Report on a reexamination of the mussels of the Little Miami River and it major tributaries: Final Report, end of year two Michael A. Hoggarth and Marshall H. Goodman Department of Life and Earth Sciences Otterbein College Westerville, Ohio 43081 Final Report 15 November 2007 Executive Summary During the summers of 1990 and 1991 Hoggarth (1992) examined the mussels of the Little Miami River system by sampling mussels at 105 sites throughout the watershed. The objective of the current study was to reexamine the best of those sites in order to determine the existing mussel resources in the watershed. A total of 26 sites were sampled in the mainstem, 10 sites were sampled in the East Fork, three sites were sampled in Todd’s Fork, and two sites were sampled in Caesar Creek. Most of these sites were sampled in 1990/91. During that original study, Hoggarth (1992) noted that the mussel fauna in the river was at a crossroads: one third of the 35 extant species were in no danger of being lost, one third were in danger of being extirpated, and one third were represented by non-viable populations. He warned that if water quality and habitat quality were allowed to suffer, the mussel fauna would suffer as well. The current study confirms these earlier dire warnings. The mussel faunas of all four streams examined during this study have declined. The upper mainstem (headwaters) has lost most of its original diversity including headwaters species of mussels not found in the lower reaches of the river. The middle section of the mainstem was degraded in 1990/91 and it has not improved. The lower reaches have more diverse mussel faunas, but much of this diversity is due to the introduction of species of mussels that use the freshwater drum as host. These species have been increasing in numbers and distribution throughout the state. The East Fork has experienced similar species loss and species replacement. Todd’s Fork and Caesar Creek have essentially lost all of their mussels (at least from the lowermost five kilometers of Todd’s Fork and from the dam to the mouth of Caesar Creek). Both of these reaches supported good mussel faunas in 1990/91. A Mussel-IBI constructed in part to compare the historic community structure with the recent data demonstrates a nearly 10 point (one fifth the value of the index) decline from 1990/91 to 2006/07 in the mainstem and the East Fork and a 20 point decline in Todd’s Fork and Caesar Creek. Water quality problems appear to be the most significant problems threatening the mussels in the mainstem and the East Fork, while competition with introduced mollusks (Corbicula fluminea and Dreissena polymorpha) appear to have negatively impacted the mussels in Caesar Creek, and habitat quality (especially excessive siltation) appears to be the most significant factor limiting the mussels in Todd’s Fork. Still there were some positive discoveries during the current study. Two species of mussels thought to be extirpated from the system (Hoggarth, 1992) were found alive in the mainstem (Megalonaias nervosa and Actinonaias ligamentina). The former species is an Ohio Endangered Species. In addition, Quadrula nodulata (Ohio Endangered Species) was found in the mainstem and the East Fork. In addition to these discoveries, some reaches of the mainstem and the East Fork have retained their mussel diversity and either scored as well or better on the Mussel-IBI than they did in 1990/91. The most significant recommendations made in this report are to fix the sedimentation issues in Todd’s Fork and improve water quality throughout the system. The midsection of the mainstem was unsuitable for mussels in 1990/91 and it still is today. Improving water quality will give the mussels in the lower reach of the mainstem access to reaches in the upper watershed as well as the tributary streams. Providing connectivity among the mussels and fish will improve both resources.
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