Young California Chinook salmon face a deadly combination of extreme droughts and violent floods on their migration to the Pacific Ocean, according to a study by researchers from the University of Essex, NOAA Fisheries, University of California Davis, and Cramer Fish Sciences.
The research reveals that salmon populations are declining at unprecedented rates during their vulnerable journey downstream. Two factors drive these losses. Extreme weather swings between drought and flooding create lethal conditions in rivers. The destruction of historical wetland habitats removes critical refuges where young salmon once survived harsh periods.
Wetlands traditionally provided shallow, protected areas where juvenile salmon could shelter during droughts and escape rapid floodwaters. As these habitats disappeared through human development, salmon lost their natural safety net. Now, when droughts strike, water temperatures spike and oxygen levels plummet. When floods arrive, torrential flows sweep young fish downstream into the ocean before they develop sufficient strength to survive.
Scientists describe the phenomenon as salmon becoming river "ghosts," present in name only as populations dwindle. The findings suggest that restoring wetland habitats alongside climate adaptation strategies could improve survival rates. Researchers plan to investigate whether creating artificial refuge areas or adjusting dam operations might buffer salmon against future extreme weather events.