Juvenile salmonid production in a Lake Erie nursery stream |
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Authors: | D. J. Gordon H. R. MacCrimmon |
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Affiliation: | Department of Zoology, University of Guelph, Guelph, Ontario, Canada NlG 2 Wl |
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Abstract: | Normandale Creek (2531m2) provides spawning and nursery grounds for lake-run rainbow trout, Salmo gairdneri Richardson, brown trout, Salmo frutta L. , and coho salmon, Oncorhynchus kisutch (Walbaum). Upstream movements are significantly correlated with peak stream discharge (P < 0.05). In 1973–1974, 59 adult salmonids constructed 86 nests of which 60% were disturbed by re-use or sand deposition. From a calculated deposition of 90 400 ova, 483 juveniles, 6 cm in fork length ( f.l. ), were resident in the stream when estimates by electrofishing first became valid. Estimated within-stream (i.e. all sections combined) monthly densities of wild juveniles >6 cm f.l. ranged from six to 22 fish (100 m2)−1, and biomass from 1.3 to 3.1 gm−2. The highest within-section biomass was 8.3 gm−2 in November. Additions of hatchery-reared rainbow trout temporarily increased monthly within-stream juvenile density up to 23 fish (100 m2)−1, and biomass to 8.2 g m−2. Density and biomass were positively correlated (P < 0.05) with both instream and bank cover, and biomass negatively correlated (P < 0.05) with gradient. The importance of substratum and flow characteristics on juvenile density and biomass was strongly indicated although not statistically significant. Annual within-section production of juveniles > 6 cm f.l. ranged from 4.79 to 5.93 g m−2 year−1 in Sections III and IV, respectively. Inclusion of calculated probable numbers of fish < 6 cm f.l. increased within-section production from 5.93 to 18.65 g m−2 year−l in upstream Section IV. |
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