Manipulative field enclosure/exclosure experiments were carried out in Carnation Creek, British Columbia to determine if patch-restricted coho fry (Oncorhynchus kisutch) affected the distribution and abundance of macroinvertebrates in the drift or benthos. Enclosures/exclosures with standardized substrate, detritus, and current velocity were buried in the streambed during the low discharge period, and four treatments used: no fish, ambient fish, double ambient fish, and quadruple ambient fish densities. Density, biomass, and size distribution of macroinvertebrates in the drift were not significantly affected by fish density treatment. Additionally, with the exception of large swimming larvae of Ameletus sp. and Baetis tricaudatus, macroinvertebrate density, size distribution, and biomass in the benthos were also not significantly affected by fish density treatments. Thus, despite fish densities being increased from two to four times above ambient patch levels, patch-restricted coho fry had little measureable effect on macroinvertebrate distribution and abundance in Carnation Creek during the low discharge period of August to September.
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Joseph M. Culp (1986) studied this question.