The Distribution and Abundance of mussels (Bivalvia: Unionidae) in Lower Big Walnut Creek from Hoover Dam to its Mouth, in Franklin and Pickaway Counties, Ohio

Abstract

Big Walnut Creek in central Ohio once supported a mussel fauna of 40 species, but no systematic study of the mussels of the creek has been done. The objective of the current study was to determine the distribution and abundance of mussels in Big Walnut Creek downstream of Hoover Dam (RM 36.7) to its mouth with the Scioto River. The extant (living and freshly dead shells) and total (extant plus weathered and subfossil shells) mussel communities were determined at 21 sites. Two techniques were used to determine the mussel community at each site: timed searches and transect/quadrat sampling. Shannon-Weiner (H’) values, Jaccard Coefficient of similarity values, and percent extant species were calculated for the mussel communities at each location. Student T-tests were used to determine where either a significant change in community structure occurred based on the metrics listed above.  The mussel communities from Hoover Dam to Whitehall (RM 22.0) had maintained their diversity.  The historic and extant communities in this reach were essentially the same (Jaccard Coefficient = 83% and percent extant species = 78%) with H’ values for this reach not significantly different when comparing the total and extant communities (t = 1.08, p > 0.05).  The communities from RM 22.0 to RM 15.0 (just downstream of Three Rivers MetroPark) had fewer extant species (Jaccard Coefficient and percent extant values of 62% and 36%, respectively), and significantly diminished species diversity (t = 2.35, p < 0.05). Diminished species diversity continued to be expressed downstream (t = 2.48, p < 0.05), with some recovery (Jaccard Coefficient = 67% and percent extant = 42%) as we approached the mouth of the creek.  This improvement may be a result of movement of mussels (as larvae attached to fish hosts) from the Scioto River.