Beluga whale (Delphinapterus leucas) presence and survey effort collected during visual surveys from aerial platforms by the Alaska Beluga Whale Committee in the Eastern Bering Sea from 1992-05-27 to 2000-06-20 (NCEI Accession 0276222)

Prior to 1992, there was little information on the distribution of EBS belugas beyond the knowledge of the traditional Alaska Native hunting areas, and places where belugas were seen on an opportunistic basis. There had been no systematic surveys of belugas in the Norton Sound/Yukon Delta region, and there were no reliable estimates of historical population size. It was known that belugas occurred throughout the coastal zone of the northeastern Bering Sea, particularly from the mouth of the Yukon River to northern Norton Sound near Nome, and few were seen far from the shoreline. Belugas were seen predominantly during ice-free months, which was usually mid-May after the breakup of sea ice until freeze-up in November. The goals of the ABWC research programs aerial surveys were to estimate the abundance and trends of the EBS stock of belugas and to compare those results with previous beluga information for this area.

Metadata for these data were not compiled at the time of the surveys, and the data existed in various forms in multiple locations. In 2022, an effort was made to pull all the data together, standardize attribute values, minimize inconsistencies, and/or correct errors, and create metadata to improve the database for future analyses. Most of the people who worked on the project and analyzed the data were either retired or deceased by 2022; for this reason, some of the values in the data fields remain undefined. For more information about this review and details of the edits that were made to the data, see contact the data steward about the EBS Beluga 1992-2000_Final files, data review, & edits document. There were survey flights flown for this survey, for which survey data do not exist. The International Whaling Commission report, Lowry, L.F., D.P. DeMaster, K.J. Frost. 1999. Alaska Beluga Whale Committee surveys of beluga whales in the Eastern Bering Sea, 1992-1995. Rep. Int. Whal. Commn. SC/51/SM34, gives detail that a survey flight was flown on 29 May 1992; however, survey data for that day are missing. Table 1 of Lowry et al. (1999) indicates that no belugas were sighted on that day. The document, NSsurveysJune95.DOC details that a flight was also flown on 9 June 1995, but there are no data for this flight. The report indicates the flight was all fog and there was no survey effort: Took off from Nome in the fog and flew about 30 miles to the south on top. The whole Sound was covered with a layer of fog about 1000 feet thick. Returned to Nome then to Fairbanks. Lowry et al. 1999 indicates that fog prevented surveys on 21 June 1995, and there are no data for this day. However, NSsurveysJune95.DOC details that there was a flight, but survey effort was not possible: Took off from Nome in the fog and flew 20 miles to the south on top. The whole Sound was covered with a layer of fog. Returned to Nome.

The survey was designed to cover coastal and offshore waters of Norton Sound and the Yukon Delta. Coastal transects were parallel to the shoreline with the centerline of the aircraft approximately 0.9 km offshore. Offshore transects were flown east to west along lines of latitude, north to south along lines of longitude, or on diagonals when travelling to and from airports. An adaptive sampling design was used in 1992 to 1995 to increase survey effort in areas where belugas had been sighted. When the belugas were seen on an offshore transect, additional parallel transects were flown at a 3.6-9.3 km spacing on both sides of the original line. Parallel transects were continued as long as belugas were seen, and usually stopped after two transects if there were no sightings. In 1999 and 2000, the survey was designed to cover all of Norton Sound and the Yukon River mouth with east to west transects regularly spaced at 9.3 km intervals. The total length of survey transects flown during each survey period was limited by the aircraft time available. The completion of transects was sometimes limited by weather conditions, particularly fog or high winds, and in June 1999 ice cover was a factor. The survey aircraft was a high-wing, twin-engine Aero Commander equipped with bubble windows, based in Nome. The crew included the pilot, a data recorder in the right front seat, and two observers seated behind the pilot on the left and right sides of the aircraft. Survey altitude was usually 305m, and ground speed was 274 km/hr (150 knots) in 1992 and 220 km/hr (120 knots) in all other years except some transit lines were flown at 274 km/hr in 1994. Navigation was done by reference to landmarks and with a Global Positioning System. The survey was done in passing mode, where whales were counted while staying on effort on the trackline. On the coastal transects, all belugas visible along the survey track were counted. The 1992 surveys were conducted as strip transect surveys; for the offshore transects, observers counted whales within 915 m wide strips on each side of the aircraft. The strips were offset 305 m from the centerline to eliminate the blind spot under the plane. The 1993 to 95 and 1999 to 2000 surveys were conducted as line transect surveys; the offshore transects on each side of the aircraft were divided into seven zones and each beluga sighting was recorded in one of the zones. Inclinometers were used to delineate the inner and outer bounds of zones from 0 to 51 deg. In 1992 and 1993, sightings and other data were recorded on datasheets by observers in one-minute intervals and were then entered into a computer database. In 1994 to 93;1995 and 1999 to 2000, a computer-based data entry program was used, logging the locations and times for the beginning and end of transects, the position on transect every 1 minute, and the exact time and position of each sighting. Environmental data and sighting conditions were also recorded. Data fields with S at the beginning of the field title (e.g., SOBSNUM, SGROUPSIZ) indicate sighting-related fields. Data fields with W at the beginning of the field title (WCLOUD, WBEAUSTAT, etc.) indicate weather-related fields.