Abstract
Beaked whales, specifically Blainville's (Mesoplodon densirostris) and Cuvier's (Ziphius cavirostris), are known to feed in the Tongue of the Ocean, Bahamas. These whales can be reliably detected and often localized within the Atlantic Undersea Test and Evaluation Center (AUTEC) acoustic sensor system. The AUTEC range is a regularly spaced bottom mounted hydrophone array covering >350 nm2 providing a valuable network to record anthropogenic noise and marine mammal vocalizations. Assessments of the potential risks of noise exposure to beaked whales have historically occurred in the absence of information about the physical and biological environments in which these animals are distributed. In the fall of 2008, we used a downward looking 38 kHz SIMRAD EK60 echosounder to measure prey scattering layers concurrent with fine scale turbulence measurements from an autonomous turbulence profiler. Using an 8 km, 4-leaf clover sampling pattern, we completed a total of 7.5 repeat surveys with concurrently measured physical and biological oceanographic parameters, so as to examine the spatiotemporal scales and relationships among turbulence levels, biological scattering layers, and beaked whale foraging activity. We found a strong correlation among increased prey density and ocean vertical structure relative to increased click densities. Understanding the habitats of these whales and their utilization patterns will improve future models of beaked whale habitat as well as allowing more comprehensive assessments of exposure risk to anthropogenic sound.
Highlights
Beaked whales are one of the least understood marine mammal taxa in the world’s oceans, the Mesoplodon genera, all of which are listed as data deficient under the IUCN red list [1]
Semi-variograms for acoustic density in the x–y dimensions corroborated these findings with no discernable sill in the variance (Figure 2)
The hydrophone range at AUTEC allowed an unprecedented measurement of the foraging habitat and behavior of these elusive predators
Summary
Beaked whales are one of the least understood marine mammal taxa in the world’s oceans, the Mesoplodon genera, all of which are listed as data deficient under the IUCN red list [1]. Due to their incredibly long and deep dives While Mesoplodon species are found in most of world’s oceans, they are often distributed offshore necessitating the use of large ships to study their behavior and distribution [3]. The lack of information on beaked whale ecology has made assessing the potential risk from anthropogenic activity much more difficult. Recent research using short-duration tags around oceanic islands (i.e., where deep waters are close to shore) has provided valuable and insightful data on diving behavior, beaked whale echolocation, and identifying beaked whale prey [6,7,8]
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