Regional patterns of kittiwake Rissa tridactyla breeding success are related to variability in sandeel recruitment

Abstract

The population dynamics of marine top predators such as seabirds may be self-regulating through local prey depletion, or they may reflect environmentally induced fluctuations in prey availability. Both mechanisms are not mutually exclusive. We examined spatio-temporal variation in breeding success of black-legged kittiwakes Rissa tridactyla, a seabird widely monitored in the British Isles. Kittiwakes here feed mostly on lesser sandeels Ammodytes marinus, a species that is strongly tied to specific sediment types and therefore shows a strong regional population structure. Neither kittiwake colony growth rate nor breeding success correlated negatively with colony size as expected under local prey depletion in the absence of regional variation in carrying capacity. We used multivariate analyses of breeding success data for 42 kittiwake colonies to identify clusters showing synchronised variation in success, and compared these with known sandeel aggregations identified from fish and fishery surveys. A number of geographically distinct clusters of kittiwakes were identified, and these were largely congruent with sandeel aggregations. Major sandeel aggregations with clear associated clusters of kittiwake colonies occurred off of east England and east Scotland, while western coasts of Britain were characterised by smaller aggregations and less obvious kittiwake clusters. There was considerable regional variability in sandeel recruitment, and this was reflected in mostly uncorrelated time series of kittiwake breeding success between different regions. These results indicate that regional variation in prey availability had a stronger effect on kittiwake dynamics than local prey depletion. An appreciation of the appropriate spatial scale of prey dynamics thus improves understanding of the dynamics of marine predator -prey systems.

Recruitment of lesser sandeel Ammodytes marinus in relation to density dependence and zooplankton composition

“…Depleted stocks are more vulnerable to changes in the environment (Brander 2005) and are therefore much more likely to crash. A decline in the North Sea sandeel stock will affect up to 10 species of predatory fishes (Engelhard et al 2008), as well as a number of bird species and marine mammals (Furness 1990, Hain et al 1995, Furness 2002, Frederiksen et al 2005.…”

“…In many ecosystems sandeel is a key prey fish linking trophic levels (Furness 1990, 2002, Hain et al 1995, Frederiksen et al 2005. The lesser sandeel Ammodytes marinus constitutes the vast majority of sandeels in the North Sea and one of the largest fish biomasses (Temming et al 2004, ICES 2005, and has supported a large industrial fishery since the 1950s.…”

Short- and long-term effects of an offshore wind farm on three species of sandeel and their sand habitat

“…Sandeels are important prey for a number of predators including fish, seabirds and marine mammals, and constitute the basis for a large-scale fishery producing raw material for the fish meal and oil industry (e.g. Robards 2000, Furness 2002, Frederiksen et al 2005, MacLeod et al 2007, Dankel et al 2008, Sharples et al 2009, Jensen et al 2011. During the growth season (spring and early summer), sandeels feed in the water column during the day and bury themselves into the sand during the night in habitats consisting of well-oxygenated sand, preferably with a weight fraction of silt+clay < 2% (Winslade 1974, Jensen 2001, Wright et al 2000, van Deurs et al 2011.…”

Environmental Impacts—Marine Ecosystems

“…Breeding success at a given colony of black-legged kittiwakes in the UK is therefore considered to reflect some measure of sandeel availability during the period that birds are associated with the colony, and this assumption is supported by a clear regional clustering of kittiwake breeding success corresponding to the known spatial structuring in sandeel populations (Frederiksen et al 2005).…”