A 23-year study by Oregon State University and Cal Poly finds that ochre sea stars along much of the Oregon coast have rebounded after steep losses from a wasting disease that began in 2013. An extraordinary influx of juveniles — at one point an 8,000% increase in young sea stars washing ashore — has helped populations at many sites return to or exceed pre-epidemic numbers. Ochre stars are again preying on California mussels and limiting dense mussel beds, but average body sizes remain 25%–65% smaller and the wasting pathogen still circulates. Researchers say the cause of the recovery is uncertain and continued monitoring is essential.
Oregon ochre sea stars stage comeback after near-collapse — a post-epidemic 'baby boom' fuels recovery
A 23-year study by Oregon State University and Cal Poly finds that ochre sea stars along much of the Oregon coast have rebounded after steep losses from a wasting disease that began in 2013. An extraordinary influx of juveniles — at one point an 8,000% increase in young sea stars washing ashore — has helped populations at many sites return to or exceed pre-epidemic numbers. Ochre stars are again preying on California mussels and limiting dense mussel beds, but average body sizes remain 25%–65% smaller and the wasting pathogen still circulates. Researchers say the cause of the recovery is uncertain and continued monitoring is essential.
02:32, 07.11.2025Environment
Oregon ochre sea stars stage a surprising recovery
Ochre sea stars, once a familiar sight clinging to surf-splashed rocks along the Oregon coast, are rebounding after years of dramatic decline caused by a wasting disease that began in 2013. A new study by researchers from Oregon State University and Cal Poly San Luis Obispo reports that a huge influx of juvenile sea stars has driven population counts at many surveyed shorelines back to levels at or above those seen before the epidemic.
The multi-decade analysis tracked ochre sea star populations at eight sites along the Oregon coast over 23 years. The researchers documented declines of up to 84% during the initial die-off and then an extraordinary increase in young sea stars — as much as an 8,000% spike in individuals washing ashore — that produced cohorts now reaching adulthood.
Sarah Gravem, the study's lead author and an assistant professor at Cal Poly who was an OSU postdoctoral researcher when the project began, said the surge of juveniles helped restore ochre star numbers and their ecological role.
Bruce Menge, a professor of integrative biology at Oregon State and Gravem's longtime collaborator, noted that ochre stars are again abundant and large enough at most sites to resume heavy predation on California mussels. That renewed predation has limited the formation of dense mussel beds that in recent years blanketed intertidal rocks and excluded other invertebrates and seaweeds.
Scientists cautioned that the cause of the rebound remains uncertain. One leading hypothesis is that the wasting event temporarily reduced adult competition and freed up food and space for larvae and juveniles, allowing a rare recruitment pulse to succeed. However, researchers also acknowledge the timing could be coincidental and that other environmental factors may have contributed.
Important caveats remain: at all but one site, average ochre sea star body sizes are still about 25% to 65% smaller than before the epidemic, and populations are more variable year to year. Wasting disease has recently been linked to a strain of bacteria and persists at low levels along the coast, so continued monitoring is crucial.
The sunflower sea star, a different and much larger species, has not shown a comparable recovery; its collapse appears tied to high susceptibility to wasting and declines in kelp forest habitat.
What this means: The study documents an encouraging ecological rebound for a keystone predator that helps maintain intertidal diversity, but it also underscores that recovery can be partial and fragile. Ongoing monitoring and research are needed to understand long-term trajectories and the continuing role of disease and environmental change.
Study locations included iconic sites such as Haystack Rock at Cannon Beach. The research integrates long-term data to reveal both the resilience and remaining vulnerability of intertidal ecosystems.