A COMPARISON OF STREAM SEGMENT AND QUADRAT MUSSEL SAMPLING
TECHNIQUES.  

Timothy L. Dickson.   Biology Department, St. Olaf College,
Northfield, MN 55057.  

The importance of freshwater mussels in river ecosystem dynamics
and as environmental indicators and endangered species is well
recognized.  Well designed, rapid methods of sampling mussels are
needed.  We tested the more traditional method of lmę quadrat
searches against 10 m long bank-to-bank searches.  Using data
collected during the summer from local streams we calculated how
well the two sampling techniques measured mussel density, mussel
richness (total number of species present), and mussel
aggregation.  We found that quadrats required more samples for a
particular level of precision in density estimates than did 10m
searches, however 10m searches may still be more time-consuming. 
A better estimate of species richness is provided by 10m
searches, and 10m searches also tended to detect uniform
distributions, while quadrats tended to detect clumped
distributions within the same population.  Ten meter long bank-
to-bank searches appear to be a viable alternative to quadrat
sampling.  

Keywords:  Unionids, sampling, quadrat, stream-segment, richness