Differences in brown trout (Salmo trutta) production among contiguous sections of an entire stream

In South Branch Creek, a limestone stream in SE Minnesota, total trout densities increased from 1600/ha in 1980 to 2300/ha in 1982. There were large and significant differences in density among sections; relative differences among sections, however, were nearly constant over the 3 yr. Mean annual standing stock and production increased over the 3 yr from 90 and 100 kg/ha, respectively, in 1980 to 150 to 174 kg/ha, respectively, in 1982. Standing stock and production also differed significantly among sections, but relative differences among sections were fairly constant. The most productive sections had standing stocks and production rates 1.5-2 times higher than the least productive sections. Year strongly influenced growth rate, with growth in 1982 almost double that in 1981, but growth rates did not differ significantly among sections. Habitat differences among sections appeared to regulate density, size, standing stock and production. Factors that affected the entire stream influenced recruitment and growth. -from Authors