Passive acoustic density estimation of sperm whales in the Tongue of the Ocean,Bahamas |
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Authors: | Len Thomas Susan Jarvis Nancy DiMarzio David Moretti Tiago A Marques Charlotte Dunn Eva Hartvig Peter Tyack |
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Institution: | 1. Naval Undersea Warfare Center Division, 1176 Howell Street, Newport, Rhode Island 02841, U.S.A.;2. Center for Research into Ecological and Environmental Modelling, University of St. Andrews, St. Andrews, KY16 9LZ, Scotland;3. Center for Research into Ecological and Environmental Modelling, University of St. Andrews, St. Andrews, KY16 9LZ, Scotland, and Centro de Estatística e Aplica??es da Universidade de Lisboa, Campo Grande, Lisboa, Portugal;4. Bahamas Marine Mammal Research Organisation, PO Box AB‐20714a, Marsh Harbour, Abaco, Bahamas, and Sea Mammal Research Unit, University of St. Andrews, St. Andrews, KY16 8LB, Scotland;5. Sea Mammal Research Unit, University of St. Andrews, St. Andrews, KY16 8LB, Scotland;6. 266 Woods Hole Road, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, U.S.A. |
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Abstract: | Long‐term passive acoustic monitoring of marine mammals on navy ranges provides the opportunity to better understand the potential impact of sonar on populations. The navy range in Tongue of the Ocean (TOTO), Bahamas contains extensive hydrophone arrays, potentially allowing estimation of the density of deep diving, vocally active species such as the sperm whale (Physeter macrocephalus). Previous visual surveys in TOTO have been of limited spatio–temporal coverage and resulted in only sporadic sightings of sperm whales, whereas passive acoustic observations suggest the species is present year round. However, until now the means of acoustically determining the specific number of individuals in each cluster has been limited. We used recently developed algorithms to identify the number of echolocating whales present during a 42 d study period. We screened a 297 h acoustic data set to determine the proportion of time animals were present; fifty 10 min samples during presence were analyzed to estimate the number of individuals vocalizing during each sample. These counts were combined with an independent estimate of the proportion of 10 min periods when tagged animals vocalize. The estimated average density was 0.16 whales/1,000 km2 (CV 27%; 95% CI 0.095–0.264). The method is potentially applicable to other areas containing dense hydrophone arrays. |
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Keywords: | animal density population size sperm whale Physeter macrocephalus passive acoustic array |
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