Importance of Snag Habitat for Animal Production in Southeastern Streams

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Abstract
The Satilla River in southeastern Georgia is a low gradient coastal plain stream with large quantities of woody debris (snags) along its banks. The major objective of this study was to assess the relative importance of the snag habitat as a site of invertebrate production in comparison to benthic habitats. This was accomplished from quantitative sampling of invertebrate habitats, analysis of drifting organisms, and gut analyses of the major fish species. Invertebrate diversity, biomass, and production were considerably higher on snag surfaces than in either sandy or muddy benthic substrates. Although snags represented a relatively small habitat surface (4% of total habitat surfaces), snags supported 60% of total invertebrate biomass and 16% of the production for a stretch of river. Drift densities from night samples collected throughout the year were relatively high, and approximately 78% of drifting invertebrate biomass originated from the snags. Four of the eight major fish species obtained at least 60% of their prey biomass from snags, although all species utilized snags to some extent. Management practices involving wood removal (snagging) from rivers such as the Satilla could be devastating to the invertebrate community and consequently to the several fish species, particularly sunfishes, that depend upon them. The return of woody material to previously snagged streams may help restore their natural levels of animal productivity.

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