Study the Science: Marine Mammals
The marine mammal ecology survey increases current knowledge of the movements, distribution and abundance of marine mammals during the open water season within the study areas. Vessel-based marine mammal data are collected as part of a multi-disciplinary environmental program during the open water season from the end of July to early October in the northeastern Chukchi Sea. Biologist observers, assisted by observers from the native communities, record all marine mammals sighted during daylight hours along north-south oriented transect lines. Besides species information, observers record other environmental data such as behavior, distance and movement of the animals relative to the vessel. The information obtained on marine mammal presence and distribution through visual observations augments the data collected through acoustic call detections. Combining the marine mammal data with information on the physical oceanography and potential food organisms (plankton, benthos, and fish) contributes to a better understanding of the relationship between marine mammals and their environment.
Although most walruses prefer to eat mollusks (such as clams), there are some rare but habitual seal-eating walruses.
In 2014, the CSESP survey design was modified to facilitate long-term monitoring while still covering the oil and gas lease areas sampled in previous years. There were six primary transect lines ranging from approximately 125 to 145 NM in length; four transect lines were perpendicular and the other two were located parallel to the northwestern Alaskan coastline. Observers on the R/V Westward Wind recorded 413 marine mammal sightings (587 individuals) in the northeastern Chukchi Sea along 4,000 km of on- and off-transect effort. There were very few walrus sightings compared to previous years.
In 2013, the survey focused on the three prospect-specific study areas similar to 2008–2010. We conducted line-transect surveys in these areas from the R/V Westward Wind in August and September. Observers on the R/V Norseman II recorded marine mammal sightings opportunistically in both the Chukchi and Beaufort Seas. Throughout August, the northern Statoil study area was inaccessible due to sea ice. The northeastern corner of the Burger study area also had a high, though navigable, concentration of sea ice in August, where observers recorded numerous Pacific walruses. Highlights of the 2013 survey included 7 polar bears on or close to the sea ice, mostly in the Burger study area. One sighting was of a sow and cub and one bear was a possible polar/grizzly bear hybrid. For the first time during the CSESP study we saw beluga whales during the survey.
The expanded study area sampled in 2011 was again sampled in 2012. Observers stationed on the bridge of the R/V Westward Wind and R/V Norseman II were recording marine mammal sightings along 10,027 km on- and off-transect in the Chukchi Sea, which included transits to and from Wainwright and Nome. An estimated total of 1,698 marine mammals were seen. The number of bowhead whales seen during the CSESP was the highest recorded since surveys started in 2008 and appeared to coincide with high abundance of copepods.
In 2011 the study area was expanded to a total of 10,987 NM2 or 37,687 km2 and included the three study areas sampled in 2008-2010. The R/V Westward Wind travelled along transect lines to collect data on marine mammals in the northeastern Chukchi Sea. Interesting this year were the relatively large number of bowhead whales sighted in August.
Statoil joined ConocoPhillips and Shell in the CSESP in 2010. A third study area was added, covering Statoil’s prospect area. In the 2010 cruise season, the R/V Westward Wind and the R/V Norseman II were deployed as marine mammal observation platforms. No sea ice was encountered in the study areas. During the last survey period in early October we saw many bowhead whales passing through the northeast corner of the Burger study area.
The vessel R/V Westward Wind was deployed as the research vessel for the 2009 cruise season. The vessel was equipped with specially constructed flying bridges which provided good exterior vantage points for marine mammal observers. When the vessel arrived in the research area in mid-August all the sea ice had already disappeared. There were not as many marine mammal sightings as in 2008.
When the R/V Bluefin arrived on site at the end of July 2008, the Klondike and Burger study areas were still covered with sea ice, which remained in the area until about mid-September. The presence of sea ice hampered the mobility of the vessel, and not all marine mammal transect lines could be covered during the first two cruises. Still, there were many sightings of seal and walrus during this time. One group of walrus observed on the sea ice (during an off-transect observation in the Burger study area) consisted of roughly 700 animals!