Cetaceans Surveyed in the Western Pacific

Early in 2010, the Center's Cetacean Research Program conducted extensive surveys of cetaceans in waters of the western Pacific. In January and February the Program conducted a visual and acoustic survey for cetaceans during the Honolulu-Guam transit of the NOAA Ship Oscar Elton Sette; the journey including a short survey around Wake Atoll. While the ship was underway, scientific observers on the Sette expended over 217 days of survey effort using high-powered binoculars , sighting 25 groups of cetaceans, including sei whales, sperm whales, striped dolphins, false killer whales, melon-headed whales, and spotted dolphins. Simultaneous acoustic monitoring using the Program's towed hydrophone array yielded nearly constant detections of minke and humpback whales along the survey trackline. In addition, a High-Frequency Acoustic Recording Package (HARP) was deployed at Wake Atoll to assess the long-term occurrence of cetacean species at the Atoll. The HARP was retrieved and redeployed during the Sette's return transit from Guam in April. Analysis of its data is pending.

In February and March, 3 scientists contracted by the Program conducted small boat surveys of cetaceans in waters around Guam and Saipan. The surveys were intended to evaluate the distribution and occurrence of near shore species, particularly humpback whales ands spinner dolphins. Despite consistently poor weather, there were several sightings of what appear to be resident spinner dolphins, as well as single sightings of sperm whales and pilot whales.

In April and May, the Program repeated the visual and acoustic survey for cetaceans in oceanic waters during the Sette's homeward transit from Guam to Honolulu, and once again included a short survey around Wake Atoll. Observers sighted 21 groups of cetaceans over 16 survey days, including spotted dolphins, false killer whales and sei whales. Minke and humpback whales were again consistently heard on the towed hydrophone array. The acoustic detections of minke whales will be used to evaluate the distribution of different minke whale stocks across the Pacific Basin and assess their abundance using modified line-transect methods.