Date of Award

5-2025

Access Control

Open Access

Degree Name

Great Lakes Ecosystem Science

Advisor

Christopher Pennuto, Ph.D.

First Reader

Christopher Pennuto, Ph.D.

Second Reader

Gavin Leighton, Ph.D.

Third Reader

Robert Warren II, Ph.D.

Abstract

Aquatic invasive species are not native to a location and have negative impacts on their surrounding environments. Crayfish invasions have been documented worldwide, but none are as widespread as the red swamp crayfish (Procambarus clarkii). Red swamp crayfish currently are found in over 40 countries globally and are invasive on every continent, except Antarctica. Outside of their native range, impacts include reduced native crayfish abundance, loss of macrophytes, increased disease transmission, loss of native snails and other macroinvertebrates, and damage to dykes and paddies. Attempted management techniques for the red swamp crayfish include habitat modification, male sterilization via ablation, and mechanical removal, although none have led to complete eradication. Management techniques continue to be modified for increased effectiveness. Red swamp crayfish behavior assessments in invaded ranges may aid natural resource managers in making management tools more efficient.

Mechanical removal via trapping is the most common management technique for controlling red swamp crayfish populations. In the present study, an intensive trapping plan was implemented for a single invaded pond to assess it for effectiveness. Overall, 1,543 baited traps were set over 55 nights from July to November 2023. From these traps, 970 crayfish were collected, of which 8 were native calico crayfish (Faxonius immunis), one was a native White River crayfish (Procambarus acutus), and the remaining 961 were red swamp crayfish. Similarly, 2,535 baited traps were set over 97 nights from April to November 2024. From these traps, 1,172 crayfish were caught, of which 20 were native calico crayfish and 1,152 were red swamp crayfish. No white river crayfish were collected. Interaction between temperature and year was a significant predictor of catch per trap night (CPUE), declining from 2023 to 2024. Year was a significant predictor of crayfish carapace area, decreasing from 2022 and 2023 to 2024. A mark-recapture study was conducted in 2023 and 2024 using visible implant elastomer (VIE) tags and suggested that nearly 300 crayfish remain in the pond after 2023 and nearly 450 after 2024. These data suggest intensive trapping is decreasing the red swamp crayfish population. However, trapping has high costs and effort and trapping all year may not be feasible. Trapping only in the summer months when water temperatures are highest will yield the highest CPUE. Similarly, combining trapping with a biocontrol may result in an even further decrease in red swamp crayfish populations. Further research into red swamp crayfish behavior is required to obtain maximum effectiveness.

Behavior determines, in part, the outcome of most direct competition interactions. A win or loss by an individual in a competition can have major effects on its behavior in future competitions and resource acquisition, a phenomenon known as the winner-loser effect. The present study investigated the influence of winner-loser effects on interspecific interactions between a native crayfish species (Cambarus robustus) and an invasive crayfish species (Procambarus clarkii) and assessed the efficacy of incorporating winner-loser effects to manage crayfish invasions. Forty-nine big water crayfish (BWC) were trained through the winner-loser effect to obtain, or enhance, a winner profile. Overall, 88 trials ensued comparing behavior between trained and untrained BWC versus invasive red swamp crayfish (RSC). Of those trials, 46 were food competition trials and 42 were non-food trials. Both non-food and food competition trials found no difference in trial outcome between trained and random BWC. During non-food trials, BWC won most interactions with RSC, regardless of training profile state. However, during food competition trials RSC dominated BWC with acquiring the food nearly 100% of the time. These data suggest using the winner-loser effect is not a reliable management technique to enhance BWC competitive ability versus RSC.

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