Abstract
Cetacean observations obtained during sighting surveys for abundance estimation can also be used to investigate cetacean habitat and prey selection, the principal processes underlying cetacean distributions. In this paper, we investigate habitat and prey selection of minke (Balaenoptera acutorostrata), fin (B. physalus) and sperm (Physeter macrocephalus) whales and Lagenorhynchus (Atlantic white-sided L. acutus and white-beaked L. albirostris) dolphins observed along predetermined cruise tracks along the Barents Sea shelf edge in 2000, 2001 and 2002. The observations were combined with simultaneously collected data on habitat (depth, sea surface temperature, and temperature gradients) and prey (plankton, 0-group fish, capelin and herring) distributions in a GeographicInformation System (GIS) to investigate habitat and prey selection. Minke whales were associated with cold waters and herring, and capelin in years with low herring abundance. Fin whales were mainly associated with northern cold and deep waters, as well as capelin, 0-group fish and plankton. Lagenorhynchus dolphins were associated with capelin. Finally, sperm whales were associated with deep waters and 0-group fish. Sperm whales were probably indirectly attracted to 0-group fish through preying on predatory fish such as Sebastes spp. and the squid Gonatus spp. The cetacean species responded differently to annual variation in habitat and prey distributions. Minke and fin whale distributions and abundances remained similar between years within the study area, suggestingthat these species are generalists responding to environmental changes by switching between prey species. Conversely, Lagenorhynchus dolphins shifted northwards, likely due to tracking the shifting capelin distributions. The results are discussed in light of how such cetacean habitat and cetacean prey relationships can be valuable for the proper assessment of population sizes and trends, both through guiding the design of sighting surveys and assessing whether changes in abundances within fixed surveyed areas are due to distribution shifts or changes in population sizes.
Highlights
Sighting surveys, like the North Atlantic Sightings Surveys (NASS), are primarily performed for assessing abundance and distribution of cetacean species, and when repeated over time, for assessing temporal trends in cetacean abundance and distribution
Cetacean habitat and prey selection should be dynamic behavioural processes responding to environmental changes rather than static behavioural rules
In the warmer Atlantic water masses the zooplankton community mainly consists of krill (Euphausiids) and copepods (Calanus finmarchichus), in colder Arctic water masses of copepods (C. glacialis, C. hyperboreus) and amphipods (e.g. Themisto libellula) (Dalpadado et al 1998, Tande et al 2000)
Summary
Like the North Atlantic Sightings Surveys (NASS), are primarily performed for assessing abundance and distribution of cetacean species, and when repeated over time, for assessing temporal trends in cetacean abundance and distribution. When combined with information on habitat and prey distributions, cetacean distributions as observed on sighting surveys may provide valuable input to investigations of cetacean habitat and prey selection, and increase our understanding of the processes underlying and causing variation in cetacean distributions. Such information allows evaluation of whether changes in abundance within repeatedly surveyed areas are due to changes in abundance or in distributions (Forney 2000). Prey tracking may result in selective habitat use, defined as significant correlations between cetacean distributions and physical habitat measures
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
