Limits...
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.

Show MeSH

Related in: MedlinePlus

Observed hydrophone data for May-October.These data are used to fit separate acoustic models for both populations. Colored circles show hydrophones and the proportion of hours calls were observed while and “x” denotes those with no observed calls for either population. The western population migrates east along the Aleutian Islands and the eastern population migrations northwest into the North Pacific. Hydrophones with observed calls from both populations clearly show overlap for much of the North Pacific.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC4043989&req=5

pone-0098974-g004: Observed hydrophone data for May-October.These data are used to fit separate acoustic models for both populations. Colored circles show hydrophones and the proportion of hours calls were observed while and “x” denotes those with no observed calls for either population. The western population migrates east along the Aleutian Islands and the eastern population migrations northwest into the North Pacific. Hydrophones with observed calls from both populations clearly show overlap for much of the North Pacific.

Mentions: Detections of ENP and WNP song calls came from six sources in the North Pacific (Table 2, Figures 4 and 5). For all hydrophones, data were converted into hourly presence or absence of ENP and WNP calls. Hydrophone sources were: (1) six hydrophones placed by the National Oceanic and Atmospheric Administration (NOAA) in the eastern tropical Pacific [26]; (2) sixteen US Navy Sound Surveillance System and other hydrophones spread across the North Pacific; note that their exact locations were classified and approximated based on previously published studies [8]; (3) six hydrophones in the Gulf of Alaska placed by NOAA - after 9 months, one of these hydrophones was discontinued and another was moved slightly [9]; (4) six hydrophones in the Channel Islands and Cortez and Tanner Banks deployed by Scripps Institution of Oceanography [12]; (5) one hydrophone moored off Oahu, Hawaii, described in [27] and used in [8]; and (6) a single hydrophone off Wake Island [8].


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)

Observed hydrophone data for May-October.These data are used to fit separate acoustic models for both populations. Colored circles show hydrophones and the proportion of hours calls were observed while and “x” denotes those with no observed calls for either population. The western population migrates east along the Aleutian Islands and the eastern population migrations northwest into the North Pacific. Hydrophones with observed calls from both populations clearly show overlap for much of the North Pacific.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0098974-g004: Observed hydrophone data for May-October.These data are used to fit separate acoustic models for both populations. Colored circles show hydrophones and the proportion of hours calls were observed while and “x” denotes those with no observed calls for either population. The western population migrates east along the Aleutian Islands and the eastern population migrations northwest into the North Pacific. Hydrophones with observed calls from both populations clearly show overlap for much of the North Pacific.
Mentions: Detections of ENP and WNP song calls came from six sources in the North Pacific (Table 2, Figures 4 and 5). For all hydrophones, data were converted into hourly presence or absence of ENP and WNP calls. Hydrophone sources were: (1) six hydrophones placed by the National Oceanic and Atmospheric Administration (NOAA) in the eastern tropical Pacific [26]; (2) sixteen US Navy Sound Surveillance System and other hydrophones spread across the North Pacific; note that their exact locations were classified and approximated based on previously published studies [8]; (3) six hydrophones in the Gulf of Alaska placed by NOAA - after 9 months, one of these hydrophones was discontinued and another was moved slightly [9]; (4) six hydrophones in the Channel Islands and Cortez and Tanner Banks deployed by Scripps Institution of Oceanography [12]; (5) one hydrophone moored off Oahu, Hawaii, described in [27] and used in [8]; and (6) a single hydrophone off Wake Island [8].

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