Fin whale (Balaenoptera physalus) population identity in the western Mediterranean Sea

Authors

  • Manuel Castellote,

    1. UCM Group for the Study of Animal and Human Behaviour (Gecah), Departamento de Psicobiología, Universidad Complutense de Madrid,
      Campus de Somosaguas, 28223 Madrid, Spain
      E-mail: manuel.castellote@noaa.gov
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    • Current address: National Marine Mammal Laboratory, Alaska Fisheries Science Center/NOAA, 7600 Sand Point Way N.E. F/AKC3, Seattle, Washington 98115-6349, U.S.A.

  • Christopher W. Clark,

    1. Bioacoustics Research Program,
      Cornell Lab of Ornithology,
      159 Sapsucker Woods Road,
      Ithaca, New York 14850, U.S.A.
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  • Marc O. Lammers

    1. Hawaii Institute of Marine Biology,
      University of Hawaii,
      Kaneohe, Hawaii 96744, U.S.A.
      and
      Oceanwide Science Institute,
      PO Box 61692,
      Honolulu, Hawaii 96744, U.S.A.
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Abstract

Archival bottom-mounted audio recorders were deployed in nine different areas of the western Mediterranean Sea, Strait of Gibraltar, and adjacent North Atlantic waters during 2006–2009 to study fin whale (Balaenoptera physalus) seasonal presence and population structure. Analysis of 29,822 recording hours revealed typical long, patterned sequences of 20 Hz notes (here called “song”), back-beats, 135–140 Hz notes, and downsweeps. Acoustic parameters (internote interval, note duration, frequency range, center and peak frequencies) were statistically compared among songs and song notes recorded in all areas. Fin whale singers producing songs attributable to the northeastern North Atlantic subpopulation were detected crossing the Strait of Gibraltar and wintering in the southwestern Mediterranean Sea (Alboran basin), while songs attributed to the Mediterranean were detected in the northwest Mediterranean basin. These results suggest that the northeastern North Atlantic fin whale distribution extends into the southwest Mediterranean basin, and spatial and temporal overlap may exist between this subpopulation and the Mediterranean subpopulation. This new interpretation of the fin whale population structure in the western Mediterranean Sea has important ecological and conservation implications. The conventionally accepted distribution ranges of northeastern North Atlantic and Mediterranean fin whale subpopulations should be reconsidered in light of the results from this study.

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