Arctic Grayling Abundance and Distribution in the Upper Little Smoky River


Kevin Fitzsimmons and Mike Blackburn


During summer 2007, we used sample angling to assess the Arctic grayling (Thymallus arcticus) population in an upper section of the Little Smoky River (235 km in length), the majority of which is a catch‐and‐release angling area. We angled 27 stream sites and captured a total of 1,734 individual Arctic grayling. Five percent of the total catch was of legal harvest size fish (350 mm total length). Catch rates were highly variable among sites ranging from 0 to 7.1 fish/h and from 0 to 96 fish/km. At seven study sites, we applied capture‐mark‐recapture techniques to estimate sample angling capture efficiency (q) for Arctic grayling. Overall, capture efficiencies were dependent on fish size. Capture efficiency of large fish (> 250 mm fork length; FL) was 2.4 times greater than that for small fish (150 ‐ 249 mm FL; q = 0.143). We incorporated these effects when modeling abundance of Arctic grayling for the entire length of the 235 km study area. Small fish were nearly twice as abundant as large fish (17,294 fish versus 9,326 fish). Estimated abundance of legal‐sized Arctic grayling was only 3% of the total estimate (i.e., 812 fish; 90% CI = 481 – 1,366). Arctic grayling were unevenly distributed in the study area. Mainstem sections located at the upper end of the Little Smoky River supported high numbers of legal‐sized Arctic grayling (i.e., > 17 fish/2 km). Total fish abundance peaked at approximately 55 km upstream of the boundary of the two‐fish bag limit (i.e., Pass Creek rail bridge). Downstream of the Tony Creek confluence the river supported low numbers of Arctic grayling. This information will assist resource managers in the development of management plans for the Little Smoky River watershed.

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