Date of Award

2007

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Ecology and Environmental Sciences

Advisor

Cynthia Loftin

Second Committee Member

Judith Rhymer

Third Committee Member

Michael Kinnison

Abstract

Translocation from areas where habitat alterations are proposed can be an important mussel conservation tool. Pending removal of the Fort Halifax dam on the Sebasticook River in Maine potentially would result in extensive mortality of two statelisted threatened species of mussels, yellow lampmussels (Lampsilis cariosa) and tidewater muckets (Leptodea ochracea), which occur in the impoundment above the dam. My study assessed populations of these two species in the impoundment, and determined the effects of within- and between-waterbody translocations on survival. I conducted a qualitative survey of the Fort Halifax dam impoundment in 2004 to determine locations of these two species and a quantitative survey near the upper end of the impoundment in 2005 where the greatest numbers of these species occur. Estimated densities in survey plots were 0.05-1.1/m2 for yellow lampmussels and 0.0-0.41/m2 for tidewater muckets. In a 2004 pilot study, I translocated a co-occurring common species, eastern lampmussel (Lampsilis radiata radiata), within the impoundment and to two other sites in the watershed, Unity Pond and Sandy Stream. Recapture rates for 2005-2006 were 34- 83% (0-9% mortality). As part of this effort, I used Passive Integrated Transponder (PIT) tags to track translocated mussels to assess the feasibility of this monitoring tool. Numbers of recaptured mussels differed among study sites; however, at all sites I found more tagged mussels with PIT pack searches with visual confirmation (72-80%) than with visual searches alone (30-47%). PIT tags offer improved recapture of translocated mussels and increased accuracy of post-translocation monitoring. I repeated the experiment in 2005 with yellow lampmussels and tidewater muckets. I recaptured 57- 90% of yellow lampmussels (0-7% mortality) and 30-86% of tidewater muckets (4-6% mortality) using PIT pack searches with visual confirmation. In Sandy Stream, sediment is redistributed annually with high late winter-early spring flows, which carry debris and stream-dwelling organisms downstream toward Unity Pond. I found 71% of recaptured eastern lampmussels >100 m from their October 2004 locations, and two yellow lampmussels and four tidewater muckets were 30-100 m downstream from their August 2005 locations. Yellow lampmussels and tidewater muckets in Sandy Stream were also significantly smaller than those found in the Sebasticook River. Although tidewater muckets and yellow lampmussels occur in this stream, the unstable stream bottom and high muskrat predation potentially threaten their survival, making this site unsuitable for translocating mussels from the Sebasticook River. I found greatest densities of yellow lampmussels and tidewater muckets in boulder and cobble substrate in the upper 1.5 km of the impoundment. This area is least likely to be reconfigured following dam removal; the channel should be stable during dewatering and may be a refuge for all mussel species. Mussels in this section could then repopulate the newly formed channel once it stabilizes in the middle of the impoundment. As long as care is taken to protect mussels during dewatering by translocating exposed mussels to the stable channel in the upper end of the impoundment, restoration of lotic habitat throughout the formerly impounded area will benefit yellow lampmussels and tidewater muckets in the long-term.

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