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Gray whale sightings in the Canadian Beaufort Sea, September 2014
Polar Science 10 (2016) 173e176
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Polar Science journal homepage: http://ees.elsevier.com/polar/
Gray whale sightings in the Canadian Beaufort Sea, September 2014 Yuka Iwahara a, *, Amane Fujiwara b, Keizo Ito a, Kazushi Miyashita c, Yoko Mitani c a
Graduate School of Environmental Science, Hokkaido University, 20-5 Benten-cho, Hakodate, Hokkaido, 040-0051, Japan Institute of Arctic Climate and Environment Research, Japan Agency for Marine-Earth Science and Technology, 2-15, Natsushima-cho, Yokosuka, Kanagawa, 237-0061, Japan c Field Science Center for Northern Biosphere, Hokkaido University, 20-5 Benten-cho, Hakodate, Hokkaido, 040-0051, Japan b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 4 March 2016 Received in revised form 5 April 2016 Accepted 11 April 2016 Available online 13 April 2016
Gray whales (Eschrichtius robustus) are distributed within the productive neritic and estuarine waters of the North Pacific Ocean, the Bering Sea, and adjacent waters of the Arctic Ocean. They migrate to highlatitude feeding grounds each spring. Their main feeding grounds in the Arctic include the Chirikov Basin, the northeastern Chukchi Sea from Pt. Hope to Cape Lisburne and Pt. Lay to Pt. Barrow, and the northwestern Chukchi Sea along the Chukotka coast. Although sightings are rare in the Canadian Beaufort Sea, we observed three gray whales in two groups in this area in September 2014. A mud plume was observed near one of the whales, suggesting the animal had been feeding. In the Alaskan Beaufort Sea, large-scale monitoring of the distributions of marine mammals has been continuously conducted since 1979; however, there has been less monitoring in the Canadian Beaufort Sea. Therefore, it is necessary to record opportunistic sightings, such as those described here. © 2016 Elsevier B.V. and NIPR. All rights reserved.
Keywords: Gray whale Eastern Beaufort Sea Eschrichtius robustus Feeding
1. Introduction Gray whales (Eschrichtius robustus) are confined to the productive neritic and estuarine waters of the North Pacific Ocean, the Bering Sea, and adjacent waters of the Arctic Ocean (Jones and Schwartz, 2009). Each spring they migrate north to feeding grounds, mainly in the Bering and Chukchi seas, covering an average distance of ~8000 km and making an annual round trip of 15,000e20,000 km (Jones and Schwartz, 2009; Rugh et al., 2001). The whales feed on a wide variety of prey (Jones and Schwartz, 2009; Nerini, 1984), mainly benthic organisms in shallow seas (Nerini, 1984; Rice and Wolman, 1971). In recent years, important feeding grounds in the eastern Chukchi and Bering seas have been located in the Chirikov Basin, off Point Hope, and from Wainwright to Point Barrow (Clarke et al., 2013, 2014, 2015b; Ferguson et al., 2015; Kuletz et al., 2015; Schonberg et al., 2014). The Chirikov Basin, in the Bering Sea, has been an important gray whale feeding area, at least intermittently, since the 1980s (Ferguson et al., 2015; Moore et al., 1986, 2003), with large numbers of feeding whales having been sighted during aerial surveys in 1980, 1981, 1982, and 1985 (Moore et al., 1986, 2003). Although the number of gray
* Corresponding author. E-mail address: [email protected] (Y. Iwahara). http://dx.doi.org/10.1016/j.polar.2016.04.007 1873-9652/© 2016 Elsevier B.V. and NIPR. All rights reserved.
