Get Full Government Meeting Transcripts, Videos, & Alerts Forever!
Get email alerts on the Waterfowl topic
No spam. Unsubscribe anytime.
Mono Lake waterfowl monitoring shows long‑term declines; lake stratification and prey biomass linked to counts
Summary
Mono Basin researchers presented standardized summer ground and fall aerial survey results showing declines in key waterfowl species (northern shoveler, ruddy duck, gadwall, mallard) since 2002 and reported positive correlations between brine shrimp biomass, a remote‑sensing wetland index (NDWI) and waterfowl abundance; presenters noted periodic lake stratification (marmixis) is linked to poor productivity years.
Dr. Matt Ryder, the Mono Basin waterfowl habitat restoration and research director, presented 20+ years of standardized monitoring showing declines in several common waterfowl species and a positive statistical relationship between measures of wetland extent (NDWI) and breeding duck numbers. "That correlates with about 50,000 birds in total counted on the fall surveys in our tallest year," Ryder said when describing multi‑survey totals and emphasized that those totals are far lower than historical counts cited from a 1948 investigation.
Context and findings: Ryder reviewed methods — three summer ground counts and six fall aerial surveys per year covering segmented shoreline units — and highlighted that northern shoveler and ruddy duck remain the most numerous fall migrants but have declined at Mono Lake since 2002. Comparative analyses with nearby reservoirs (Crowley, Bridgeport) suggest some declines are local to Mono Lake rather than part of a uniform regional trend.
Drivers and mechanisms: Ryder showed that brine shrimp biomass (artemia) and NDWI correlate positively with waterfowl abundance, suggesting food availability and lake fringe wetlands influence counts. He and other presenters also described marmixis (lake stratification driven by large freshwater inputs) as reducing productivity in some years; multiple speakers noted that repeated boom‑and‑bust hydrologic cycles make the lake more susceptible to prolonged stratification and depressed shrimp productivity.
What it does not establish: Presenters described the analyses as observational associations rather than experimental causation; Ryder cautioned that correlation does not prove cause and that additional research is needed to explain why adult counts can decline while some productivity indices (broods, ducklings) remain stable in certain years.
Next steps: The scientific record and data products from these monitoring programs will be posted on the Mono Basin website; board staff requested questions by July 2 to inform ongoing analysis and any hearing planning.
