Introduction & Objectives

Three (Hawaii, Mexico, and Central America) of 14 Distinct Population Segments (DPSs) of humpback whales (Megaptera novaeangliae) designated by the National Marine Fisheries Service (NMFS) for listing under the Endangered Species Act (ESA) based on their winter breeding grounds can be found along the western coast of North America during the summer feeding season. The mixing of whales from these DPSs in the feeding areas in different proportions complicates assignment of individuals to distinct groups for management purposes without further information. As a result, there is an urgent need for data to help identify and quantify which DPS an individual belongs to as well as how they are using the habitat.  This will help determine their overlap with shipping traffic, fishing grounds, and areas of military operation, in order to prioritize management actions and to mitigate the impacts from these activities.

This project combines tagging, biopsy sampling, and photo-identification efforts along the United States west coast and Hawaii to assign DPS, examine movement patterns and whale use of Navy training and testing areas and NMFS-identified Biologically Important Areas (BIAs), examine migration routes, and analyze dive behavior and ecological relationships between whale locations and oceanographic conditions.

Technical Approach

Humpback whales were studied off the coast of northern Washington, central Oregon, southern California, and Maui, Hawaii.  Whales were tagged with long-duration implant satellite tags.  Satellite locations and depth data from the tags, satellite-sourced ecological data, and models were utilized to examine home range, foraging areas, migration routes and speeds, dive behavior, and ecological relationships. Photos were collected for individual identification and to evaluate effects of tagging.  In addition, photos were uploaded to the HappyWhale database where other researchers as well as citizen scientists also contributed photos, leading to further determinations of migration routes and wound healing.  Biopsy samples were collected for genetic sex determination, and stock identification. Final analyses also took into account humpback whale data from individuals previously tagged by the researchers beginning in 1995.

Progress & Results

Tracking data were obtained for a total of 81 whales, with an overall tracked duration ranging from

0.1 to 164.2 days [d] (mean = 39.1 d, standard deviation [SD] = 33.6 d). The distribution of the tracked animals supported humpback whale affinity for continental shelf and shelf-edge habitat and documented extensive use of the northwestern coast of Washington and the central coast of California, and to a lesser degree, the northern California coast and the Columbia River mouth at the Oregon/Washington border.

Complete or partial migrations were documented for eight whales, with recorded or presumed breeding destinations including Mexico, Guatemala, and Hawaii. The most intensively used Navy range was the Northwest Training and Testing Study Area (NWTT), with 73 percent of whales (59 of 81) having locations there and a maximum residency of 86.6 d. The second most intensively used range was Warning Area-237 (W237) of the NWTT, with 47 percent of whales having locations there and a maximum residency of 65.4 d.

Only 6.2 percent of whales migrated through the Southern California Range Complex and only 1.2 percent migrated through the Southern California Anti-Submarine Warfare Offshore Range subarea. Nine percent of whales had locations within the formerly named, Point Mugu Range Complex, spending between 6.1 and 33.8 d there.

Most of the occupancy in NWTT was by whales tagged in NWA and NCA/OR, and only 13 percent of whales tagged in SCCA had locations in NWTT. The occupancy of U.S. West Coast Area BIAs and National Marine Sanctuaries (NMS also suggested spatial separation of whales throughout feeding areas, as there was very little overlap of locations in BIAs or NMSs of whales tagged in the different regions. The most intensively used were the Northern Washington BIA and the Olympic Coast NMS for whales tagged in NWA, the Point St. George BIA and Greater Farallones NMS for whales tagged in NCA/OR, and the Gulf of the Farallones to Monterey Bay BIA and Greater Farallones NMS for whales tagged in SCCA.

A total of 79 individual whales were genetically identified from skin biopsy samples collected during tagging efforts (n = 14 from SCCA; n = 15 from NCA/OR; n = 50 from NWA). The composition of haplotype frequencies suggested a differentiation between the SCCA and NCA/OR feeding aggregations that had not been previously recognized. The relative likelihood of individual assignment to each of the four recognized DPSs in the North Pacific based on the genetic profiles indicated that the majority of individuals from SCCA (64 percent) assigned with highest likelihood to the Central America DPS, whereas the largest proportion of individuals from NCA/OR (47 percent) and NWA (48 percent) assigned with highest likelihood to the Hawaii DPS. The remaining individuals assigned to the Mexico and Western North Pacific DPSs.

Publications:

An at-sea assessment of Argos location accuracy for three species of large whales, and the effect of deep-diving behavior on location error.
Irvine, L.M., Winsor, M.H., Follett, T.M., Mate, B.R., Palacios, D.M. 2020.  Animal Biotelemetry 8, 20. doi: 10.1186/s40317-020-00207-x