A secondary upstream invasion of round goby in the Great Lakes Basin over fourteen years following a dam removal

Dam removal projects are increasingly used restoration approaches to support fishmigration and freshwater biodiversity. Unfortunately, improved watershed connectivitycan promote the spread of invasive species. The Rouge River (Michigan, USA), aGreat Lakes Area of Concern, is a degraded ecosystem undergoing ongoingrestoration and improvement. To evaluate tradeoffs between restoration benefits andinvasion risk, we examined the spread of invasive round goby, Neogobiusmelanostomus, over 14 years (2012-2025) following the removal of the Wayne RoadDam in the Rouge River watershed. Using community fish data collected through aparticipatory science program run by Friends of the Rouge, we found round gobytraveled approximately 23 river kilometers upstream, with an average speed of 1.9river km/year. Invasion speed peaked in downstream sites with a maximum speed of9.3 river km/year. Within sites, increases in round goby relative abundance slowedover time. Across sites, relative abundance of round goby was best predicted byjohnny darter relative abundance (Etheostoma nigrum), modeled July watertemperature, abundance of gravel substrate, Time Since Invasion (TSI), and baseflow.The relative abundance of johnny darter, a small benthic fish with similar traits to roundgoby, was related to the abundance of cobble and gravel substrate, baseflow, TSI, andround goby relative abundance. Our findings illustrate the complex responses that canemerge when restoration efforts such as dam removals occur in freshwaterecosystems that are often simultaneously facing the spread and impact of invasivespecies.