Mortality was estimated for three, 2‐ or 3‐d, professional, live‐release tournaments for walleye Stizostedion vitreum and sauger S. canadense held on the Lake Winnebago system, Wisconsin, in 1991 and 1992. Estimated initial mortalities for the three tournaments were high—48%, 34%, and 80%—perhaps because the lake temperature exceeded 20°C. Estimated delayed mortalities (within 1 week of release of tagged fish) were 18%, 9%, and 0%. Estimated tournament‐related long‐term mortalities, based on tag return rates during the ensuing year, were 1%, 2%, and 0% of the total catch for each tournament. Comparison of the estimated harvest for tournament and nontournament anglers for the month of tournament activity indicated that the tournaments accounted for up to 25% of the estimated total harvest of walleyes in June. Tournament mortality might be reduced by holding tournaments when water is cool, by limiting stress on fish (e.g., by requiring aeration of live wells and holding tanks and by avoiding large temperature changes), and by limiting catch (e.g., by restricting creel limits, fishing time, and angler participation; by increasing size limits; and by establishing a “catch‐measure–release” procedure).
We compared the proportionality of scale to body growth and length estimates produced by the Fraser-Lee and Weisberg back-calculation models using individually tagged smallmouth bass Micropterus dolomieu and walleyes Stizostedion vitreum marked and recaptured in spring. Individual fish were tagged and later recaptured, providing multiple intervals of known growth to compare with back-calculated lengths (BCLs). There was no significant difference between total radii of scales collected when fish were younger and radii measured to the same annulus for scales collected from the same fish at final capture. Scale increment lengths remained constant and accrediting an annulus to the scale edge for fish caught in spring was valid. Known scale growth was not proportional to known body growth for smallmouth bass or walleyes; the body generally grew at a faster rate than the scales. Multiple regression analyses found that known scale growth described the most variance in known body growth, age was not always significant, and neither sex nor geographic location was ever significant. Fraser-Lee BCLs generally underestimated the actual lengths at tagging with errors ranging from Ϫ10 to ϩ4% for both species. Weisberg BCLs were as accurate as Fraser-Lee estimates for older age groups but overall were less accurate, particularly for young fish (overall error range: Ϫ12 to ϩ25%). The Fraser-Lee model is recommended for use over the Weisberg model because Fraser-Lee BCLs had lower overall range of error, Weisberg BCLs excessively overestimated lengths for age 1 fish, and the Weisberg model assumption of independence of successive scale increments within and between fish may not be valid.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.