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FACTORS INFLUENCING MINNOW TRAP CAPTURES

Abstract

Freshwater fish diversity nationwide is diminishing rapidly due to increasing threats. In the last 50 years, freshwater populations have declined by 76%. Therefore, frequent and minimally invasive sampling of habitats is vital to monitor these declines and evaluate management effectiveness. Minnow traps are relatively inexpensive, easy to operate, and have potential to produce valuable data via citizen science monitoring projects. Unfortunately, minnow trap design biases are poorly understood and have the potential to significantly impact capture rates, perceived diversity, and relative abundance. Our overarching objective was to better understand factors that influence minnow trap captures via a series of small undergraduate projects to evaluate the influence of 1) minnow trap construction, 2) trap color, and 3) incorporation of light bait as an attractant on captures. In our initial study, approximately 77% of 1159 total captures were obtained in galvanized G-40 traps, 18% in vinyl coated Frabill 1271 traps, and 5% were captured in plastic traps. Based on subsequent sampling, we determined this difference is most likely related to design/construction difference and not the color difference between the two trap brands as conjectured by previous researchers, with the vast majority of captures again coming from G-40 traps (81%) regardless of color manipulation. We found no influence of phototaxis; therefore, we do not believe using lights as an attractant has potential to increase minnow trap captures (t-test; t(160) = -0.4058, p = 0.6854). Our data obtained from these projects can be used to refine minnow sampling methods and improve trapping performance overall.

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