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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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Fits for ENP acoustic, WNP acoustic, and base case prediction models for May-October.These models are fit to the acoustic data in Figures 4 and 5. The third column shows the base case prediction model which is the proportion of ENP to WNP calls, such that red areas correspond to predicted WNP occurrence and blue areas to ENP. The white line denotes where the model predicts an equal chance of observing an ENP or WNP blue whale.
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pone-0098974-g006: Fits for ENP acoustic, WNP acoustic, and base case prediction models for May-October.These models are fit to the acoustic data in Figures 4 and 5. The third column shows the base case prediction model which is the proportion of ENP to WNP calls, such that red areas correspond to predicted WNP occurrence and blue areas to ENP. The white line denotes where the model predicts an equal chance of observing an ENP or WNP blue whale.

Mentions: AICc provided clear justification for the more complex beta-binomial structure for acoustic models as well as additive terms on parameters and in both the ENP and WNP acoustic models (Table 3). Therefore the full acoustic models were selected for both ENP and WNP populations and used throughout the rest of the analysis. These model predictions depended on the month, but generally classified parts of the Gulf of Alaska, the west coast of the US, and the eastern tropical Pacific as being predominantly ENP (Figures 6 and 7).


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)

Fits for ENP acoustic, WNP acoustic, and base case prediction models for May-October.These models are fit to the acoustic data in Figures 4 and 5. The third column shows the base case prediction model which is the proportion of ENP to WNP calls, such that red areas correspond to predicted WNP occurrence and blue areas to ENP. The white line denotes where the model predicts an equal chance of observing an ENP or WNP blue whale.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0098974-g006: Fits for ENP acoustic, WNP acoustic, and base case prediction models for May-October.These models are fit to the acoustic data in Figures 4 and 5. The third column shows the base case prediction model which is the proportion of ENP to WNP calls, such that red areas correspond to predicted WNP occurrence and blue areas to ENP. The white line denotes where the model predicts an equal chance of observing an ENP or WNP blue whale.
Mentions: AICc provided clear justification for the more complex beta-binomial structure for acoustic models as well as additive terms on parameters and in both the ENP and WNP acoustic models (Table 3). Therefore the full acoustic models were selected for both ENP and WNP populations and used throughout the rest of the analysis. These model predictions depended on the month, but generally classified parts of the Gulf of Alaska, the west coast of the US, and the eastern tropical Pacific as being predominantly ENP (Figures 6 and 7).

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