PACES Cetacean Survey Completed in Northwestern Hawaiian Islands

As part of NOAA's efforts to understand and conserve marine mammals and their pelagic ecosystems across the Pacific, PIFSC researchers recently conducted the Papahānaumokuāakea Associated Cetacean Ecology Survey (PACES), a multi-disciplinary cetacean assessment survey from Nihoa Island to Pearl and Hermes Reef in the Northwestern Hawaiian Islands. The PACES expedition was carried out from May 7 to June 5, 2013 on the NOAA Ship Oscar Elton Sette. It included several scientific operations including a visual and acoustic line-transect survey, collection of photo-IDs and tissue biopsy samples, and satellite tagging of individual animals in encountered groups of cetaceans. Oceanographic sampling was also conducted at fixed intervals along the survey tracks and during selected cetacean encounters.

The primary goal of the PACES survey was to better understand the distribution and ecology of cetaceans in the Northwestern Hawaiian Islands, including the connectivity of cetacean populations there to either broadly distributed pelagic populations or island-associated populations in the main Hawaiian Islands. Twenty-eight days of on-effort surveying were completed along both standard and non-standard transect lines, resulting in 88 ship-based visual sightings of at least 14 cetacean species. The geographic distribution of search effort and sightings is shown in the accompanying figure.

Sightings of at least 14 cetacean species were recorded as the Sette moved along standard and non-standard tracklines 
               (grey lines) within the PACES survey area (black outline): (A) dolphins; (B) all other whales.
Sightings of at least 14 cetacean species were recorded as the Sette moved along standard and non-standard tracklines (grey lines) within the PACES survey area (black outline): (A) dolphins; (B) all other whales.

Researchers on the Sette acoustically detected 120 cetacean groups using the Sette's towed hydrophone array. While 37 of the visual detections were not detected acoustically, 69 acoustic detections (mostly sperm whales and unidentified dolphins) were not detected visually, although many of these detections were beyond the visual survey search area. Over 2,800 photographs of 12 cetacean species in 36 sightings were collected from the Sette and a small boat launched from the ship. Between the ship and small boat, a total of 23 biopsy samples were obtained from six species: six spinner dolphins, seven bottlenose dolphins, five false killer whales, two pilot whales, two sperm whales, and one humpback whale. Two satellite tags were deployed, both on false killer whales, one on May 15 off Laysan Island and the other on May 26 at a location 40 nmi SE of Maro Reef. On May 29, a High-frequency Acoustic Recording Package (HARP) was recovered and redeployed near Pearl and Hermes Reef, contributing valuable data to a long-term cetacean monitoring project ongoing since 2009.