Effect of rewards on lake trout tag returns in northwestern Lake Michigan

We determined the effect of a reward of one free case of Stroh's beer (retail value of US$7.50 in 1986 dollars) on lake trout Salvelinus nantaycush tag returns made by two voluntary-return fisheries (recreational and commercial) in northwestern Lake Michigan during 1984-1990. To examine the effect of the reward, which was offered in 1986 and 1987, we determined the proportion of tags that were returned by assessment, recreational, and commercial fisheries. We used the log-likelihood G-statistic to test for homogeneity of recapture rates among years for the three fisheries. Comparison of individual G-statistics in the reward years versus the nonreward years yielded the impact of the reward. Recapture rates varied significantly among years for assessment, recreational, and commercial fisheries, and were also significantly different among the three fisheries. The reward of a free case of Stroh's beer increased the recapture rate in both of the voluntary tag-return fisheries (recreational and commercial), but the impact was greater in the commercial fishery. Despite the poor design of the reward program, recapture rates increased with the reward. However, we believe that increased recapture rates can be as much harmful as beneficial without careful a priori consideration of the impact of various types of rewards on response rates.