Fishing effort

Organic pollution

In addition to determining the composition of the biological community and monitoring it for any evidence of natural or human-induced change, any SAC management scheme will also have to identify and assess the potential causes of environmental change at that locality. In the context of the ‘Sea pens and burrowing megafauna’ biotope complex, these are most likely to be the Nephrops fishery and any localized sources of organic pollution.

The frequency of trawler visits to a locality should ideally be recorded, as should the number of boats engaged in creel fishing for Nephrops. The estimation of trawling pressure may be difficult because site observation is unlikely to be continuous, and trawlers have been known to operate at night in order to avoid detection. Within an SAC, fishing activity could be monitored by the requirement to record accurate catch and effort data in logbooks provided for the purpose. Needless to say, gaining any of this information will require an SAC officer to maintain good relations with the local community and regional fisherman’s organization, both of which will be represented on the local SAC management group.

Only a few candidate marine SACs are in locations so remote as to be unaffected by the human input of organic matter to the sea. In most sites harbouring the ‘Sea pens and burrowing megafauna’ biotope complex there will be some degree of sewage input, while sites in the west of Scotland will be potentially affected by salmon or shellfish farming. Point sources of organic matter in or close to a marine SAC should be identified, and also the quantities of material involved. Data on volumes of effluent emitted from sewage outfalls or tonnage deposited at sludge disposal grounds will be obtainable from the relevant regional water authorities or environmental agencies. Aquaculture sites should be monitored for fish tonnage (which will determine the output of waste from the farm), and for the usage of anti-parasite chemical treaments. Computer models are now available to predict the dispersal distances and sedimentation rates of particulate organic matter from sewage outfalls and fish farms, and these should be an important aid to management of marine sites in the future.

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