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The use of flashing strobe lights to deter salmon from dam intakes and other hazardous underwater structures has become an appealing method for reducing salmon mortalities. However, no research has been carried out to determine how strobe light emission could affect the visual system of salmonid fishes. The present study investigated behavioral and ocular system changes after short-term (1-and 5-min) and longterm (3-h) exposure of kokanee and sockeye salmon (the lacustrine and anadromous forms of Oncorhynchus nerka). The onset of the escape response to an overhead shadow was different between treatments. Fish exposed for 1 or 5 min showed a response within 5 and 25 min of treatment, respectively, whereas the 3-hexposed sockeye salmon responded a minimum of 64 h postexposure. All the retinas and lenses examined showed the same characteristics regardless of treatment. We conclude from these results that strobe exposure for 1 min or more induces a state of torpor in sockeye salmon, but exposure for no longer than 5 min does not induce permanent damage to the ocular system.

Excessive fine sediment is a focus of stream restoration work because it can impair the structure and function of streams, but few methods exist for removing sediment in spring-fed streams. We tested a novel method of sediment removal with the potential to have minimal adverse effects on the biological community during the restoration process. The Sand Wand system, a dredgeless vacuum developed by Streamside Technologies, was used to experimentally remove fine sediment from Kackley Springs, a spring creek in southeastern Idaho. We assessed the effects of the Sand Wand on stream physical habitat and macroinvertebrate composition for up to 60 days after the treatment. We documented changes in multiple habitat variables, including stream depth, median particle size, and the frequency of embedded substrate in stream reaches that were treated with the Sand Wand. We also found that macroinvertebrate composition was altered even though common macroinvertebrate metrics changed little after the treatment. Our results suggest that the Sand Wand was effective at removing fine sediments in Kackley Springs and did minimal harm to macroinvertebrate function, but the Sand Wand was not ultimately effective in improving substrate composition to desired conditions. Additional restoration techniques are still needed to decrease the amount of fine sediment.

The distribution of drifting semi-buoyant fish eggs within a river is useful for understanding the ecology of pelagic-broadcast spawning fish. The vertical position of semi-buoyant eggs in the water column is an important parameter describing transport processes for these species. We designed a multiple drift net (five rectangular nets attached to a frame) to vertically divide the water column into stacked horizontal layers to sample drifting semi-buoyant particles. We deployed the multiple drift net gear beside Moore egg collectors in a wadeable channel to sample the vertical distribution of semi-buoyant polyacrylamide gel beads as surrogates for fish eggs in the water column. The vertical distribution of beads was predominantly found in the deeper nets of the multiple drift net gear while the surface nets and Moore egg collectors had fewer beads which is similar to the results in other studies of pelagic-broadcast spawning fish. The multiple drift net gear is a tool that demonstrates the capability to sample the water column under variable flow conditions (depth, velocity and turbulence) for field data on the vertical distribution of drifting eggs (or surrogates). These empirical data can quantify drift patterns of eggs for modeling transport and retention in pelagic-broadcast spawning species.