Graduate Thesis Or Dissertation
 

Effects of stream restoration on macroinvertebrate communities in an Oregon Coast Range system

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/3f462870x

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  • Stream-restoration projects are usually designed to improve habitat quality for fishes. These projects manipulate flow patterns, substrate distribution, and amount and placement of large woody debris. Consequently, they also affect the size and composition of the aquatic macroinvertebrate community. This research evaluates two types of fish habitat restoration: off-channel structures (alcoves) and in-channel structures (log weirs). I compared macroinvertebrate habitats and communities in natural and artificial alcoves in Upper and South Fork Lobster Creeks, Lane Co., and examined the effects of log weirs on in-channel habitat diversity, community composition, drift patterns, and fish consumption of macroinvertebrates. Macroinvertebrate samples were collected from artificial and natural alcoves using hand pumps and D-nets. Within the channel, macroinvertebrates were collected from restored and unrestored reaches with a Hess sampler and using a stratified random sampling scheme. Forty-eight hour invertebrate drift samples were obtained at outlets of log-weir pools. Stomach contents were obtained from coho salmon (Oncorhynchus kisutch) and cutthroat trout (O. clarki) in restored reaches. Although natural alcoves differed from artificial in location within the floodplain, morphology, permanence, and degree of interaction with the stream channel, both alcovetypes provided similar habitats and contained similar macroinvertebrate communities. Average densities and diversity within the alcoves depended on habitat and time of year. Average densities were higher in artificial than in natural. Alcoves contained 29% of species richness within Upper Lobster Creek. Within the stream channel, the diversity of macroinvertebrate habitat was lower in restored than in unrestored sections. Log weirs were associated with reduced taxonomic and functional feeding-group diversity. Composition of drift was not significantly different in restored and unrestored areas; however, drift densities were significantly lower in restored reaches. Diets of fishes in restored areas were composed primarily of organisms produced from outside restored areas. Although in-channel structures may enhance physical habitat for fishes, they may alter or reduce the availability of food for fishes feeding on drifting invertebrates. Recommendations are given for improving the design of stream restoration projects with respect to macroinvertebrates; however stream restoration should focus on restoring whole-system integrity and function, instead of targeting just one or two types of organisms.
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file details ChristensenMJo1996.pdf 2017-08-15 Público Descargar