By Dr. Holly Fearnbach, Marine Mammal Research Director
The SR3 team has had a successful start to their fourth year of assessing the body condition of the “Sounders” gray whales during their spring feeding stopover to feed on ghost shrimp in northern Puget Sound. The team uses an octocopter drone to non-invasively collect high resolution aerial images that are measured to assess changes in body condition to infer nutritional health during each spring stopover, and between years. By collaborating with Cascadia Research Collective, measurements from aerial images can be linked to known individuals to track changes in condition of the same whales over time. So far in 2023, aerial images of 10 individual gray whales have been collected over four days. All 10 of these whales have been imaged and measured in previous years, with six of these individuals being imaged in all four years. The reliable use of Puget Sound as a feeding stopover highlights the importance of this area for the whales as they fatten up before they continue to migrate to summer feeding grounds in the Arctic. We will continue to assess the nutritional health of the Sounders until they depart in early summer and results from this study will provide important information on the body condition and health of gray whales during the ongoing Unusual Mortality Event.
Aerial images of the same “Sounder” gray whale (CRC ID #21, “Shackleton”) in each of the past four years. Differences in body condition are quantified by measuring breadths along the profile of the whale, with the leanest profile documented in 2021. Images were collected non-invasively using an octocopter drone flown at >150ft over the whales under NMFS research permits 19091 and 22306.