Chapter 6 Environmental Issues Associated with Offshore Aquaculture & Modeling Potential Impact

Real and perceived aquaculture environmental impacts that must be considered prior to expansion to open ocean locations include: 1) benthic carbon loading, 2) water column nutrification, 3) stimulation of harmful algal blooms, and 4) escapement and implications to wild populations. A simulation model was developed for predicting the benthic impacts from offshore cage culture. The model simulates the impact of feed and feces from one cage on a 600 m2 area on the seafloor using total organic carbon (TOC) as an indicator. A Gaussian error was added to all variable means to represent variation about central tendencies. Cobia, red snapper, and red drum were the cultured species. We also considered depths of 20, 40, and 60 m between feces and feed point of release from the cage and the seafloor. Variables associated with management scenarios and fish biology were held constant throughout simulation runs. Cobia culture resulted in the least impact on TOC accumulation. Cages operated at 40 m depth resulted in 20% less TOC accumulation than those operated at 20 m. Operations at 60 m resulted in an accumulation of TOC of over 60% less of that from 40 m. Additional research is necessary to validate model results with data collected from operating open ocean aquaculture ventures prior to industry usage of the simulation model for site selection and management planning purposes.