Ecological Consequences of Oyster Culture

Originally published in Journal of Fisheries & Livestock Production

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It is now stated that aquaculture activities cause environmental disturbances [6,8,9]. Oysters farming usually results in a net removal of nutrients from the water column and may also compete with other organisms for survival (e.g seagrass) and this is generally considered to cause environmental damage. In the Pertuis Charentais (SW France), oysters have traditionally been cultivated directly on the sediment, hereafter called on-bottom culture, but currently the most common technique is on tray culture (Figure 1), hereafter called off-bottom culture.

This involves placing the oysters in plastic mesh bags tied to metal trestles. The presence of trestles arranged in parallel rows in the intertidal area [10] significantly reduces the strength of tidal currents [4]. This limits the dispersal of pseudo-faeces and faeces in the water column and thus increases the natural sedimentation process by several orders of magnitude [11]. The adverse effects of aquaculture-derived organic matter loads on subtidal benthic assemblages are known [12], so in view of the features of on- bottom and off-bottom culture methods, it is plausible that off-bottom cultures cause more disturbance than on-bottom cultures to intertidal benthic environments. Other potential negative impacts associated with oyster farming include; physical impacts associated with farming structures and farm operations, reductions in native stocks caused by the collection of result wild seed and impacts associated with the introduction of exotic or invasive species