Research progress on application of environmental enrichment techniques in fish aquaculture and stock enhancement

In recent years, the wild fisheries resources have been decreasing, the aquaculture production has been flourishing, and meanwhile the fish welfare has gained increasing attention from the public and scientists. Under these backgrounds, environmental enrichment, as a new technology in the fields of aquaculture and fisheries, has gained wide attention and is considered to have great potential in improving life skills of released fish, increasing the production output of farmed fish, and improving the welfare of captive fish. Environmental enrichment refers to the methods of environmental optimization aimed at increasing production yield, improving fish welfare, controlling fish behaviors and improving physiological status by a deliberate increase in environmental heterogeneity and complexity of water environment. In general, the international studies on environmental enrichment technology has been flourishing, and the theoretical system is constantly improved. However, relevant research in China is still in the initial stage. This paper first briefly introduces the concept and classification of environmental enrichment, and then reviews the effects of physical enrichment (which has received the most attention at present) on fish aquaculture-related traits (such as aggressive behavior, stress response, metabolism, and growth) and adaptive behaviors and individual fitness after release. This review focuses on the possible causes and the potential neuroplasticity mechanism of the differences in results between studies and discusses the shortcomings of the previous studies and future directions of the field. This review aims to provide reference for research in this field and provide valuable information for sustainable aquaculture and stock enhancement programs.