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Abstract <p>The frequency of occurrence of harbor porpoises, <i>Phocoena phocoena</i> (Linnaeus, 1758), off the northeastern coast of Sakhalin Island (Sea of Okhotsk) was studied in 2008–2021. As the results showed, the frequency of occurrence of this cetacean species in the study area was subject to significant seasonal and interannual variations. The median seasonal frequency of occurrence of harbor porpoises was the highest in October (0.16 individuals per observation hour, ind./h) and was significantly different from that in all other study months (0.09 ind./h). The high frequency of occurrence was presumably related to the seasonal southward migration of harbor porpoises. The years 2014, 2016, and 2017 were significantly distinguished by the highest frequency of occurrence of <i>P. phocoena</i> (0.19 ind./h), while the lowest values were recorded in 2008, 2010, 2013, and 2019 (0.07 ind./h). In the remaining 7 study years, the frequency of occurrence was stable, at 0.12&#xa0;ind./h.</p>

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Interannual and Seasonal Variability in the Frequency of Occurrence of Harbor Porpoises, Phocoena phocoena (Linnaeus, 1758) (Cetacea: Phocoenidae), off the Northeastern Sakhalin Coast, Sea of Okhotsk, in 2008–2021

  • 期刊论文

  • 发表日期：

    2025年2月1日

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  • V. Ya. Kavun,
  • E. B. Lebedev

摘要

Abstract

The frequency of occurrence of harbor porpoises, Phocoena phocoena (Linnaeus, 1758), off the northeastern coast of Sakhalin Island (Sea of Okhotsk) was studied in 2008–2021. As the results showed, the frequency of occurrence of this cetacean species in the study area was subject to significant seasonal and interannual variations. The median seasonal frequency of occurrence of harbor porpoises was the highest in October (0.16 individuals per observation hour, ind./h) and was significantly different from that in all other study months (0.09 ind./h). The high frequency of occurrence was presumably related to the seasonal southward migration of harbor porpoises. The years 2014, 2016, and 2017 were significantly distinguished by the highest frequency of occurrence of P. phocoena (0.19 ind./h), while the lowest values were recorded in 2008, 2010, 2013, and 2019 (0.07 ind./h). In the remaining 7 study years, the frequency of occurrence was stable, at 0.12 ind./h.