Indexing Age‐0 Walleye Abundance in Northern Wisconsin Lakes before Fall

Abstract

AbstractRecruitment of age‐0 Walleye Sander vitreus is often indexed using fall electrofishing surveys. However, collecting fish before fall may provide timely information regarding stocking decisions and factors influencing recruitment. We evaluated sampling methods for age‐0 Walleye in northern Wisconsin lakes that could be used to assess recruitment in spring and summer. Initial assessments on two lakes indicated surface tows of ichthyoplankton nets at night during May to early June and 0.64‐cm‐micromesh gill nets set in July provided the highest catches of age‐0 Walleye among the methods we evaluated. Additional sampling on 13 lakes over 2 years indicated catch per effort (CPE) of age‐0 Walleye using these two methods did not correlate with age‐0 CPE in fall electrofishing. However, presence or absence of age‐0 Walleye in micromesh gill nets was 92% accurate in predicting whether age‐0 CPE in fall electrofishing was ≥15 fish/h, the threshold above which eventual recruitment to the fishery is expected to occur. Micromesh gill netting may provide a useful tool for allocating fingerling Walleye that are stocked in fall, a resource that is often limited due to space and forage constraints associated with propagation. Additionally, our sampling protocol may help to identify timing of potential recruitment bottlenecks occurring in some lakes.