The round goby (Neogobius melanostomus) is a bottom-dwelling fish whose native range in Eurasia. It was first observed in the St. Clair River, presumably a ballast water introduction, and is now widespread in all of the Great Lakes except Lake Superior where it is reported from only a few locations. It is especially abundant in Lakes Erie and Ontario. The round goby population of western Lake Erie was estimated at 9.9 billion individuals in 2002.1
Impacts of round goby invasion
- The round goby is extremely aggressive and is a prolific breeder, often spawning several times each season. Once established, it can quickly become the dominant fish species in an area.
- The round goby prefers rocky, shallow areas but flourishes in a wide variety of habitats. It out-competes native species, particularly other bottom-dwelling species like mottled sculpin, logperch, and darters, for food and space, and preys on eggs and fry of other fish.
- The round goby also preys heavily on zebra mussels, which are often high in contaminants, leading to concerns about increased risk of contaminant exposure for sport fish and other round goby predators.
Mapping round goby as a Great Lakes stressor
The round goby stressor map was developed using a habitat suitability model. Model inputs included:
- Records of observed round goby locations within the Great Lakes and from rivers within 5 km of the Lakes2
Environmental variables hypothesized to influence goby distributions
- Mean summer water temperature (over the warmest 3 months for 17 years, July 1-Sept. 30 1994-2010)
- Mean chlorophyll a levels in May 2008 (based on SeaWiFS satellite imagery)
- Water depth
- Dreissenid mussel densities
We ran models both with and without substrate type as a measure of habitat suitability, but the resulting models were statistically equivalent, so we present results from the model without substrate. Models were run using Maxent software with default settings, and they were validated with 10-fold cross-validation and test omission. The resulting model was highly discriminative based on standard performance measures (mean AUC = 0.94).
Spatial distribution of round goby as a stressor in the Laurentian Great Lakes (Inset: Western Lake Erie)*
*The predicted habitable locations for round gobies represent probable extent of occupancy and do not reflect relative abundance. This map also excludes deep water observations which are too few to model at present and generally are from autumn and winter surveys.