“The Exploration of the Pacific”

Marine Mammal Science and Conservation

Current Research

The cetacean research unit (CRU) at PIFSC studies the populations of whales and dolphins within the U.S. EEZ waters of the Pacific Islands Region (PIR), which includes the waters of Hawai‘i, Palmyra Atoll, Jarvis Island, Johnston Atoll, Howland and Baker Islands, Wake Island, American Samoa, Guam and the Commonwealth of the Northern Mariana Islands.  A variety of information is needed in order to properly manage human effects on these populations and protect them from current or future depletion.  This includes details on stock structure, abundance, habitat use, natural and anthropogenic threats as well as estimates of reproduction and mortality rates. 

Research methods currently used by the CRU to collect these data include:

• Visual and acoustic line transect surveys
• Photo-Identification studies
• Passive acoustic monitoring
• Habitat modeling and ecosystem observations

Visual and acoustic line transect surveys

Visual surveys are conducted from the flying bridge of a large (> 200 ft.) research vessel using 25X150 “big eye” binoculars or from a small (< 30 ft.) boat using handheld binoculars and the naked eye.  Observers scan for cetaceans while the vessel follows predetermined transect lines.  Data such as the location (latitude/longitude), species present, general behavior and group size estimates for each cetacean encounter are recorded.  The sighting data are then used in distance sampling statistical models and also imported into GIS for further spatial analysis. Whenever possible, digital photographs of encountered cetaceans are obtained for species identification confirmations and individual photo-identification.  Simultaneous acoustic observations are also conducted using a towed hydrophone array. A typical towed array consists of 4 hydrophone elements with linear sensitivity to frequencies between 1kHz and 100 kHz. The array is towed behind the ship and acoustic signals are transmitted up the cable to computers outfitted with software for real-time visualization/recording and spatial localization of cetacean sounds.  Acoustic detections of cetaceans are noted and the locations of these detections can be used in line transect modeling and incorporated into GIS databases for comparisons with visual detections and habitat data.

Photo-identification studies

Long-term photo-identification studies are an excellent tool to gain insight into habitat use, movements, and life history of individuals within a population.  Some species of cetaceans have naturally occurring markings on their bodies, flukes, or dorsal fins (e.g., scars, nicks, notches, color patterns) that can be used to identify individuals.  Photographs are collected and sighting data (e.g., location, group size and structure, behavior) are recorded during each encounter.  Individuals can be tracked over time and between locations. The CRU is a member of the Pacific Islands Photo-Identification Network (PIPIN), which is a group of researchers from the around the Hawaiian Islands who are studying spinner dolphins and using photo-id.  PIPIN is in the process of creating a collaborative photo-identification database of spinner dolphin populations within the Hawaiian Islands in order to look at movements between islands (if they occur), and to determine if differences in populations exist from one island to the next.   One of the greatest concerns for this species in Hawai‘i are intensive interactions with humans and with the growing swim-with tourism sector.

Passive acoustic monitoring

Passive acoustics are useful for assessing temporal and spatial changes in the density and behavior of some animals, for augmenting visual surveys in finding animals and can provide important details regarding the acoustic environments that cetaceans live within.  In collaboration with researchers at the Scripps Institute of Oceanography and the PIFSC EOD, the CRU currently uses bottom-mounted data recorders – called High-frequency Acoustic Recording Package or HARPs - to conduct passive acoustic monitoring studies. The HARP dataloggers are moored to the sea bottom and remain there for an extended period of time (e.g., 6 mos. to 1 yr.).  The acoustic data is downloaded when the HARP is retrieved from its mooring. The CRU currently has three HARPs deployed around the PIR  - one at Palmyra Atoll, one at Cross Seamount, and one at Ladd Seamount in the Papahonaumokuakea Marine National Monument.

The CRU is also collaborating with researchers at the University of Hawaii to study whale vocalizations detected by the newly deployed hydrophone on the Station Aloha Cabled Observatory System. This hydrophone is located on the sea floor about 100 km north of Oahu. In a joint study with scientists at Duke University, the CRU is using T-POD acoustic data loggers to study the occurrence of echolocating cetaceans near longline gear deployed by Hawaii commercial fishing vessels. 

Habitat modeling and ecosystem observations

Understanding more about the biogeochemical characteristics of cetacean habitat may be crucial for future management options.  Habitat modeling based on various in situ and satellite-derived observations can be a useful tool for locating essential habitat for particular species and specific populations, as well as providing predictive tools to guide further research efforts. The CRU is utilizing habitat modeling for three different species (spinner dolphins, humpback whales, and right whales).  One project aims to quantify the physical characteristics of observed spinner dolphin resting habitats (in the Main Hawaiian Islands) in comparison to regions that are not used by resting animals by conducting fine-scale physical habitat mapping exercises.  If there are common, fine-scale features (e.g. percent cover of various bottom types) among resting habitats that can be detected by physical habitat mapping then these features could be incorporated into a quantitative habitat model and used to identify additional unobserved resting habitats.  Some of the known resting habitats that spinner dolphins use during daylight hours are heavily used by ecotour operations focusing on diving and snorkeling, but also activities such as kayaking, dolphin-watching and in some cases swim-with-dolphin tours.  Potential effects on spinner dolphins include habitat displacement, where spinners may simply avoid sheltered bays that are frequently used for ecotourism, or more subtle effects which may manifest because animals are prevented from conducting crucial resting behaviors due to interactions with boats or people.  Information from the habitat modeling may be used to locate resting habitat that should be the focus of protection.

We are also using simple habitat modeling to identify humpback whale breeding habitat in Hawai‘i.  Humpback whales winter and breed in the Main Hawaiian Islands and have been well-studied.  However, the Hawaiian Archipelago actually extends 1800 km northwest beyond the Main Hawaiian Islands, and almost no data exists on humpback habitat use there.  We predicted the extent and spatial location of wintering habitat across the Hawaiian Archipelago using bathymetry and sea surface temperature data to identify areas shallower than 200m and warmer than 21ºC as potential wintering habitat.  We then can compare these habitat predictions with the locations of visual and acoustic detections of humpbacks during cetacean surveys across the NWHI. We are also using similar techniques to predict potential North Pacific right whale breeding habitats.  North Pacific right whales are currently listed as endangered under the ESA and as depleted under the MMPA and very little is known about the long-term movements and habitat of these rare whales. Right whales in other oceans are known to migrate seasonally to warmer waters in lower latitudes to calve and mate, and no efforts have been made to assess their migratory paths and locate breeding habitats of North Pacific right whales. Locating the breeding habitats of these animals is critical for management, as they may harbor threats that limit recovery. We are currently conduct predictive habitat modeling of right whale breeding habitat using hydrographic and remotely sensed data from the Pacific Islands region, based on the physical characteristics of breeding habitat in other right whale breeding locations.

Other Ongoing Projects 

I also involved with several research projects outside the CRU. I am currently working on a project that examines climate variability in the NW Atlantic and its effects on sea-ice off eastern Canada. It appears that the North Atlantic Oscillation (NAO) controls, to some extent, the amount of sea-ice available for breeding ice seals. We have examined ice dynamics on the east coast of Canada now, and are planning to examine ice availability across the NW Atlantic, focusing on the breeding regions of harp seals. This research as important implications for how the harp seal hunt in Canada, and elsewhere, is prosecuted.

I am also collaborating with folks at Duke University to study pilot whales off of Cape Hatteras, NC and their interactions with the commercial longline fishery. This includes at-sea surveys and photo-identification and mark/recapture studies as well as using passive acoustics to assess how and when pilot whales interact with fishing gear.