The Influence of Riparian Forest Characteristics on Terrestrial Invertebrate Input and Brook Trout Diet in Headwater Streams

The importance of terrestrial invertebrates has as an energy subsidy for stream dwelling salmonines has been acknowledged widely.  However, reliance on this prey source has been shown to vary both spatially and temporally.  In addition, relatively little research has been conducted to examine the connection between riparian vegetation and terrestrial invertebrate input.  We investigated the influence of riparian forest characteristics on terrestrial invertebrate infall in headwaters streams of western Maine and northeastern New Hampshire across a gradient of deciduous and coniferous stand dominance.  Additional riparian vegetation metrics included understory cover, ground cover and canopy closure.  We also assessed the availability of terrestrial and aquatic insects and their relative contributions to brook trout diet.  We collected terrestrial invertebrates using pan traps and aquatic insects using drift nets.  Brook trout stomach contents were collected by gastric lavage.  Sampling was conducted during three time intervals: late May/early June, mid-July and late August.  The results of this study should be useful in making recommendations regarding management of riparian areas to benefit brook trout populations.