A COMPARATIVE STUDY OF MISSISSIPPI RIVER UNIONOID SURVEYS, 
ST. PAUL, MINNESOTA, TO CAIRO, ILLINOIS. 

Marian E. Havlik, Malacological Consultants, 1603 Mississippi Street, La Crosse, 
WI 54601-4969.  havlikme@aol.com (608-782-7958). 

Prior to agency sponsored unionoid studies started in the 1970's, most Upper 
Mississippi River (UMR) researchers were aware of mollusk surveys by Utterback, 
Grier, and Ellis.  Almost unknown is a survey done in 1907 by Dr. Paul W. 
Bartsch, from Mississippi River Mile 838.5-0.0.  The Bartsch locations have been 
converted to present day Mississippi River Miles.  In 1907, unionoids were found 
at 88 of 140 sites.  Bartsch recorded 15 negative mainstem sites upstream of the 
Missouri River, and 17 negative sites downstream of the Missouri River.  
Overall, four species, Quadrula pustulosa (Lea 1831), Amblema plicata (Say 
1817), Lampsilis cardium (Rafinesque 1820), and Leptodea fragilis (Rafinesque 
1820), were found more frequently than Fusconaia ebena (Lea 1831), although the 
latter was apparently the most abundant species.  Lampsilis higginsi (Lea 1857) 
were retained from 39 sites, Potamilus capax (Green 1832) from 13 sites, and 
Cumberlandia monodonta (Say 1829) from eight sites, but Leptodea leptodon 
(Rafinesque 1820), was only retained from a single site.  Three species common 
today, Utterbackia imbecillis (Say 1829), Toxolasma parvus (Barnes 1823), and 
Anodonta suborbiculata (Say 1831), and several rare species including Quadrula 
fragosa (Conrad 1835), Epioblasma triquetra (Rafinesque 1820), and Simpsonaias 
ambigua (Say 1825), were either not found, or else not retained.  Even in 1907, 
five to10 species appeared to be extralimital including Ligumia subrostrata (Say 
1831), Potamilus purpuratus (Lamarck 1819), Uniomerus tetralasmus (Say 1831), 
Alasmidonta viridis (Rafinesque 1820), and Lasmigona compressa (Lea 1829).  The 
1907 areas with the highest species diversity continue to have the highest 
diversity today: Pools 10 (36 species), Pool 3 and 13 (35 species), Pool 8 and 9 
(34 species), and Pool 14 and 15 (33 species).  No more than two species were 
retained at 28 of the 140 sites. 
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A recent summary of archeological records reported 39 species from Pools 4-16.  
The 1907 survey retained 39 unionoid species, and the 1930 Ellis survey also 
reported 39 unionoid species.  Havlik and Sauer (2000) reported that 51 unionoid 
species have been recorded from the Upper Mississippi River since the 1870's.  
Forty-four of these species have been recorded since 1968, with at least 38 
species being reported alive since 1991.  All of the rare species in the UMR 
today were rare even in 1907, but all of those rare species still survive today 
in tributaries within 100 miles of the Upper Mississippi River.  I compare early 
Mississippi River unionoid distributions, rank, and frequency of occurrence, 
with present day UMR records, by Pool.  Over the past century, the total fauna 
has remained stable, but some species have become more abundant, while others 
have become rare, or locally extirpated.  

Keywords: Mississippi River, unionoids, unionoid surveys, unionoid species, 
Mississippi River mussels
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