Reared to become wild-like: addressing behavioral and cognitive deficits in cultured aquatic animals destined for stocking into natural environments—a critical review

Hatchery-reared aquatic animals tend to perform worse in natural environments than wild conspecifics. This was pointed out over a century ago and while there are many possible causes, one persistent observation is that unnatural rearing environments cause behavioral expressions unsuitable for a life in the wild. Behavioral traits being adaptive in barren, food-rich, and predator-free hatchery tanks likely differ from those being adaptive in nature. More recently, suspicions of cognitive deficiencies due to sensory deprivation have also been raised. Over the last few decades, substantial research has been devoted to produce more wild-like phenotypes in animals reared for stocking. This research includes life-skills training programs, where animals learn to cope with important features of the natural environment (e.g., live food and predation risk), and environmental modifications aimed at stimulating the formation of adequate cognitive and behavioral traits (e.g., environmental enrichment and reduction of the number of individuals per tank). The main purpose of this paper is to provide a summary of the current state-of-knowledge of interventions aimed at ameliorating cognitive and behavioral deficiencies in aquatic animals reared for stocking. Furthermore, it aims to provide a foundation to assist in the development of future questions, hypotheses, and experiments to eventually improve the postrelease performance of these animals.