A Quadrat-Sieve System for Sampling Freshwater Mussels Using SCUBA

We describe a simple combined-quadrat-sieve system, suitable for in-river surveys of unionoid populations where SCUBA is required. The apparatus has allowed us to survey and excavate 0.25-m2 quadrats with mean search times of <7 min quadrat-1 over 4-hour dives. We have successfully detected mussels near the minimum size, more often retrieved by sieving at the surface, while minimizing habitat disturbance.