Ecology of Columbia River redband trout (Oncorhynchus mykiss gairdneri) in high desert streams Dry Creek October 2012 Chris A. Walser Ph.D., Professor of Biology Department of Biology and Environmental Studies The College of Idaho
Why study redband trout? One of only a few native salmonids to this region Redband trout status/threats Very little is known about this species Dry Creek October 2012
Evolutionary origins of redband trout? 30,000-45,000 years in Columbia River Close cutthroat trout ancestry (bright coloration, larger spots, elliptical parr marks) Limited to tributaries below barrier falls Not native above Shoshone Falls Dry Creek October 2012
Coastal rainbow trout (dotted pattern-a) Columbia River redband trout distribution (hatched pattern-b)
Species status Occupy 64% of their historic range--only 30% of watersheds support strong populations Major threats: water diversion, overgrazing, and hybridization with hatchery rainbow trout Species of special concern by the US Fish and Wildlife Service throughout their historic range BLM recognizes redband trout as a sensitive species Grazing in riparian areas Hybridization with hatchery trout
General biology Dry Creek October 2012 Life history anadromous, fluvial, ad-fluvial, resident Habitat Deep complex pool habitats (>0.5-m), low gradient, low velocity (0.5-m/s), gravel substrate Thermal tolerance 29 degrees Celsius and daily temperature fluctuations of 8.5-11 degrees Celsius (Zoellick, 1999)
Study objectives and significance (Jordan Creek population) Determine whether redband trout exhibit stream reach fidelity from year to year. Examine autumn movements of redband trout Direction Home-range size Current status of redband trout Lack of published data on home-range size of redband trout Jordan Creek as source population
Study Area: Jordan Creek Silver City
Land cover
Redband trout stream reach fidelity Electro-fishing pools along study reach Total length and weight measured 248 individual trout > 50-g were PIT-tagged Stream reach was surveyed annually in the late summer and early fall of 2002-2007
Reach fidelity: Results Only 5 fish (~2%) were recaptured in 6-km stream reach after 1+ year Suggests extensive year to year movement of redband trout within Jordan Creek.
Radio telemetry study Objective: Fall movement patterns and home-range size of redband trout 1.5-g ATS transmitters (external antenna) were surgically implanted into 15 adult redband trout (> 150-g) adapted from (Ross 1982) Fish locations recorded with a hand-held GPS and entered into ArcGIS Fish tracked over a 55-day period
Autumn movement patterns Trout144 DATE 92305 93005 100705 101505 102205 102905 11 of the 14 fish (79%) moved downstream 2 moved upstream; 1 sedentary; 1 transmitter lost Movement coincided with availability of large complex pool habitats 111805
Autumn home-range size: Results Home-range Min-Max= 13-1041-m Mean= 397-m Total distance traveled during study Min-Max= 29-1197-m Mean= 460-m
Jordan Creek redband trout 1. Low year-to-year stream reach fidelity 2. During autumn months, most redband trout moved downstream in association with the availability of complex pools (beaver dams). 3. Mean fall home-range size of redband trout in Jordan Creek was ~5x larger than reported for redband trout in the Kootenai River system.
Dry Creek redband trout Community Demonstration Project The College of Idaho, Trout Unlimited, National Fish and Wildlife Foundation, Wells Fargo, Idaho Fish and Game, Treasure Valley Land Trust, Biomark, BSU
Study objectives (Dry Creek redband trout) Distribution, abundance, and size structure Genetic makeup Movement and habitat use
Redband trout distribution (preliminary study) 2012 sampling locations (160 redband trout) No other fish species Watershed boundary
Dry Creek redband trout size structure Mean= 120 mm TL 95% of population= 112-128 mm TL Range= 36-322 mm TL
Genetic structure 108 fish *Low genetic diversity No hatchery alleles 28 fish *Low genetic diversity Hatchery alleles in one fish
Spring 2013-Fall 2014 project activities Watershed-level fish survey and PIT tagging (distribution) PIT-tag arrays; radio telemetry (movement) Community partnership events Habitat assessment Stream restoration projects (fencing, re-vegetation, trail work)
Questions.