TY - JOUR
T1 - An integrated approch to the foraging ecology of marine birds and mammals
AU - Croll, Donald A.
AU - Tershy, Bernie R.
AU - Hewitt, Roger P.
AU - Demer, David A.
AU - Fiedler, Paul C.
AU - Smith, Susan E.
AU - Armstrong, Wesley
AU - Popp, Jacqueline M.
AU - Kiekhefer, Thomas
AU - Lopez, Vanesa R.
AU - Urban, Jorge
AU - Gendron, Diane
N1 - Funding Information:
We thank the participants of the Bioacoustical Oceanography Workshop, and our many Þeld assistants and vessel crews for their dedication and support. We particularly thank the researchers and crew of the R/V Ballena, R/V David Starr Jordan, R/V Amigo, and R. Pavia owner and captain of the S/V Star Rover. In particular, we thank Ed Cassano and Steve Beckwith of the Channel Islands National Marine Sanctuary for their Þeld support, D. Costa for his enthusiastic input in approach development, and D. Breese for her participation at every level. J. Goodyear andB. Mate provided useful insight into tag design. Jamie Stamps and Dick Jones of Sandia National Laboratory provided many hours of engineering expertise and design. K. Firstrup and C. Greene provided useful comments on the manuscript. Sheryl Aronson, Vicki Case, and Sue Kato helped insure the smooth functioning of our research operations. This research was supported by Office of Naval Research Grant N00014-95-10646 to D. Croll, National Oceanic and Atmospheric Administration Contracts 40ABNC602168 and 40ABNF600916 to D. Croll and B. Tershy, National Oceanic and Atmospheric Administration Contract 50ABNF500153 to D. Costa, D. Croll, T. Williams, and J. Harvey, and Scripps Institution of Oceanography ARPA MDA 972-93-1-003 to D. Costa.
PY - 1998/7
Y1 - 1998/7
N2 - Birds and mammals are important components of pelagic marine ecosystems, but our knowledge of their foraging ecology is limited. We distinguish six distinct types of data that can be used in various combinations to understand their foraging behavior and ecology. We describe methods that combine concurrent dive recorder deployment, oceanographic sampling, and hydroacoustic surveys to generate hypotheses about interactions between the physical environment and the distribution, abundance, and behavior of pelagic predators and their prey. Our approach is to (1) map the distribution of whales in relation to the distribution of their prey and the physical features of the study area (bottom topography, temperature, and salinity); and (2) measure the foraging behavior and diet of instrumented whales in the context of the fine-scale distribution and composition of their prey and the physical environment. We use this approach to demonstrate a relationship between blue whale distribution, sea surface temperature, and concentrations of their euphausiid prey at different spatial scales offshore of the Channel Islands, California. Blue whale horizontal spatial distribution was correlated with regions of high acoustic backscatter. Blue whale dive depths closely tracked the depth distribution of krill. Net sampling and whale diet revealed that whales fed exclusively upon dense schools of Euphausia pacifica (between 100 and 200 m) and Thysanoessa spinifera (from the surface to 100 m). Whales concentrated foraging efforts upon those dense euphausiid schools that form downstream from an upwelling center in close proximity to regions of steep topographic relief. We propose that (1) the distribution of Balaenoptera whales in the coastal California Current region is defined by their attraction to areas of predictably high prey density; (2) the preferred prey of these whales are several species of euphausiids (E. pacifica, T. spinifera, and N. simplex) that are abundant in the California Current region; (3) blue whales concentrate their foraging efforts on dense aggregations of euphausiids found at discrete depths in the water column; (4) these localized areas of high euphausiid densities are predictable and sustained by enhanced levels of primary productivity in regions which are located downstream from coastal upwelling centers (indicated by sea surface temperature); (5) topographic breaks in the continental shelf located downstream from these upwelling centers work in concert with euphausiid behavior to collect and maintain large concentrations of euphausiids swarms, and (6) despite seasonal and inter-annual variability, these processes are sufficiently consistent that the distribution of Balaenoptera whales can be predicted.
AB - Birds and mammals are important components of pelagic marine ecosystems, but our knowledge of their foraging ecology is limited. We distinguish six distinct types of data that can be used in various combinations to understand their foraging behavior and ecology. We describe methods that combine concurrent dive recorder deployment, oceanographic sampling, and hydroacoustic surveys to generate hypotheses about interactions between the physical environment and the distribution, abundance, and behavior of pelagic predators and their prey. Our approach is to (1) map the distribution of whales in relation to the distribution of their prey and the physical features of the study area (bottom topography, temperature, and salinity); and (2) measure the foraging behavior and diet of instrumented whales in the context of the fine-scale distribution and composition of their prey and the physical environment. We use this approach to demonstrate a relationship between blue whale distribution, sea surface temperature, and concentrations of their euphausiid prey at different spatial scales offshore of the Channel Islands, California. Blue whale horizontal spatial distribution was correlated with regions of high acoustic backscatter. Blue whale dive depths closely tracked the depth distribution of krill. Net sampling and whale diet revealed that whales fed exclusively upon dense schools of Euphausia pacifica (between 100 and 200 m) and Thysanoessa spinifera (from the surface to 100 m). Whales concentrated foraging efforts upon those dense euphausiid schools that form downstream from an upwelling center in close proximity to regions of steep topographic relief. We propose that (1) the distribution of Balaenoptera whales in the coastal California Current region is defined by their attraction to areas of predictably high prey density; (2) the preferred prey of these whales are several species of euphausiids (E. pacifica, T. spinifera, and N. simplex) that are abundant in the California Current region; (3) blue whales concentrate their foraging efforts on dense aggregations of euphausiids found at discrete depths in the water column; (4) these localized areas of high euphausiid densities are predictable and sustained by enhanced levels of primary productivity in regions which are located downstream from coastal upwelling centers (indicated by sea surface temperature); (5) topographic breaks in the continental shelf located downstream from these upwelling centers work in concert with euphausiid behavior to collect and maintain large concentrations of euphausiids swarms, and (6) despite seasonal and inter-annual variability, these processes are sufficiently consistent that the distribution of Balaenoptera whales can be predicted.
UR - http://www.scopus.com/inward/record.url?scp=0032124734&partnerID=8YFLogxK
U2 - 10.1016/S0967-0645(98)00031-9
DO - 10.1016/S0967-0645(98)00031-9
M3 - Artículo
SN - 0967-0645
VL - 45
SP - 1353
EP - 1371
JO - Deep-Sea Research Part II: Topical Studies in Oceanography
JF - Deep-Sea Research Part II: Topical Studies in Oceanography
IS - 7
ER -