Past research has focused on the effects of sediment action on stream morph
ology and the habitat of brook trout Salvelinus fontinalis. Throughout the
Appalachian Mountains, the watersheds in which brook trout reside are bring
influenced by timber harvesting and related road construction. Although th
ese streams may have gradients steep enough to prevent deleterious sediment
deposition, elevated stream turbidity is nevertheless common. An understan
ding of the sublethal effects of increased sedimentation and turbidity is e
ssential to further our knowledge of the effects of increased sediment load
ing on stream fish production and how these effects differ among species li
ving in sympatry. The specific objectives of this study were to determine (
1) the effects of turbidity on the reactive distance of brook trout, (2) ho
w turbidity affects encounter rates between brook trout and their prey, and
(3) how turbidity affects brook trout's foraging success. We used videogra
phic techniques to study brook trout foraging behavior in an artificial str
eam. Three brook trout were tested during each sampling period, creating a
competitive situation under which a more accurate measure of reactive dista
nce could be made. Treatment turbidity levels ranged from 0 to 43 nephelome
tric turbidity units. The reactive distance of brook trout decreased curvil
inearly with increasing turbidity. The probability of a brook trout's react
ing to a given prey item was correlated with reactive distance and also dec
reased with turbidity. However, turbidity had no influence on the probabili
ty of attack given a reaction, the probability of capture given an attack,
or the probability of ingestion given capture. In natural streams, inverteb
rate drift densities typically increase with turbidity as Rows increase, bu
t this increase may not be enough to compensate for the decreased ability o
f brook trout to detect drifting prey.