Hunter Based Observations of Bowhead and Gray Whales Near … · The recommendations and general...
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e recommendations and general content presented in this poster do not necessarily represent the views or position of the Department of Commerce, the National Oceanic and Atmospheric Administration, or the National Marine Fisheries Service. Annual Sightings & Effort Distribution of Each Cetacean Species Distribution (Annual v. All Years) PLOTTING METHOD: Each species distribuon was calculated for all whale sighngs (weighted by group size) over the 2008-2011 period (using 1SD “Direconal Distribuon” ellipses in ArcView capturing ~68% of sightings). Overall each species occupied a unique region within the study area: bowheads on the continental shelf along the 20m isobath (in all years except 2011); and gray whales along the 50m isobath. (note: 2012 data have not been analyzed yet). ABSTRACT The North Slope Borough has been conduct- ing hunter-led small boat surveys near Barrow, Alaska for the past five summers as part of the BOEM-funded Bowhead Whale Feeding Ecology Study (BOWFEST). Informaon from this study will be used by BOEM for pre- and post-lease analysis and documentaon under the Naonal Environmental Policy Act (NEPA) for Beaufort Sea and Chukchi Sea Lease Sales. The study will also add to the general body of knowledge regard- ing the feeding ecology of large cetaceans. As a broad paern, bowhead whales of the Bering- Chukchi-Beaufort Seas Stock (BCBS) typically winter in the Bering Sea and migrate to the Cana- dian Beaufort Sea in summer to feed, returning again to the Chukchi and Bering Seas in autumn/ winter. Gray whales generally migrate from far more southern latudes to the Bering and Chuk- chi Seas to feed in summer. Feeding and relave abundance paerns of these two species were studied using local hunters to record posions and behaviors of whales in the Barrow region during summer and early autumn. In some years bowhead whales occur near Barrow, Alaska in low numbers with abundance varying consider- ably by year. Gray whales consistently occur and feed near Barrow, however abundance varies but much less so than bowheads. Bowheads and gray whales show spaal segregaon within the study area with gray whales aggregang west of 156 W longitude and bowheads mainly occur- ring east of that line. In 2008, 2009 and 2012 bowheads were more frequent near Barrow in July to early September, than in 2010 and 2011. Very few bowheads were seen in August and September in 2011 despite the highest sight- ing effort of any survey year. We speculate on why this may have occurred. Locally operated boat surveys are an effecve, relavely low- cost means to support various scienfic stud- ies including whale distribuon and abundance surveys. The strengths and limitaons of this research approach are discussed. Photograph of a feeding whale offshore of Barrow on 24 July 2009. Several whales appeared to be feeding with mud plumes associated with them. Local whalers did not ever recall seeing feeding whales during July. Note the whales were fluke-up diving in only 5.5 to 6 m water depth. Photo: Dave Thoreson. METHODS Local whale hunters were hired to locate bow- head whales in the BOWFEST study area, deter- mine their behavior, assist with deploying acousc oceanographic instruments, and other projects. The following figure shows catch or sighting rates (sightings/hr) of bowhead whales (CPUE) by year after correcting for effort. Note the strong variation in CPUE of bowheads between years. Whale sighting rates were lowest in 2011 during the study period despite the high- est effort of any season, and highest in 2009. Bowheads arrived very late in the BOWFEST study area in 2011. Whalers reported bow- heads were scarce even into October which is very uncommon. RESULTS AND SUMMARY • Bowheads summer near Barrow in low but vari- able numbers. Local knowledge suggests that bow- heads, parcularly very large bowheads, have always been present near Barrow in summer but may have increased over the last 30 years. • In at least the last decade, gray whales have con- sistently engaged in summer feeding in the Barrow area primarily in the Chukchi Sea. Gray whale rela- ve abundance varied by year but were higher and more consistent than bowheads. • Bowheads and grays show spaal segregaon within the BOWFEST study area (see distribution plots above). • In 2008 and 2009 bowheads were more frequent (near Barrow) in July to early September, than in 2010 and 2011. • Very few bowheads were seen in August and September of 2011 despite the highest sighting effort of any year. We speculate that the eastward migraon from Canada was delayed in 2011. • Hunter-based small boat surveys are an effecve, relavely low-cost method to conduct whale sur- veys and support various scienfic studies in Arcc near-shore waters. We thank the AEWC, NSB and BWCA for allowing us to sample their whales and for supporting research in their whaling grounds. We thank BOEM for funding and Charles Monnett for his guidance and encouragement. Hunter Based Observations of Bowhead and Gray Whales Near Barrow, Alaska J. Craig George 1 , Rob Delong 2 , Barb Tudor 1 , Lewis Brower 1 , Fredrick Brower 1 , Billy Okpeaha 1 , & Billy Adams 1 1 North Slope Borough Department of Wildlife Management, Box 69 Barrow, AK 2 Delongview, Fairbanks, AK 2 0 1 1 2 0 1 0 2 0 0 9 2 0 0 8 2 0 1 1 2 0 1 0 2 0 0 9 2 0 0 8 Gray Whales Bowhead Whales A small group of bowhead whales feeding north of Cooper Island in 2008 (photo by Henry Elavgak). Boat survey tracks and locations of gray whale and bowhead sightings for the years 2008 to 2011 by year. 0.00 0.50 1.00 1.50 2.00 2.50 2008 2009 2010 2011 Mean CPUE Mean CPUE by Year
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Transcript of Hunter Based Observations of Bowhead and Gray Whales Near … · The recommendations and general...