whales dramatically decreased during the 1990s, in parallel with the collapse of populations of their amphipod prey (Moore et al., 2003), in September 2014 a large aggregation of gray whales was observed in the Chirikov Basin (Ferguson et al., 2015). Therefore, the Chirikov Basin remains an important feeding area (Ferguson et al., 2015). Since the 1980s, marine mammal aerial surveys have consistently documented gray whales feeding during summer and fall in the northeastern Chukchi Sea, from Pt. Hope to Cape Lisburne and from Pt. Lay to Pt. Barrow (Clarke et al., 2015a; Kuletz et al., 2015; Schonberg et al., 2014). Gray whales were consistently seen feeding near Hanna Shoal in September and October in the late 1980s and early 1990s (Clarke and Moore, 2002), but were generally absent after 2008 (Clarke et al., 2014, 2015a). This suggests that local changes in feeding grounds have occurred during recent decades in the eastern Chukchi and Bering seas. Although gray whales were occasionally seen in the 1950s near Point Barrow, which is the entrance to the Beaufort Sea (Maher, 1960), their abundance there was likely also low in the 1970s (Marquette and Braham, 1980). Moore et al. (2006) noted that in recent years hunters have reported increasing numbers of gray whales near Barrow in the late summer and autumn, and aerial surveys conducted each summer and fall in that area since 2009 have confirmed the common occurrence of these whales (Clarke et al., 2015b). The increasing occurrence of gray whales near Barrow could reflect an increase in their population (Rugh et al., 2005), climate-induced changes in
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habitat (Moore et al., 2003), or both. Despite this, they have been rare visitors to the Beaufort Sea since the 1950s (Maher, 1960), and there have been few records of sightings (Brower et al., 2015; Marquette and Braham, 1980; National Marine Mammal Laboratory, Historical BWASP and COMIDA database: http://www. afsc.noaa.gov/nmml/software/bwasp-comida.php). In the Canadian Beaufort Sea in particular, sightings were only reported in 1980 (Rugh and Fraker, 1981), although surveys have been limited in this region. Following a gap of 27 years, one gray whale was observed in an aerial survey in 2007, and another was sighted and satellite tagged in 2009 (Conlan et al., 2013; Harris et al., 2008; Quakenbush et al., 2010). Here we report on gray whale sightings recorded during a ship sighting survey in the Canadian Beaufort Sea in 2014.
71600 N, 155 300 W; St. 2: 70 300 N, 146 W; St. 3: 70 N, 136 W; St. 4: 70 500 N, 130 250 W) from 1979 to 2014; this was based on historical remotely-sensed sea ice concentration (SIC) data, calculated using NASA-Team Algorithm 2 (Markus and Cavalieri, 2000). The SIC datasets at 25-km gridded resolution were collected using the scanning multichannel microwave radiometer (SMMR) and the special sensor microwave/imager (SSM/I), and were retrieved from the National Snow and Ice Data Center (NSIDC). We defined nonice-covered pixels when sea ice concentrations were <20%. In addition, to investigate the relationship between sea-ice-edge and gray whale position, we calculated the distance between the observed gray whale positions and the sea-ice edge. We defined the sea-ice edge as the outer line of the area where the average sea ice concentration in the survey period was 20%.
2. Material and methods
3. Results
The visual survey was conducted in the Beaufort Sea from the bridge (14 m above sea level) of the Canadian research icebreaker Amundsen, from 10 September to 25 September 2014 (Fig. 1). Observations were conducted while the vessel was moving between sampling stations during daylight hours, and commenced 1 h following sunrise and ceased 1 h prior to sunset. During the cruise, two observers constantly scanned the survey area (90 to each side of the bow), using 8 power binoculars (Nikon). Both observers had previous experience in identifying marine mammals during shipboard surveys, including in the Chukchi Sea. When marine mammals were seen, the time (UTC), number of animals, position in latitude and longitude of the ship, distance from the ship, angle from the front of the ship, and animal behavior were recorded. The ship did not approach any marine mammals. We also recorded the weather, wind speed, wind force (Beaufort scale), wave height, visibility, and glare every 30 min. The vessel speed was automatically recorded every minute. To determine the interannual change in the ice-free period at the locations where gray whales were sighted and where they potentially used to reach the Canadian Beaufort Sea, we determined the number of ice-free days at the four stations (St. 1:
On 24 September 2014 we observed three gray whales, comprising one pair and one individual (Fig. 1). The pair was observed at 70 480 N, 130 460 W on 24 September 2014 at 00:01, and the individual was observed at 70 550 N, 13010 W on the same day, at 01:20. The bottom depths at the observation points were 32 m and 30 m, respectively. Species identification was based on observation of the mottled gray skin, and the back having a hump followed by a series of fleshy knobs along the tailstock. The ship sailed continuously in a direct line without diverting to the Amundsen Gulf, and therefore the individual whale was not one of the pair. We observed several blows and dives during each sighting. One of the two whales in the pair made a mud plume (Fig. 2). At the time of the sightings the ship speed was approximately 12 knots, the wind force was 2 on the Beaufort scale, and there was no fog or glare. We did not observe any sea ice during the day on which we observed the whales. The distance of the ice edge from the ship when we observed the whales was >90 km (Fig. 1). 4. Discussion The area in which we observed gray whales is characterized as a
Fig. 1. Map of the study area in the Beaufort Sea. Red lines represent visual surveys. White circles represent whales observed in 1980 (Rugh and Fraker, 1981) and black circles represent whales observed in this study, in 2014. Gray triangles represent the stations where interannual variations in the number of ice-free days were monitored. The blue line represents the location of the sea ice edge during our survey period (10e25 September 2014).
