Entanglement risk to western gray whales from commercial fisheries in the Russian Far East

Lowry, Lloyd F.; Burkanov, Vladimir N.; Altukhov, Alexey; Weller, David W.; Reeves, Randall R.

doi:10.3354/esr00914

Cited by 14 publications

(15 citation statements)

References 28 publications

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“…If most of the whales feeding off Sakhalin represent whales with recent ancestry rooted in the ENP, the rare, but continuing, sightings of gray whales off Japan and China during winter and spring (Nakamura et al, 2019; Nambu et al, 2010; Wang, 1985; Wang et al, 2015; Zhu & Yue, 1998), as well as estimates that 20%–55% of the SI whales do not utilize ENP wintering grounds (Cooke et al, 2019), indicate that some whales are remaining in the WNP year‐round. This group of whales, which is of unknown origin but may include the last remnants of the population of gray whales that was historically hunted off Japan and Korea, faces multiple threats to its persistence, including but not limited to the risk of mortality due to entanglement in coastal net fisheries off Japan (Nakamura et al, 2019; Weller et al, 2008), China (Wang et al, 2015), and Sakhalin Island (Lowry et al, 2018); exposure to potentially harmful activities associated with oil and gas development in the Okhotsk Sea; and possible ship strikes while migrating coastal waters of Japan and Korea, with substantial nearshore industrialization (Weller et al, 2002b). Obtaining additional information on the distribution, movements and origin of these whales is critical to understanding their significance to the conservation of gray whales in the North Pacific.…”

Section: Discussionmentioning

confidence: 99%

Population structure of North Pacific gray whales in light of trans‐Pacific movements

Lang

Weller

Burdin

et al. 2021

Marine Mammal Science

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Recent findings that some gray whales that feed off Sakhalin Island (SI), Russia, in the western North Pacific (WNP) overwinter in the eastern North Pacific (ENP) indicate that population structure in this species is more complex than originally thought. We generated mitochondrial DNA (mtDNA) control region sequences and microsatellite genotypes (n = 12 loci) from 156 whales sampled off SI and compared them to available data from 106 ENP whales. Significant mitochondrial and nuclear genetic differentiation between the SI and ENP whales was found. Genetic cluster analysis identified two groups among the SI whales, one of which was genetically similar to ENP whales. Photographs collected from the biopsied SI whales showed that both groups comprised whales known to migrate to the ENP, suggesting that the clustering pattern was not reflective of some SI whales interbreeding while overwintering in the WNP. Instead, the genetic differentiation observed between the SI and ENP whales may be due to assortative mating of SI whales while west of eastern migratory routes. The rare but continued reports of gray whales off the coasts of Japan and China, however, confirm that some gray whales overwinter in the WNP and highlight the need to collect additional data from these whales.

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Section: Discussionmentioning

confidence: 99%

Population structure of North Pacific gray whales in light of trans‐Pacific movements

Lang

Weller

Burdin

et al. 2021

Marine Mammal Science

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“…2016, Lowry et al. 2018). We simulated a total of 30 disturbance scenarios that varied in the start date of disturbance within the foraging season (15 June [early] or 15 August 15 [late]), the spatial location of the disturbance (cells), the effect of multiple concurrent or sequential surveys, and the probability of disturbance (Table 2).…”

Section: Methodsmentioning

confidence: 99%

Predicting the population consequences of acoustic disturbance, with application to an endangered gray whale population

McHuron

Aerts²,

Gailey³

et al. 2021

Ecological Applications

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Acoustic disturbance is a growing conservation concern for wildlife populations because it can elicit physiological and behavioral responses that can have cascading impacts on population dynamics. State‐dependent behavioral and life history models implemented via Stochastic Dynamic Programming (SDP) provide a natural framework for quantifying biologically meaningful population changes resulting from disturbance by linking environment, physiology, and metrics of fitness. We developed an SDP model using the endangered western gray whale (Eschrichtius robustus) as a case study because they experience acoustic disturbance on their summer foraging grounds. We modeled the behavior and physiological dynamics of pregnant females as they arrived on the feeding grounds and predicted the probability of female and offspring survival, with and without acoustic disturbance and in the presence/absence of high prey availability. Upon arrival in mid‐May, pregnant females initially exhibited relatively random behavior before they transitioned to intensive feeding that resulted in continual fat mass gain until departure. This shift in behavior co‐occurred with a change in spatial distribution; early in the season, whales were more equally distributed among foraging areas with moderate to high energy availability, whereas by mid‐July whales transitioned to predominate use of the location that had the highest energy availability. Exclusion from energy‐rich offshore areas led to reproductive failure and in extreme cases, mortality of adult females that had lasting impacts on population dynamics. Simulated disturbances in nearshore foraging areas had little to no impact on female survival or reproductive success at the population level. At the individual level, the impact of disturbance was unequally distributed across females of different lengths, both with respect to the number of times an individual was disturbed and the impact of disturbance on vital rates. Our results highlight the susceptibility of large capital breeders to reductions in prey availability, and indicate that who, where, and when individuals are disturbed are likely to be important considerations when assessing the impacts of acoustic activities. This model provides a framework to inform planned acoustic disturbances and assess the effectiveness of mitigation strategies for large capital breeders.

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“…2h,i) periods. Gill nets and set-nets are used extensively in the coastal waters of Japan and the Russian Far East and are known to be associated with gray whale entanglements (Lowry et al 2018). Fleets of small motorized watercraft usually support these types of fishery.…”

Section: Risk From Commercial Fisheriesmentioning

confidence: 99%

Co-occurrence of gray whales and vessel traffic in the North Pacific Ocean

Silber¹,

Weller

Reeves³

et al. 2021

Endang. Species. Res.

Self Cite

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All species of large whales are susceptible to vessel strikes, but the true scale and geographical extent of such strikes is not known. This paper provides a qualitative assessment of the range-wide risks posed to gray whales Eschrichtius robustus by vessels, by comparing patterns of whale distribution with the density of vessel traffic seasonally throughout the North Pacific in 2019. Areas of very high vessel density were evident year-round near many coastlines, along inter-continental trade routes, and at hubs of commercial shipping near port entrances. Gray whales were exposed to vessel strikes throughout their range and in their feeding, southbound migration, wintering, and northbound migration periods. Areas of apparently high risk were in the Russian Far East (Kamchatka peninsula and Okhotsk Sea), Bering Sea (including the Aleutian Islands), Gulf of Alaska, and along the entire west coast of North America. Risk appeared greatest during south- and northbound migration when much of the gray whale population is moving through waters near shore. Tanker, container, and bulk-carrier ships represent considerable risk to whales in the North Pacific Ocean, but the large geographical extent of commercial fishing activities suggests that fisheries are also a substantial source of risk. Vessel-strike risk maps indicate the relative extent of exposure of gray (and other) whales to underwater vessel noise. The number of gray whales killed by ship strikes each year may be in the tens, or perhaps the low hundreds. Additional analyses, including quantitative assessments, are warranted to further clarify the risk of vessel strikes to gray whales.

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Entanglement risk to western gray whales from commercial fisheries in the Russian Far East

Cited by 14 publications

References 28 publications

Population structure of North Pacific gray whales in light of trans‐Pacific movements

Population structure of North Pacific gray whales in light of trans‐Pacific movements

Predicting the population consequences of acoustic disturbance, with application to an endangered gray whale population

Co-occurrence of gray whales and vessel traffic in the North Pacific Ocean

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