By Eric Mooney
If you’ve happened to be paying attention to the weather in the western Pacific near Guam and the Marianas Archipelago this week, Typhoon Dolphin might sound familiar. Remarkably, the storm just so happens to coincide with the Cetacean Research Program’s (CRP) cruise SE15-02 Leg II aboard the Oscar Elton Sette. The main mission of the cruise is to study the distribution and abundance of whales and dolphins throughout the Mariana Archipelago by using a passive acoustic array and visual observers. The objective is to sight, identify, photograph, tag and biopsy whales and dolphins throughout the Mariana Archipelago. The observers, stationed on the fly bridge use high powered mounted binoculars called Big Eyes to scan the sea surface looking for the presence of cetaceans. In addition to visual observation, an acoustic array containing 6 in-line hydrophones is towed approximately 300 meters behind the ship. At a sampling frequency of 192 kHz, the acousticians listen for whistles and clicks of the whales and dolphins. The acousticians are able to determine the mammals location in relation to the ship by using the time delay of the vocalization between hydrophones. Unfortunately, dolphin storms don’t make finding dolphins and whales any easier and the observer team has their work cut out for them. Sighting cetaceans is difficult in high winds and choppy seas, but despite the conditions the observers have sighted a Bryde’s whale mother and calf, Melon-head whales, Blainville’s beaked whales, and a lone sperm whale just yesterday.
In addition to sighting and identifying Cetaceans we are also recovering and deploying a series of High-Frequency Acoustic Recording Packages, known as HARPs. HARPs are deployed to the ocean floor to record whale and dolphin sounds, as well as any other ocean noise for a year.
The 30 day cruise has been out to sea for 7 days so far and with a typhoon strengthening to the south west we have changed course, heading to the northern islands ahead of schedule and away from the storm in hopes of getting some calmer waters. The Sette arrived at the beautiful island of Maug this morning, but we have not escaped the rough seas. So, we continued to move north, now beyond our study area and will be waiting to see what Typhoon Dolphin does next.