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Abstract
The River Continuum Concept (RCC) is an overarching paradigm in stream ecology that makes predictions regarding the trophic status, fish community, and invertebrate community of rivers based on stream order. The RCC, however, ignores the role of adventitious streams, which are low-ordered tributaries to larger rivers. I examined the fish and invertebrate community and habitat of the fifth-order mainstem, two second-order adventitious tributaries to the mainstem, and three second-order headwater streams of the Pine River (Alcona County, Michigan) from May through August 2000. Fish species richness generally increased with increasing stream order and was higher in the adventitious streams than in the headwater streams. The fish species composition of adventitious streams was more similar to the mainstem than to the headwater streams, but showed greater month-to-month variability than either the mainstem or headwater streams. Adventitious streams had a preponderance of tolerant fish and had lower scores for invertebrate Indices of Biotic Integrity, suggesting that water quality was impaired in these streams. Habitat conditions in headwater and adventitious streams were similar except adventitious streams were generally warmer. These results suggest that factors in addition to stream order, such as stream connectivity and temperature, are important determinants of stream fish assemblage.
