The Distribution and Abundance of Invertebrates in the Grande Ronde River, Oregon, U. S. A.

Teejay A. O'Rear

The River Continuum Concept (RCC; Vannote et al. 1980) predicts that the composition of invertebrate communities will change gradually in the longitudinal direction with the concomitant, smooth gradation of physical stream features. However, alternative hypotheses incongruous to the RCC have explained the distribution of invertebrates with different factors (e.g., geomorphic stochasticity, tributaries, flow regime, floodplains). The Grande Ronde River in northeastern Oregon and southeastern Washington provides a perfect example for evaluating these different views. In this paper I discuss in depth the RCC and its opposing hypotheses, followed by a summary detailing the important ecological attributes of the invertebrates found in northeastern Oregon. I then present the major abiotic and biotic factors controlling the distribution and abundance of aquatic invertebrates, and provide the expected invertebrate communities to be found in different reaches of the Grande Ronde River. I conclude by reconsidering the RCC in light of the distribution and abundance of the Grande Ronde River's invertebrates.