Environmental impacts on aquaculture

The major drivers of ecosystem changes and their relative importance for aquaculture

All human activities have an impact on the environment and as such, aquaculture is expected to affect the environment in various degrees. None the less, aquaculture is at the same time strongly dependent on ecosystem quality and its resources. It therefore appears vulnerable to environmental change and pollution caused by nature, other users of the coastal zone or by its own activities. Evidently, for the development of a sustainable aquaculture industry it is very important to know what forces affect most the water quality in aquaculture zones, and to what extent. That could, in turn, help in establishing appropriate indicators of the aquaculture-environment interactions which would further enable farmers, regulators and other groups of policy makers to effectively select sites for aquaculture activities and for monitoring the environmental impacts on aquaculture.

Assessing anthropogenic impact

An extensive bibliographic review along with experts’ opinion revealed that aquaculture is primarily affected by other uses of the coastal zone. Table 1 summarises the different human activities that have an impact on aquaculture and their strength. All studied activities are conceived as having a detectable effect on aquaculture; industrial activities, intensive agriculture, and even recreational activities may cause chemical pollution in the vicinity of aquaculture zones through their effluents; urbanization and tourism is more likely to cause bacteriological pollution; the biological aspect of pollution and disease transmission are connected with maritime activities and aquaculture itself. It is worth noting that though some human activities may occasionally have a catastrophic effect on aquaculture, e.g. oil spills caused by tanker accidents. The  fact that these occur scarcely does not consider them more risky for the aquaculture industry and therefore their potential impact on aquaculture is rated lower.

A questionnaire based survey that was carried out among farmers of a well developed aquaculture area in Portugal indicated that the farmers, indeed, fear more the effect other uses of the coastal zone may have on the environment and eventually on them. However, insurance data collected from Mediterranean areas revealed that only a low percentage of aquaculture damages are due to anthropogenic activities, which could be explained by the fact that farmers try to avoid conflicts with other users of the coastal zone by simply not sharing the same water body with them.

Table 1. List of sources of pressure on aquaculture and their extent of impact. Numbers “3”, “2”, “1” denote increasing impact strength of the pressure. e.g. 1 = high impact, 3 = low impact.

The following measurements are proposed as potential indicators for efficient site selection and as a good proxy of incompatibilities between aquaculture and other anthropogenic activities.