Evaluation of sea lamprey-associated mortality sources on a generalized lake sturgeon population in the Great Lakes

Lake sturgeon populations in the Laurentian Great Lakes experience two age-specific mortality sources influenced by the sea lamprey Petromyzon marinus control program: lampricide (TFM) exposure-induced mortality on age-0 fish and sea lamprey predation on sub-adults (ages 7-24). We used a generic age-structured population model to show that although lampricide-induced mortality on age-0 lake sturgeon can limit attainable population abundance, sea lamprey predation on sub-adult lake sturgeon may have a greater influence. Under base conditions, adult lake sturgeon populations increased by 5.7% in the absence of TFM toxicity if there was no change in predation; whereas, a 13% increase in predation removed this effect, and a doubling of sea lamprey predation led to a 32% decrease in adult lake sturgeon. Our estimates of lake sturgeon abundance were highly dependent on the values of life history and mortality parameters, but the relative impacts of ceasing TFM treatment and increasing predation were robust given a status quo level of predation. The status quo predation was based on sea lamprey wounding on lake sturgeon, and improvements in this information would help better define tradeoffs between the mortality sources for specific systems. Reduction or elimination of TFM toxicity on larval lake sturgeon, while maintaining TFM toxicity on larval sea lamprey, can promote lake sturgeon restoration and minimize negative impacts on other fish community members.