The effects of invasive Hydrilla (Hydrilla verticillata) on largemouth bass (Micropterus nigricans) fishing inferred from state data and digital catch logs

Hydrilla (Hydrilla verticillata) is an invasive aquatic plant often assumed to enhance Largemouth Bass (Micropterus nigricans) fisheries by providing complex structure. However, its actual effects on bass size and angler behavior remain uncertain at broad spatial and temporal scales. We analyzed extensive public and private datasets from 2017 to 2023, including angler-reported catches from the Fishbrain app, to assess how Hydrilla, other aquatic vegetation, and lake features influence bass fisheries across Florida waterbodies. We used tree-boosted mixed-effects models and Shapley Additive Explanations (SHAP) to evaluate how vegetation, lake morphology, and landscape features affect bass size and the number of reported trips. Based on our results, Hydrilla had no unique advantage over native vegetation in supporting larger bass or attracting more anglers. We also applied a linear selectivity index and paired t-tests across 28 lakes, revealing that anglers caught more bass near vegetation edges formed by Tape Grass (Vallisneria americana). However, observed differences in fish size near Hydrilla were likely due to aggregation along dense vegetation mats rather than superior habitat quality. These findings challenge the perceived fisheries value of Hydrilla and underscore the importance of conserving diverse native vegetation in aquatic habitat management strategies across Florida.