| Summary: | The distribution and abundances of marine top predators are being threatened by climate change. The trophic position and warm blooded physiology of seabirds makes the abundance and distribution of these organisms susceptible to the indirect effects of climate change affecting the demographies of their prey. Due to the complexity of the marine ecosystem other factors, such as fishing activities, can also have a dramatic influence on the abundance and distribution of seabirds. Using a long-term data set of at-sea observations, investigations to identify any abundance and distribution changes of nine seabird species between 1995 and 2010 in the Bay of Biscay and English Channel was undertaken. Three explanatory variables (sea surface temperature, chlorophyll-a concentration and fishing catch statistics) were used to examine if climate change and fishing activities had any influence on seabird abundance changes. Northerly shifts in distribution were recorded for the northern gannet (Morus bassanus) and the great skua (Stercorarius skua) whereas; a southerly shift was identified for the cory’s shearwater (Calonectris borealis). The abundance of northern fulmars (Fulmarus glacialis) increased and the abundance of northern gannets in parts of the Bay of Biscay and English Channel decreased. Although the independent effect of the three explanatory variables did influence the abundance of some species their effect actually contradicted the abundance trends identified. This implies that there are numerous factors acting on the abundance of seabirds in this area and highlights the importance of choosing the appropriate type of variable that will best explain seabird demographic trends. As the effects of climate change in this region are predicted to intensify the findings are essential for the development of future conservation management plans in the Bay of Biscay and English Channel. Faculty of Science
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