Individual study: Livestock Grazing, Golden Trout, and Streams in the Golden Trout Wilderness, California: Impacts and Management Implications
Knapp R.A. & Matthews K.R. (1996) Livestock Grazing, Golden Trout, and Streams in the Golden Trout Wilderness, California: Impacts and Management Implications. North American Journal of Fisheries Management, 16, 805-820
This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.
Other biodiversity: Exclude grazers
A replicated site comparison in 1993–1994 in alpine meadows in central California, USA, found more golden trout Oncorhynchus mykiss aguabonita in streams, and more willows on stream banks, in areas of meadows from which cattle were excluded, compared to grazed areas. Ungrazed plots also contained larger willows and more young willows. Fish: More golden trout were found in streams in ungrazed plots, compared those in three of four grazed plots (1.4–2.7 vs 1.3–2.2 fish/m2). Golden trout biomass was higher in streams in ungrazed plots, compared those in three of four grazed plots (20–21 vs 16–18 g/m2). Plants: Ungrazed plots contained more willows than grazed plots (124–246 vs 11–70 trees/125 m of bank), and contained larger willows than three of four grazed plots (140–220 vs 20–70 cm height for largest tree). Young willows less than 20 cm were more abundant in ungrazed plots (16–134 vs 1–8 trees/125 m of bank). Canopy shading over streams was higher in ungrazed plots, for three of four plots (32–35% vs 2–24% shading). Methods: Fences were erected in 1983 and 1991 in two meadows to exclude cattle from a total of three areas. Fish and vegetation were monitored in 125 m sections either upstream or downstream of the exclosures and inside them (a total of seven sites, three ungrazed) in August 1993–1994. Fish were surveyed by electrofishing and vegetation using transects every 5 m along the stream. Areas outside the exclosures were grazed by cattle in July and September.