Introduction & Objectives

Oregon State University (OSU) conducted a multi-year tagging operation in support of the U.S. Navy’s (Navy) marine mammal monitoring in five areas along the U.S. West Coast: (1) the Southern California Range Complex (SOCAL), which is a portion of the HawaiiSouthern California Training and Testing Study Area, (2) the Point Mugu Range Complex (PT MUGU), (3) the Southern California Anti-submarine warfare Offshore Range subarea (SOAR), (4) the Northwest Training and Testing Study Area (NWTT), and (5) Warning Area 237 (W237) within the NWTT. The focus of these studies is to address key science objectives the Navy has committed to complete as part of regulatory requirements promulgated from the National Marine Fisheries Service (NMFS). In particular, this multi-year project was designed to address the following questions:

1. What are the movement patterns, occurrence, and residence times of blue and fin whales within Navy training and testing areas along the U.S. West Coast as compared to other areas visited by tagged whales outside of Navy training and testing areas?

2. What are the residency time/occupancy patterns of blue whales within NMFS-designated Biologically Important Areas (BIAs) for this species along the U.S. West Coast? (i.e., the areas identified by Calambokidis et al. [2015] and referenced in the Navy’s Letter of Authorization and Environmental Impact Statement)

3. Are there bathymetric, annual oceanographic conditions (e.g., sea surface temperature, frontal zones, etc.), and/or climatic and ocean variations (e.g., global warming, North Pacific Gyre Oscillation [NPGO], Pacific Decadal Oscillation [PDO], El Niño/La Niña events, etc.) that can help explain blue and fin whale affinity for any identified areas of high residency along the U.S. West Coast? 

Technical Approach

Three types of Argos (satellite-monitored) tags were used: Location-Only (LO) tags, providing long-term tracking information; Dive-Monitoring (DM) tags, providing intermediate- to long-duration tracking and dive behavior (duration, depth, number of feeding lunges per dive); and pop-off Advanced Dive Behavior (ADB) tags, providing intermediate-duration, fine-scale dive profile information upon tag recovery and Global Positioning System-quality locations. 

Progress & Results

Twenty-four blue whales (20 LO tags, 4 ADB tags) and six fin whales (3 LO, 3 ADB) were tagged in 2014. Twenty-two blue whales (18 LO, 4 ADB), and 11 fin whales (9 LO, 2 ADB) were tagged in 2015. Nineteen blue whales (11 LO tags, 8 DM tags) and 14 fin whales (5 LO tags, 9 DM tags) were tagged in 2016. Twenty-seven blue whales (13 LO tags, 14 DM tags) and one fin whale (1 LO tag) were tagged in 2017. 

Both blue and fin whales were widespread in their tracked distributions, with locations over the four years extending from the northern tip of Vancouver Island, British Columbia, to very close to the equator for blue whales; and from Haida Gwaii, British Columbia, to the northern coast of Baja California, Mexico, for fin whales. Differences existed between years, however, for both species, in sizes of home ranges (HRs) and core areas (CAs), in latitudinal extent of movements, in total distance traveled, and in whales’ use of Navy training ranges and National Marine Fisheries Service-identified Biologically Important Areas (BIAs) for blue whales. Blue whales were distributed farther north, traveled significantly longer distances, and had significantly larger HRs and CAs in 2014 than in the other three years.

Publications:

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

Irvine, L. M., D. M. Palacios, B. A. Lagerquist, and B. R. Mate. 2019. Scales of blue and fin whale feeding behavior off California, USA, with implications for prey patchiness.Frontiers in Ecology and Evolution 7:338. doi: 10.3389/fevo.2019.00338

Mate, B.R., L.M. Irvine, and D.M. Palacios. 2017. The development of an intermediate-duration tag to characterize the diving behavior of large whales. Ecology and Evolution 7:585-595.