Minnesota Statewide Mussel (Bivalvia: Unionidae) Survey: 2003-04
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SWG Mussel Survey Report, December 2004 Minnesota Statewide Mussel (Bivalvia: Unionidae) Survey: 2003-04. Prepared for: U. S. Fish and Wildlife Service Minnesota Department of Natural Resources, Ecological Services Division December 2004 - SWG Mussel Survey Report, December 2004 Tables and Figures TABLES Table 1. Number of sites sampled within each drainage by stream, river, or lake, July 2003 through December 2004. Table 2. Species and relative abundance of mussels from the Minnesota River Drainage, July 2003 through December 2004. Table 3. Species and relative abundance of mussels from the Red River of the North Drainage, July 2003 through December 2004. Table 4. Species and relative abundance of mussels from the Upper (Headwaters) Mississippi River Drainage, July 2003 through December 2004. Table 5. Species and relative abundance of mussels from the Lower Mississippi Drainage, July 2003 through December 2004. FIGURES Figure 1. Distribution of mussel survey sample sites, July 2003 through December 2004. Figure 2. Species richness of mussels in sampled streams within the Minnesota River Drainage. Figure 3. Catch per unit effort of mussels in sampled streams within the Minnesota River Drainage. Figure 4. Species richness of mussels in sampled streams and lakes within the Red River of the North Drainage. Figure 5. Catch per unit effort of mussels in sampled streams and lakes within Red River of the North Drainage. Figure 6. Species richness of mussels in sampled streams and lakes within the Upper Mississippi River Drainage. - SWG Mussel Survey Report, December 2004 Figure 7. Catch per unit effort of mussels in sampled streams and lakes within the Upper Mississippi River Drainage. Figure 8. Species richness of mussels in sampled streams within the Lower Mississippi River Drainage. Figure 9. Catch per unit effort of mussels in sampled streams within the Lower Mississippi River Drainage. ii SWG Mussel Survey Report, December 2004 Abstract The Minnesota Department of Natural Resources began a systematic survey of the state's freshwater mussel fauna in 1999. From July 2003 through October 2004, as part of this ongoing effort, and with funding provided by Minnesota's State Wildlife Grants Program, 386 stream and lake sites were sampled for mussels, primarily in the Minnesota, Red River of the North, Lower Mississippi, and Upper (Headwaters) Mississippi River drainages. A total of 37,233 live mussels of 20 species were documented, including live individuals of Minnesota Threatened Alasmidonta marginataand Venustaconcha ellipsiformis, and Minnesota Special Concern Lasmigona compressa, Lasmigona costata, and Ligtunia recta. Surveys during the project period demonstrated that the mussel fauna of the Minnesota River Drainage has been degraded as evidenced by the apparent loss of several species, the proportion of species found alive vs dead, and the relatively lower catch per unit effort of live mussels. Based on these same criteria, with some exceptions, the Red River of the North, and to a lesser extent the Upper Mississippi River Drainage have relatively healthy mussel faunas. Acknowledgements This project was funded by the U.S.F.W.S through a State Wildlife Grant to the state of Minnesota. iii SWG Mussel Survey Report, December 2004 Introduction In August 1999, the Minnesota Department of Natural Resources' (MNDNR) Division of Ecological Services began a freshwater mussel survey to determine the distribution and abundance of unionid mussels in Minnesota. Between August 1999 and June 2003, 1230 sites were sampled in various river systems, primarily in the southern and eastern portion of the state. More limited surveys were done in the Red River of the North and Upper Mississippi River (Headwaters). Completing surveys in the latter two drainages was a high priority areas based on expected species richness of mussels and presence state listed species. Therefore, a successful proposal was submitted to Minnesota's State Wildlife Grants (SWG) program for additional funding to survey for mussels in these drainages. This report summarizes the results of the mussel survey effort funded by SWG from July 2003 through December 2004. Ultimately, these data will be used for a variety of conservation purposes, including land use and watershed management planning, review of proposed development projects so that they avoid or minimize impacts to mussel species, and evaluating state and federal mussel protection needs. Methods The objectives outlined in the proposal were to complete sampling in the Upper Mississippi (Headwaters) Drainage and the Red River of the North Drainage. Although the majority of sites sampled were in these two drainages, high water during part of the 2003 field season prevented sampling in some areas of these drainages, and low water levels in some areas of the Minnesota River provided the opportunity for more intensive sampling of this drainage. A small number of sites were also sampled in the Lower Mississippi River Drainage (Root and Vermillion