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Fig. 2. Mud plume observed during the gray whale encounter (sighting number one).
shelf-break upwelling area (Williams and Carmack, 2008). It is rich re et al., 2007), particularly ampein benthic communities (Bessie liscid amphipods (Conlan et al., 2013), which may be a food resource for gray whales. Furthermore, the water depths at the sighting locations are shallow. Rugh and Fraker (1981) also observed a gray whale associated with a mud plume in this area, indicating that gray whales use it as a feeding ground. The observations of Rugh and colleagues were made within 19e66 km of those made in the present report (Fig. 1). Our observations were made in September, whereas theirs were made in August. In addition, the area concerned is densely populated by bowhead whales, because of the large populations of calanoid copepods that occur there (Citta et al., 2015). The occurrence of sea ice in the Beaufort Sea has been decreasing annually since the 1980s, as is evident from the increase in the total number of ice-free days (Fig. 3). This is particularly evident at St. 1 (Fig. 1), at the entrance to the Beaufort Sea, where icy years (years having <50 days with no ice cover) occurred at least every 2e3 years prior to 1984. However, since then the total number of ice-free days has gradually increased, and there have
been no icy years since 2001. Consequently, gray whales can potentially enter the Beaufort Sea earlier and stay longer to feed in this area. Conlan et al. (2013) suggested that the Cape Bathurst area may become of increasing importance to gray whales and other benthic predators because of the decreasing seasonal ice cover in the Beaufort Sea, which results in longer periods of wind-driven upwelling, and easier and extended whale access. Gray whales feed in various geographic areas, and could change their feeding grounds in response to environmental change (Bluhm and Gradinger, 2008; Moore, 2008, 2010; Moore et al., 2003; Stafford et al., 2007). Therefore, they may act as sentinels for ecosystem change (Moore, 2008). In the Alaskan Beaufort Sea, large-scale monitoring of the distribution of marine mammals has been continuously conducted for several decades through the aerial surveys of Arctic marine mammals (ASAMM) project (2011e2015), BWASP (1979e2010), and the COMIDA marine mammal aerial survey project (2008e2010), and very few gray whales (<10) have been observed (National Marine Mammal Laboratory. Historical BWASP and COMIDA database). In the Canadian Beaufort Sea, visual surveys for marine
Fig. 3. Temporal changes in the number of ice-free days. Sea ice concentrations were derived from scanning multichannel microwave radiometer (SMMR, 1979e1987) and special sensor microwave imager (SSMI, 1987e2014) satellite sensors. The spatial scale of all sensors was 25 km. The datasets from duplicate periods were averaged.
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mammals have been conducted only sporadically in recent years (1992, 2007, 2008, and 2009), although such surveys were conducted from the 1970s to the 1980s (Harwood et al., 1996, 2010; Harwood and Kingsley, 2013; Richardson et al., 1987; Rugh and Fraker, 1981). It is possible that gray whales used this area during the 1990s and early 2000s but were not observed because of the relatively small survey effort. Therefore, it is important to accumulate opportunistic sighting records, including this report. Acknowledgments We acknowledge the captain, crew, and researchers on board on the Canadian icebreaker Amundsen for their endless support and hard work during the 2014 cruise. This study was supported by the Green Network of Excellence Program's (GRENE Program) Arctic Climate Change Research Project: ‘Rapid Change of the Arctic Climate System and its Global Influences.’ References re, A., Nozais, C., Brugel, S., Demers, S., Desrosiers, G., 2007. Metazoan Bessie meiofauna dynamics and pelagicebenthic coupling in the southeastern Beaufort Sea, Arctic Ocean. Polar Biol. 30, 1123e1135. Bluhm, B.A., Gradinger, R., 2008. Regional variability in food availability for Arctic marine mammals. Ecol. Appl. 18, S77eS96. Brower, A., Clarke, J., Ferguson, M., 2015. Gray whale occurrence in the Beaufort Sea. In: Alaska Marine Science Symposium, Anchorage, AK, USA, January 19e23, 2015, p. 199. Abstract. Citta, J.J., Quakenbush, L.T., Okkonen, S.R., Druckenmiller, M.L., Maslowski, W., Clement-Kinney, J., George, J.C., Brower, H., Small, R.J., Ashjian, C.J., 2015. Ecological characteristics of core-use areas used by BeringeChukchieBeaufort (BCB) bowhead whales, 2006e2012. Prog. Oceanogr. 