Monitoring of ecological effects of coastal aquaculture wastes.

Abstract

Soluble inorganic and particulate waste from coastal aquaculture farms can result in organic enrichment of the local aquatic environment. To prevent unacceptable changes to the environment, an environmental management framework should be established as a means of regulating development and evaluating potential impacts before permission to develop is granted. However, any environmental assessment and monitoring effort should be related to the scale of perceived impact of a given aquaculture opera tion. An Environmental Impact Assessment should be undertaken to predict significant potential impacts, and monitoring carried out (once production has begun) to detect and evaluate the scale of impact. Monitoring is therefore part of the regulatory process which ensures that ecological change associated with aquaculture waste is kept within pre-determined, acceptable levels. Monitoring programmes may provide the information base for decisions to allow for further expansion or development should measured levels prove that observed ecological change is below unacceptable limits. Accordingly, information from monitoring can be essential for deciding whether or not to allow the expansion of existing aquaculture operations. Successful monitoring will depend on a baseline survey being carried out in conjunction with an Environmental Impact Assessment. The purpose of the baseline survey is to obtain data which can assist in designing an appropriate monitoring programme, and to provide ref erence data against which changes caused by farm waste can be measured. To optimise resources, the level of monitoring (number of variables and frequency of monitoring) should be related to the size of the operation and the sensitivity of the receiving water body. Additional elements of monitoring programmes which need to be given careful consideration include: selection of reference stations; standardisation of sampling and analytical procedures; analysis and interpretation of data. Given that a particular monitoring programme should be matched to the size, type and location of a coastal aquaculture installation, it is not appropriate to recommend standard monitoring programmes. However, a range of variables commonly used in monitoring are discussed together with an evaluation of their value in interpreting changes resulting from release of waste from farms. To illustrate how particular monitoring programmes might be developed, five example scenarios are presented.