Choosing streams for sea lamprey control: Using alternative models of metamorphosis to optimize the stream selection process

Control of sea lamprey (Petromyzon marinus) in the Great Lakes is primarily achieved through the application of lampricide to streams harbouring abundant populations of larvae. For lampricide treatments to be efficient, streams are prioritized for treatment based on forecasts concerning the escapement of recently-metamorphosed parasitic juveniles relative to the cost of treating each stream. Computer simulations confirmed that while this is the most effective method to employ when the actual number of lamprey is known, uncertainty associated with assessment surveys and the use of predictive models of metamorphosis decreases the efficiency of this method. Building on laboratory experiments that suggest the accumulation of lipids is a critical stage prior to the onset of metamorphosis, I adapted a non-invasive method to estimate lipid content in larval sea lamprey. Predicted lipid content was combined with other biotic and abiotic stream measurements in a mark-recapture study to investigate the relative importance of various factors influencing metamorphosis. The predictive metamorphic model that was developed was evaluated for its ability to accurately estimate transformer abundance and compared with the performance of other models used in the stream selection process. The results suggest that the incorporation of stream-specific measures can greatly improve our ability to accurately predict metamorphosis, allowing for better stream treatment decisions, and further reductions in sea lamprey abundance.