136, 201e222. Clarke, J.T., Brower, A.A., Christman, C.L., Ferguson, M.C., 2013. Distribution and Relative Abundance of Marine Mammals in the Northeastern Chukchi and Western Beaufort Seas, 2012. Annual Report, OCS Study BOEM 2013-00117. National Marine Mammal Laboratory, Alaska Fisheries Science Center, NMFS, NOAA. Clarke, J.T., Brower, A.A., Christman, C.L., Ferguson, M.C., 2014. Distribution and Relative Abundance of Marine Mammals in the Northeastern Chukchi and Western Beaufort Seas, 2013. Annual Report, OCS Study BOEM 2014-018. National Marine Mammal Laboratory, Alaska Fisheries Science Center, NMFS, NOAA. Clarke, J.T., Brower, A.A., Ferguson, M.C., Kennedy, A.S., Willoughby, A.L., 2015b. Distribution and Relative Abundance of Marine Mammals in the Eastern Chukchi and Western Beaufort seas, 2014. Annual Report, OCS Study BOEM 2015-040. Final Report. National Marine Mammal Laboratory, Alaska Fisheries Science Center, NMFS, NOAA. Clarke, J.T., Ferguson, M.C., Curtice, C., Harrison, J., 2015a. Biologically important areas for cetaceans within US waterseArctic region. Aquat. Mammal. 41, 94e103. Clarke, J.T., Moore, S.E., 2002. A note on observations of gray whales in the southern Chukchi and northern Bering Seas, AugusteNovember, 1980e89. J. Cetacean Res. Manag. 4, 283e288. Conlan, K., Hendrycks, E., Aitken, A., Williams, B., Blasco, S., Crawford, E., 2013. Macrofaunal biomass distribution on the Canadian Beaufort shelf. J. Mar. Syst. 127, 76e87. Ferguson, M.C., Waite, J.M., Curtice, C., Clarke, J.T., Harrison, J., 2015. Biologically important areas for cetaceans within US waterseAleutian islands and bering sea region. Aquat. Mammal. 41, 79e93. Harris, R.E., Lewin, A., Hunter, A., Fitzgerald, M., Davis, A.R., Elliott, T., Davis, R.A., 2008. Marine Mammal Mitigation and Monitoring for GX Technology's Canadian Beaufort Span 2-D Marine Seismic Program, Open-water Season 2007.
Prepared for GX Technology, Houston TX. LGL Report TA4460-01-1. Harwood, L.A., Auld, J., Joynt, A., Moore, S.E., 2010. Distribution of bowhead whales in the SE Beaufort Sea during late summer, 2007e2009. DFO Can. Sci. Advis. Secr. Res. Doc. iv þ 22. Harwood, L.A., Innes, S., Norton, P., Kingsley, M.C., 1996. Distribution and abundance of beluga whales in the Mackenzie estuary, southeast Beaufort Sea, and west Amundsen Gulf during late July 1992. Can. J. Fish. Aquat. Sci. 53, 2262e2273. Harwood, L.A., Kingsley, M.C.S., 2013. Trends in the offshore distribution and relative abundance of Beaufort sea Belugas, 1982e85 vs 2007e09. Arctic 66, 247e256. Jones, M.L., Schwartz, L.S., 2009. Gray whale Eschrichtius robustus. In: Perrin, F., Wursig, B., Thewissen, M. (Eds.), Encyclopedia of Marine Mammals, second ed. Academic Press, San Diego, USA, pp. 503e511. Kuletz, K.J., Ferguson, M.C., Hurley, B., Gall, A.E., Labunski, E.A., Morgan, T.C., 2015. Seasonal spatial patterns in seabird and marine mammal distribution in the eastern Chukchi and western Beaufort seas: identifying biologically important Pelagic areas. Prog. Oceanogr. 136, 175e200. Maher, W.J., 1960. Recent records of the California Grey Whale (Eschrichtius glaucus) along the north coast of Alaska. Arctic 257e265. Markus, T., Cavalieri, D.J., 2000. An enhancement of the NASA team sea ice algorithm. IEEE Trans. Geosci. Remote 38, 1387e1398. http://dx.doi.org/10.1109/ 36.843033. Marquette, W.M., Braham, H.W., 1980. The Take and Distribution of Gray Whales in Northern Alaskan Waters. Paper SC/32/PS12 submitted to the International Whaling Commission Scientific Committee, p. 8. Moore, S.E., 2008. Marine mammals as ecosystem sentinels. J. Mammal. 