Evaluation of efficacy of dispersal barrier between Illinois River and Lake Michigan. From 10,000 to 5,000,000 veligers per second move from Lake Michigan to the Sanitary and Ship Canal during the summer. The flux at Lockport is approximately one tenth the flux at Lake Michigan. We have gotten data on veliger growth rates and mortality. We have obtained data on expected advective losses in the Illinois River and are able to adjust abundances in order to obtain mortality rates.
Mortality is initially low, until the veligers move from the D-stage to the umbonal stage.
During this transition, mortality is extremely high, and again declines following this transition. This is the first measurement of a critical period in Dreissena larval development and may have implications for control, but the finding needs to be confirmed in additional float trips. This mortality rate measurement is also one of the first field-based measurements of invertebrate larval mortality to take into account losses expected from water movement, and will have implications for marine as well as freshwater research. These samples have not yet been analyzed. These plates were photographed each month to track individual mussels.