Distribution, Abundance, and Biomass of Freshwater Mussels (Bivalvia:Unionidae) in Lake St. Clair

Abstract

A mussel population survey was conducted in Lake St. Clair with divers using SCUBA to sample at 29 stations throughout the lake. Mean abundance was 2 m~2 and mean biomass was 4.4 g dry wt m~2. Of the 18 species collected, Lampsilis radiata siliquoidea was by far the most abundant, accounting for 45% of all individuals. The age-frequency distribution ofL. r. siliquoidea was dominated by individuals between 9 and 12 years old. In contrast, the second most abundant species, Leptodea fragilis, showed yearly variation in recruitment with no apparent trends in year class strength. Annual production of L. r. siliquoidea was 0.20 g m~2 y~l and the turnover ratio was 0.13. The diversity and composition of mussels in Lake St. Clair appear little changed since the turn of the century, but there are indications that population numbers may be declining in the future.

Long-Term Decline in Freshwater Mussels (Bivalvia: Unionidae) of the Western Basin of Lake Erie

“…1980). However, an abundant and diverse mussel population still exists in Lake St. Clair (Nalepa and Gauvin 1988); this is probably because this lake is continuously flushed with high quality water from Lake Huron and oxygen concentrations remain close to saturation (Herdendorf et al 1986). Although conditions in the western basin have generally improved since the 1960s, as evidenced by a recovering Hexagenia population (Thornley 1985), it may take several decades before these improvements are reflected, if at all, in a recovery of the unionid population.…”

“…The greater "shockwave" of the Peterson, which blows away small organisms at the sediment surface just before impact, should not have any effect on these large, heavy-shelled forms. The effect is minimal even for the shelled but much smaller Sphaeriidae (Flannagan 1970, Nalepa et al 1988. While grab samplers generally underestimate unionid abundances (Haukioja and Hakala 1974, Isom and Gooch 1986, Nalepa and Gauvin 1988, any bias in abun- dance estimates should be reflected similarly in the three surveys.…”

“…The effect is minimal even for the shelled but much smaller Sphaeriidae (Flannagan 1970, Nalepa et al 1988. While grab samplers generally underestimate unionid abundances (Haukioja and Hakala 1974, Isom and Gooch 1986, Nalepa and Gauvin 1988, any bias in abun- dance estimates should be reflected similarly in the three surveys. The coarser mesh screen used by Roth and Mozley to sieve sediments was fine enough to retain all mussels older than 1 year.…”

Biota of Lake St. Clair: habitat evaluation and environmental assessment

“…Leach (unpublished data) found 15 species of Trichoptera in Mitchell Bay . Nalepa & Gauvin (1988) found 18 species of bivalves in the lake with a total biomass of 4 .4 g DW m -2 . Both Hudson et al (1986) and Griffiths (1987) found 10 taxa of gastropods in the lake ; Leach (unpublished data) found 12 taxa in Mitchell Bay .…”

“…Clair have been studied to various degrees by Hiltunen (1971), Hiltunen & Manny (1982), Thornley (1985), Hudson et al (1986), Griffiths (1987) Nalepa & Gauvin (1988) and Leach (unpublished data) . The benthic community is diverse .…”