Mussel Survey, Summer 2004, Bean Creek Watershed
17 species found, "special concern" in Michigan
Aquatic zoologists with the Michigan Natural Features Inventory (MNFI), a program of Michigan State University, conducted a survey of native freshwater mussels in the Bean Creek Watershed in July and August, 2004.
Fat mucket clam, Bean Creek, August 2004
Freshwater mussels, or clams, are among the most endangered organisms in North America. Mussels are a good indicator of water quality in streams. If sediment or pollutants threaten their habitat, they can’t move far -they can't swim away like fish. A site with many different species of mussels and many individuals indicates good water conditions. Some contaminants, like ammonia in waste runoff, can jeopardize mussel reproduction. The MNFI report notes "ammonia disproportionately affects juveniles versus adults, and could prevent recruitment in the population in spite of an abundance of live adults."
The MNFI team surveyed 9 sites in Bean Creek and three tributaries. They found 17 different species of clams, including 1 species Threatened in Michigan – slippershell mussel; and 2 species of "special concern" – round pigtoe and rainbow mussel. In Michigan, special concern is a designation for rare species needing special protection, before they reach dangerously low population levels. According to the Michigan Natural Features Inventory, should these species continue to decline, they would be recommended for Threatened or Endangered status.
In the mussel survey, MNFI documented two excellent sites - one in St. Joseph Creek, a tributary of Bean Creek in Pittsford Twp; and the second site in lower Bean Creek near Morenci. These two sites included diverse species, with dozens of individual mussels found alive. The mussels of special concern and Threatened were found only in St. Joseph Creek. This tributary was also recently listed as an excellent quality cold water stream by a Michigan Department of Environmental Quality bio-survey.
St. Joseph Creek, with flags marking live mussels;slippershell mussel, Threatened in Michigan
Poorer sites were documented in the middle Bean Creek in Medina Twp, and Lime Creek in Medina Twp, where only a few live clams were found. Two tributaries, which were recently listed as “impaired” because of nutrients and manure discharges, feed into middle Bean Creek and into Lime Creek.
The worst sites were in Silver Creek near Morenci, where no live clams at all were found. Silver Creek is a heavily drained agricultural area, and in some stretches had silt more than 6 inches deep. Recent drainwork upstream had removed vegetation and scoured streambanks. Because clams can’t move very far, they often suffocate under heavy deposits of silt.
“The good news is, some parts of the Bean watershed are in excellent shape,” said Janet Kauffman, volunteer working with the mussel survey. “The bad news is, some streams have very little life left in them. We need to protect what we’ve got and restore what we’ve lost.”
Mussels have complex life cycles -- they need fish to reproduce. Young
larval clams hitch rides on fish and then drop off at new sites to grow.
“Where you’ve got clams, you’ve got fish,” said
Kauffman. “We need to protect these important stream habitats.”
Pink heelsplitter mussel shell, Bean Creek; live Three-ridge mussel, Bean Creek
See more photos of the mussel-surveying, more clams
Mussel species found include:(*marks species of special concern in Michigan; **denotes Threatened)
Fat mucket - Lampsillis siliquoidea
**Slippershell - Alasmidonta viridis
Cylindrical papershell - Anodontoides ferussacianus
Giant floater - Pyganodon grandis
*Round pigtoe - Pleurobema coccineum
Fingernail clams - Sphaeriidae
*Rainbow -Villosa iris
Strange floater - Strophitus undulatus
Wabash pigtoe - Fusconaia flava
Fluted-shell - Lasmigona costata
Three-ridge - Amblema plicata
Pink heelsplitter -Potamilis alatus
Creek heelsplitter - Lasmigona compressa
White heelsplitter - Lasmigona complata
Pocketbook - Lampsilis ventricosa
Fragile papershell - Leptodea fragilis
Spike - Elliptio dilatata