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

Abstract

Round goby (Neogobius melanostomus Pallas, 1814) is a benthic fish native to the Ponto-Caspian region in Europe that was first introduced to the Laurentian Great Lakes region in the 1990s. Following their initial introduction, round gobies have spread outside of the Great Lakes themselves, and are moving upstream into surrounding tributaries. Often, upstream migration by round gobies is blocked within several river miles of the lake of origin due to anthropogenic barriers, such as dams. However, dam removal projects are becoming increasingly common restoration efforts. The Wayne Road Dam barred upstream round goby migration in the Rouge River until its removal in 2012. Friends of the Rouge (FOTR), a local nonprofit, began conducting fish community surveys at that time. Using data collected over a period of 13 years (2012–2024) by FOTR and participatory scientists, we analyzed biotic and abiotic factors that influence round goby and native fish relative abundances. We found that johnny darter relative abundance, modeled July temperature, Time Since Invasion (TSI), and baseflow best predicted round goby relative abundance. Round goby relative abundance, TSI, and the random effect of site best predicted johnny darter relative abundance. Round gobies have traveled approximately 23 river kilometers upstream in 12 years with an average speed of 1.91 river km/year. Invasion speed peaks in downstream sites with a maximum speed of 9.3 river km/year. Round goby relative abundance follows logarithmic growth patterns, with faster population growth in early invasion dates that slows over time. The Rouge River serves as a case study highlighting complex responses that can arise from restoration efforts, such as dam removals.