FACTORS LIMITING COLONIZATION OF WESTERN NEW-YORK CREEKS BY THE ZEBRAMUSSEL (DREISSENA-POLYMORPHA)

The New York State Erie Barge Canal was first colonized by the zebra m ussel (Dreissena polymorpha) in 1989. Canal water supplements flows in many creeks in western New York, including six creeks in Monroe Count y that have not been colonized by zebra mussels. We chose Salmon Creek to study why zebra mussels have not colonized regional creeks because the rocky substrate of the creek appears ideal for colonization, yet 100 meters downstream from the input of canal water to the creek adult zebra mussel densities drop to less than one mussel m(-2). In the sum mer of 1993 veliger counts in the canal averaged 52 times greater than they were in Salmon Creek, yet water quality, current velocity, and p articulate organic carbon concentrations in the creek and the canal we re very similar. Chlorophyll a in the canal was higher than in the cre ek. Given the appropriate physical habitat and water quality condition s and an abundant source of veligers, the factors limiting zebra musse l colonization in Salmon Creek remain unknown, but three factors appea r important: 1) Partial retention of zebra mussel veligers by the wetl and through which the canal discharge flows, 2) Filtering of phytoplan kton and veligers by the dense bed of adult zebra mussels at the begin ning of the outfall channel from the canal to the creek, or 3) Inappro priate food quality (e.g., lack of phytoplankton with important fatty acid constituents) in the creek.