Graduate Degree Type
The North Branch of the Au Sable River is located in the northern lower peninsula of Michigan and is known for prolific hatches of Ephemeroptera (mayflies), Trichoptera (caddisflies), and Plecoptera (stoneflies). Macroinvertebrates play an important role in processing and recycling organic material in rivers and are a valuable food source for trout. In 2018, anglers were reporting catching fewer numbers of brook and brown trout (Salmo trutta and Salvelinus fontinalis). The Michigan Department of Natural Resources (MDNR) determined significantly lower abundance than the historical average. We hypothesized that trout abundances were lower due to a lack of prey availability. Quantitative sampling techniques were used to assess each available substrate and respective aquatic macroinvertebrates throughout the river. Our estimates indicate that coarse woody debris substrates supported the highest abundances with the most individuals/m2. Originally, we hypothesized gravel substrates to have the highest abundances from past literature. We determined community composition and total abundance of macroinvertebrates. We determined that there was a shift in the community composition from mostly Ephemeroptera, to a 1:1 ratio of Ephemeroptera and Trichoptera. Chironomidae was the most abundant taxa of macroinvertebrates on every substrate. Our results suggest that the current macroinvertebrate composition and population would support the current trout population.
Dingman, Paul David, "Comparing Macroinvertebrate Total Abundance and Total Biomass on Five Substrate Types from Upstream to Downstream on the North Branch of the Au Sable River" (2021). Masters Theses. 1031.
Available for download on Saturday, December 16, 2023