EFFECTS OF SILTATION ON STREAM FISHES AND THE POTENTIAL MITIGATING ROLE OF THE BUFFERING RIPARIAN ZONE

Riparian buffer zones serve several important roles in linking a strea m to its watershed. A main function is controlling the dynamics of sed imentation. This paper documents how siltation impacts fish communitie s and how proper riparian management can mitigate the negative effects of sedimentation. Two studies examined the relation between stream si ltation and fish community characteristics. Community responses to sil tation were poorly described by common structural indices. Community l evel responses to varying siltation were most consistently described b y changes in functional characteristics of the resident fish species u sing a guild-based analysis. Herbivores, benthic insectivores and simp le lithophilous spawners were most sensitive to siltation while other guilds were not. These results were repeatable in both intraregional c omparisons among sites of similar size and character, and in interregi onal comparisons of streams which varied in characteristics besides si ltation. This suggests the index may be useful in separating the effec ts of siltation from other environmental variables. A discussion of bu fferstrip characteristics important in mitigating against, or preventi ng, excess siltation is presented.