How jellyfish swarms could impact the food supply for salmon in Puget Sound

Moon jellies, a species of jellyfish living in Puget Sound, appear to be able to consume large portions of zooplankton, according to new research. Zooplankton are also a food source for young salmon and many other forage fish. 

Moon jellies can form large aggregations in Puget Sound, sometimes so big they can be seen from aircraft, according to the Department of Ecology. Researchers there say the number of jellyfish may be increasing, raising questions about what their impact will be on the ecosystem.

In a study led by the University of Washington (UW) in collaboration with Western Washington University, Highline College and the National Oceanic and Atmospheric Administration, researchers set out to learn more about the relationships between moon jelly and zooplankton populations. 

“Understanding how much [moon jellies] may be eating can give us an understanding of how they may be impacting the food webs in these areas,” said lead author of the study Haila Schultz, a graduate student at UW.

Researchers took samples at a number of hotspots in the summers of 2019, 2020 and 2021. They found dramatically lower levels of zooplankton inside moon jelly aggregations as opposed to outside those aggregations.