Date of Award


Publication Type

Master Thesis

Degree Name



Biological Sciences


ecological condition, macroinvertebrates, sampling methods, stream


Jan Ciborowski




Evaluating the ecological of condition streams can be accomplished by assessing the community composition of macroinvertebrates whose differential sensitivity to perturbations reflect the conditions of their habitat. Two sampling protocols used to assess Ontario streams (Canadian Aquatic Biomonitoring Information Network (CABIN) (employed across Canada), and the Ontario Benthic Biomonitoring Network (OBBN)) recommend using D-framed dip nets (D-nets) to effectively assess streams, most of which have rapid flow and either hard bottoms or coarse sediment. I assessed the relative effectiveness of D-nets and Petite Ponar grabs to sample macroinvertebrates during the summer in 19 southwestern Ontario clay-plain streams, which typically have fine sediments and slow or nondetectable velocity. The two methods identified similar community composition; but the D-net captured more aquatic invertebrates and greater family richness than the Petite Ponar grabs. Although both protocols recommend processing and subsampling samples using a Marchant Box I found that sorting up to 300 animals per size fraction of a series of nested sieves took approximately half the time, yielded significantly greater richness estimates and reduced the marked overestimates of abundance sometimes observed when subsampling to fixed counts with the Marchant Box. Effective bioassessment of southwestern Ontario clay plain streams can be achieved by collecting 2-3 jab-and-sweep D-net samples from glide region in late April-early May and processing subsamples separated into size fractions using nested sieves. Most streams sampled were dominated by tolerant organisms producing HBI scores ranging from 7-8. Tolerance scores for streams in Essex County were significantly higher than scores for streams in the Lower Thames Valley conservation region.