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Researchers document rapid dewatering and fish kills on Lower Kern River
Summary
Cal State Bakersfield researchers reported a rapid dewatering event in summer 2024 that stranded thousands of fish across multiple river miles and led to higher temperatures and localized oxygen stress; the observations are informing monitoring, outreach and litigation.
Ray McNish, freshwater ecologist at Cal State Bakersfield, described intensive weekly monitoring of the Lower Kern River last summer and an abrupt dewatering event that left hundreds-to-thousands of fish stranded and dead over short river reaches.
McNish showed before‑and‑after field photos documenting a widely flowing river turned into largely dry riverbed with isolated refugia pools. He said a single refugia pool contained more than 300 dead and stranded fish during team visits. Field teams recorded water‑quality parameters with YSI probes and deployed eDNA sampling; McNish reported that eDNA results generally aligned with field observations and that veliger/juvenile fish detections and carcass surveys were being processed.
The presenter reported substantial increases in water temperature in downstream reaches during low‑flow intervals and observed dissolved oxygen patterns that were sometimes paradoxically high near dense aquatic invasive vegetation but generally declined downstream. He also described a marked rise in anthropogenic litter where flows receded and human users moved upriver.
McNish said the observations have prompted public outreach, a public letter read at a city council meeting, and that his data are being used in an active lawsuit arguing that diversions and operation of weirs contributed to dewatering and ecological harm. He cited Fish and Game Code (Fish & Game Code §5937) and public‑trust arguments as components of the legal discussion; he said a city and other entities are named in litigation and that some monitoring data have been made publicly available to interested parties.
Questions from attendees addressed diel oxygen variability (noted as measured in the morning; nighttime measures suggested for future work), whether water‑table wells could help verify flow duration (cost prohibitive now), and the timing of eDNA sampling relative to the hydroperiod. McNish said his team is continuing sampling when water is present and is expanding eDNA efforts as logistics permit.
