Study on the Effects of Flow Fields Under the Refuge Effect of Artificial Reefs on the Behavior and Physiology of Juvenile Lutjanus erythopterus.

Nearshore artificial facilities greatly alter coastal flow fields and habitats. As typical underwater artificial structures, offshore wind turbine pile foundations have unclear mechanisms for influencing fish habitats. Given the high similarity of flow disturbance and sheltering functions between wind pile foundations and artificial reefs, artificial reef models can be applied to analyze the ecological effects of pile foundations. Therefore, this study selected juvenile crimson snapper (Lutjanus erythropterus) as the research object and adopted cubic artificial reefs to simulate sheltered habitats so as to explore the behavioral and physiological responses of juvenile L. erythropterus under different flow-velocity conditions. The results indicated a significant positive correlation between flow velocity and oxygen consumption rate in the experimental area. Behavioral analysis showed that the time percentage spent stationary at 3 BL/s (63.23%) was significantly higher than that in the 1 BL/s (43.02%) and 5 BL/s (41.09%) groups. In contrast, the proportion of backward swimming time was highest at 5 BL/s and was comparable to the percentage of time spent stationary. Physiological analysis revealed that the GLU level in the 1 BL/s group was significantly higher than that in all other groups (p < 0.05). LD content peaked in the 5 BL/s group, where experimental fish also exhibited partial wall-hugging behavior and difficulty in controlling their swimming. There was no significant difference in LD levels between the 0 BL/s and 1 BL/s groups (p > 0.05). Additionally, as the flow velocity increased, the hepatic COR levels in L. erythropterus showed a corresponding upward trend, peaking at 5 BL/s. This study confirms that under the sheltering conditions of artificial reefs, flow-field differences significantly affect the behavioral and physiological characteristics of fish. These findings provide an important scientific basis and theoretical reference for the ecological design and site selection of offshore wind farm pile foundations, as well as for assessing the impacts of habitat alterations following pile foundation construction on fishery resources.