FOLLOW-UP ON TRANSLOCATED ALASMIDONTA MARGINATA FROM THE SOUTH FORK OF THE 
ZUMBRO RIVER, ROCHESTER, MINNESOTA.  Marian E. Havlik, Malacological 
Consultants, La Crosse, WI 54601-4969.
Prior to construction of a new forcemain, six sites were surveyed in 2005 
within two miles of the South Fork of the Zumbro River, downstream of Silver 
Lake Dam, Rochester, MN.  Each site was sampled from 30 m upstream to 61 m 
downstream of the proposed pipe centerlines.  River widths ranged from 15-46 
m, while depths were mostly 1 m or less.  The substrata were mostly cobble 
and gravel, with sand increasing as we moved downstream.  Mussel 
translocations were done in 2006 at four sites chosen for forcemain 
crossings.  Although densities averaged a low 0.05/m2 from all sites, nearly 
20.3% of the mussels were living Alasmidonta marginata, a state endangered 
species, likely the highest concentration in Minnesota.  All living mussels 
were collected, including Lasmigona costata (2.0%) and L. compressa (1.8%), 
both Minnesota special concern species.  There was modest reproduction of 
most of the nine living species.  Minnesota listed mussels (24.1%) were 
externally aged, measured for length and height, and etched with unique 
numbers on both anterior valves, while common mussels were hash-marked on 
both anterior valves.  Over 600 mussels were translocated to an area between 
Site 1 and Silver Lake Dam: 404 (18.6% T & E mussels) were from Site 1, the 
largest area; 136 (44.8% T & E mussels) were from Site 2, while 33 (10.9% T & 
E mussels), and 31 mussels (21.9% T & E mussels) were found at Sites 3 and 4 
respectively.  At least nine fish species were identified from Site 1, the 
most productive mussel area.  In September 2006 gravid A. marginata were 
collected for host fish studies.  

During follow-up, 9 August 2007, 211 mussels were recovered from the 
Translocation Site: 81 hand-planted/numbered mussels, 70 hash-marked mussels, 
and 60 un-marked mussels (including five listed mussels).  There was a 95.3% 
survival of the three numbered, listed mussel species, and 85.7% survival of 
the hash-marked common mussels.  One of the reported host fish species, 
Catostomus commersoni, white sucker, was reportedly seen by divers.  Follow-
up studies will be repeated in 2008.

SiteNumberedMarkedUn-markedTotal1Pyganodon grandis112Anodontoides 
ferussacianus13Strophitus undulates284Alasmidonta marginata7025775  Lasmigona 
costata91106Lasmigona compressa227Lasmigona complanataDDead8Toxolasma parvus         
9Lampsilis siliquoidea          10Lampsilis cardium28Total live mussels:               
817060211Total listed mussels       812689Total live mussel species 3667Total 
dead mussels5101631Keywords: mussel distribution, Mississippi River tributary 
mussel species, threatened and endangered mussels, unionid age and density 
data 
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