Creel Surveys: Boise River Popular with Local Anglers

By Art Butts, Idaho Department of Fish and Game Through the center of Idaho's capital city flows the Boise River, creating a destination for those seeking quick access to solitude and recreation. With the adjacent Boise Greenbelt path system, the river offers access to many outdoor opportunities including some pretty darn good trout fishing. Rainbow trout, brown trout, and mountain whitefish provide year-round angling, and in the fall, steelhead trout trapped at Hell's Canyon Dam are transported to the river. Boise River anglers are very passionate about the resource and some have raised concerns about the number of anglers and the associated fish harvest that occurs in the river. In response to these concerns, Fish and Game conducted a year-long "creel survey" to measure fishing activity and fish harvest. From June 2007 through June 2008 anglers were surveyed along the river from Barber Dam downstream to the Americana Boulevard Bridge. Creel surveys are useful for fishery biologists to estimate angler catch and harvest. Generally, a creel clerk makes multiple counts of anglers along the entire survey area, and interviews anglers to determine how long each angler has fished and the number of fish caught, harvested or released. Using the total number of anglers and catch rates estimated from angler interviews, managers can then estimate the total number of fish caught during a particular time. During the year-long Boise River creel survey, 1,358 anglers were interviewed and nearly 700 angler counts were conducted on 109 separate dates. Anglers spent an estimated 33,056 hours fishing the Boise River during the year; about 89 percent of the fishing effort was by anglers using bait and lures. Rainbow trout comprised the bulk of the catch. The average catch rate of fish per hour, for rainbow trout was 0.6 fish per hour. During the survey, 20,704 rainbow trout were caught and of those, 4,277 were harvested. Nearly 80 percent of the rainbow trout caught in this section of river were released even though harvest is legal in most of the section. Brown trout were caught less frequently, and the average catch rate was 0.01 fish per hour, which resulted in an estimate of 330 fish caught throughout the survey period. No brown trout were recorded as harvested during the creel survey and thus brown trout had an estimated release rate of 100 percent. Observed harvest rates do not appear to be high in relation to the number of fish in the river. Fish population density estimates for the creel survey area, obtained in 2007, include 13,908 wild rainbow trout, 2,398 wild brown trout, and 34,754 mountain whitefish. In addition, about 20,000 hatchery rainbow trout are stocked annually throughout the year - population estimates noted above do not include hatchery rainbow trout. Using the 2007 estimates, roughly 5 percent of the wild rainbow trout population is being harvested over the course of one year. Not surprisingly, creel survey results reveal that the Boise River is indeed a very popular destination for local anglers. It also suggests that a majority of anglers prefer to release fish to be caught again rather than take them home. In the future, Fish and Game biologists will be applying some statistical modeling for estimated catch and harvest rates in relation to existing population data to gain a better understanding of the trout population dynamics within the Boise River. Art Butts is a fisheries biologist in the Southwest Region