Management of marine cage aquaculture |
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Authors: | Cai Huiwen Sun Yinglan |
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Institution: | (1) College of Environmental Science and Engineering, Ocean University of China, Yu Shan Road 5, 266003 Qingdao, China |
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Abstract: | Goal, Scope and Background Marine cage aquaculture produces a large amount of waste that is released directly into the environment. To effectively manage
the mariculture environment, it is important to determine the carrying capacity of an aquaculture area. In many Asian countries
trash fish is dominantly used in marine cage aquaculture, which contains more water than pellet feed. The traditional nutrient
loading analysis is for pellet feed not for trash fish feed. So, a more critical analysis is necessary in trash fish feed
culturing areas.
Methods Corresponding to FCR (feed conversion rate), dry feed conversion rate (DFCR) was used to analyze the nutrient loadings from
marine cage aquaculture where trash fish is used. Based on the hydrodynamic model and the mass transport model in Xiangshan
Harbor, the relationship between the water quality and the waste discharged from cage aquaculture has been determined. The
environmental carrying capacity of the aquaculture sea area was calculated by applying the models noted above.
Results Nitrogen and phosphorus are the water quality parameters considered in this study. The simulated results show that the maximum
nitrogen and phosphorus concentrations were 0.216 mg/L and 0.039 mg/L, respectively. In most of the sea area, the nutrient
concentrations were higher than the water quality standard. The calculated environmental carrying capacity of nitrogen and
phosphorus in Xiangshan Harbor were 1,107.37 t/yr and 134.35 t/yr, respectively. The waste generated from cage culturing in
2000 has already exceeded the environmental carrying capacity.
Discussion Unconsumed feed has been identified as the most important origin of all pollutants in cage culturing systems. It suggests
the importance of increasing the feed utilization and improving the feed composition on the basis of nutrient requirement.
For the sustainable development of the aquaculture industry, it is an effective management measure to keep the stocking density
and pollution loadings below the environmental carrying capacity.
Conclusions The DFCR-based nutrient loadings analysis indicates, in trash fish feed culturing areas, that it is more critical and has
been proved to be a valuable loading calculation method. The modeling approach for Xiangshan Harbor presented in this paper
is a cost-effective method for assessing the environmental impact and determining the capacity. Carrying capacity information
can give scientific suggestions for the sustainable management of aquaculture environments.
Recommendations and Perspectives It has been proved that numerical models were convenient tools to predict the environmental carrying capacity. The development
of models coupled with dynamic and aquaculture ecology is a requirement of further research. Such models can also be useful
in monitoring the ecological impacts caused by mariculture activities.
ESS-Submission Editor: Hailong Wang (hailong.wang@ensisjv.com) |
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Keywords: | Cage aquaculture dry feed conversion rate environmental carrying capacity hydrodynamic model mass transport model response relationship Xiangshan Harbor |
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