| Redband trout (Oncorhynchus mykiss gairdneri) have experienced reductions in
abundance and geographic range as the result of the compounding effects of habitat
alteration, fragmentation, and stream-flow diversion. Redband trout in southwestern
Idaho currently persist in contrasting desert and montane conditions characterized by
highly differing temperature and flow conditions. I used a bioenergetic model to estimate
the availability of suitable habitat for redband trout to examine their adaptability to
environments that are predicted to change dramatically under climate change scenarios.
I conducted monthly sampling of invertebrate drift, and habitat transects for wetted
width, depth, and current velocity. Demographic surveys were conducted in July and
October to assess redband trout abundance, growth rates, and overwinter survival.
Desert streams consistently provided higher net energy intake (NEI) and had a larger
proportion of energetically profitable habitat during the four-month monitoring period
than montane streams. Fish in desert streams exhibited significantly higher biomass
and a larger size structure, as well as higher growth and estimates of apparent survival.
Increasing stream temperatures extended the growing season for fish occupying
montane streams, but decreased habitat suitability during all months of the study period
in desert streams and July-September in montane streams. Increases in stream
temperature resulted in corresponding decreases in habitat suitability, with larger
decreases occurring in larger fish.
Keywords: bioenergetics, habitat suitability, redband trout, desert, seasonality, climate
change, Oncorhynchus mykiss gairdneri |