A new research report on struggling Southern Resident killer whales says these whales have shown a strong increase in the prevalence of skin disease, with highly correlated gray patches and gray targets on their skin from 2004 to 2016.
The University of California Davis study, released on June 29, was also published on that date in the online peer review research journal PLOS ONE.
Researchers said that after ruling out potential environmental factors, such as changes in water temperature or salinity, that they hypothesized that the most plausible explanation is an infectious agent, and that increased occurrence of lesions may reflect a decrease in the ability of the whales’ immune systems to combat disease. This could pose yet another significant threat to the health of Southern Resident killer whales who already face a litany of challenges, they said.
The research team is led by wildlife veterinarian Joseph K. Gaydos, the science director for the SeaDoc Society, a program of the School of Veterinary Medicine at UC-Davis.
Gaydos and his team analyzed many digital photos obtained from the Center for Whale Research, spanning over a decade, including images of nearly 20,000 individual whale sightings in the Salish Sea.
During evaluation of these images, which the Center has been collecting since 1976, biologists noticed transient and occasionally persistent abnormal skin changes in these whales. Those skin changes had not, however, been systematically characterized or tracked over time for such purposes, they said.
While these photos show six different skin disease syndromes, none were associated with mortality.
Researchers said understanding the occurrence and significance of skin changes in these whales is crucial for assessing their overall health and potential impact on population recovery.
There are currently fewer than 75 of these whales still roading coastal and inland waters from Southeast Alaska to California and they are structured socially into three pods: J, K and L.
They are also the subject of a lawsuit filed by the Wild Fish Conservancy (WFC) in Seattle, which is seeking to halt the commercial harvest of Chinook salmon in Southeast Alaska by trollers. The WFC contends that these Chinooks are needed by the endangered orcas for sustenance. The trollers contend that studies show that halting their fishery, which is critical to the economy of Southeast Alaska, would not help the endangered orcas. After recent Ninth Circuit Court of Appeals action the trollers were granted the right to begin their summer fishery on July 1.
