Habitat Characteristics and Fish Use of Cold-water Refuges in the Upper Grande Ronde River
Cold-water refuges in streams can provide critical rearing and holding habitat for fishes and other aquatic taxa, particularly in streams with stressful summer water temperatures. We used forward looking infrared (FLIR) imagery combined with field surveys to describe the distribution, physical habitat characteristics, and fish use of cold-water refuges in the Upper Grande Ronde River basin in Northeast Oregon. Cold-water refuges were widespread throughout the Chinook-bearing portions of the Upper Grande Ronde basin, with refuge surface area totaling 17,945 m². Refuges were 5.8 °C cooler on average than the ambient water temperature, with temperature differences between ambient and refuges reaching as high as 12.7 °C. Despite having significantly cooler water temperatures, habitat conditions in cold-water refuges were generally poor, with the majority of refuges having shallow depths, very low water velocity, relatively little shade and cover for fish, and moderate to high levels of fine sediment. We predicted that cold-water refuges could support a maximum of 14,891 Chinook Salmon summer parr, and 1,980 juvenile steelhead. This represents approximately 10 % of the total estimated Chinook Salmon parr capacity for the Upper Grande Ronde Spring Chinook population. If we consider only refuges that were connected to the main channel (i.e., had refuge crest depths > 0.05 m) and contained salmonids, the predicted refuge capacity for Chinook parr and juvenile steelhead was 8,431 and 1,628, respectively. This equates to 5.6 % of the total Chinook Salmon parr capacity. These results provide managers with a baseline understanding of the distribution, habitat characteristics, and fish production potential of cold-water refuges in the Upper Grande Ronde Basin which can be used to aid in fish management decisions and direct future restoration actions including the preservation, enhancement, and creation of new cold-water refuges.
Justice, C., D.A. McCullough, and S. White. 2017. Habitat characteristics and fish use of cold-water refuges in the upper Grande Ronde River. Columbia River Inter-Tribal Fish Commission Technical Report 17-09. Portland, OR. 59p.