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Abstract

Abundance patterns of aquatic macroinvertebrates that utilize coarse particulate organic matter as a food source are important indicators of non--point source pollution associated with silviculture activities. This group, referred to as shredders, typically decreases in abundance as its food source—primarily leaves—is removed from the ecosystem. We tested whether larval biomass of the crane fly Tipula, a common member of the group, was an effective estimator of shredder abundance. Additionally, we used regression analysis to test whether the length to dry mass relationship of Tipula differed among geographic regions, between seasons, and between years. Results did not indicate significant differences in the relationship among these variables. Thus, we concluded that a general length to dry mass relationship was appropriate for Tipula in streams of the Interior Highlands. Our results were similar to those reported from North Carolina and Virginia. Tipula biomass was positively correlated with the total richness of the macroinvertebrate assemblage, a common measurement of stream quality, but was not correlated with the numerical abundance of the shredder functional feeding group. Thus, we concluded that Tipula biomass would not be an effective surrogate for whole assemblage metrics in biological assessments.

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