Relative abundance and growth of mussels (Mollusca: Eulamellibranchia) in pools 8,9 and 10 of the Mississippi River

SUMMARY. Twenty‐three species of unionid mussels were sampled during the summer of 1975 from a 76‐mile reach of the Upper Mississippi River; this represented eight species fewer than were recorded in a 1930–31 survey for the same section of the river. Of the 244 sites sampled in 1975, mussels were found at 116 sites and the ten most productive sites accounted for 40.8% of the 1205 mussels collected. There were as many as thirteen different mussel species taken from one sampling site. The two most abundant species ( Amblema peruviana and Megalonaias gigantea ) constituted 54.5% of the mussels sampled in 1975; these two species made up only 8.3% of the 1930–31 survey. Individuals of the twelve most abundant mussel species were aged, and shell‐length growth equations were determined. In addition, shell‐free dry weight growth rate and shell weight growth rate was determined for Amblema peruviana . The calculated annual production for A. peruviana (assuming a mean density of 1 per m 2 ) was 482 mg/m 2 shell‐free dry weight, and 14.471 g/m 2 shell weight.