2005 Annual Report pdf file

Abstract

This first year interim report synthesizes the findings to date on how the magnitude, timing, and frequency of flow variation influences Foothill Yellow-legged Frog (Rana boyii):  1) egg and tadpole survival; 2) population dynamics; 3) tadpole behavior, growth, and development; and 4) availability and stability of habitat conditions for eggs and tadpoles.

Based on a review of current literature and FERC-related study reports, egg masses are negatively affected by pulsed flows via scouring, if flows occur during or after oviposition, and desiccation, if oviposition occurs during high flows and then water levels drop. Evidence of tadpole stranding and potential negative effects on newly metamorphosed individuals is documented by multiple studies. South Fork Eel River field studies show that the magnitude and timing of spring pulse flows are key factors in survival of eggs and tadpoles. While large magnitude spring pulses decrease egg survival, smaller magnitude pulses later in the spring cause even higher mortality. Annual fluctuations in population growth were associated with spring pulse flow events 3 years prior. Preliminary findings from field and laboratory experiments suggest that during pulse flows a portion of tadpoles will seek refuge from higher velocities in the substrate, while most are swept downstream. Tadpoles confined to substrate refugia face energetic costs in terms of growth and development that may influence future reproductive output and population dynamics.

These preliminary results will be verified in experiments and additional data analysis conducted during 2006. Questions regarding changes in habitat availability during a pulsed flow will be addressed in the hydrodynamic modeling portion of this study.    

Flow through enclosures in which tadpoles were reared	Close up of the interior of a high velocity treatment enclosure
Drift fence experiment set up. Flags mark the corners of each grid. Blue box contains tadpoles to be released.	North Fork Feather River, Flea Valley Creek Site, view looking upstream.
North Fork Feather River, Flea Valley Creek Site, view looking downstream	South Fork Eel River, Walker Meadow Crossing Site, view looking upstream
South Fork Eel River, Walker Meadow Crossing Site, view looking downstream	Alameda Creek, Gage Site, view looking upstream

Alameda Creek, Gage Site, view looking downstream

Photo credit: S. Kupferberg et al.
(Please request permission from bskupferberg@pacbell.net for use of pictures)