Growing abalone on a novel offshore platform: An on-site test of the effects of stocking density and diet

Abstract Offshore wind-wave resistant mechanized platform is a new mode of abalone farming in China compared to the traditional raft-based system. A series of on-site experiments was conducted to identify the optimal cultivation conditions for this new model. The effects of different stocking densities and diets on the survival rate and growth rate were examined. Abalones were placed in four stocking densities (20, 30, 40, and 50% coverage of available surface area of the culture cage) in this platform, and a control group with one density was set in the traditional aquaculture system. In addition, the effects of different diets (formulated diet, dried Laminaria japonica, and fresh Gracilaria lemaneiformis) for abalone were also studied. Over 240 days, reductions of the survival rate and growth rate of shell length and body weight were observed with the increase of the stocking density. Although the abalone were fed adequate food, the growth rate was limited by the stocking density. Condition index increased with the culture time but decreased with the increase of the stocking density. The growth rates of the shell length and body weight in the formulated diet group were significantly higher than the other two diets. The results also indicated that the medium and large-sized abalone may be more suitable for the new platform, as the medium and large-sized abalone had a higher growth rate when culturing on the mechanized platform, whereas small abalone grew faster on the traditional model. The results from this study can provide fundamental data supporting the offshore mechanized farming of abalone, which will not only promote the yield and reduce the stress of coastal aquaculture environments, but also will contribute to the transformation and upgrading of the abalone farming industry.