Pearly mussels in Unadilla River and tributaries

Shelby Zemken1, Paul Lord1 and Tim Pokorny1

ABSTRACT

Pearly mussels (i.e., Figure 1) are widespread freshwater bivalves important for their particle filtration and status as indicators of water quality. North American bivalves are declining at an alarming rate due to a variety of circumstances. We document the current status of pearly mussels in the Unadilla River and its tributaries in Otsego County, Madison County, and Chenango County, New York. Using tactile and visual searching methods, we report previously unknown distribution patterns, diversity, and range within the Unadilla watershed. Results indicate the presence of mussels is primarily dependent on stream size and physical geology.

Figure 1. Living Elktoe (Alasmodonta marginata) found 21 July 2012.

1 SUNY College at Oneonta. INTRODUCTION Pearly mussels are widespread freshwater mollusks found in lakes, rivers, and streams. Pearly mussels are important to ecosystems in North America and Europe for their ability to process phytoplankton, bacteria, and particles organic matter (Vaughn 2001). These long-lived, slow growing suspension feeders are sentinels of water quality and are sensitive to alterations in the environment including toxic substances and dam introduction (Strayer 1999). The mystery of population decline in North America and Europe has led to increased investments in conservation, biology, and ecology (Strayer 2004). Population and diversity decline is documented in numerous places in the United States. In Clinton River, Michigan, industrial pollution and urban development in the 1950s caused massive mussel kills that have not recovered (Strayer 1980). Gangloff (2009) attributes decreased mussel distribution and population to degrading habitat and upstream urbanization. In the Hudson River of New York, pearly mussel density has decreased significantly since 1992 (Strayer 1999). Research has led to conservation efforts from government agencies. The New York State Department of Environmental Conservation (NYDEC) has listed the following Susquehanna River drainage pearly mussels as Species of Greatest Conservation Need (SGCN): Yellow Lamp Mussel (Lampsilis cariosa), Elktoe (Alasmidonta marginata), Green Floater (Lasmigona subvirdis), and Brook Floater (Alasmidonta varicosa).

METHODS

We surveyed the Unadilla River and several tributaries (Figures 2 and 3), Wharton Creek, Beaver Creek, Tallette Creek, and Center Brook, to document the current status of pearly mussels in the area. Survey locations were chosen by their ease of access from roadways, paths, and DEC fishing access points, using Google™ maps. Search methods were consistent with Strayer and Fetterman (1999). Using a Garmin™ GPS, we recorded survey location start and end points as well as live mussel and dead mussel locations. We assigned a waypoint at the start and end of the search of each location. We assigned a single waypoint to high population densities, single live mussel locations, and SGCN. Using Strayer and Jirka (1997), we identified spent shells on location, bagging, labeling, and saving them for further examination and, some, for voucher specimens. We removed, identified, and captured images of live animals (as in Figure 1) using a digital camera and, then, carefully replaced the mussels back into the substrate.

We categorized data by species of living and dead mussels and appended specific notes for each point describing substrate conditions. Using the data collected, we created maps using ArcMap™ 10 to represent survey locations. We calculated a one-hour catch per unit of effort (CPUE) from the total number of individual mussels collected, the number of searchers, and the timeframes of the collection.

Figure 2. Unadilla watershed location in New York State.

Figure 3. Unadilla River drainage locations surveyed in 2012 for this work.

RESULTS

Principal results of our work are displayed in Tables 1-3, and Figures 4-6. Table 1. CPUE for live pearly mussels in the Unadilla River in 2012 sorted by descending CPUE. Surveys were limited to headwater areas. SGCN indicates species is on current DEC list for species of greatest conservation need.

Common Name Species SGCN Total # CPUE Eastern elliptio Elliptio complanata 226 5.75 Squawfoot Strophitus undulatus 61 1.55 Yellow Lampmussel Lampsilis cariosa 42 1.07 Elktoe Alasmidonta marginata 28 0.71 Triangle Floater Alasmidonta undulata 16 0.41 Eastern Lampmussel Lampsilis radiata 7 0.18 Green Floater Lasmigona subvirdis 2 0.05 Brook floater Alasmidonta varicosa 0 0 Eastern Floater Pyganodon cataracta 0 0 Table 2. CPUE for live pearly mussels in Wharton Creek in 2012 sorted by descending CPUE. SGCN indicates species is on current DEC list for species of greatest conservation need.

Common Name Species SGCN Total # CPUE Squawfoot Strophitus undulatus 52 2.46 Eastern elliptio Elliptio complanata 31 1.47 Eastern Floater Pyganodon cataracta 9 0.43 Elktoe Alasmidonta marginata 3 0.14 Triangle Floater Alasmidonta undulata 3 0.14 Yellow Lampmussel Lampsilis cariosa 0 0 Eastern Lampmussel Lampsilis radiata 0 0 Green Floater Lasmigona subvirdis 0 0 Brook floater Alasmidonta varicosa 0 0 Table 3. Survey totals for all sites in 2012 sorted by descending live mussels found. SGCN indicates species is on current DEC list of greatest conservation need.

Common Name Species SGCN Live Dead Squawfoot Strophitus undulatus 428 145 Eastern elliptio Elliptio complanata 283 657 Yellow Lampmussel Lampsilis cariosa 41 140 Elktoe Alasmidonta marginata 32 13 Triangle Floater Alasmidonta undulata 19 50 Eastern Floater Pyganodon cataracta 11 60 Eastern Lampmussel Lampsilis radiata 7 75 Green Floater Lasmigona subvirdis 2 22 Brook Floater Alasmidonta varicosa 0 1 Figure 4. Location of Live Yellow Lampmussel (Lampsilis cariosa)

Figure 5. Location of Live Elktoe (Alasmidonta Marginata).

Figure 6. Location of Live Green Floater (Lasmigona Subvirdis) DISCUSSION

Comparing Tables 1 and 2, mussel diversity is higher in the Unadilla River. Wharton Creek contains similar populations but harbors less species richness than the Unadilla River. The Unadilla River held the most diversity and richness of the five bodies surveyed in 2012. Tallette Creek and Center Brook were the smallest water bodies surveyed, and we found no live pearly mussels or spent shells in those small waters. Our results in the last two years are consistent with Strayer (1983) in that mussel species richness increases with stream size. Elktoe (A. marginata) was found only in the two largest of the five streams further supporting Strayer’s (1983) conclusion. Our sampling methods did not detect any SGCN in Beaver Creek, Tallette Creek, or Center Brook. Time constraints limited our survey to 23 sites within the watershed. We spent 102 hours of search time in the water and found nine of the 10 previously found living species in the watershed (Lord and Pokorny 2011). We found three of the four SGCN in the sites searched in 2012. Living brook floater (A. varicosa) was the only SGCN that was not found in our 2012 search. Previous searches located brook floater (A. varicosa) in downstream reaches of the Unadilla River (Lord and Pokorny 2011). We saw evidence of continued mussel kills in April; most of the recent dead mussels appeared to have died in 2011 with the exception of a sizeable kill just upstream of the Chenango County Route 25 bridge on the Unadilla River. Those dead mussels appeared to have died in 2010. Our sampling methods were not exhaustive, and pearly mussels could have been overlooked in our surveys. To further analyze mussel populations in this watershed, a reproduced sampling of the sites needs to take place followed by a linear regression analysis of population size to document the status of pearly mussels.

ACKNOWLEDGEMENTS

We thank the Upper Susquehanna Coalition and the Otsego County Soil and Water Conservation District for the financial support facilitating this research. We further acknowledge, with gratitude, Scott Fickbohm’s participation in our April survey.

REFERENCES

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