By Marie Hill, Adam Ü, Allan Ligon, and Tom Ninke
After leaving Guam, the Cetacean Research Program conducted small-boat surveys for whales and dolphins off Saipan and Tinian during May 17-26, 2017. During our second day on the water, we encountered a Bryde’s whale, which was only our 5th encounter with this species in the Mariana Islands and the first time that we have seen one off Saipan. Our four previous encounters were in August 2015 off Guam and Rota. Bryde’s whales are baleen whales and can grow to 51 ft in length. They are sometimes mistaken for sei whales, but can be distinguished by the presence of three longitudinal ridges on the top of their rostrum.
A few days later, we encountered two groups of bottlenose dolphins. We recognized a few of the individuals from our existing photo-identification catalog. The others may be new individuals.
We deployed two satellites tags on bottlenose dolphins, on one dolphin from each group. They spent the next several days moving up and down the west side of Saipan and Tinian, going as far north as Marpi Reef (~10 nautical miles north of Saipan). The tagged dolphins spent a few days moving around together, but went their separate ways and on 29 May, one was off the northern tip of Saipan, while the other was off the northern tip of Tinian.
The third species that we encountered was the spinner dolphin. Spinner dolphins get their name from their aerial behavior. Check out the following video where you can see a dolphin underwater preparing to launch out of the water and then see it spin in the air.
During our surveys off Saipan, we encountered spinner dolphins five times. We saw some of the same individual dolphins during each encounter. These individuals are in our spinner dolphin photo-identification catalog, and we have seen some of them in multiple years since 2010, when we began conducting small-boat surveys in the Marianas.
We were joined by our colleagues Kym Yano and Erik Norris on several days. They were out here to refurbish and re-deploy the bottom-mounted passive acoustic recorders called High-Frequency Acoustic Recording Packages (HARPs) that are listening for cetaceans year-round. We have one off the northeast side of Tinian and another off the west side of Saipan out at 300 Reef. The NOAA ship Hi‘ialikai helped us out by picking up the Tinian HARP.
All survey operations including satellite tagging, photo-id, and biopsy sampling were conducted under NMFS permit. Funding was provided by the NOAA Fisheries and the U.S. Navy Commander, U.S. Pacific Fleet. We would like to thank the owner and captains of Sea Hunter, the CNMI NOAA Fisheries field office, and all of our volunteers during the surveys.