Mussel (Bivalvia: Unionidae) Survey Of The Mississippi National River And Recreation Area Corridor, 2000-2001

Kelner, Dan; Davis, Mike

During 2000 and 2001, we sampled 152 sites for mussels along the entire Mississippi National River and Recreation Area (MNRRA) Corridor which encompasses a 72-mile stretch of the Upper Mississippi River (UMR) (138 sites), a four-mile reach of the lower Minnesota River (MNR) near its confluence with the UMR (14 sites), and the lower Rum River (RR) near its confluence with the UMR (one site). The UMR stretch extends from approximately 20 miles north of the Twin Cities, through the Twin Cities, to just below Hastings, Minnesota. Five pools or reaches were surveyed and include from upstream to downstream: Coon Rapids Pool; St. Anthony Falls Pool; and Pools 1, 2, and Upper Pool 3. Sample methods were consistent throughout the study and consisted of timed searches and hand collection of mussels while wading, snorkeling, and diving. Quantitative samples were also collected and mussel bed boundaries mapped at five sites within the UMR. Over 12,000 live mussels representing 28 species were collected with an additional 12 species collected as empty shells. The mussel fauna of UMR Pools 1-3 appears to be recovering since its reported decimation by pollution during the first half of the 1900s. This survey provided clear evidence of recent and ongoing recruitment, and many of the individuals collected were less than 10 years old. Several state listed species were collected including two listed as endangered in Minnesota, rock pocketbook (Arcidens confragosus) and wartyback (Quadrula nodulata). Recolonization is probably due to improved water quality conditions over the past 15-20 years. Furthermore, mussels are expanding their range above St. Anthony Falls (historically a faunal barrier to upstream dispersal) as fish now circumnavigate the two navigation locks. A total of 16 live species were collected from the St. Anthony Falls Pool including 10 species previously not reported there. Zebra mussels were absent above Lock and Dam 1 and very scarce from UMR Pool 2 and Upper Pool 3 and the lower MNR. These UMR pools differ from those downstream (Pool 4 and below) where zebra mussels are extremely abundant and are decimating the native mussel communities. Ironically, this reach of the Mississippi River between the Twin Cities and Hastings, MN, once nearly a dead zone, may now be one of the last big river mussel refuges in the Midwestern United States.

Mussel (Bivalvia: Unionidae) Survey Of The Mississippi National River And Recreation Area Corridor, 2000-2001

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