EFFECTS OF PULSED TURBIDITY AND VESSEL TRAFFIC ON LAKE HERRING EGGS AND LARVAE

Proposals to extend commercial shipping in the St. Marys River (connec ting Lakes Superior and Huron) to include winter months have raised co ncerns regarding its effect on lake herring (Coregonus artedi). Becaus e lake herring spawn in fall and their eggs overwinter in the river an d hatch in spring, their hatching success could be impacted by early o pening of the locks in spring. Our laboratory studies showed that unde r the range of turbidities expected in the river due to vessel traffic , lake herring eggs hatched and larvae fed adequately. Field incubatio n studies produced about 75% survival and 70% hatching success of lake herring eggs at two of three study sites. Collections in the river th roughout the month following ice-out showed that sufficient plankton o f appropriate size were available to ensure growth and survival of lar val lake herring. We did not detect any negative impacts on the early life stages of lake herring as a result of sedimentation in the labora tory or field. However, detailing the spawning sites of lake herring a nd defining the normal survival-to-hatch in these areas are necessary before making accurate predictions of the effects of early season vess el traffic on lake herring hatching success.