Attraction effect of artificial reef model and macroalgae on juvenile Sebastes schlegelii and Hexagrammos otakii

A field survey in an artificial reef zone of Laoshan Bay was conducted to assess the demersal nekton and macroalgae in the area, and five dominant macroalgae (Hterosiphonia japonica, Ulvaper tusa, Grateloupia turuturu, Gelidium amansii and Corallina pilulifera) and two dominant fish species (Sebastes schlegelii and Hexagrammos otakii) and artificial reef model were studied to examine the attraction of artificial reef model and the five macroalgae to juvenile S. schlegelii and H. otakii in an experimental trough. The results showed that without artificial reef model and macroalgae in trough, S. schlegelii and H. otakii preferred to stay in the edge area of the trough, and the distribution rate was 75.71% and 73.63% respectively. After the artificial reef model and macroalgae were deployed in the trough, these two kinds of fish would swim into artificial reef holes and macroalgae cluster quickly after a short escape response; their response time to G. turuturu was the shortest (12.75–21.00 s) and the longest was to artificial reef (66.50–151.25 s); the aggregation time ofS. schlegelii was shortest to G. turuturu (151.50±8.14 s) and that of H. otakii was shortest to H. japonica (56.00±2.53 s); the aggregation time of H. otakii in artificial reef was (216.25±5.59) s, much less than that of S. schlegelii (1343.50±5.38 s); the dwell time of two kinds of fish in artificial reef is much longer than the time in macroalgae cluster, and the dwell time of H. otakii (211.85±7.96 s) is longer than S. schlegelii (199.75±16.82 s).Artificial reef and macroalgae cluster were attractive to them, increasing distribution ratio in the experimental areas from 0.91%–8.78% to 4.21%–31.42%, and the highest aggregation rates were observed in higher density of G. turuturu for S. schlegelii (30.42%±1.14%) and H. japonica for H. otakii (31.42%±1.74%), respectively, but the aggregation by the lower-density C. pilulifera was not apparent.