PIFSC Mariana Archipelago cetacean surveys 2010-2019

Original provider: NOAA Pacific Islands Fisheries Science Center (PIFSC) Dataset credits: NOAA Pacific Islands Fisheries Science Center (PIFSC) Abstract: The Pacific Islands Fisheries Science Center (PIFSC) Cetacean Research Program has conducted research on cetaceans in the Mariana Archipelago since 2010 (Hill et al. in review). A cooperative effort with funding from U.S. Navy Pacific Feet and PIFSC has included summer and winter small-boat surveys off the southernmost islands (Saipan, Tinian, Aguijan, Rota, and Guam). Across all summer and winter small-boat survey efforts, PIFSC conducted 270 days of surveys. Most of the survey effort occurred in summer months (May–September) and there was no effort during October–December. There were 362 groups (excluding within-day re-sights) identified to 14 species including (in order of frequency of occurrence) spinner dolphin, pantropical spotted dolphin, bottlenose dolphin, short-finned pilot whale, rough-toothed dolphin, sperm whale, false killer whale, dwarf sperm whale, pygmy killer whale, Bryde's whale, melon-headed whale, Blainville's beaked whale, and Cuvier's beaked whale. Humpback whales were encountered in January–March 2015–2019 when targeted surveys were conducted off Saipan. Across all PIFSC small-boat surveys, there were 19 mixed-species groups, each including 2–3 species. Some groups could not be identified to species, and are indicated as unidentified beaked whales, unidentified whales, and unidentified dolphins. The overall effort resulted in collection of 130,066 photos and 435 biopsy samples, and deployment of 44 satellite tags. Purpose: The goal of these efforts has been to collect the data necessary to conduct population assessments for cetaceans within the Mariana Archipelago, including the determination of their occurrence, population structure, and abundance, movements, distribution, and habitat use. In addition, these data may be used to evaluate the potential exposure of cetaceans to human-caused stressors within the waters surrounding the Mariana Archipelago including U.S. Navy operations (e.g., sonar, use of explosives), fisheries interactions, and dolphin tourism. Supplemental information: PIFSC has conducted visual surveys for cetaceans in the waters off the southernmost islands of the Mariana Archipelago (Saipan, Tinian, Aguijan, Rota, and Guam) aboard small vessels (5.8–12.2 m). Survey tracks did not follow a randomized design, but instead were spread out from day to day to ensure broad survey coverage over a wide range of depths and were also dictated by weather and sea conditions. The survey vessels traveled at a speed of 15–26 km/h, depending on the size of the vessel and sea conditions. Between 4 and 6 observers scanned for marine mammals with unaided eyes or, occasionally handheld binoculars, collectively searching 360-degrees around the vessel. All cetacean groups encountered were approached for species confirmation, group size estimates, photo-identification, and biopsy sampling/sloughed skin collection. In 2013, satellite tagging was implemented to investigate movements and spatial use of individuals of some species. Additional data collected during each sighting included the location (latitude/longitude), behavior, and estimates of calf numbers. Survey conditions (e.g., Beaufort sea state, swell height) and effort status were recorded regularly as conditions changed. A handheld Global Positioning System (GPS) automatically recorded the vessel’s track at 1-minute intervals.