Dee Estuary

March 2008

Any estuaries around the UK are classified as Special Protection Areas (SPAs) for shorebirds. Conservation agencies have to monitor these estuaries to make sure there is enough food for the important shorebird species living there and that human activities on the estuary do not disturb the birds too much. We are developing models for three Welsh SPAs – the Burry Inlet, Traeth Lafan and the Dee Estuary – which contain large populations of cockles and are important wintering sites for oystercatchers and knot.

Issues

There are three main issues. (1) What is the best way of monitoring the amount of food available to the birds in each estuary (2) How much food is needed to support the oystercatcher and knot populations currently found in each estuary (3) How much disturbance can occur on each estuary without affecting the birds.

Modelling

In the past, cockle populations in each SPA have been sampled only for fisheries purposes. The surveys provide a good estimate of cockle stocks in the fished areas, but do not estimate the total stock throughout the site. We designed grid-based sampling schemes to estimate the abundance and location of cockles and mussels throughout each site and all three estuaries were surveyed. The data were used to develop individual-based models for each site.

Results

The individual-based models showed how dependent oystercatchers and knot were on shellfish stocks at each site. They are now used as a tool to provide evidence when making decisions about the fishery.

Funding and Collaboration

Countryside Council for Wales, Environment Agency Wales.

Related Paper:

….