Boat Noise Is Associated With Reduced Behavioral Lateralization in Juvenile Large Yellow Croaker (Larimichthys crocea)

The large yellow croaker (Larimichthys crocea) is an endangered coastal fish species for which the post-release performance of hatchery-reared juveniles may influence the effectiveness of stock enhancement. Anthropogenic underwater noise is increasingly prevalent in coastal habitats, yet whether it affects cognitively relevant behavioral phenotypes in this species remains unclear. We quantified turning bias in juvenile L. crocea using a T-maze detour test in two independent cohorts and examined whether boat-noise exposure was associated with changes in lateralization expression and behavioral performance. Under quiet conditions, approximately one third of fish showed detectable turning bias and were classified as lateralized. These lateralized individuals displayed higher swimming speed and shorter reaction time than non-lateralized fish during the assay. When the same individuals were retested after boat-noise exposure, the magnitude of lateralization shifted toward zero and behavioral performance declined, with larger changes observed in lateralized fish before exposure. In the 2024 cohort, noise-exposed fish showed higher individual and mass-specific oxygen consumption than quiet controls under the present respirometry conditions, indicating elevated metabolic demand. In the 2025 cohort, noise exposure was accompanied by lower gut microbial diversity, altered community composition, and higher intestinal short-chain fatty acid (SCFA) concentrations. Several microbial taxa and SCFAs covaried with lateralization strength, swimming speed, and reaction time, although these relationships were exploratory. Together, these findings are consistent with the hypothesis that boat-noise exposure is associated with reduced expression of behavioral lateralization, and poorer behavioral performance, and concurrent metabolic and gut-associated shifts in juvenile L. crocea.