Would hydrologic climate changes in Sierra Nevada streams influence trout persistence?
Authored by HI Jager, Winkle W Van, BD Holcomb
Date Published: 1999
DOI: 10.1577/1548-8659(1999)128<0222:whccis>2.0.co;2
Sponsors:
United States Department of Energy (DOE)
Electric Power Research Institute (EPRI)
Pacific Gas & Electric (PG&E)
Platforms:
No platforms listed
Model Documentation:
Other Narrative
Mathematical description
Model Code URLs:
Model code not found
Abstract
We predicted the consequences of climate change for sympatric
populations of brown trout Salmo trutta and rainbow trout
Onco,Oncorhynchus mykiss in an upstream and a downstream reach of a
Sierra Nevada stream with the help of an individual-based trout
population model. The model evaluated the ecological effects of two
anticipated responses to climate change: (1) a shift in peak flows from
spring to winter and (2) an increase in stream temperature. Changes in
temperature and flow regime both influenced simulated persistence of the
two trout species. We hypothesized a decrease in the fall-spawning brown
trout population as a result of winter hoods that scour brown trout
redds. Although scouring mortality showed the expected pattern, effects
of seasonal shifts in flow on simulated dewatering of redds was equally
important and tended to compensate for scouring. Because trout are
coldwater fishes, we hypothesized that a rise in mean stream temperature
would be harmful to both species, particularly in downstream reaches. We
found that a climate change scenario with a 2 degrees C increase in
average stream temperature benefited both species in the cooler upstream
reach but was harmful in the warmer downstream reach. Overall, our
results supported the hypothesis that climate change will restrict trout
to higher elevations in the Sierra Nevada. Finally, the combined effects
of elevated temperature and shifted flow differed from the effect of
elevated temperature alone. In combination, the two climatic factors
produced threshold effects in rainbow trout abundance by shifting the
age at first maturation. Complex interactions between the period of
incubation and various causes of redd mortality (dewatering, scouring, and temperature-related mortality) also lead to nonadditive effects of
the two climatic factors on abundances. We conclude that focusing on one
factor alone (i.e., temperature) may not be sufficient to predict
climate change effects in the stream environment.
Tags
Individual-based model
growth
United-states
California
Temperature
Fish
Brown trout
Rainbow-trout
Salmo-gairdneri
Potential habitat loss