Determining Size- and Sex-Specific Capture and Harvest Selectivity for Walleye

Estimates of size- and sex-specific selectivity of fishing gear are important for making informed management decisions.  We distinguished between capture selectivity (relative catchability of population components) and harvest selectivity (combined effects of capture selectivity and the decision to retain a fish). We used short-term recaptures from three tagging programs in Minnesota and Wisconsin to estimate selectivity of angling for captured and for harvested walleye Sander vitreus, and of spear fishing for harvested walleye. Estimates were obtained using generalized linear models. Angling capture and harvest selectivity are both greater for females than males in every length group from < 325 to > 675 mm total length.  Spearing harvest selects primarily males.  For both sexes, angling and spearing harvest selectivity peaks around 400 - 450 mm.  Capture selectivity of anglers peaks at 350 – 375 mm total length. Sex-size interaction for capture selectivity is significant for angling with the sex effect for small fish being less than that for large fish.  Spearing selectivity for males and females does not appear to vary with length above 400 mm but appears to decrease below that at least for males.  These estimates provide information needed for a statistical catch at age model for a walleye fishery.