Effects of the artificial reef and flow field environment on the habitat selection behavior of Sebastes schlegelii juveniles

Abstract

With pollution and disturbances in marine ecological environments, the quality and structure of fish habitats in offshore regions have exhibited drastic decreasing trends. Artificial reefs are a vital engineering measure for restoring such degraded marine habitats. In this study, the quantitative behavioral responses of Sebastes schlegelii juvenile fish to different artificial reefs (cubic artificial reef (CAR), pyramidal artificial reef (PAR), star-shaped artificial reef (SAR) and tubular artificial reef (TAR)) and flow field environments were investigated in a laboratory pool. The mean gathering rate (MGR) and wavelet analysis were adopted to analyze the distribution patterns of Sebastes schlegelii juveniles around the four reefs under three flow field environments (FE1, FE2, FE3). The MGR of juvenile fish reflected significant gathering behaviors around the artificial reefs at the experimental observation times. In static water (FE1), the MGR of juvenile fish decreased in the order CAR > SAR > PAR >TAR. With increasing flow velocity (FE2 and FE3), the MGR of juvenile fish showed a different trend (CAR > PAR > SAR > TAR), and the juvenile fish quickly gathered into CAR and PAR, whereas their numbers decreased in SAR and TAR. The number of juvenile fish in CAR displayed the highest wavelet spectrum continuity and large fluctuations, as the diurnal change in the number of fish was strongly significant, whereas the opposite trend was found in TAR. Wavelet analysis showed that the fluctuations in the gathering behaviors of juveniles decreased with increasing flow velocity. According to a two-factor analysis of variance, the reef structure had a more significant effect than the flow velocity on the gathering of juvenile fish. As a result, CAR and PAR are recommended to restore the habitats of juvenile fish in marine ranches because they have complex geometric shapes that provide a more suitable environment and richer habitat for juvenile fish.