Walleye Population Trends from 2002-2012 in Lake Roosevelt, WA

Walleye were introduced to Lake Roosevelt in the 1950’s and favorable conditions have made them an abundant and a popular sportfish. However, as an apex predator they have potentially negative effects on native fish. Population trends of Walleye were evaluated using a random stratified sampling design conducted yearly via gill nets (n = 150) during the first week of November from 2002-2012. Analyses showed an increase in catch per unit effort and length frequency histograms revealed that growth rates declined considerably once Walleye reached ≈300 mm and very few grew past ≈400 mm. Age frequency histograms showed a wide range of ages (0-19 years) but few fish greater than four years of age. Annual mortality ranged from 28% to 47% (mean = 39.3%). Walleye condition was poor during all years with an average relative weight of 82.5 (range = 79.4-85.5). Once Walleye grew past ≈400 mm they tended to exhibit a higher average Wr. During this period Walleye exploitation was considered to be low. Therefore, these population characteristics are indication of an overabundant Walleye population and is likely having negative effects on native fauna.