Optimizing Saugeye Sampling Protocol

Monthly electrofishing samples for saugeye (walleye x sauger hybrids; Stizostedion vitreum x S. canadense) were collected on 3 reservoirs during spring and fall, 1996. Sampling was stratified by day type (day and night) and habitat type (bass-cove and saugeye-main-lake shoreline and points). CPUE (N fish/hour) was calculated for 4 size classes and compared for each sampling stratum. Precision of the estimates was calculated and sampling recommendations made. Differences in seasonal catch rates were inconsistent among reservoirs and size classes. CPUEs of night samples were higher for size class A (≤ 310 mm; age 0) on all reservoirs. However, no clear diel pattern in catch rates of size classes B (311-400 mm; age 1), C (401-456 mm), or D (≥ 457 mm) was observed. Habitat type had little effect on CPUE and its associated precision. Precision of most samples was poor. A minimum of 10 hours of electrofishing would be needed to obtain estimates ±25% of the mean for most sampling strata tested. Sampling recommendations included collecting data on size class A using fall night electrofishing. However, reservoir-specific differences in catch rates and precision of the sampling strata tested would make statewide recommendations for appropriate sampling strategies of the larger size classes of saugeye suspect. It was recommended to change from a catch rate-based evaluation program to one based on size structure indices.

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