Rivers) and one lake each in the Lake of the Woods and St. Croix Drainages were sampled (Table 1). Sample sites were located at bridges and other access points near roads, or accessed by boat on the larger rivers. At each site, up to four biologists did timed searches by wading, snorkeling or SCUBA. All live and dead mussels were collected by sweeping hands over the surface of the substrate and by probing the substrate by hand to find buried mussels. River banks and sand and gravel bars were also searched for empty shells. All microhabitats at each site were sampled to locate areas of high mussel density and to maximize the number of species documented. All live mussels collected were identified to species, their age estimated by counting external annuli to place SWG Mussel Survey Report, December 2004 them in one of three age classes; 1-5, 6-10, and >10 years old. Within each age class, minimum and maximum length were determined for each species (maximum shell length, anterior-posterior axis). Mussel species found only as dead shells were identified and shell condition was noted. Voucher specimens of live or dead mussels were collected from most sites and deposited at the University of Minnesota's James Ford Bell Museum of Natural History Mollusk Collection. All other live mussels were returned to the approximate location where collected. For each site, time spent searching and general habitat conditions (i.e., min. max. depth, substrate, and general riparian zone comments) were recorded. A GPS coordinate was recorded at each site to mark the site's general location. Results were summarized for comparison among streams and lakes as catch per unit effort (CPUE). Data were entered in the MNDNR's Natural Heritage Information System where they will be available to land managers, researchers, local, and state and federal agency staff. Results and Discussion During the project period, 386 sites were sampled (Figure 1, Table 1). Overall, 37,233 live mussels of 20 species were found, and an additional 18 species were found only as empty shells. An overview of results for each drainage basin sampled is given below. Minnesota River Drainage A total of 51 sites from 13 streams were sampled in the Minnesota River Drainage (Table 1). The locations of these sites were selected to fill gaps left from previous sampling years. A total of 1,816 live mussels of 16 species were documented (Table 2). An additional 16 species were found as dead shells only. Among the dead-only species were the following state listed species: 5 endangered, 7 threatened, and 3 special concern species. Most of these state listed species were collected at a single mainstem Minnesota River site at Carver. The only live specimens of listed species from this drainage were one individual each of the Minnesota special concern Lasmigona compressa and Ligumia recta, from the Cottonwood and Maple Rivers, respectively. Dead individuals of Minnesota Threatened Pleurobemacoccineum and Actinonaias ligamentinawere found at six sites each (Table 2). The prevalence of dead shells indicates a decline in species richness from historical conditions in most of the streams sampled, but particularly in the mainstem Blue Earth and Minnesota Rivers (Figure 2). The Cottonwood, Maple, and Yellow Medicine Rivers had the highest live species richness in the drainage, with only 25 to 30% of their species represented by dead shells only. The Little Cobb and East Branch Blue Earth Rivers appear to have retained the majority of their historic species, although both richness and abundance in these streams is relatively low (Figure 2). The range of several species has also been reduced as shown by the frequency of occurrence of live and dead individuals (Table 2), including species that are relatively common 5 - SWG Mussel Survey Report, December 2004 elsewhere, such as Amblema plicata, Anodontoidesfertssacianus,Fusconaiaflava, and Lampsilis siliquoidea. No stream in the drainage had an average CPUE of >50 mussels/hr (Figure 3), and the overall average CPUE of the drainage as a whole was 23.0 mussels/hr. This was among the lowest average CPUE of any drainage sampled. Red River of the North Drainage A total of 136 sites from 18 streams and 2 lakes were sampled in the Red River of the North Drainage, and 21,068 live mussels of 13 species were collected (Table 3). This represents the entire compliment of species historically known to occur in the drainage, indicating that no species have been lost (all species were found alive). Relatively few rivers exhibited a loss of species, and typically only one (or no) species were found as dead shells only in any river sampled (Figure 4). All species were found at considerably more sites live than dead, suggesting that they have stable populations in the drainage as a whole. No Minnesota Threatened or Endangered species were known to occur in the drainage prior to the current project, and none were found during the project; but live individuals of three Special Concern species (Lasmigona compressa, Lasmigona costata, and Ligurnia recta) were collected at 42, 26, and 41 sites, respectively (Table 3).