ABSTRACT
Introduction ............................................................................................................................................ 376 Materials and Methods ........................................................................................................................... 378
Study Site .......................................................................................................................................... 378 Sampler Experiment ......................................................................................................................... 379 Recruitment Study .............................................................................................................................381 Survivability Experiment ...................................................................................................................381 Environmental Parameters ................................................................................................................ 382 DataAnalyses ................................................................................................................................... 382
Results .................................................................................................................................................... 383 Comparison of Samplers ................................................................................................................... 383
FallTrial ....................................................................................................................................... 383 SummerTrial ............................................................................................................................... 383
Recruitment Experiment ................................................................................................................... 384 Environmental Parameters: Recruitment Experiment ....................................................................... 385
WaterTransparency ..................................................................................................................... 385 WaterTemperature ....................................................................................................................... 386 Dissolved Oxygen ........................................................................................................................ 386 IncomingVeliger Source .............................................................................................................. 387
Recruitment and Environmental Parameters ..................................................................................... 388 Environmental Parameters: Survivability Experiment ...................................................................... 389
Otay Reservoir ............................................................................................................................. 389 Miramar Reservoir ....................................................................................................................... 389
Survivability Experiment ...................................................................................................................391 Otay Reservoir ..............................................................................................................................391 Miramar Reservoir ....................................................................................................................... 392
Discussion .............................................................................................................................................. 392 How to Monitor ................................................................................................................................. 392 When to Monitor ............................................................................................................................... 394 Where to Monitor .............................................................................................................................. 395 Implications ...................................................................................................................................... 396
Conclusions ............................................................................................................................................ 397 Acknowledgments .................................................................................................................................. 397 References .............................................................................................................................................. 398
ABSTRACT Development of effective and ef‘cient monitoring programs for quagga mussels, Dreissena bugensis, requires knowledge of settlement preferences, patterns of recruitment, and survivability.While these topics have been investigated extensively, additional studies are warranted in the recently invaded region of the southwestern United States where environmental conditions differ considerably from other invaded areas. In this study, we (1) evaluated the ef‘cacy of four samplers by measuring mussel recruitment among samplers, (2) identi‘ed spatial and temporal patterns of mussel recruitment by quantifying monthly recruitment at eight water depths for 13 months, (3) explored potentialrelationships between mussel recruitment and environmental parameters (water transparency, water temperature, dissolved oxygen, and incoming veligers), and (4) assessed mussel survivorship within the strati‘cation layers (epilimnion, metalimnion, and hypolimnion). Mussel densities were low where we investigated settlement preferences and recruitment.
