Larval dynamics of a riverine metapopulation: Implications for zebra mussel recruitment, dispersal, and control in a large-river system
Control, Dispersal, Dreissena polymorpha, Larvae, Metapopulation, Recruitment, Zebra mussel
Zebra mussels (Dreissena polymorpha) in the Illinois River are likely to function as a metapopulation (a system of local populations connected by dispersal). River currents reduce or eliminate internal recruitment by local populations, making them dependent upon external recruitment from propagules (larvae) produced by upriver populations. Because of the importance of external recruitment, understanding the population dynamics of riverine zebra mussels requires knowledge of larval flux. In 1994 and 1995, larval drift past a fixed site on the Illinois River was characterized by pulses of similar-sized individuals. These pulses were composed primarily of D-stage (straight hinge) larvae, not yet competent to settle. The continual passage of pulses of young larvae suggests that the upriver source population(s) spawned in frequent distinct bursts throughout the summer months rather than spawning only once or twice. Overall larval abundance was a poor predictor of availability of competent larvae. Although larvae were frequently present in high numbers, larvae >200 μm in shell height (competent to settle) were present only sporadically at our fixed study site from May to November in 1994, and present only from June to early July in 1995. Settlement at a given site on the Illinois River is likely to be sporadic rather than constant. Colonization and population growth at a given site will occur only if suitable habitat and environmental conditions are available during the windows when competent larvae are available. Changes in mean size as a larval cohort drifted downriver suggested a growth rate of 6.72 μm/d. At this growth rate, most larvae probably travel a minimum of 304.6 km (190.4 miles) before settling. Thus, larvae spawned in the main channel of the lower 70% of the Illinois River are most likely to settle in the Mississippi River. We suggest that colonization and population growth in the upper 70% of the Illinois River are strongly dependent upon larvae produced at upriver source sites in Lake Michigan and the Chicago area waterways. Control of zebra mussels in a given stretch of the fiver will depend upon control of the upriver source populations.
Stoeckel, James A., Daniel W. Schneider, Lori A. Soeken, K. Douglas Blodgett, and Richard E. Sparks. "Larval dynamics of a riverine metapopulation: implications for zebra mussel recruitment, dispersal, and control in a large-river system." Journal of the North American benthological society 16, no. 3 (1997): 586-601.
DOI for the article