Population Estimates of the Kakwa River Bull Trout Fall 2000


John Tchir


Bull trout (Salvelinus confluentus) were captured by pulsed direct current (PDC) electrofishing and test angling. Sampling was conducted in late September 2000, over a 4-day period (Sept. 25-28). Stock assessment was accomplished through estimation of population abundance in a 32 km section of the Kakwa River. An estimate of comparable design was conducted in 1997 on the same portion of the river. A total of 101 bull trout were marked of which 80 were examined for marks and 27 of those were recaptured. Population estimates were calculated using the bias corrected Peterson-Lincoln method, which produced the following results. The population of bull trout for the section of river sampled was estimated to be 132 (S.E. 39.36) from angling, 214 (S.E.50.07) from electrofishing, and 294 (S.E.105.1) for combined methods. The estimated abundance of fish > 400 mm FL calculated from the pooled sample was 111 (SE 17.53). In 1997 the combined methods population estimate was 226 (S.E.55.86). There was a significant difference in the mean fork length of fish sampled by electrofishing and angling. Angling and electrofishing crews captured bull trout with mean fork lengths of 430 mm (SE 6.95) and 370 mm (SE 10.36) respectively. A large portion (53.5%) of bull trout from pooled data were > 400 mm FL.

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