Abstract:

Since their invasion a century ago, sea lampreys have posed a threat to the Great Lakes because of their economic and ecological repercussions. Various control measures have been implemented to limit their abundance, with lampricides (TFM and Bayluscide®) becoming one of the most effective treatments. There is growing concern about the risk posed to non-target organisms like mussels, not only because many endangered species reside in areas overlapping application sites, but because Bayluscide® was initially developed as a molluscicide. To determine susceptibility of mussels to this toxin, adult washboard mussels (Megalonaias nervosa) were exposed to varying concentrations of Bayluscide® (ranging from 0.0002 – 0.014 g) for 7 days followed by a 7-day recovery period to estimate mortality. In addition, scope for growth was determined for 6 mussels exposed to 0.005 g Bayluscide® for 24 hours. To do so, their filtering ability (clearance rate), rate of oxygen consumption, and absorption efficiency were measured following exposure and calculated based on Widdow et al. (2006). No mortalities were observed in any of the treatments following the 7-day exposure. There was no significant difference between the scope for growth of control mussels and those exposed to Bayluscide®, although notably one individual appeared to be severely affected by exposure. This individual may have ingested a granule of Bayluscide®, which sparked a closer look at the effects of mussels accidentally ingesting a granule. Although our results show that washboard mussels can withstand low amounts of Bayluscide® exposure, there is potential for considerable effects to occur when a pellet is ingested.