Response of Trout Populations and Pool Depths to Large Wood in Streams
Matt Kondratieff
Colorado Parks and Wildlife
Fort Collins, CO
Overwinter habitat was identified as a limiting factor for Brown Trout (Salmo trutta) and Rainbow Trout (Oncorhynchus mykiss) populations in the Middle Fork of the South Platte River near Hartsel, CO. To address this, a 2.1-mile habitat restoration project was initiated within a portion of the degraded watershed with the purpose of converting shallow, over-widened pools into deeper, larger-volume pools to improve overwinter habitat. Pools were constructed in one of three ways: 1) excavation of a deep pool and construction of a point bar (non-wood), 2) excavation of a deep pool, construction of a point bar, and introduction of large wood placed at the bank toe of the outside bend in a haphazard manner (haphazard), and 3) excavation of a deep pool, construction of a point bar, and introduction of large wood intentionally placed at the bank toe of the outside bend to function as an undercut bank (undercut). Monitoring of pool depths and fish populations occurred in two years, 8 and 10 years post-construction. Fish populations were surveyed using multi-pass depletion electrofishing techniques with block nets to satisfy the assumption of closure. Project effectiveness monitoring was based on data for Brown Trout as it is a wild population (not stocked), a popular game species, and less sensitive to confounding variables such as whirling disease and impaired water quality. Fish population monitoring consisted of estimating Brown Trout abundance (number/100 ft of pool), quality Brown Trout abundance (number >14” TL/ 100 ft of pool), and Brown Trout biomass (lbs/100 ft of pool). In addition to Brown Trout, White Sucker (Catostomus commersonii), Rainbow Trout, and total fish abundance and biomass were estimated. Pool depths were analyzed as a function of wood presence/absence, pool type (non-wood, haphazard, undercut), pool length, radius of curvature, and upstream riffle length. Analyses were conducted to determine which pool types were most effective at maintaining deep pools, the response of trout and sucker populations to the introduction of large wood, and which pool type conferred the greatest benefit to trout populations.
About Matt Kondratieff
Matt Kondratieff is an Aquatic Research Scientist for Colorado Parks and Wildlife in Fort Collins, CO. He completed his undergraduate work at U.C. Davis, received his Master’s from Colorado State University and he worked for three years as a fisheries biologist for Wyoming Game and Fish in Pinedale, WY. Matt has 15 years experience involving the design, construction, and monitoring of habitat restoration and enhancement projects in Colorado. Recent research has focused on the biological response of aquatic organisms to stream habitat restoration treatments. Additional research interests involve studying the influence of in-channel structures, such as whitewater parks and water diversions, on fish populations and fish passage.