Salinity tolerance of the exotic round goby: Experimental implications for seawater ballast exchange

The Eurasian round goby invaded the North American Great Lakes in 1990 via ballast water introduction from the Black Sea area (0-15 ppt salinities), and since spread throughout watersheds and adjacent riverine systems. Legislation now requires oceanic ballast water exchange of vessels entering the Great Lakes, whose salinity effects are unknown on gobies. We tested 230 juvenile and adult round gobies in salinity tolerance experiments with 20 per treatment at 0 (control), 5, 10, 15, 20, 25, 30, 35, and 40 ppt in immediate immersion versus longer-term acclimation experiments (increasing 5 ppt every 3 days). Immersion experiments yielded 95-100% survivorship at 0-10 ppt, 70-80% for 15-20 ppt, 20% at 25 ppt, and 0% in 30-40 ppt. Acclimation experimental results were 95-100% survival in salinities of 0-20 ppt, 80% in 25 ppt, and 0% at 30 ppt. In long-term experiments, Lake Erie round gobies lived at salinities to 20 ppt for 3+ months. Thus, round gobies readily tolerate and acclimate to estuarine conditions, and are unlikely to be affected by oceanic ballast water exchange. We predict that the round goby will spread to North American coastal estuaries, where their success will be enhanced by their native mytilid mussel prey.