Abstract
During summer and fall 2023, the Pacific Islands and Southwest Fisheries Science Centers conducted a comprehensive line-transect survey for cetaceans and seabirds within the U.S. waters surrounding the Hawaiian Islands. The Hawaiian Islands Cetacean and Ecosystem Assessment Survey (HICEAS) 2023 project was conducted as part of the Pacific Marine Assessment Program for Protected Species (PacMAPPS) 2.0, the second partnership between NOAA Fisheries and the Bureau of Ocean Energy Management (BOEM). PacMAPPS includes rotational ship surveys in regions of joint interest throughout the Pacific designed to estimate the abundance of cetaceans and seabirds and to assess the ecosystems supporting these species. HICEAS 2023 surveyed approximately 20,200 km of trackline over 145 days at sea aboard NOAA Ships Oscar Elton Sette and Reuben Lasker. Sette sailed for 106 days in July–November and Lasker sailed 39 days in October–December. The team conducted visual and passive acoustic surveys during daylight hours when weather permitted. There were 310 sightings of at least 24 cetacean species and approximately 35,600 photos were collected during 154 sightings for individual or species identification. The most frequently sighted species during the project were Bryde’s whales (Balaenoptera edeni, 33 sightings), short-finned pilot whales (Globicephala macrohynchus, 26 sightings), and sperm whales (Physeter macrocephalus, 24 sightings). Six biopsy samples were collected from bottlenose dolphins (Tursiops truncatus) and three biopsy samples from pygmy killer whales (Feresa attenuata). During towed array surveys, there were 526 acoustic detections of cetaceans, of which 131 were linked to sighted groups. Two seasonal species of baleen whales, humpback (Megaptera novaeangliae) and common minke (Balaenoptera acutorostrata) whales, were detected by the towed array during the project. Fifteen Drifting Acoustic Spar Buoy Recorders (DASBRs) were deployed and recovered throughout the survey area and will contribute additional information on the distribution of deep-diving whales difficult to survey from the ship. The seabird observers counted 20,595 individual birds in 7,354 sightings of 55 individual species (plus 18 additional taxonomic groupings). Three common seabird species breeding in the Hawaiian Islands accounted for 50% of sightings and 56% of total individuals observed: the Wedge-tailed Shearwater (Puffinus pacificus; 2,362 sightings, 32% relative abundance), Sooty Tern (Onychoprion fuscata; 445 sightings, 6% relative abundance), and Red-footed Booby (Sula sula; 861 sightings, 11% relative abundance). Two hundred and twenty-one seabird feeding flocks were observed. Oceanographic sampling was conducted with at least twice daily CTD casts when conditions permitted, with a total of 169 casts throughout the survey area. Twenty of the CTD casts also collected water to process for eDNA samples. Eighty-eight evening net tows were conducted and collected a broad range of taxa of ichthyoplankton including larvae of mesopelagic, reef, large pelagic, and forage fish.