[MARMAM] New publication - Site fidelity of North Pacific gray whales off Sakhalin, Russia
Koen.Broker at shell.com
Koen.Broker at shell.com
Tue Aug 18 07:04:59 PDT 2020
My co-authors and I are pleased to announce the following open-access publication:
Site-fidelity and spatial movements of western North Pacific gray whales (Eschrichtius robustus) on their summer range off Sakhalin, Russia. PLoS ONE, 2020, 15(8):e0236649. https://doi.org/10.1371/journal.pone.0236649. Bröker, K., Tyurneva, O., Gailey, G., Dupont, J., Yakovlev, Yu., Vertyankin, V., Sychenko, O., Shevtsov, E. & Drozdov, K.M.
The Western North-Pacific (WNP) gray whale feeding grounds are off the northeastern coast of Sakhalin Island, Russia and is comprised of a nearshore and offshore component that can be distinguished by both depth and location. Spatial movements of gray whales within their foraging grounds were examined based on 13 years of opportunistic vessel and shore-based photo-identification surveys. Site fidelity was assessed by examining annual return and resighting rates. Lagged Identification Rates (LIR) analyses were conducted to estimate the residency and transitional movement patterns within the two components of their feeding grounds. In total 243 individuals were identified from 2002-2014, among these were 94 calves. The annual return rate over the period 2002-2014 was 72%, excluding 35calves only seen one year. Approximately 20% of the individuals identified from 2002-2010were seen every year after their initial sighting (including eight individuals that returned for13 consecutive years). The majority (239) of the WNP whales were observed in the near shore area while only half (122) were found in the deeper offshore area. Within a foraging season, there was a significantly higher probability of gray whales moving from the nearshore to the offshore area. No mother-calf pairs, calves or yearlings were observed in the offshore area, which was increasingly used by mature animals. The annual return rates, and population growth rates that are primarily a result of calf production with little evidence of immigration, suggest that this population is demographically self-contained and that both the nearshore and offshore Sakhalin feeding grounds are critically important areas for their summer annual foraging activities. The nearshore habitat is also important for mother-calf pairs, younger individuals, and recently weaned calves. Nearshore feeding could also be energetically less costly compared to foraging in the deeper offshore habitat and provide more protection from predators, such as killer whales.
The paper is available at:
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