|Abstract or Summary
- 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
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