Marianas 2015 Summer Cetacean Surveys: Guam (August 13-19)

by Andrea Bendlin, Marie Hill, Allan Ligon, and Adam Ü

It’s been a windy and rainy one for the first week of our yearly summer surveys in the Marianas!  This is our sixth year of conducting surveys for cetaceans around the southernmost islands of the Mariana Archipelago.  We were originally planning to start our efforts with 20 days of field work on Saipan, but due to the devastating effects of recent Typhoon Soudelor, we’ve decided to cancel our time there and spend more time on Guam.  So far we’ve had five days on the water and have sighted three different species:  spotted dolphins (Stenella attenuata), spinner dolphins (Stenella longirostris), and pygmy killer whales (Feresa attenuata).

We often see spotted dolphins near some of the FAD (Fish Aggregating Device) buoys several miles west of Guam, and our sightings this year so far have been no exception.  Over the summer, we have had Emily Laub, our PIFSC Young Scientist Opportunity (PYSO) intern, analyzing photos from previous years to determine feasibility of developing a photo catalog of the spotted dolphins here in the Marianas and analyzing photos for unusual scarring and cookie cutter wounds.  During two of our three encounters, we were able to collect dorsal fin-ID photos and overall body condition photos to continue this effort.

GM-000058

A group of spotted dolphins. One of the animals is missing the top part of its fin. (photo credit: Adam Ü)

Our most interesting encounter thus far involves the third species of our trip:  pygmy killer whales.  In the six years we have been doing surveys here, this is the only group of pygmy killer whales we have seen off Guam.  We have seen the same group for three years in a row now!  When first seen in June 2013, the group numbered eight individuals.  In April of 2014, there was a new calf seen in the group, bringing the group number up to nine.  This calf still swims in close association with its mother.  Over the past year, it has obtained several (very small) nicks on its fin that will help make it more easily identifiable in the future, especially once it separates from its mother.  This year, there are now 11 individuals in the group, including another calf that has probably been born sometime in the last 6 months.   We are excited about being able to learn more about this group over the long-term future!

GM-000059

Pygmy killer whale mother and calf (photo credit: Adam Ü)

We have had several “weather days” during our effort so far, mainly due to the significant monsoonal energy this year in the western Pacific. “The sea was angry this week my friends…”

Fig 3_radar picture

Two typhoons (Goni and Atsani) are currently spinning in the western North Pacific. Atsani is pulling monsoon weather up from the south into the Marianas.

All survey operations including satellite tagging, photo-id, and biopsy sampling are conducted under NMFS permit 15240. Funding was provided by the NOAA Fisheries and the US Navy, Pacific Fleet.

This entry was posted in Protected Species. Bookmark the permalink.