Sport Fish Abundance and Distribution in the Simonette River, Alberta, 2004
Tyler Johns and John Tchir
Declines in the abundance and distribution of lotic sport fish in Alberta including Arctic grayling (Thymallus arcticus) and bull trout (Salvelinus confluentus) have been widely documented and both species are currently listed as "sensitive" presumably as a result of their vulnerability to angler pressure and habitat alteration. Similar threats are faced by mountain whitefish (Prosopium williamsoni) and walleye (Sander vitreus). In order to monitor these threats, fisheries managers require baseline data that can be used to detect longer term changes in stream fish populations relative to regulations and increasing industrial development.
The purpose of this study was to estimate the abundance of Arctic grayling, bull trout, mountain whitefish and walleye in the Simonette River that can be used to assess impacts of increased industrial development and fishing pressure. We used raftmounted electrofishing and mark-recapture techniques to determine fish abundance from 6 July to 30 August 2004. The river was divided into four strata based on natural breaks related to sub-watersheds of major tributaries, and abundance of each species was estimated for each stratum.
The estimated density of Arctic grayling in stratum one was 0.90 fish/100 m (95% CI = 0.50 – 1.00) and in stratum two was 1.40 fish/100 m (95% CI = 0.05 – 2.40). The estimated density of mountain whitefish was 5.00 fish/100 m (95% CI = 3.00 – 6.00) in stratum one and 1.00 fish/100 m (95% CI = 0.40 – 1.50) in stratum two. Using the catchability coefficient, q, estimated from a previous study, bull trout density was estimated at 0.44 fish/100 m (95% CI = 0.20 – 0.60) in stratum one and 0.04 fish/100 m (95% CI = 0.002 – 0.10) in stratum two. Due to limited sample size, walleye densities were not calculated.