89, 534e540. Moore, S.E., 2010. Whales facing climate change in the Pacific Arctic. Whalewatcher 39, 7e11. Moore, S.E., Grebmeier, J.M., Davies, J.R., 2003. Gray whale distribution relative to forage habitat in the northern Bering sea: current conditions and retrospective summary. Can. J. Zool. 81, 734e742. Moore, S.E., Stafford, K.M., Mellinger, D.K., Hildebrand, J.A., 2006. Listening for large whales in the offshore waters of Alaska. BioScience 56, 49e55. Moore, S.E., Ljungblad, D.K., Van Schoik, D.R., 1986. Annual Patterns of Gray Whale (Eschrichtius robustus) Distribution, Abundance and Behavior in the Northern Bering and Eastern Chukchi Seas, July 1980e83. Rep. Int. Whaling Comm. Spec. Issue 8, pp. 231e242. National Marine Mammal Laboratory. Historical BWASP and COMIDA database. http://www.afsc.noaa.gov/nmml/software/bwasp-comida.php (accessed 16.02.02.). Nerini, M., 1984. A review of gray whale feeding ecology. In: Jones, M.L., Swartz, S.L., Leatherwood, S. (Eds.), The Gray Whale, Eschrichtius robustus. Academic Press, Orlando, Florida, USA, pp. 423e450. Quakenbush, L.T., Small, R.J., Citta, J.J., 2010. Satellite Tracking of Western Arctic Bowhead Whales, p. 118. Final report. OCS Study BOEMRE 2010e033. Rice, D.W., Wolman, A.A., 1971. The Life History and Ecology of the Gray Whale (Eschrichtius robustus). American Society of Mammalogists, Oklahoma. Richardson, W.J., Davis, R.A., Evans, C.R., Ljungblad, D.K., Norton, P., 1987. Summer distribution of bowhead whales, Balaena mysticetus, relative to oil industry activities in the Canadian Beaufort Sea, 1980e84. Arctic 40, 93e104. Rugh, D.J., Fraker, M.A., 1981. Gray whale (Eschrichtius robustus) sightings in eastern Beaufort Sea. Arctic 34, 186e187. Rugh, D.J., Hobbs, R., Lerczak, J., Breiwick, J., 2005. Estimates of abundance of the eastern North Pacific stock of gray whales (Eschrichtius robustus) 1997e2002. J. Cetacean Res. Manag. 7, 1e12. Rugh, D.J., Shelden, K.E.W., Schulman-Janiger, A., 2001. Timing of the gray whale southbound migration. J. Cetacean Res. Manag. 3, 31e39. Schonberg, S.V., Clarke, J.T., Dunton, K.H., 2014. Distribution, abundance, biomass and diversity of benthic infauna in the Northeast Chukchi sea, Alaska: relation to environmental variables and marine mammals. Deep Sea Res. Part. II 102, 144e163. Stafford, K.M., Moore, S.E., Spillane, M., Wiggins, S., 2007. Gray whale calls recorded near Barrow, Alaska, throughout the winter of 2003e04. Arctic 60, 167e172. Williams, W.J., Carmack, E.C., 2008. Combined effect of wind-forcing and isobath divergence on upwelling at Cape Bathurst, Beaufort sea. J. Mar. Res. 66, 645e663.
Contents lists available at ScienceDirect
Polar Science journal homepage: http://ees.elsevier.com/polar/
Gray whale sightings in the Canadian Beaufort Sea, September 2014 Yuka Iwahara a, *, Amane Fujiwara b, Keizo Ito a, Kazushi Miyashita c, Yoko Mitani c a
Graduate School of Environmental Science, Hokkaido University, 20-5 Benten-cho, Hakodate, Hokkaido, 040-0051, Japan Institute of Arctic Climate and Environment Research, Japan Agency for Marine-Earth Science and Technology, 2-15, Natsushima-cho, Yokosuka, Kanagawa, 237-0061, Japan c Field Science Center for Northern Biosphere, Hokkaido University, 20-5 Benten-cho, Hakodate, Hokkaido, 040-0051, Japan b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 4 March 2016 Received in revised form 5 April 2016 Accepted 11 April 2016 Available online 13 April 2016
Gray whales (Eschrichtius robustus) are distributed within the productive neritic and estuarine waters of the North Pacific Ocean, the Bering Sea, and adjacent waters of the Arctic Ocean. They migrate to highlatitude feeding grounds each spring. Their main feeding grounds in the Arctic include the Chirikov Basin, the northeastern Chukchi Sea from Pt. Hope to Cape Lisburne and Pt. Lay to Pt. Barrow, and the northwestern Chukchi Sea along the Chukotka coast. Although sightings are rare in the Canadian Beaufort Sea, we observed three gray whales in two groups in this area in September 2014. A mud plume was observed near one of the whales, suggesting the animal had been feeding. In the Alaskan Beaufort Sea, large-scale monitoring of the distributions of marine mammals has been continuously conducted since 1979; however, there has been less monitoring in the Canadian Beaufort Sea. Therefore, it is necessary to record opportunistic sightings, such as those described here. © 2016 Elsevier B.V. and NIPR. All rights reserved.
