Assessing policy effectiveness trends in nonindigenous aquatic species introduction in the Ohio River basin

Aquatic invasive species (AIS) create costly, detrimental effects when established. Recognition of this in the United States reached a threshold in 1990 with the federal passage of the Nonindigenous Aquatic Nuisance Prevention and Control Act. This act created six regional panels, the national Aquatic Nuisance Species Task Force, and incentivized state-level AIS planning. The management of the Ohio River basin fell under the Mississippi River Basin Panel and the state-led Mississippi Interstate Cooperative Resource Association, which developed a joint action plan in 2010 to prevent, contain, and manage AIS. All Ohio River basin states besides West Virginia created aquatic nuisance species plans between 1999 and 2021. This study aims to utilize the best available data, the USGS Nonindigenous Aquatic Species (NAS) database, to examine how legislative and planning milestones have influenced the rate of new AIS arrivals and the spread of existing and new AIS. Arrival and spread of AIS were assessed at the HUC-8 scale (8-digit hydrological unit code) along the Ohio, Wabash, Cumberland, Alleghany, Monongahela, and Tennessee rivers. A near-linear increase in new AIS across all rivers was determined. Most AIS species (35–55%) did not spread beyond the HUC they were first detected in, while less than 10% spread to all HUCs in a river. The findings indicate no clear correlation between legislative and planning milestones and changes in AIS spread. More work could help to fill data gaps in detecting and monitoring AIS through coordinated local and regional programs, as expanding the quality and quantity of data collection efforts can improve understanding of AIS dynamics, assessments of management effectiveness, and inform future policy. Future work could expand the analysis to evaluate the effectiveness of policy and planning programs in reducing AIS, considering the variability in on-the-ground approaches and spread prevention efforts across states.