Monster Seminar JAM - Seasonal variation in the relative importance of factors influencing growth, survival and movement of stream salmonids: towards a hierarchical model of population persistence
Dr. Ben Letcher, Silvio O. Conte Anadromous Fish Research Center, U.S. Geological Survey
A wide variety of biotic and abiotic factors can influence population persistence. With movements restricted to 1-dimensional networks, the ability to detect movements out of study areas, and high recapture rates of tagged fish, stream fish represent an ideal system to study mechanisms of population regulation. I will present models of body growth, survival and movement for three species of east coast salmonids based on over ten years of data collection on ~25,000 individually-tagged fish. We constructed generalized linear mixed models to identify sources of variation in body growth and movement. Variation in stream discharge had the strongest effect on body growth and interacted with temperature in a complex way across seasons, indicating that models including only temperature will not generate accurate predictions of body growth. Within-stream movement also varied seasonally and large fish in small habitats were most likely to move. Higher summer temperature reduced survival of all size classes, but only larger fish had diminished survival at low summer flows. These models form the foundation for models of population persistence, but to use the models to evaluate and predict responses outside of conditions in our focal study stream we are currently developing hierarchical models that include data from other less intensively-studied rivers.
Date and Time:
October 1, 2009,
11:00 am - 12:00 pm