Keywords: Gray whale Eastern Beaufort Sea Eschrichtius robustus Feeding
1. Introduction Gray whales (Eschrichtius robustus) are confined to the productive neritic and estuarine waters of the North Pacific Ocean, the Bering Sea, and adjacent waters of the Arctic Ocean (Jones and Schwartz, 2009). Each spring they migrate north to feeding grounds, mainly in the Bering and Chukchi seas, covering an average distance of ~8000 km and making an annual round trip of 15,000e20,000 km (Jones and Schwartz, 2009; Rugh et al., 2001). The whales feed on a wide variety of prey (Jones and Schwartz, 2009; Nerini, 1984), mainly benthic organisms in shallow seas (Nerini, 1984; Rice and Wolman, 1971). In recent years, important feeding grounds in the eastern Chukchi and Bering seas have been located in the Chirikov Basin, off Point Hope, and from Wainwright to Point Barrow (Clarke et al., 2013, 2014, 2015b; Ferguson et al., 2015; Kuletz et al., 2015; Schonberg et al., 2014). The Chirikov Basin, in the Bering Sea, has been an important gray whale feeding area, at least intermittently, since the 1980s (Ferguson et al., 2015; Moore et al., 1986, 2003), with large numbers of feeding whales having been sighted during aerial surveys in 1980, 1981, 1982, and 1985 (Moore et al., 1986, 2003). Although the number of gray
* Corresponding author. E-mail address: [email protected] (Y. Iwahara). http://dx.doi.org/10.1016/j.polar.2016.04.007 1873-9652/© 2016 Elsevier B.V. and NIPR. All rights reserved.
whales dramatically decreased during the 1990s, in parallel with the collapse of populations of their amphipod prey (Moore et al., 2003), in September 2014 a large aggregation of gray whales was observed in the Chirikov Basin (Ferguson et al., 2015). Therefore, the Chirikov Basin remains an important feeding area (Ferguson et al., 2015). Since the 1980s, marine mammal aerial surveys have consistently documented gray whales feeding during summer and fall in the northeastern Chukchi Sea, from Pt. Hope to Cape Lisburne and from Pt. Lay to Pt. Barrow (Clarke et al., 2015a; Kuletz et al., 2015; Schonberg et al., 2014). Gray whales were consistently seen feeding near Hanna Shoal in September and October in the late 1980s and early 1990s (Clarke and Moore, 2002), but were generally absent after 2008 (Clarke et al., 2014, 2015a). This suggests that local changes in feeding grounds have occurred during recent decades in the eastern Chukchi and Bering seas. Although gray whales were occasionally seen in the 1950s near Point Barrow, which is the entrance to the Beaufort Sea (Maher, 1960), their abundance there was likely also low in the 1970s (Marquette and Braham, 1980). Moore et al. (2006) noted that in recent years hunters have reported increasing numbers of gray whales near Barrow in the late summer and autumn, and aerial surveys conducted each summer and fall in that area since 2009 have confirmed the common occurrence of these whales (Clarke et al., 2015b). The increasing occurrence of gray whales near Barrow could reflect an increase in their population (Rugh et al., 2005), climate-induced changes in
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habitat (Moore et al., 2003), or both. Despite this, they have been rare visitors to the Beaufort Sea since the 1950s (Maher, 1960), and there have been few records of sightings (Brower et al., 2015; Marquette and Braham, 1980; National Marine Mammal Laboratory, Historical BWASP and COMIDA database: http://www. afsc.noaa.gov/nmml/software/bwasp-comida.php). In the Canadian Beaufort Sea in particular, sightings were only reported in 1980 (Rugh and Fraker, 1981), although surveys have been limited in this region. Following a gap of 27 years, one gray whale was observed in an aerial survey in 2007, and another was sighted and satellite tagged in 2009 (Conlan et al., 2013; Harris et al., 2008; Quakenbush et al., 2010). Here we report on gray whale sightings recorded during a ship sighting survey in the Canadian Beaufort Sea in 2014.
71600 N, 155 300 W; St. 2: 70 300 N, 146 W; St. 3: 70 N, 136 W; St. 4: 70 500 N, 130 250 W) from 1979 to 2014; this was based on historical remotely-sensed sea ice concentration (SIC) data, calculated using NASA-Team Algorithm 2 (Markus and Cavalieri, 2000). The SIC datasets at 25-km gridded resolution were collected using the scanning multichannel microwave radiometer (SMMR) and the special sensor microwave/imager (SSM/I), and were retrieved from the National Snow and Ice Data Center (NSIDC). We defined nonice-covered pixels when sea ice concentrations were <20%. In addition, to investigate the relationship between sea-ice-edge and gray whale position, we calculated the distance between the observed gray whale positions and the sea-ice edge. We defined the sea-ice edge as the outer line of the area where the average sea ice concentration in the survey period was 20%.
