Biological Control of Macroalgae Fouled on the Net of Marine Cage Using Siganus oramin in Northern China

Abstract:

Accumulation of macroalgae fouled on the net of marine cage during hot seasons is one of the major problems of the cage culture in Northern China. Biological clearance is an effective way to solve this problem. In this study, Siganus oramin was used as the potential “cleaner” fish to control the fouling macroalgae. From June to November in 2015, a series of laboratory experiments and field observations were carried out in the cage culture area around Chudao in the Sanggou Bay. We investigated the monthly variation of the biomass and diversity of fouling macroalgae in different layers, the feeding activity of S. oramin on the dominant specie of fouling macroalgae, and the cleaning effect of S. oramin on the fouling macroalgae. The results showed that in the same month, the growth rates of fouling macroalgae varied according to their layers; from 7th August to 14th September, the growth rate of fouling macroalgae was significantly higher than in other months in different layers (P<0.01). Plocamium telfairiae was the dominant species in this area. A carbon budget equation for the S. oramin feeding on Plocamium telfairiae (100C=11.69G+10.82F+6.06U+71.43R) was constructed under the appropriate seawater temperature. The initial average wet weight of S. oramin was (1.44±0.61) g and it reached (45.38±4.22) g after a 152-day cultural period; the growth rate was 0.26 g/d. The removal rate for fouling macroalgae varied between 80.28% and 90.15% in the cage culture area. These results suggested that the removal of fouling macroalgae was more efficient using this method and thus it could be used to control the fouling macroalgae on the net of marine cages.