Scientists Join Forces to Survey Cetaceans in the Main Hawaiian Islands

February 6, 2009
False killer whale
False killer whale

The NOAA Pacific Islands Fisheries Science Center (PIFSC) is leading a 30-day collaborative research expedition to survey cetaceans within the 200-mile Exclusive Economic Zone (EEZ) of the main Hawaiian Islands. Also participating in the project are scientists from the NOAA Southwest Fisheries Science Center, Scripps Institution of Oceanography, and the University of Hawai'i Joint Institute for Marine and Atmospheric Research. Dr. Erin Oleson of PIFSC is directing the cruise.

Working from the NOAA Ship Oscar Elton Sette, the team is conducting a systematic survey along designated transects through the study area and counting cetaceans seen from the ship. Results of the counts will be used to estimate the abundance of each species in the area.

While operating from the Sette and smaller launches, scientists will also collect biopsy samples of cetaceans and take photos of each encountered animal to help identify them and assess the structure of populations or subpopulations of cetaceans within the main Hawaiian Islands. Throughout the sighting and counting surveys, the Sette will tow an array of acoustic sensors that allow the scientists to detect the presence of cetaceans by the sounds they emit. While all species of cetaceans will be surveyed, particular emphasis will be placed on study of false killer whales (Pseudorca crassidens).

Bottlenose dolphins
Bottlenose dolphins

In addition to surveying and sampling cetaceans, scientists will collect a variety of environmental data to help analyze the whales' movements in relation to physical characteristics of their surrounding habitat and their forage. They will regularly deploy CTD and XBT instruments throughout the cruise to measure how the ocean's conductivity (salinity) and temperature vary with depth, geographical location, and time. Sonar (acoustics) equipment on the Sette will be used to collect "backscatter" data that will be analyzed to measure the density of small fish and crustaceans in the water column that are important to false killer whales and other cetaceans as potential prey. The acoustics data will reveal how prey density changes from day to night and with distance from shore.

Scientists on the expedition will also service and recover data from a High Frequency Acoustic Recording Package (HARP) which has been anchored on the seafloor off the Kona coast of the Island of Hawai'i since mid-December 2008. The HARP records sounds made by marine organisms in the surrounding waters, including cetaceans. By analyzing the acoustic data and knowing the patterns of sound produced by different whale species, scientists can determine which species frequent the area and how often they occur, and draw conclusions about their abundance and seasonal patterns.