on adequately adapting methods to species and life stage-specific conditions.

European sturgeon (Acipenser sturio L.) young of the year performance in different rearing environments –study within a stocking program

“…Generally, major concerns of stocking for conservation purposes focused on the impact of genetic drift (Busack and Currens 1995;Campton 1995;Yokota et al 2003), introgression (Susnik et al 2004;Lamaze et al 2012) and genotypic fitness (Zhu et al 2002;Aprahamian et al 2003;Jager 2005) on wild populations. Nowadays, rearing environment of hatchery fish for stocking purposes is a subject raising attention (Brown et al 2003;Strand et al 2010;Roberts et al 2011;Bergendahl et al 2016) because artificial environments may induce behavioral responses different from those expected in wild fish (Johnsson et al 2014). Indeed, hatcheries often expose the fish to selective reproduction and early life experiences in a safe setting, which could strongly influence the behavioral (Brown et al 2003;Klefoth et al 2012), genetic, morphological and physiological attributes necessary to respond adequately to natural conditions after stocking (Brown et al 2003;Braithwaite and Salvanes 2005).…”

Wildlife Conservation: Is Domestication a Solution?

“…In order to mitigate as much as possible the efect of domestication and promote wild-like types," atention should be paid to both sampling of ish for the founder population (suicient diversity of genetic and life-history phenotypes to allow re-establishment of viable populations in the wild) and its subsequent management in captivity [55]. The most efective way of minimizing both loss of genetic diversity and the efects of domestication is to minimize the time spent in captivity [55] and release the ish at an early stage (eggs or larvae) to reduce environmental efects of the hatchery [57]. In other words, only one part of the life cycle should be controlled in captivity (level 2 in Table ).…”

“…In other words, only one part of the life cycle should be controlled in captivity (level 2 in Table ). "esides, the post-release performance of captive-reared ishes can be improved by modifying the captive environment of hatchery to try to mimic key aspects of natural conditions [57]. Relatively simple modiications of the captive environment, among which physical enrichment (modiications or additions of physical structure to the tanks, such as shelters) and reduced rearing density, can help produce a more wild-like ish that will perform beter in the wild [57].…”

“…"esides, the post-release performance of captive-reared ishes can be improved by modifying the captive environment of hatchery to try to mimic key aspects of natural conditions [57]. Relatively simple modiications of the captive environment, among which physical enrichment (modiications or additions of physical structure to the tanks, such as shelters) and reduced rearing density, can help produce a more wild-like ish that will perform beter in the wild [57]. Yet, where populations must be maintained in captivity for multiple generations (thus reaching level 3 and perhaps level 4), there is an inherent trade-ofs between the goals of maintaining diversity (avoid inbreeding and genetic drift) and minimizing adaptation because the potential for genetic adaptation is directly proportional to the heritable genetic diversity [55].…”

“…Yet, clear goals should be formulated for ish culture and domestication strategies [ 2], bearing in mind that diferent uses of ish (e.g., ish consumption versus wildlife conservation) call for very diferent approaches [3 , 55]. "t last, it should be stressed that hatchery releases should only be considered in cases where there are no realistic ways to save or maintain sensitive natural populations [57]. "s a long-term strategy, habitat restoration should always be the irst choice in ish conservation eforts to allow the natural" recolonization of rivers or lakes by ish from which it has been extirpated [ 1].…”