Mortality was estimated for three, 2‐ or 3‐d, professional, live‐release tournaments for walleye Stizostedion vitreum and sauger S. canadense held on the Lake Winnebago system, Wisconsin, in 1991 and 1992. Estimated initial mortalities for the three tournaments were high—48%, 34%, and 80%—perhaps because the lake temperature exceeded 20°C. Estimated delayed mortalities (within 1 week of release of tagged fish) were 18%, 9%, and 0%. Estimated tournament‐related long‐term mortalities, based on tag return rates during the ensuing year, were 1%, 2%, and 0% of the total catch for each tournament. Comparison of the estimated harvest for tournament and nontournament anglers for the month of tournament activity indicated that the tournaments accounted for up to 25% of the estimated total harvest of walleyes in June. Tournament mortality might be reduced by holding tournaments when water is cool, by limiting stress on fish (e.g., by requiring aeration of live wells and holding tanks and by avoiding large temperature changes), and by limiting catch (e.g., by restricting creel limits, fishing time, and angler participation; by increasing size limits; and by establishing a “catch‐measure–release” procedure).

Algae and aquatic plants support river food webs through in-situ primary production. However, gross primary production (GPP) and ecosystem respiration (ER) are rarely evaluated in the context of river management or habitat restoration. We estimated daily GPP and ER during 2 growing seasons for 7 reaches in the Kootenai River and 1 reach in the Elk River, spanning 290 river km across British Columbia, Canada, and Montana and Idaho, USA. We characterized responses of GPP and ER to river management, including reaches with unregulated flow, regulated flow, nutrient addition, and habitat restoration. Downstream GPP and ER generally increased after changes in river management, and higher management intensity led to greater increases. GPP and ER followed a seasonal pattern with low initial values in spring, elevated values in mid-summer, and a return to low values in late summer and autumn. Timing and duration of the elevated period for GPP and ER also differed among reaches following changes in river management. Our results suggest that river management affects GPP and ER, likely through reducing turbidity and the frequency and magnitude of extreme flow events, nutrient additions, and enhanced floodplain connectivity, thereby altering the timing and amount of autochthonous carbon available to the food web.

Increased nutrient loading in aquatic environments can have a long-lasting influence on ecosystem processes and functions. The Kootenai River was historically oligotrophic, but nitrate levels have been steadily increasing since the mid-2000s, while phosphorus levels have remained low. Our study objective was to evaluate the current nutrient distribution throughout the Kootenai River watershed in the context of land use and land cover change. Each of the three land cover types we assessed, agriculture, developed areas, and surface mines, encompass less than 1% of the land area in the Kootenai River watershed. We measured nitrate, ammonium, and soluble reactive phosphorus (SRP) monthly at sites spanning 400 river km on the Kootenai River, and co-located tributary sites in British Columbia, Canada, and Montana and Idaho, USA. During July 2017, we measured the same nutrients along each of the selected tributaries with co-located sites at sub-catchment tributaries. Sites were selected to include a range of contributing drainage areas identified as agricultural, developed, or mining. Nutrient concentrations ranged from 0.012 to 4.

To quantify fine-scale Kootenai River white sturgeon (Acipenser transmontanus) staging and spawning habitat selection and preference within a recently restored reach of the Kootenai River, the U.S. Geological Survey, in cooperation with the U.S. Fish and Wildlife Service, integrated acoustic telemetry data with two-dimensional hydraulic model simulations within a 1.5-kilometer reach of the Kootenai River near Bonners Ferry, northern Idaho. Twenty-seven individual Kootenai River white sturgeon were detected in the study reach during May 6-June 30, 2017. The largest concentration of fish positions occurred near the edge of the gravel bar adjacent to the right bank pool-forming structure and additional concentrations of fish positions occurred near two recently constructed rock substrate clusters. The difference in preferred and available depth distributions quantifies that Kootenai River white sturgeon generally preferred depths of 7-11.5 meters, deeper than the most frequently available depths. About 71 percent of the detections occurred within the lower one-third of the water column, placing Kootenai River white sturgeon at or near the channel bed. The difference in available and preferred water velocities indicated that Kootenai River white sturgeon generally preferred a wide range of velocities from 0.0 to 1.0 meters per second, and generally preferred velocities that were less than the most frequently occurring available velocities. Kootenai River white sturgeon generally preferred the downstream part of the study area where water velocities were less than those in the upstream part. This study concludes that Kootenai River white sturgeon generally