HR: 1330h
AN: NB33P-01    [Abstracts]
TI: Mussel Assemblages Below a Dam: High Density, Large Size and Low Recruitment
AU: * Hornbach, D J
EM: hornbach@macalester.edu
AF: Macalester College, Department of Biology 1600 Grand Ave., St. Paul, MN 55105 United States
AU: Hove, M C
EM: Mark.Hove@fw.umn.edu
AF: Macalester College, Department of Biology 1600 Grand Ave., St. Paul, MN 55105 United States
AU: Berg, M S
EM: mberg@grantsburg.k12.wi.us
AF: Grantsburg High School, 480 East James Ave., Grantsburg, WI 54840 United States
AB: We examined the demographic structure of mussel assemblages at three locations in the St. Croix River watershed, Wisconsin and Minnesota between 1998-2004. One assemblage, below a small dam on a tributary (Sunrise River), has 113 mussels/m². On the mainstem, Wild River (not below a dam) and Interstate Park (below a larger dam) have 21 and 24 mussesl/m², respectively. There is little recruitment at Sunrise and mussels are larger than those at mainstem sites. Larger size is apparently due to higher growth rates at this site. Low recruitment may be due to competition for space with adults. Live and dead mussels comprise much of the substrate at Sunrise with living mussels occupying 23-60% of available space, compared with <5% at the mainstem sites. Course stable sand, thought to be important juvenile habitat, accounts for 35% of the substrate at Sunrise compared with 41-64% at the mainstem sites. Preliminary qualitative data from two other sites below small dams on tributaries indicate similar patterns of high density, large mussel size and little recruitment. Variable recruitment at sites below small dams coupled with long lifespan of mussels (decades) could have profound influences on management decisions to maintain or remove dams.
DE: 9810 New fields (not classifiable under other headings)
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly