Application of a salmonid life cycle model for evaluation of alternative flow regimes.

The SALMOD Chinook (Oncorhynchus tshawytscha) life cycle model for the Klamath River, California, USA was updated to address a number of computational and life history limitations based on over 10 years of accumulated experience. SALMOD II incorporates a complete spatial delineation of each mesohabitat unit between Iron Gate Dam and the Klamath estuary (~320 km). Mesohabitat specific relationships for Chinook spawning, fry, presmolt and immature smolt life stages are based on site specific hydrodynamic modeling from 8 representative study sites that incorporate target mesohabitat characteristics of channel width and base flow magnitude. SALMOD II was calibrated and validated to multi-year collection data and incorporated improved density dependant movement and mortality factors, a disease factor, an improved water temperature simulation model and other key life history requirements. We explain the underlying computational framework for the modeling system, highlight the spatial delineation and extrapolation methodology for mesohabitat specific habitat versus flow relationships for each Chinook life stage, and highlight important factors such as emigration and density dependant habitat movement factors.