The objective of this study was to determine whether juvenile Chinook salmon Oncorhynchus tshawytscha are negatively influenced by the intraperitoneal implantation of acoustic transmitters. We evaluated swimming performance and predator avoidance of juvenile salmonids implanted with acoustic transmitters that weighed up to 6.7% of the fish's body weight in air. Critical swimming speeds (U crit ) of tagged, sham-tagged (surgery but no tag), and control fish were measured in a respirometer to determine tag effects on swimming performance. Swimming performance was similar among treatment groups at 1-d and 21-d postsurgery intervals. Predator avoidance of fish implanted with active tags was evaluated to determine whether tagged fish were impaired by the operation of the tags or predators were attracted to the signals emitted from the tags. Predator avoidance was evaluated by comparing the proportion of each treatment group consumed (active tag, inactive tag, sham, and control) during exposure to piscivorous adult rainbow trout O. mykiss. Surgical implantation of acoustic tags in juvenile fall Chinook salmon did not significantly affect swimming performance. Implantation of acoustic transmitters (active and inactive) did not result in greater predation susceptibility in tagged fish than in untagged fish.

A surface flow bypass takes advantage of the natural surface orientation of most juvenile salmon Oncorhynchus spp. and steelhead O. mykiss by providing a route in the upper water column that downstream migrant fishes can use to pass a hydroelectric dam safely. A prototype structure, called the surface bypass and collector (SBC), was retrofitted on the powerhouse of Lower Granite Dam and was evaluated annually with biotelemetry and hydroacoustic techniques during the 5‐year life span of the structure (1996–2000) to determine the entrance configuration that maximized passage efficiency and minimized forebay residence time. The best tested entrance configuration had maximum inflow (99 m3/s) concentrated in a single surface entrance (5 m wide, 8.5 m deep). We identified five important considerations for future surface flow bypass development in the lower Snake River and elsewhere: (1) an extensive flow net should be formed in the forebay by use of relatively high surface flow bypass discharge (>7% of total project discharge); (2) a gradual increase in water velocity with increasing proximity to the surface flow bypass (ideally, acceleration <1 m/s per meter) should be created; (3) water velocities at an entrance should be high enough (>3 m/s) to entrain the subject juvenile fishes; (4) the shape and orientation of the surface entrance(s) should be adapted to fit site‐specific features; and (5) construction of a forebay wall to increase fish availability to the surface flow bypass should be considered. The efficiency of the SBC was not high enough (maximum of 62% relative to passage at turbine units 4–5) for the SBC to operate as a stand‐alone bypass. Anywhere that surface‐oriented anadromous fish must negotiate hydroelectric dams, surface flow bypass systems can provide cost‐effective use of typically limited water supplies to increase the nonturbine passage, and presumably survival, of downstream migrants.

No abstract

We evaluated the feasibility of using passive integrated transponder (PIT) tags to mark and track individual shorthead sculpins (Cottus confusus). We implanted PIT tags in 80 shorthead sculpins in 2 size categories (60-80 mm and 81-106 mm total length) and in 1 of 2 locations (subcutaneous along the spinous dorsal fin or in the body cavity). We evaluated tag retention, sculpin survival, and net-avoidance behavior for 29 days. We observed no mortality directly attributable to PIT-tag injection at either tagging location. We observed a 38.8% loss rate of dorsal tags and a 2.5% loss rate of body-cavity tags. No change in net-avoidance behavior was observed. We released 97 PIT-tagged sculpins into an artificial stream and monitored them with 3 stationary and 1 portable antenna. Sixty sculpins were detected at least once, and 18 sculpins were detected multiple times with the portable antenna. These results indicate that PIT-tagging within the body cavity is a feasible method for marking and tracking individual shorthead sculpins.