Report on a reexamination of the mussels of the Little by armedman1


									    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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