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Estimating historical eastern North Pacific blue whale catches using spatial calling patterns.

Monnahan CC, Branch TA, Stafford KM, Ivashchenko YV, Oleson EM - PLoS ONE (2014)

Bottom Line: Blue whales (Balaenoptera musculus) were exploited extensively around the world and remain endangered.In the North Pacific their population structure is unclear and current status unknown, with the exception of a well-studied eastern North Pacific (ENP) population.The results of this study provide information for future studies investigating the recovery of these populations and the impact of continuing and future sources of anthropogenic mortality.

View Article: PubMed Central - PubMed

Affiliation: Quantitative Ecology and Resource Management, University of Washington, Seattle, Washington, United States of America.

ABSTRACT
Blue whales (Balaenoptera musculus) were exploited extensively around the world and remain endangered. In the North Pacific their population structure is unclear and current status unknown, with the exception of a well-studied eastern North Pacific (ENP) population. Despite existing abundance estimates for the ENP population, it is difficult to estimate pre-exploitation abundance levels and gauge their recovery because historical catches of the ENP population are difficult to separate from catches of other populations in the North Pacific. We collated previously unreported Soviet catches and combined these with known catches to form the most current estimates of North Pacific blue whale catches. We split these conflated catches using recorded acoustic calls from throughout the North Pacific, the knowledge that the ENP population produces a different call than blue whales in the western North Pacific (WNP). The catches were split by estimating spatiotemporal occurrence of blue whales with generalized additive models fitted to acoustic call patterns, which predict the probability a catch belonged to the ENP population based on the proportion of calls of each population recorded by latitude, longitude, and month. When applied to the conflated historical catches, which totaled 9,773, we estimate that ENP blue whale catches totaled 3,411 (95% range 2,593 to 4,114) from 1905-1971, and amounted to 35% (95% range 27% to 42%) of all catches in the North Pacific. Thus most catches in the North Pacific were for WNP blue whales, totaling 6,362 (95% range 5,659 to 7,180). The uncertainty in the acoustic data influence the results substantially more than uncertainty in catch locations and dates, but the results are fairly insensitive to the ecological assumptions made in the analysis. The results of this study provide information for future studies investigating the recovery of these populations and the impact of continuing and future sources of anthropogenic mortality.

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Estimated annual catches of ENP and WNP blue whales for the base case.Grey values contain 95% of the population uncertainty, and if above the line are more likely to be WNP, below the line more likely to be ENP. The uncertainty in the 1960s is caused by the unreported Soviet catches with high location uncertainty.
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pone-0098974-g011: Estimated annual catches of ENP and WNP blue whales for the base case.Grey values contain 95% of the population uncertainty, and if above the line are more likely to be WNP, below the line more likely to be ENP. The uncertainty in the 1960s is caused by the unreported Soviet catches with high location uncertainty.

Mentions: Each successful iteration of the algorithm provided distinct series of ENP catches and WNP catches, which were then aggregated by year (Tables 4–5). Most catches were taken in the early part of the century (1905–1930), with another spike in the 1950s and 1960s from Soviet pelagic whaling (Figure 11). Likewise, the uncertainty was highest during the early part of the 20th century when many catches were reported without location and/or month, and in the 1960s due to misreported Soviet catches which contained large catch uncertainty. Examples of specific ENP catch series demonstrate the general approach implemented here, including catch and statistical uncertainty predicted by the model (Figure 12). The catch uncertainty is reflected by the difference in locations of the catches between cases, and the statistical uncertainty by the differences in the region of uncertainty between cases.


Estimating historical eastern North Pacific blue whale catches using spatial calling patterns.

Monnahan CC, Branch TA, Stafford KM, Ivashchenko YV, Oleson EM - PLoS ONE (2014)

Estimated annual catches of ENP and WNP blue whales for the base case.Grey values contain 95% of the population uncertainty, and if above the line are more likely to be WNP, below the line more likely to be ENP. The uncertainty in the 1960s is caused by the unreported Soviet catches with high location uncertainty.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4043989&req=5

pone-0098974-g011: Estimated annual catches of ENP and WNP blue whales for the base case.Grey values contain 95% of the population uncertainty, and if above the line are more likely to be WNP, below the line more likely to be ENP. The uncertainty in the 1960s is caused by the unreported Soviet catches with high location uncertainty.
Mentions: Each successful iteration of the algorithm provided distinct series of ENP catches and WNP catches, which were then aggregated by year (Tables 4–5). Most catches were taken in the early part of the century (1905–1930), with another spike in the 1950s and 1960s from Soviet pelagic whaling (Figure 11). Likewise, the uncertainty was highest during the early part of the 20th century when many catches were reported without location and/or month, and in the 1960s due to misreported Soviet catches which contained large catch uncertainty. Examples of specific ENP catch series demonstrate the general approach implemented here, including catch and statistical uncertainty predicted by the model (Figure 12). The catch uncertainty is reflected by the difference in locations of the catches between cases, and the statistical uncertainty by the differences in the region of uncertainty between cases.

Bottom Line: Blue whales (Balaenoptera musculus) were exploited extensively around the world and remain endangered.In the North Pacific their population structure is unclear and current status unknown, with the exception of a well-studied eastern North Pacific (ENP) population.The results of this study provide information for future studies investigating the recovery of these populations and the impact of continuing and future sources of anthropogenic mortality.

View Article: PubMed Central - PubMed

Affiliation: Quantitative Ecology and Resource Management, University of Washington, Seattle, Washington, United States of America.

ABSTRACT
Blue whales (Balaenoptera musculus) were exploited extensively around the world and remain endangered. In the North Pacific their population structure is unclear and current status unknown, with the exception of a well-studied eastern North Pacific (ENP) population. Despite existing abundance estimates for the ENP population, it is difficult to estimate pre-exploitation abundance levels and gauge their recovery because historical catches of the ENP population are difficult to separate from catches of other populations in the North Pacific. We collated previously unreported Soviet catches and combined these with known catches to form the most current estimates of North Pacific blue whale catches. We split these conflated catches using recorded acoustic calls from throughout the North Pacific, the knowledge that the ENP population produces a different call than blue whales in the western North Pacific (WNP). The catches were split by estimating spatiotemporal occurrence of blue whales with generalized additive models fitted to acoustic call patterns, which predict the probability a catch belonged to the ENP population based on the proportion of calls of each population recorded by latitude, longitude, and month. When applied to the conflated historical catches, which totaled 9,773, we estimate that ENP blue whale catches totaled 3,411 (95% range 2,593 to 4,114) from 1905-1971, and amounted to 35% (95% range 27% to 42%) of all catches in the North Pacific. Thus most catches in the North Pacific were for WNP blue whales, totaling 6,362 (95% range 5,659 to 7,180). The uncertainty in the acoustic data influence the results substantially more than uncertainty in catch locations and dates, but the results are fairly insensitive to the ecological assumptions made in the analysis. The results of this study provide information for future studies investigating the recovery of these populations and the impact of continuing and future sources of anthropogenic mortality.

Show MeSH
Related in: MedlinePlus