The potential of Big Silver as a pilot stream for examining the benefits of low-level nutrient additions was assessed during 1992 and 1993. Water levels, habitat quality, water temperatures and nutrient concentrations were initially assessed in 1992, and more intensively from May to October in 1993. Also in 1993, water transparency, benthic insect density, periphyton chlorophyll A, fish abundance, growth and age were examined throughout the stream. In summer, temperatures (mean, 12-13 deg C), transparency (2-5 m) and the flow regime (mean, 14 m3/sec) were highly favourable to trophic enrichment, as was the amount of prime fish habitat and aesthetic angling pools. Low-level nutrient analyses indicated phosphorus was extremely limited, in contrast to nitrate-nitrogen, in three reaches of the mainstem and two main tributaries during June to September. Rainbow trout were relatively abundant (90-340 fish/km, > 10 cm) above a waterfalls barrier from km 6-15. However, they were growing at only a small percentage of their potential at ambient temperatures; only about 20/km were >20 cm, at age 3+ and 4+. Thus, the Big Silver appears ideally suited for generating a rapid and detectable response to low level nutrient additions, with benefits to resident rainbow trout, winter-run steelhead trout and three species of salmon, and particularly lacustrine migrant trout and char from Harrison Lake. The accessibility and quantity of aesthetic angling waters in the middle and upper reaches should produce a quality resident trout fishery in the lower mainland where stream angling opportunities in summer are in high demand, but are rare.
Toth, B. M., Slaney, P. A.; Godin, T. I.; Ashley, K. I.. 1993. Development of a Premier River Fishery: Big Silver Pre-fertilization Progress 1993. BC Ministry of Environment, Lands and Parks. Fisheries Project Report. RD37
Topic: Fish and Fish Habitats
Keywords: British Columbia
Harrison Hot Springs
benthic insect density
Scientific Name: Oncorhynchus mykiss
English Name: Rainbow Trout
Other Identifier: FPR37
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