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Students present two-year river ecology project showing rusty crayfish presence but moderate diversity
Summary
Students and a presenter described a two-year river ecology study using hand sampling and electrofishing; findings showed abundant rusty crayfish in riffle and run habitats, no invasive species at the furthest upstream site, and moderate Shannon diversity scores.
Students from the district presented results of a two-year river-ecology project, and the presenter, identified in the transcript as Stuart, described field methods and preliminary findings that suggest invasive rusty crayfish are present in riffle and run habitats but had not reached the furthest upstream site sampled.
Why it matters: The presence and upstream movement of rusty (invasive) crayfish could alter aquatic communities and reduce biodiversity; students used both hand-sampling and, in the second year, electrofishing to collect fish and crayfish specimens to measure species counts and diversity indices.
The presenter described methods: teams sampled matched square-foot areas in riffle and run microhabitats, flipping rocks and sieving sediment for invertebrates in year one, then added electrofishing in year two to collect fish specimens for comparison. Students recorded counts by species and used a Shannon diversity index (a natural-log based measure) and an equitability index to evaluate diversity; values in the twos indicated moderate diversity.
The presenter said the data mirrored last year's results: rusty crayfish dominated the runs and riffles but were less common upstream. No invasive species were recorded at the furthest upstream site sampled. The presenter and board members discussed next steps, including additional days in the field to better pinpoint upstream limits and potential eradication strategies, though presenters cautioned eradication would be labor intensive.
Students who participated presented photos and counts and helped answer board questions; the presenter thanked the board for support and said he hopes to continue the study next year. Board members commended the students and suggested returning with updated results at a future meeting.
The presentation is recorded as part of the board meeting public record; the board did not take a formal vote on the study but publicly thanked the student group and the presenter.
