Abstract:

Sea lampreys (Petromyzon marinus) are an invasive species that pose an ecological threat to the Great Lakes since their introduction. To control sea lamprey populations, biologists have been dosing Great Lake tributaries with lampricides to target the larval form of the lamprey since the 1950s. Granular Baylusicde® is a lampricide used since the 1990s that is applied to slow-moving and deeper waters. Despite being registered with Health Canada, there is currently limited toxicological data that informs the risk of this lampricide to non-target species. Freshwater mussels in the Unionidae family are a group of filter-feeding organisms that have experienced notable population declines due to habitat destruction, invasive species, and poor water quality. The range of many of these mussel species coincide with the zones of Bayluscide® application. Past research has shown that Unionidae species are sensitive to environmentally relevant concentrations of Bayluscide®, but the earliest life stages have yet to be tested. In this study, early metamorphosed and sub-adult Lampsilis siliquoidea (fatmucket) mussels were exposed to 0.0625 to 3 times the Bayluscide® application rate in kg/ha to determine an LC50 (lethal concentration). In addition, burial was monitored for sub-adults and growth for early metamorphosed mussels. The LC50 for sub-adult L. siliquoidea was 0.55 (0.41 – 0.68) x the application rate (kg/ha), and <0.0625 x the application rate (kg/ha) for the early metamorphosed stage. Both life stages were found to be relatively sensitive to the lampricide, especially the early metamorphosed stage which was affected in each concentration tested in this study. Lampsilis siliquoidea have often served as a surrogate species for other mussels that are threatened or endangered, and their sensitivity to various chemicals have proven to be significantly similar. Based on these findings, the inclusion of Unionidae data is crucial to an updated risk assessment of Bayluscide®.