<p>With the increasing scarcity of fisheries resources and the global decline trend of fish diversity, the ecological adaptability of fish has attracted close attention from biologists, animal protectionists, governments, and the public. The fish's ecological adaptability is closely related to its behavioral capacity, and most fish behaviors are directly or indirectly controlled by neural development. Several studies have shown that physical enrichment, a method of increasing the structural complexity of husbandry water with the aim to improve fish fitness in hatchery release projects, significantly improved the development of fish brain tissue, but the results were sharply mixed. Based on a compiled dataset that included 52 effect sizes from eight fish species in ten studies, this study conducted a meta-analysis to elucidate the factors causing heterogeneity between studies. The results showed that physical enrichment did not significantly affect fish brain size in general, in contrast, the effect size significantly decreased with the increase in the body size of experimental fish. These results provide preliminary but novel insights into the driving forces of fish neural plasticity and offer theoretical references for applying environmental enrichment to improve fish adaptability.</p>