The Role of Lake Sturgeon in a Dreissenid Dominated Ecosystem

The population of lake sturgeon in the Great Lakes is estimated at approximately 1% of historic levels and only five known spawning populations exist in Lake Huron out of 33 historic populations. Active restoration work is underway for lake sturgeon in the Great Lakes, including the construction of artificial spawning reefs and the removal of dams to allow greater access to spawning habitat. Since their invasion in the 1980s, dreissenid mussels have reached dominant biomass levels in the Great Lakes. The question arises of whether lake sturgeon, a native molluscivore, could impact a dreissenid dominated ecosystem.  As a case study, we examined the ability of lake sturgeon to impact dreissenid density in Lake St. Clair. Approximately 45,500 lake sturgeon occupy Lake St. Clair (5.4 kg/ha), which is within the range of estimated historic biomass for Lake Huron. Diets of 41 lake sturgeon were analyzed in the early 2000s. Chironomids were in the highest proportion of diets and about 50% contained dreissenids. Despite the high density of lake sturgeon feeding on dreissenids, populations did not appear to be impacted.  Therefore, even if lake sturgeon were restored to historic densities in Lake Huron they likely would not significantly impact the dreissenid population.