Revised 12/15/2000 DWARF SPERM WHALE (Kogia sima): Hawaiian Stock

• Main Authors: Stock Definition, Geographic Range
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Pacific; Sperm whale
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.295.187; http://www.nmfs.noaa.gov/pr/pdfs/sars/po2000whds-hi.pdf

Dwarf sperm whales are found throughout the world in tropical to warm-temperate waters (Nagorsen 1985). One sighting in an unspecified locality, one stranding on Oahu (Tomich 1986), and one stranding on Lanai (Nitta 1991) constitute the only evidence that this species inhabits Hawaiian waters (Tomich 1986). Two sightings of pygmy or dwarf sperm whales were made between Hawaii and Maui during 1993-98 aerial surveys within about 25 nmi of the main Hawaiian Islands (Figure 1; Mobley et al. 1999). The difficulty of detecting and identifying it at sea, as well as its confusion with the pygmy sperm whale, may partially explain the paucity of records. For the Marine Mammal Protection Act (MMPA) stock assessment reports, there is a single Pacific management stock of dwarf sperm whales including only animals found within the U.S. Exclusive Economic Zone of the Hawaiian Islands. Rice (1998) recently argued that the species name simus, is incorrect and should be replaced by sima. This change is not taxonomic, but merely reflects rules of Latin usage. Figure 1. Pygmy or dwarf sperm whale sighting locations during 1993-98 aerial surveys within about 25 nmi of the main Hawaiian Islands (see Appendix 2 for details on timing and location of survey effort). Outer line indicates approximate boundary of survey area. POPULATION SIZE Wade and Gerrodette (1993) provided an estimate for the eastern tropical Pacific, but no data are available to estimate population size for this species in the central Pacific. As part of the Marine Mammal Research Program of the Acoustic Thermometry of Ocean Climate (ATOC) study, a total of twelve aerial surveys were conducted within about 25 nmi of the main Hawaiian Islands in 1993, 1995 and 1998. Two sightings of five pygmy or dwarf sperm whales were made; however these sightings were excluded during recent abundance analyses (Mobley et al. 2000), because they were made during poor observation conditions. Therefore, no abundance estimate is available for dwarf sperm whales within Hawaiian waters.