2. Material and methods
3. Results
The visual survey was conducted in the Beaufort Sea from the bridge (14 m above sea level) of the Canadian research icebreaker Amundsen, from 10 September to 25 September 2014 (Fig. 1). Observations were conducted while the vessel was moving between sampling stations during daylight hours, and commenced 1 h following sunrise and ceased 1 h prior to sunset. During the cruise, two observers constantly scanned the survey area (90 to each side of the bow), using 8 power binoculars (Nikon). Both observers had previous experience in identifying marine mammals during shipboard surveys, including in the Chukchi Sea. When marine mammals were seen, the time (UTC), number of animals, position in latitude and longitude of the ship, distance from the ship, angle from the front of the ship, and animal behavior were recorded. The ship did not approach any marine mammals. We also recorded the weather, wind speed, wind force (Beaufort scale), wave height, visibility, and glare every 30 min. The vessel speed was automatically recorded every minute. To determine the interannual change in the ice-free period at the locations where gray whales were sighted and where they potentially used to reach the Canadian Beaufort Sea, we determined the number of ice-free days at the four stations (St. 1:
On 24 September 2014 we observed three gray whales, comprising one pair and one individual (Fig. 1). The pair was observed at 70 480 N, 130 460 W on 24 September 2014 at 00:01, and the individual was observed at 70 550 N, 13010 W on the same day, at 01:20. The bottom depths at the observation points were 32 m and 30 m, respectively. Species identification was based on observation of the mottled gray skin, and the back having a hump followed by a series of fleshy knobs along the tailstock. The ship sailed continuously in a direct line without diverting to the Amundsen Gulf, and therefore the individual whale was not one of the pair. We observed several blows and dives during each sighting. One of the two whales in the pair made a mud plume (Fig. 2). At the time of the sightings the ship speed was approximately 12 knots, the wind force was 2 on the Beaufort scale, and there was no fog or glare. We did not observe any sea ice during the day on which we observed the whales. The distance of the ice edge from the ship when we observed the whales was >90 km (Fig. 1). 4. Discussion The area in which we observed gray whales is characterized as a
Fig. 1. Map of the study area in the Beaufort Sea. Red lines represent visual surveys. White circles represent whales observed in 1980 (Rugh and Fraker, 1981) and black circles represent whales observed in this study, in 2014. Gray triangles represent the stations where interannual variations in the number of ice-free days were monitored. The blue line represents the location of the sea ice edge during our survey period (10e25 September 2014).
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Fig. 2. Mud plume observed during the gray whale encounter (sighting number one).
shelf-break upwelling area (Williams and Carmack, 2008). It is rich re et al., 2007), particularly ampein benthic communities (Bessie liscid amphipods (Conlan et al., 2013), which may be a food resource for gray whales. Furthermore, the water depths at the sighting locations are shallow. Rugh and Fraker (1981) also observed a gray whale associated with a mud plume in this area, indicating that gray whales use it as a feeding ground. The observations of Rugh and colleagues were made within 19e66 km of those made in the present report (Fig. 1). Our observations were made in September, whereas theirs were made in August. In addition, the area concerned is densely populated by bowhead whales, because of the large populations of calanoid copepods that occur there (Citta et al., 2015). The occurrence of sea ice in the Beaufort Sea has been decreasing annually since the 1980s, as is evident from the increase in the total number of ice-free days (Fig. 3). This is particularly evident at St. 1 (Fig. 1), at the entrance to the Beaufort Sea, where icy years (years having <50 days with no ice cover) occurred at least every 2e3 years prior to 1984. However, since then the total number of ice-free days has gradually increased, and there have
been no icy years since 2001. Consequently, gray whales can potentially enter the Beaufort Sea earlier and stay longer to feed in this area. Conlan et al. (2013) suggested that the Cape Bathurst area may become of increasing importance to gray whales and other benthic predators because of the decreasing seasonal ice cover in the Beaufort Sea, which results in longer periods of wind-driven upwelling, and easier and extended whale access. Gray whales feed in various geographic areas, and could change their feeding grounds in response to environmental change (Bluhm and Gradinger, 2008; Moore, 2008, 2010; Moore et al., 2003; Stafford et al., 2007). Therefore, they may act as sentinels for ecosystem change (Moore, 2008). In the Alaskan Beaufort Sea, large-scale monitoring of the distribution of marine mammals has been continuously conducted for several decades through the aerial surveys of Arctic marine mammals (ASAMM) project (2011e2015), BWASP (1979e2010), and the COMIDA marine mammal aerial survey project (2008e2010), and very few gray whales (<10) have been observed (National Marine Mammal Laboratory. Historical BWASP and COMIDA database). In the Canadian Beaufort Sea, visual surveys for marine
Fig. 3. Temporal changes in the number of ice-free days. Sea ice concentrations were derived from scanning multichannel microwave radiometer (SMMR, 1979e1987) and special sensor microwave imager (SSMI, 1987e2014) satellite sensors. The spatial scale of all sensors was 25 km. The datasets from duplicate periods were averaged.
