However, there was evidence of gradual erosion (0.23 m y−1) of the saltmarsh’s front cliff edge that may be related to sea level rise (~1.5 mm y−1 in SW England). Aerial photographs of the Tamar showed that the Egypt salt marsh, creeks and mudflat maintained a remarkably consistent structure over a period of >50 years. These species also showed a negative correlation with the NAO index suggesting the declines were related to the milder winters possibly reducing their need to migrate south as far as SW England. There were no significant correlations between over-wintering numbers and dredging activity, but there were significant declines in teal and wigeon over 30 years. Ten species of wildfowl and wader birds were analysed. There were also significant correlations between the number of salmon caught in the Tamar and other rivers of the SW of England. The sea trout abundance was significantly negatively correlated with the NAO index, suggesting that sea trout may be adversely affected by mild winters, which have been a feature of the late 1980’s and 1990’s. There was a significant correlation between the number of salmon caught by rod and the Tamar river flow. Commercially and ecologically important fish species (salmon and sea trout) showed a steady decline in numbers caught in the Tamar since the 1970’s. Spatial and temporal changes in the abundance of intertidal macrofauna (between 19) were analysed but there was insufficient comparable data to enable us to draw any conclusions about long-term changes in the Tamar estuary. Other physical variables, such as Tamar river flow and the North Atlantic Oscillation (NAO) index, representing potential drivers of changes in the abundance of biota, were also examined.

The main objective of this study was to investigate whether there is any evidence of significant temporal changes in key species (intertidal macrofauna, fishes, birds) and habitats (intertidal mudflats and saltmarsh) that could be related to dredging activities in the lower Tamar. The lower Tamar is also the site of the Devonport naval dockyard which requires annual maintenance dredging, as well as occasional capital dredging for new installations. The Tamar estuary is a Special Area of Conservation (SAC) under the EU Habitats and Species Directive and a Special Protection Area under the Wild Birds Directive (1979).

Ecological changes and potential drivers An assessment of the potential impact of dredging activity on the Tamar Estuary over the last. An assessment of the potential impact of dredging activity on the Tamar Estuary over the last century: II.

Data dredging correlations