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of all sites but Elkhorn and Pipe Creek. There were distinctive differences in the abundance of insects by order at the regulated and control sites. In general, stoneflies,caddisflies and beetles were found in much higher numbers in the Fisher River. Mayflies were found in qreater numbers in the Kootenai near the dam but the two downstream sites were more comparable to the Fisher River. Annual mean biomass (x cc/m2) was not significantly different in the two rivers (Table 2, Figure 4). An ANOVA test of monthly biomass means at the four stations generally did not show significar+ differences. The only pairwise comparison of sites which was significa:;tly different for monthly biomass mean was between the Elkhorn and Pipe Creek stations (p<.05). Monthly mean biomass for each insect order (cc/m2) at each station are given in Appendix 2. A two-way ANOVA which incorporated both sites and sampler types was run using density and biomass data for four seasons (October, January, March and July). Density (number/m2) was significantly different between sampler types in all months. This may have been related to the difference in mesh size between the kick (150 ~m) and Knapp-Waters (472 ~m) samplers more than to the design of the samplers. Biomass (cc/m2) differences were not significant between sampler types in any month except July. These differences relate only to overall density and biomass. One might expect species differences in catchabil ity between the different sampl er types. Percent composition was calculated from the annual density and biomass means (Tables 1 and 2). The annual percentages by numbers and volumes were averaged in the Density-Biomass Index (Table 3, Figure 5) to give an overall mean comparison of the sampling stations. The percent composition of each insect order is presented for density (Table 4) and biomass (Table 5) data for each sample date. Samples for the Fisher River during May and June were not quantitative, since these collections were made during spring runoff conditions and were not included in the calculation of the annual means. A one-way ANOVA test was run on transformed (arcsin 1% composition) data of the present composition by insect order at the four stations. Densities by insect order were significantly different (P<O.05) for the following pairwise comparisons between sampling sites: Order Paired Sampling Sites Dunn vs Fisher, Elkhorn vs Fisher, Pipe vs Fisher, Dunn vs. Pipe, Elkhorn vs Pipe Dunn vs F i she r , Elkhorn vs Fisher, Pipe vs Fisher Dunn vs Fisher, Elkhorn vs Fisher, Pipe vs Fisher, Dunn vs Elkhorn, Dunn vs Pipe Ephemeroptera (Mayflies) Plecoptera (Stoneflies) Trichoptera (Caddisflies) -9-