Solway Firth UK 1 – Oystercatcher and Knot

March 2008

The Solway Firth (54°45’N, 03°40’W) is a large coastal area consisting of estuaries, intertidal sediments and saltmarshes, fed by nine major freshwater inputs. In terms of the shellfish assemblage, the key species of interest to fishermen are cockles (Cerastoderma edule L.), whilst shorebirds consume cockles, mussels (Mytilus edulis L.) and Baltic tellin (Macoma balthica L.) (Howell et al., 2007). The area is of high importance for shorebird conservation, supporting internationally significant populations of many species. As a consequence of its importance for shorebird conservation, the Solway Firth has been designated as a Special Protection Area (SPA), Site of Special Scientific Interest (SSSI) and Ramsar site. The Solway estuary is recognised as a site of international importance for both Eurasian oystercatcher (Haematopus ostralegus L.) and red knot (Calidris canutus L.), supporting the second and tenth largest populations respectively, within the UK (Holt et al., 2012).

Issues

The shared shellfish resources within estuarine areas have led to conflicts between economic and conservation interests across estuaries in northwest Europe (Tinker, 1974; Ens, 2006; Laursen et al., 2010; Stillman & Wood, accepted). Enough shellfish must be left unharvested to allow the birds to meet their food requirements. The responses of shorebird species to insufficient food supplies during the overwinter period, which include reduced individual body condition, increased mortality and reduced population sizes, have been well-documented in the scientific literature (Camphuysen et al., 1996; Verhulst et al., 2004; Atkinson et al., 2003; Atkinson et al., 2005; Atkinson et al., 2010). Therefore, a central question facing statutory authorities of estuaries is: how much food should be left unharvested for the bird population?

Modelling

The model is based on the energy requirements of the birds together with the energy value of their shellfish food. The model predicts the quantity of shellfish required to maintain high survival rates, and hence avoid significant mortality events within the oystercatcher and knot populations.

Results

….

Funding and Collaboration

Scottish Natural Heritage and Marine Scotland

Related Paper:

Stillman, R.A. & Wood, K.A. (2013). Predicting food requirements of overwintering shorebird populations on the Solway Firth. A report to Scottish Natural Heritage and Marine Scotland. Bournemouth University, Poole. 37 pp.