by Marie C. Hill, Amanda L. Bradford, Allan D. Ligon, and Adam C. Ü
During 29 February – 14 March 2016, the Pacific Islands Fisheries Science Center (PIFSC) Cetacean Research Program (CRP) was on Saipan to expand our surveys from last year searching for humpback whales (Megaptera novaeangliae). Two cetacean researchers who study humpback whales in other parts of the world joined us this year for most of the survey period. Robert Brownell (Southwest Fisheries Science Center) led an effort to conduct shore-based scans for humpback whales, and Sarah Mallette (Virginia Aquarium and Marine Science Center) assisted with both the shore- and boat- based surveys.
We were on the water nine days from 2-13 March and encountered humpback whales during four of those days. Unlike last year, when the majority of our humpback whale sightings were over Chalan Kanoa (CK) Reef (3-5 nmi west of Saipan), this year all but one of our humpback whale sightings were on Marpi Reef (7-10 nmi north of Saipan) despite our repeated searches over CK Reef (Figure 1).
We had six encounters with five humpback whale mom-calf pairs. We collected biopsy samples from all of the moms. We took fluke photos of one of the moms and discovered something very exciting! She matches an individual that was photographed in 2007 on Marpi Reef during a shipboard survey called the Mariana Islands Sea Turtle and Cetacean Survey (MISTCS) (Fulling et al. 2011) (Figure 2).
In addition to our small-boat surveys, we attempted to survey from shore on several days, including when the conditions were too rough for us to go out on the water (Figure 3). On 8 March, Allan and Adam flew to Tinian to look from shore while Bob, Sarah, Amanda, and Marie broke up into two teams and surveyed from the Saipan shore. Unfortunately, we didn’t see any humpback whales during our shore surveys.
In addition to humpback whales, we encountered two other species during our surveys. We had two encounters with bottlenose dolphins (Tursiops truncatus). During the first encounter we saw three individuals, two of which are in our photo-id catalog. We collected a biopsy sample from one individual that we first saw in April 2014 off Aguijan (Goat Island), then off Tinian in June 2014, but had not biopsied before (Figure 4). The second bottlenose dolphin encounter was with 10 individuals that only stayed near the boat for a couple minutes before vanishing in the rough seas. Unfortunately, the quickness of the encounter meant we were unable to obtain any photos or biopsy samples.
Spinner dolphins (Stenella longirostris) were the third species we encountered (Figure 5). We saw one group off the east side of Tinian and had six sightings off Saipan, including two on Marpi Reef where we see them regularly during our summer surveys (Figure 1). One spinner dolphin group was observed during a shore survey on the west side Saipan.
Have you seen humpback whales in the Marianas? We are interested in hearing about it. Add your observations to our iNaturalist project of Humpback Whales of the Mariana Islands.
This research was conducted under NMFS permit 15240 and CNMI DFW license no. 03292-2016 issued to PIFSC CRP. Funding was provided by Commander U.S. Pacific Fleet, PIFSC, and the National Marine Fisheries Service. We would like to thank those individuals and organizations that provided us logistical support, including Mike Trianni (PIFSC CNMI), Steve McKagan (PIRO CNMI), the CNMI DFW, Sam Markos, Benigno Sablan, Ymanuel Sablan, Aesha Sablan, and Claire Sablan (owner, captains, and crew of the Sea Hunter), and the Hyatt Regency. We would also like to thank Robert Brownell and Sarah Mallette for participating in the surveys.