Book contents
- Frontmatter
- Contents
- List of contributors
- Preface
- 1 Introduction
- 2 Effects of fisheries on ecosystems: just another top predator?
- 3 Physical forcing in the southwest Atlantic: ecosystem control
- 4 The use of biologically meaningful oceanographic indices to separate the effects of climate and fisheries on seabird breeding success
- 5 Linking predator foraging behaviour and diet with variability in continental shelf ecosystems: grey seals of eastern Canada
- 6 Distribution and foraging interactions of seabirds and marine mammals in the North Sea: multispecies foraging assemblages and habitat-specific feeding strategies
- 7 Spatial and temporal variation in the diets of polar bears across the Canadian Arctic: indicators of changes in prey populations and environment
- 8 Biophysical influences on seabird trophic assessments
- 9 Consequences of prey distribution for the foraging behaviour of top predators
- 10 Identifying drivers of change: did fisheries play a role in the spread of North Atlantic fulmars?
- 11 Monitoring predator–prey interactions using multiple predator species: the South Georgia experience
- 12 Impacts of oceanography on the foraging dynamics of seabirds in the North Sea
- 13 Foraging energetics of North Sea birds confronted with fluctuating prey availability
- 14 How many fish should we leave in the sea for seabirds and marine mammals?
- 15 Does the prohibition of industrial fishing for sandeels have any impact on local gadoid populations?
- 16 Use of gannets to monitor prey availability in the northeast Atlantic Ocean: colony size, diet and foraging behaviour
- 17 Population dynamics of Antarctic krill Euphausia superba at South Georgia: sampling with predators provides new insights
- 18 The functional response of generalist predators and its implications for the monitoring of marine ecosystems
- 19 The method of multiple hypotheses and the decline of Steller sea lions in western Alaska
- 20 Modelling the behaviour of individuals and groups of animals foraging in heterogeneous environments
- 21 The Scenario Barents Sea study: a case of minimal realistic modelling to compare management strategies for marine ecosystems
- 22 Setting management goals using information from predators
- 23 Marine reserves and higher predators
- 24 Marine management: can objectives be set for marine top predators?
- Index
- References
5 - Linking predator foraging behaviour and diet with variability in continental shelf ecosystems: grey seals of eastern Canada
Published online by Cambridge University Press: 31 July 2009
Book contents
- Frontmatter
- Contents
- List of contributors
- Preface
- 1 Introduction
- 2 Effects of fisheries on ecosystems: just another top predator?
- 3 Physical forcing in the southwest Atlantic: ecosystem control
- 4 The use of biologically meaningful oceanographic indices to separate the effects of climate and fisheries on seabird breeding success
- 5 Linking predator foraging behaviour and diet with variability in continental shelf ecosystems: grey seals of eastern Canada
- 6 Distribution and foraging interactions of seabirds and marine mammals in the North Sea: multispecies foraging assemblages and habitat-specific feeding strategies
- 7 Spatial and temporal variation in the diets of polar bears across the Canadian Arctic: indicators of changes in prey populations and environment
- 8 Biophysical influences on seabird trophic assessments
- 9 Consequences of prey distribution for the foraging behaviour of top predators
- 10 Identifying drivers of change: did fisheries play a role in the spread of North Atlantic fulmars?
- 11 Monitoring predator–prey interactions using multiple predator species: the South Georgia experience
- 12 Impacts of oceanography on the foraging dynamics of seabirds in the North Sea
- 13 Foraging energetics of North Sea birds confronted with fluctuating prey availability
- 14 How many fish should we leave in the sea for seabirds and marine mammals?
- 15 Does the prohibition of industrial fishing for sandeels have any impact on local gadoid populations?
- 16 Use of gannets to monitor prey availability in the northeast Atlantic Ocean: colony size, diet and foraging behaviour
- 17 Population dynamics of Antarctic krill Euphausia superba at South Georgia: sampling with predators provides new insights
- 18 The functional response of generalist predators and its implications for the monitoring of marine ecosystems
- 19 The method of multiple hypotheses and the decline of Steller sea lions in western Alaska
- 20 Modelling the behaviour of individuals and groups of animals foraging in heterogeneous environments
- 21 The Scenario Barents Sea study: a case of minimal realistic modelling to compare management strategies for marine ecosystems
- 22 Setting management goals using information from predators
- 23 Marine reserves and higher predators
- 24 Marine management: can objectives be set for marine top predators?
- Index
- References
Summary
Upper-trophic-level marine predators are presumed to respond to environmental variability. However, the nature of these responses has been studied in few pinnipeds, particularly during the non-breeding season. Between 1992 and 2003, we measured a suite of behavioural, dietary and life-history variables in grey seals; variables which were expected to vary in response to changes in prey availability. We found significant inter-annual variation in some diving variables indicative of foraging effort and in the species composition of their diets. Postpartum body mass of adult females did not vary inter-annually, but duration of offspring investment (lactation length), total energy investment (offspring weaning mass) and the difference in weaning mass of male and female pups did. There was considerable inter-annual variation in the estimated biomass of grey seal prey species from summer bottom-trawl surveys; however, there was little correlation between grey seal response variables with those estimates. There could be several reasons for this result, but three stand out. First, grey seal numbers on the Scotian Shelf have increased exponentially over the past four decades, implying overall favourable environmental conditions. Grey seals may have adjusted their behaviour and diet to account for variability in prey characteristics other than biomass. Secondly, foraging grey seals and their prey were not sampled at the same time of year. Finally, trends in the biomass of many of the species eaten by grey seals are poorly estimated, thus limiting our understanding of predator responses to ecosystem state.
- Type
- Chapter
- Information
- Top Predators in Marine EcosystemsTheir Role in Monitoring and Management, pp. 63 - 81Publisher: Cambridge University PressPrint publication year: 2006
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