Cetacean and seabird data collected during the Mariana Archipelago Cetacean Survey (MACS), May-July 2021

In summer 2021, the Pacific Islands Fisheries Science Center conducted a comprehensive line-transect survey for cetaceans and seabirds within the U.S. of the Guam and the Commonwealth of the Northern Mariana Islands exclusive economic zones. The Mariana Archipelago Cetacean Survey (MACS) 2021 project was part of the multi-year Pacific Marine Assessment Program for Protected Species (PacMAPPS) plan to conduct surveys and estimate density for cetacean species in regions of joint NOAA Fisheries, Bureau of Ocean Energy Management, and U.S. Navy interest. MACS 2021 sailed for 59 days at sea aboard the NOAA Ship Oscar Elton Sette in May-July, 2021 and surveyed 8,711.7 km of trackline. The team conducted visual and passive acoustic surveys during daylight hours when weather permitted. There were 77 cetacean sightings of at least 12 species. The most frequently sighted species during the project were sperm whales (Physeter macrocephalus, 18 sightings), false killer whales (Pseudorca crassidens, 10 sightings), and pantropical spotted dolphins (Stenella attenuata, 8 sightings). Approximately 2,300 photos of 9 cetacean species were collected for individual or species identification during 20 cetacean sightings. Two biopsy samples were collected from false killer whales. During towed array surveys there were 245 acoustic detections of cetaceans, of which 47 were linked to visually sighted groups. Twenty-two Drifting Acoustic Spar Buoy Recorders were deployed and recovered throughout the survey area and will contribute additional information on beaked whale, Kogia, and baleen whale distribution and abundance. The seabird observers counted 3,266 individual birds in 1,605 seabird sightings among 29 species (plus 12 additional taxa). The most frequently sighted seabird species included the Sooty Tern (Onychoprion fuscata, 654 individuals), Short-tailed Shearwater (Ardenna tenuirostris, 547 individuals), and Red-footed Booby (Sula sula, 368 individuals). Oceanographic sampling was conducted with twice daily CTD casts when conditions permitted, with a total of 79 casts throughout the survey area.

The primary goals of MACS 2021 were to collect data required to estimate the abundance and distribution, examine the population structure, and understand the habitat of cetaceans within the U.S. waters around the Mariana Archipelago. There were 5 major research components to the project:

-visual observations for cetaceans following a line-transect survey design;

-passive acoustic monitoring for cetaceans using towed hydrophone arrays, sonobuoys, and autonomous drifting acoustic recorders;

-collection of photographs and tissue samples for select cetacean groups;

-visual observations for seabirds following a strip-transect survey design; and

-ecosystem measurements for assessment of cetacean and seabird habitat.

Yano KM, Hill MC, Oleson EM, McCullough JLK, and Henry AE. 2022. Cetacean and seabird data collected during the Mariana Archipelago Cetacean Survey (MACS), May-July 2021. U.S. Department of Commerce, NOAA Technical Memorandum NOAA-TM-NMFS-PIFSC-###, 59 p. doi:10.###

The Mariana Archipelago Cetacean Survey (MACS) 2021 project was a shipboard survey for cetaceans and seabirds around the Mariana Archipelago. MACS 2021 sailed aboard the Oscar Elton Sette, hereafter referred to as the Sette, for 59 days at sea. The project was conducted during 2 survey "legs"; Leg 1 sailed from 3 to 31 May and Leg 2 sailed from 15 June to 14 July.

This project used many of the same methods as previous projects conducted by the Pacific Islands Fisheries Science Center (PIFSC), most recently the Winter Hawaiian Islands Cetacean and Ecosystem Assessment Survey in 2020 (Winter HICEAS; Yano et al. 2020) and the Hawaiian Islands Cetacean and Ecosystem Assessment Survey in 2017 (HICEAS; Yano et al. 2018).

The MACS 2021 study area included the waters surrounding the Mariana Archipelago out to 200 nmi (370.4 km) from shore, which is the U.S. exclusive economic zone of Guam and the Commonwealth of the Northern Mariana Islands, hereafter referred to as the Marianas.