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

Abstract

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.

Examining current best-practices for the use of wild post-larvae capture, culture, and release for fisheries enhancement

“…Substantial development in culturing technology has enabled cost-effective rearing of fish (Kitada, 2020), with technical guidelines freely available for developing appropriate facilities and practices (Lovatelli and Holthus, 2008). Key aspects include aquaria design, nutritional requirements and feeding regimes (which may include weaning onto artificial food for rearing and then back onto live food prior to release), duration of grow-out and release size, and conditioning animals for release, including acclimation to local ocean temperatures and behavioural training (Taylor et al, 2017;Näslund, 2021).…”

“…Drastic differences between captive and natural environments may elicit physiological, morphological, behavioural and ecological effects on captive-reared juveniles which can impede survival in the wild (Lorenzen et al, 2012;Näslund, 2021). Nonetheless, as rearing practices and technology have advanced, wild post-larvae captured during settlement are likely to be inherently better adapted for life in natural conditions than those reared from captive broodstock in hatcheries (Bartley and Bell, 2008).…”

“…Nonetheless, as rearing practices and technology have advanced, wild post-larvae captured during settlement are likely to be inherently better adapted for life in natural conditions than those reared from captive broodstock in hatcheries (Bartley and Bell, 2008). While some facets of behaviour may be innate, others are learned during juvenile development so preparation can enhance post-release growth and survival (Kieffer and Colgan, 1992;Näslund, 2021). Behavioural training may include aspects of foraging, predator recognition and avoidance (Kieffer and Colgan, 1992;Ferrari et al, 2015;Näslund 2021), ensuring animals do not habituate to life in aquaria (Kieffer and Colgan, 1992;Näslund, 2021).…”

“…While some facets of behaviour may be innate, others are learned during juvenile development so preparation can enhance post-release growth and survival (Kieffer and Colgan, 1992;Näslund, 2021). Behavioural training may include aspects of foraging, predator recognition and avoidance (Kieffer and Colgan, 1992;Ferrari et al, 2015;Näslund 2021), ensuring animals do not habituate to life in aquaria (Kieffer and Colgan, 1992;Näslund, 2021). These principles were followed in our example of rearing D. sargus in the laboratory (Table 2).…”

Greater Consideration of Animals Will Enhance Coastal Restoration Outcomes

“… 2021 , Murray et al. 2022 ). Restoration is therefore necessary to reverse coastal habitat loss and degradation, enhance biodiversity, and reestablish ecosystem services such as fisheries production, coastline protection, and climate change mitigation (Wood et al.…”