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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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Results of the sensitivity analysis to the conversion between song call frequency and density of whales.The sensitivity to the base case assumption that  to the final results is explored with histograms of the total catches of the ENP (blue) and WNP (red) populations for three levels of .  is the ratio of the unknown WNP and ENP factors which convert density of whales to song call occurrence.
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pone-0098974-g013: Results of the sensitivity analysis to the conversion between song call frequency and density of whales.The sensitivity to the base case assumption that to the final results is explored with histograms of the total catches of the ENP (blue) and WNP (red) populations for three levels of . is the ratio of the unknown WNP and ENP factors which convert density of whales to song call occurrence.

Mentions: Our methods allowed uncertainty to be estimated for the catch series, and incorporated into the results. The largest source of uncertainty for the base case came from bootstrapping the acoustic data. The catch uncertainty was relatively small compared to the statistical uncertainty, thus additional acoustic data has the potential to decrease the uncertainty in the results the most (Table 6). The ecological sensitivity run where ranged uniformly between 0.5 and 2 contributed more uncertainty than catch uncertainty, but less than statistical uncertainty (Table 6). As expected a higher value of for all algorithm iterations lead to smaller estimates for the total ENP catches (Figure 13).


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)

Results of the sensitivity analysis to the conversion between song call frequency and density of whales.The sensitivity to the base case assumption that  to the final results is explored with histograms of the total catches of the ENP (blue) and WNP (red) populations for three levels of .  is the ratio of the unknown WNP and ENP factors which convert density of whales to song call occurrence.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0098974-g013: Results of the sensitivity analysis to the conversion between song call frequency and density of whales.The sensitivity to the base case assumption that to the final results is explored with histograms of the total catches of the ENP (blue) and WNP (red) populations for three levels of . is the ratio of the unknown WNP and ENP factors which convert density of whales to song call occurrence.
Mentions: Our methods allowed uncertainty to be estimated for the catch series, and incorporated into the results. The largest source of uncertainty for the base case came from bootstrapping the acoustic data. The catch uncertainty was relatively small compared to the statistical uncertainty, thus additional acoustic data has the potential to decrease the uncertainty in the results the most (Table 6). The ecological sensitivity run where ranged uniformly between 0.5 and 2 contributed more uncertainty than catch uncertainty, but less than statistical uncertainty (Table 6). As expected a higher value of for all algorithm iterations lead to smaller estimates for the total ENP catches (Figure 13).

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