Comparison of sampling strategies for freshwater mussels in wadable streams of northeast Wisconsin, USA

Author / Creator

Weinzinger, Jesse, author

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Summary

Freshwater mussels continue to be one of the most imperiled groups of animals in North America. Management actions for many mussel species today are critical and might have lasting impacts on preve...

Freshwater mussels continue to be one of the most imperiled groups of animals in North America. Management actions for many mussel species today are critical and might have lasting impacts on preventing local, regional, and perhaps even global extinctions. Citizen scientists can play an important role in gathering field data for informed conservation strategies, which are more important today than ever before. This project aims to develop an inexpensive sampling protocol for freshwater mussels that is teachable and effective for engaging citizen scientists. We developed and tested a rapid assessment survey design based on 10 m x 1 m transects. Results describe mussel community structure and microhabitat associations at 32 sites within five watersheds of the Green Bay Hydrological Basin in northeastern Wisconsin, USA. To gauge the effectiveness of the rapid assessment design, we re-surveyed six productive sites, two within the Oconto River, Pensaukee River, and Duck Creek, using the more intensive Wisconsin Department of Natural Resources (WDNR) standard sampling protocol. This method evaluates mussels in 5 m x 5 m grids sub-sampled in smaller 0.25 m x 0.25 m quadrats. Habitat variables were measured at each transect and grid area to explore the effects of watershed and habitat-level factors on the presence of freshwater mussels. Overall, 4,205 records from 20 mussel species were recorded. Observed richness and abundance varied significantly among these sites; highest numbers of mussels were recorded at the Oconto River, whereas no living mussels were present at any sites within the Little Suamico River. The average time among all watersheds to conduct individual surveys was significantly faster (P<0.05) when sampling with the rapid assessment model compared to the WDNR standard protocol. Patterns of species accumulation between the rapid assessment by snorkeling and the standard method of survey were similar. The rapid assessment protocol seems to be a viable method for sampling freshwater mussels in streams such as these, with the advantage that sampling units (10 m x 1 m transects) can be covered by citizen scientists who are unable to invest the time and effort required for the more intensive WDNR standard protocol. Multiple transects (perhaps by different individuals at different times) can be sampled to provide comparable and perhaps even greater stream coverage than the standard protocol. Substrate composition significantly influenced the presence of freshwater mussels. In general, mussels were more likely to occur at stream segments with fine-grained material (sand vs. gravel, boulders, or bedrock) and higher amounts of detritus. The presence of fingernail clams (Sphaeriidae) was a significant predictor for presence of freshwater mussels, while presence of algae and macrophytes were negative predictors. These observations provide valuable insights into formulating quantitative approaches to improve monitoring the distribution and abundance of freshwater mussels in wadable streams of Wisconsin.

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