In cooperation with the National Oceanic and Atmospheric Administration, UW News has posted a story about new research on the plight of southern resident orcas in the Salish Sea. In a paper published Sept. 10 in Global Change Biology, a team led by scientists at the UW and NOAA reports that underwater noise pollution — from both large and small vessels — forces northern and southern resident orcas to expend more time and energy hunting for fish. The din also lowers the overall success of their hunting efforts. Noise from ships likely has an outsized impact on southern resident orca pods, which spend more time in parts of the Salish Sea with high ship traffic.

Lead author on the study is Dr. Jennifer Tennessen, a senior research scientist at the UW’s Center for Ecosystem Sentinels, who began this study as a postdoctoral researcher with NOAA’s Northwest Fisheries Science Center.

“Vessel noise negatively impacts every step in the hunting behavior of northern and southern resident orcas: from searching, to pursuing and finally capturing prey,” said lead author Jennifer Tennessen, a senior research scientist at the UW’s Center for Ecosystem Sentinels, who began this study as a postdoctoral researcher with NOAA’s Northwest Fisheries Science Center. “It shines a light on why southern residents in particular have not recovered. One factor hindering their recovery is availability and accessibility of their preferred prey: salmon. When you introduce noise, it makes it even harder to find and catch prey that is already hard to find.”

Northern and southern resident orcas search for food via echolocation. Individuals transmit short clicks through the water column that bounce off other objects. Those signals return to orcas as echoes that encode information about the type of prey, its size and location. If the orcas detect salmon, they can initiate a complex pursuit and capture process, which includes intensified echolocation and deep dives to try to trap and capture fish.

Read the full article in UW News.