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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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Related in: MedlinePlus

Fits of the independent variables for the probability of observing a song call (parameter).The original model (black lines) and subsequent bootstrapped models (thin colored lines) are shown. Each panel shows the relationship between the dependent and independent variable after all other independent variables have been accounted for (i.e. the centered partial residuals). Higher relative values indicate a higher probability of observing a call. For longitude and latitude, -axis tick marks show positions of the observed hydrophones with a small amount of noise added to prevent overplotting. See text for further discussion.
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pone-0098974-g008: Fits of the independent variables for the probability of observing a song call (parameter).The original model (black lines) and subsequent bootstrapped models (thin colored lines) are shown. Each panel shows the relationship between the dependent and independent variable after all other independent variables have been accounted for (i.e. the centered partial residuals). Higher relative values indicate a higher probability of observing a call. For longitude and latitude, -axis tick marks show positions of the observed hydrophones with a small amount of noise added to prevent overplotting. See text for further discussion.

Mentions: GAMLSS model additive fits are interpreted by plotting the smoothers fit to “partial residuals” which have an arbitrary absolute scale and instead are judged via the relative change within a single independent variable (i.e. longitude, latitude, and month). In this case, increasing partial residual values indicated that the model predicted higher call rates for , or higher variance for . For instance, both populations showed increased calling in the summer and fall months, ENP calls decreased from east to west, and WNP calls increased for east to west (Figures 8 and 9).


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 of the independent variables for the probability of observing a song call (parameter).The original model (black lines) and subsequent bootstrapped models (thin colored lines) are shown. Each panel shows the relationship between the dependent and independent variable after all other independent variables have been accounted for (i.e. the centered partial residuals). Higher relative values indicate a higher probability of observing a call. For longitude and latitude, -axis tick marks show positions of the observed hydrophones with a small amount of noise added to prevent overplotting. See text for further discussion.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0098974-g008: Fits of the independent variables for the probability of observing a song call (parameter).The original model (black lines) and subsequent bootstrapped models (thin colored lines) are shown. Each panel shows the relationship between the dependent and independent variable after all other independent variables have been accounted for (i.e. the centered partial residuals). Higher relative values indicate a higher probability of observing a call. For longitude and latitude, -axis tick marks show positions of the observed hydrophones with a small amount of noise added to prevent overplotting. See text for further discussion.
Mentions: GAMLSS model additive fits are interpreted by plotting the smoothers fit to “partial residuals” which have an arbitrary absolute scale and instead are judged via the relative change within a single independent variable (i.e. longitude, latitude, and month). In this case, increasing partial residual values indicated that the model predicted higher call rates for , or higher variance for . For instance, both populations showed increased calling in the summer and fall months, ENP calls decreased from east to west, and WNP calls increased for east to west (Figures 8 and 9).

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