Survey of Cetaceans Completed in the Mariana Islands

In June and July, 2013, the Pacific Islands Fisheries Science Center's Cetacean Research Program conducted surveys for cetaceans in the waters surrounding Guam and the Commonwealth of the Northern Mariana Islands (CNMI). The survey objectives were to further develop a record of cetacean occurrence in the region and to gather photos and biopsy samples for cetacean population studies. Similar surveys have occurred each year since 2010.

The 2013 project was carried out using small boats (7.6-12.2 m) in partnership with the U.S. Navy. Surveys were conducted during 30 days, including 10 days around Guam, 6 days near Rota, and 14 days near Saipan and Tinian. Altogether, 3208 km of trackline were surveyed and there were 42 sightings of 8 cetacean species (bottlenose dolphin, false killer whale, pantropical spotted dolphin, pygmy killer whale, rough-toothed dolphin, short-finned pilot whale, sperm whale, and spinner dolphin). Three of the sightings were of mixed-species groups of pilot whales and bottlenose dolphins; false killer whales and bottlenose dolphins; and rough-toothed dolphins, bottlenose dolphins and spinner dolphins. Over 18,500 photos were taken and will be evaluated to establish individual dolphin identification. Identifiable individuals will be compared to existing photo-ID catalogs for spinner dolphins, bottlenose dolphins, and short-finned pilot whales, or will be part of new catalogs for other species. Photo-ID catalogs will be used for evaluating population structure and the distribution and movement of individual cetaceans, eventually providing the basis for abundance estimation for commonly encountered species.

When conditions allowed scientists to approach cetaceans safely in the small boat, 76 biopsy samples were collected from the 8 cetacean species and 8 sloughed skin samples were collected from sperm whales. All biopsy samples collected since 2010 are being analyzed by the Southwest Fisheries Science Center genetics lab to evaluate the phylogeography of Marianas cetaceans. In addition to the biopsy sampling, 10 satellite tags were deployed: 2 on bottlenose dolphins, 4 on false killer whales, 3 on short-finned pilot whales, and 1 on a rough-toothed dolphin. Four tags, including 2 on false killer whales and two on short-finned pilot whales were still operating as of August 30, 2013, transmitting location data each day.

False killer whale tracks in the Mariana Islands for July 5 through August 26, 2013 based on satellite tag transmitter data.  The 
               red and purple tracks are for transmitters still active as of August 30, 2013. Transmissions from 2 other tags represented by yellow 
               and blue tracks ended on July 8 and July 29, respectively.
False killer whale tracks in the Mariana Islands for July 5 through August 26, 2013 based on satellite tag transmitter data. The red and purple tracks are for transmitters still active as of August 30, 2013. Transmissions from 2 other tags represented by yellow and blue tracks ended on July 8 and July 29, respectively.