Freshwater mussel records collected by the Maryland Department of ...

Pyganodon cataracta had previously been encountered 26 times at 24 sites
(Figure 18). In 2009, we collected P. cataracta at 7 sites (Table 1), three of which
represent new watershed records. Two confirmed host fish (L. gibbosus and L.
macrochirus) were frequently collected at sites where P. cataracta was also encountered
(Table 5). The four remaining confirmed host fishes were uncommon and two species
are non-natives. A majority of confirmed host fishes for congeneric mussels were also
infrequent or absent. Chemical and physical variables collected from streams where P.
cataracta were present (N = 17) and absent (N = 104) were similar for most variables
(Figure 19). A majority of occupied sites had nitrate and total nitrogen concentrations of
2-3 mg/L, while none were collected where concentrations >5 mg/L. The scores of
physical habitat variables and biological indices at sites with P. cataracta were similar to
sites where they were absent; however, they were not found at sites with pool glide
quality >7. Mean percent forest and agricultural land cover of catchments with P.
cataracta was higher than catchments where they were absent while urban land cover
was lower at sites where they were present. We typically encountered P. cataracta in
wider streams (>2 m) in larger catchments (1000-5000 ac) with very low gradient
(