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Fraser River Action Plan 3rd Research Workshop Introduction Human Impact on Aquatic and Riparian Ecosystems in Two Streams of the Thompson River Drainage R.L. Vadas CWS/NSERC Research Chair in Wildlife Ecology Simon Fraser University In order to determine biological indicators of deforestation, aquatic and riparian fauna and habitat were sampled in two agriculturally impacted river valleys of the southern interior. The mainstems of the Salmon (SR) and Nicola (NR) rivers were examined during the fall of 1994 for riparian vertebrates (identified by sight and sound), riparian invertebrates (caught with a sweep net and aquatic emergence traps), drift and benthic invertebrates (respectively caught with drift vs. Hess nets), and aquatic mega-invertebrates and fishes (caught with seine nets and an electroshocker). Whereas vertebrates were indentified to species, invertebrates were identified to higher taxonomic levels (usually order, suborder or family). Riparian and aquatic habitat were sampled to determine the relative abundance of habitat types, which included five lower riparian floral substratum categories, five aquatic-lateral habitat types and seven aquatic-hydraulic categories. For both streams, middle and lower river sites were examined to make triplet-wise comparisons among sites of differing upper riparian intactness. The habitat types included forested (FO), semi-forested (SF), shrubby (SH), and grassy (GR); FO-SF-GR and SF-SH-GR comparisons were made in SR vs. NR, respectively. Riparian and Aquatic Habitat Habitat diversity, which was compared in the middle and lower sections of the two rivers (four comparisons), was often highest at semi-forested sites. Treed sites showed the highest habitat diversity in the lower riparian zone, via greater abundance of woody vegetation. Aquatic habitat diversity along the lateral gradient was also hoghest at treed sites of SR, reflecting the greater abundance of edge habitats (backwaters and/or side channels), whereas NR trends were ambiguous. Semi-forested sites showed the highest hydraulic diversity because pool, run, and riffle habitats were all abundant, whereas diversity differences among other floral habitat types were inconsistent. The two most sedimented sites (i.e., the uppermost reaches sampled in SR and NR), were relatively low in aquatic habitat diversity. Riparian Vertebrates Riparian-vertebrate assemblages differed among sites. Higher species diversity and percent abundance of agricultural species were seen at less-forested sites, whereas logging-sensitive, cavity-nesting birds showed highest percent abundance at semi-forested sites. Trends for species richness were inconsistent across rivers. Classification of species into floral habitat-use guilds, as defined in the literature for western North America, showed that: • generalists were usually dominant; and, • treed sites (FO-SF) did not always show greater abundance of treed guilds; and lesser abundance of unforested guilds. Guild classification based on the SR-NR data set yielded two ‘treed’ habitat-use guilds (i.e., ‘forested’ (one bird species) and ‘semi-forested’ (one amphibian and three bird species). There were also five ‘generalist’ bird species and two ‘unforested’ guilds of birds, including ‘shrubby-grassy’ (one species) and ‘grassy (two species). Micro- and Macroinvertebrates Page 247
Fraser River Action Plan 3rd Research Workshop Invertebrate assemblages also differed among sites, taxonomic diversity generally being higher for more-forested conditions. Riparian invertebrates were most diverse at treed sites in three of four comparisons, the general order was FO > SF > SH & GR. Drift invertebrates were also most diverse at treed sites in three of four comparisons; the general order was SF > FO > SH & GR. Benthic invertebrates showed the highest diversity at forested sites in SR, but differences among less forested sites were inconsistent. The percent abundance of terrestrial invertebrates was inconsistent across samples; whereas benthic samples showed highest values at grassy sites, drift samples showed lowest values for grassy (SR) or shrubby sites (NR). In contrast, invertebrate density in the river was generally higher for agricultural (grassy) conditions. Drift invertebrates were more dense at grassy sites in three of four comparisons; the general order was GR > FO > SF & SH. Benthic invertebrates were also more dense at grassy sites in SR, but differences among NR sites were inconsistent; the general order was also GR > FO > SF & SH. Based on literature trophic data, herbivorous aquatic invertebrates were generally more dominant for unforested conditions. Drift invertebrates showed higher herbivore: predator (H:P) ratios at shrubby and grassy sites, whereas benthic invertebrates showed highest values at grassy sites. Pollution indices gave ambiguous results. The percent abundance of large-bodied, pollution-sensitive taxa, namely mayflies, stoneflies and caddisflies (EPT), was partially consistent across sites. Semi-forested sites had the highest values in SR benthic samples and SR-NR drift samples, whereas % EPT was highest for grassy conditions in the NR benthos. Pollution indices that required assignment of points based on pollution tolerance gave inconsistent results across rivers and samples (drift vs. benthos). Floral guild classification based on the SR-NR data set yielded a ‘treed’ guild (three aquatic taxa), a ‘generalist’ guild (eight aquatic, two semi-aquatic, and three terrestrial taxa), and an ‘unforested’ guild (one semi-aquatic and four aquatic taxa). Aquatic insect larvae and pupae and microcrustaceans were in the treed and/or unforested guilds, suggesting that both micro- and macroinvertebrate taxa are useful as agricultural indicators. Aquatic Megainvertebrates and Fishes Nekton assemblages also differed among sites. Mesonekton diversity (megainvertebrates and fish larvae) and percent abundance of fish larvae (relative to megainvertebrates) were higher for treed sites in SR, wheras NR showed lowest values for shrubby conditions. Larger fishes were most diverse at semi-forested sites in three of four comparisons, but differences among other floral habitat types were inconsistent. Trends for percent abundance of pollution-sensitive shiners (relative to larger fishes) and fish species richness were ambiguous; redside shiners were relatively rare at semi-forested and grassy sites. Nekton density was often lowest for agricultural (grassy) conditions. Mesonekton showed highest density for semi-forested sites in SR, whereas wooded sites (SF-SH) had the highest densities in NR; grassy sites were consistently lowest. Trends were inconsistent for larger fishes; grassy sites showed lowest values in middle-river sections, whereas semi-forested sites showed lowest values in lower-river sections (where grassy sites showed intermediate densities). Floral-guild classification based on the SR/NR data set were done on multi-specific fish families and individual nekton species. The family analysis yielded two wooded guilds (i.e., ‘generalized-forest’ [salmonids] and ‘partially-wooded’ [minnows]. Two families were ‘generalists,’ namely suckers and sculpins. The species analysis yielded three wooded guilds (i.e., ‘treed-shrubby’ [four fish species], ‘semi-forested’ [one megainvertebrate taxon], and ‘generalized-SF’ [two fish species]). There were four unforested guilds (i.e., ‘generalized-shrubby’ [one megainvertebrate taxon], ‘shrubby’ [one fish species], ‘shrubby-grassy’ [two fish species], and ‘grassy’ [three fish species]). Because aquatic insect nymphs and fishes were in the treed and unforested superguilds, both taxa appeared to be useful as agricultural indicators. Page 248
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PROCEEDINGS 3rd RESEARCH WORKSHOP F
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TABLE OF CONTENTS Participants ....
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Development of a Citizen’s Monito
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Fraser River Action Plan 3rd Resear
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SESSION 1 PULP MILL EFFLUENT ISSUES
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SESSION 4 AGRICULTURAL ISSUES
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