The recommendations and general content presented in this poster do not necessarily represent the views or position of the Department of Commerce, the National Oceanic and Atmospheric Administration, or the National Marine Fisheries Service.
Annual Sightings & Effort Distribution of Each Cetacean Species Distribution (Annual v. All Years)
Plotting Method: Each species distribution was calculated for all whale sightings (weighted by group size) over the 2008-2011 period (using 1SD “Directional Distribution” ellipses in ArcView capturing ~68% of sightings). Overall
each species occupied a unique region within the study area: bowheads on the continental shelf along the 20m isobath (in all years except 2011); and gray whales along the 50m isobath. (note: 2012 data have not been analyzed yet).
ABStRACtThe North Slope Borough has been conduct-ing hunter-led small boat surveys near Barrow, Alaska for the past five summers as part of the BOEM-funded Bowhead Whale Feeding Ecology Study (BOWFEST). Information from this study will be used by BOEM for pre- and post-lease analysis and documentation under the National Environmental Policy Act (NEPA) for Beaufort Sea and Chukchi Sea Lease Sales. The study will also add to the general body of knowledge regard-ing the feeding ecology of large cetaceans. As a broad pattern, bowhead whales of the Bering-Chukchi-Beaufort Seas Stock (BCBS) typically winter in the Bering Sea and migrate to the Cana-dian Beaufort Sea in summer to feed, returning again to the Chukchi and Bering Seas in autumn/winter. Gray whales generally migrate from far more southern latitudes to the Bering and Chuk-chi Seas to feed in summer. Feeding and relative abundance patterns of these two species were studied using local hunters to record positions and behaviors of whales in the Barrow region during summer and early autumn. In some years bowhead whales occur near Barrow, Alaska in low numbers with abundance varying consider-ably by year. Gray whales consistently occur and feed near Barrow, however abundance varies but much less so than bowheads. Bowheads and gray whales show spatial segregation within the study area with gray whales aggregating west of 156 W longitude and bowheads mainly occur-ring east of that line. In 2008, 2009 and 2012 bowheads were more frequent near Barrow in July to early September, than in 2010 and 2011. Very few bowheads were seen in August and September in 2011 despite the highest sight-ing effort of any survey year. We speculate on why this may have occurred. Locally operated boat surveys are an effective, relatively low-cost means to support various scientific stud-ies including whale distribution and abundance surveys. The strengths and limitations of this research approach are discussed.
Photograph of a feeding whale offshore of Barrow on 24 July 2009. Several whales appeared to be feeding with mud plumes associated with them. local whalers did not ever recall seeing feeding whales during July. note the whales were fluke-up diving in only 5.5 to 6 m water depth. Photo: dave thoreson.
MethodSLocal whale hunters were hired to locate bow-head whales in the BOWFEST study area, deter-mine their behavior, assist with deploying acoustic oceanographic instruments, and other projects.
The following figure shows catch or sighting rates (sightings/hr) of bowhead whales (CPUE) by year after correcting for effort. Note the strong variation in CPUE of bowheads between years. Whale sighting rates were lowest in 2011 during the study period despite the high-est effort of any season, and highest in 2009.
Bowheads arrived very late in the BOWFEST study area in 2011. Whalers reported bow-heads were scarce even into October which is very uncommon.
ReSultS And SuMMARy• Bowheads summer near Barrow in low but vari-
able numbers. Local knowledge suggests that bow-heads, particularly very large bowheads, have always been present near Barrow in summer but may have increased over the last 30 years.
• In at least the last decade, gray whales have con-sistently engaged in summer feeding in the Barrow area primarily in the Chukchi Sea. Gray whale rela-tive abundance varied by year but were higher and more consistent than bowheads.
• Bowheads and grays show spatial segregation within the BOWFEST study area (see distribution plots above).
• In 2008 and 2009 bowheads were more frequent (near Barrow) in July to early September, than in 2010 and 2011.
• Very few bowheads were seen in August and September of 2011 despite the highest sighting effort of any year. We speculate that the eastward migration from Canada was delayed in 2011.
• Hunter-based small boat surveys are an effective, relatively low-cost method to conduct whale sur-veys and support various scientific studies in Arctic near-shore waters.
We thank the AeWC, nSB and BWCA for allowing us to sample their whales and for supporting research in their whaling grounds. We thank BoeM for funding and Charles Monnett for his guidance and encouragement.
Hunter Based Observations of Bowhead and Gray Whales Near Barrow, Alaska
J. Craig George1, Rob Delong2, Barb Tudor1, Lewis Brower1, Fredrick Brower1, Billy Okpeaha1, & Billy Adams1
1North Slope Borough Department of Wildlife Management, Box 69 Barrow, AK2Delongview, Fairbanks, AK
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gray Whales
Bowhead Whales
A small group of bowhead whales feeding north of Cooper island in 2008 (photo by henry elavgak).
Boat survey tracks and locations of gray whale and bowhead sightings for the years 2008 to 2011 by year.
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Mean CPUE by Year