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mammals have been conducted only sporadically in recent years (1992, 2007, 2008, and 2009), although such surveys were conducted from the 1970s to the 1980s (Harwood et al., 1996, 2010; Harwood and Kingsley, 2013; Richardson et al., 1987; Rugh and Fraker, 1981). It is possible that gray whales used this area during the 1990s and early 2000s but were not observed because of the relatively small survey effort. Therefore, it is important to accumulate opportunistic sighting records, including this report. Acknowledgments We acknowledge the captain, crew, and researchers on board on the Canadian icebreaker Amundsen for their endless support and hard work during the 2014 cruise. This study was supported by the Green Network of Excellence Program's (GRENE Program) Arctic Climate Change Research Project: ‘Rapid Change of the Arctic Climate System and its Global Influences.’ References re, A., Nozais, C., Brugel, S., Demers, S., Desrosiers, G., 2007. Metazoan Bessie meiofauna dynamics and pelagicebenthic coupling in the southeastern Beaufort Sea, Arctic Ocean. Polar Biol. 30, 1123e1135. Bluhm, B.A., Gradinger, R., 2008. Regional variability in food availability for Arctic marine mammals. Ecol. Appl. 18, S77eS96. Brower, A., Clarke, J., Ferguson, M., 2015. Gray whale occurrence in the Beaufort Sea. In: Alaska Marine Science Symposium, Anchorage, AK, USA, January 19e23, 2015, p. 199. Abstract. Citta, J.J., Quakenbush, L.T., Okkonen, S.R., Druckenmiller, M.L., Maslowski, W., Clement-Kinney, J., George, J.C., Brower, H., Small, R.J., Ashjian, C.J., 2015. Ecological characteristics of core-use areas used by BeringeChukchieBeaufort (BCB) bowhead whales, 2006e2012. Prog. Oceanogr. 136, 201e222. Clarke, J.T., Brower, A.A., Christman, C.L., Ferguson, M.C., 2013. Distribution and Relative Abundance of Marine Mammals in the Northeastern Chukchi and Western Beaufort Seas, 2012. Annual Report, OCS Study BOEM 2013-00117. National Marine Mammal Laboratory, Alaska Fisheries Science Center, NMFS, NOAA. Clarke, J.T., Brower, A.A., Christman, C.L., Ferguson, M.C., 2014. Distribution and Relative Abundance of Marine Mammals in the Northeastern Chukchi and Western Beaufort Seas, 2013. Annual Report, OCS Study BOEM 2014-018. National Marine Mammal Laboratory, Alaska Fisheries Science Center, NMFS, NOAA. Clarke, J.T., Brower, A.A., Ferguson, M.C., Kennedy, A.S., Willoughby, A.L., 2015b. Distribution and Relative Abundance of Marine Mammals in the Eastern Chukchi and Western Beaufort seas, 2014. Annual Report, OCS Study BOEM 2015-040. Final Report. National Marine Mammal Laboratory, Alaska Fisheries Science Center, NMFS, NOAA. Clarke, J.T., Ferguson, M.C., Curtice, C., Harrison, J., 2015a. Biologically important areas for cetaceans within US waterseArctic region. Aquat. Mammal. 41, 94e103. Clarke, J.T., Moore, S.E., 2002. A note on observations of gray whales in the southern Chukchi and northern Bering Seas, AugusteNovember, 1980e89. J. Cetacean Res. Manag. 4, 283e288. Conlan, K., Hendrycks, E., Aitken, A., Williams, B., Blasco, S., Crawford, E., 2013. Macrofaunal biomass distribution on the Canadian Beaufort shelf. J. Mar. Syst. 127, 76e87. Ferguson, M.C., Waite, J.M., Curtice, C., Clarke, J.T., Harrison, J., 2015. Biologically important areas for cetaceans within US waterseAleutian islands and bering sea region. Aquat. Mammal. 41, 79e93. Harris, R.E., Lewin, A., Hunter, A., Fitzgerald, M., Davis, A.R., Elliott, T., Davis, R.A., 2008. Marine Mammal Mitigation and Monitoring for GX Technology's Canadian Beaufort Span 2-D Marine Seismic Program, Open-water Season 2007.
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