Effects of Two Environmental Enrichment Methods on Cognitive Ability and Growth Performance of Juvenile Black Rockfish Sebastes schlegelii

SIMPLE SUMMARY: The purpose of this study was to investigate the effects of two environmental enrichment methods on the growth and cognitive ability of Sebastes schlegelii. The main results showed that seven weeks of environmental enrichment affected their growth performance negatively, but the growth-related indicators were affected positively. Additionally, the cognitive abilities of individuals in the enrichment groups were significantly enhanced compared with those of individuals in the control group. These phenomena revealed that the S. schlegelii reared in two types of enrichment environments showed stronger learning and cognitive ability. The results can provide a reference for improving the efficiency of stock enhancement projects for this species. ABSTRACT: A widely used approach to restoring marine fishery resources is stock enhancement using hatchery-reared fish. However, artificial rearing environments, which are often lacking in enrichment, may negatively affect the cognition, welfare, and adaptive capacity to new environments of juvenile fish, thereby leading to low post-release survival rates. This study examined the effects of habitat and social enrichment on the growth performance and cognitive ability of Sebastes schlegelii. Following seven weeks of environmental enrichment, a T-maze experiment was conducted, and the telencephalon and visceral mass of the fish were sampled to measure the growth (growth hormone: GH; insulin-like growth factor-1: IGF-1; and somatostatin: SS) and cognitive abilities (brain-derived neurotrophic factor: BDNF; and nerve growth factor: NGF)-related indicator levels. The results indicated that, although the final body length, final body weight, and specific growth rate of both enrichment groups were lower than those of the control group, both methods of enrichment had a positive impact on growth-related factors (increased GH, increased IGF-1, and decreased SS). The enrichment groups demonstrated a stronger learning ability in the T-maze test, and the levels of BDNF and NGF in the telencephalon were significantly higher in the enrichment groups than those in the control group. Additionally, there was a significant interaction between the two enrichment methods on the NGF level. This study confirms that a more complex and enriching environment is beneficial for cultivating the cognitive abilities of cultured juvenile S. schlegelii, and the result can provide a reference for the improvement of the stock enhancement of this species.