Determination of Salmonid Smolt Yield with Rotary-Screw Traps in the Situk River, Alaska, to Predict Effects of Glacial Flooding

Abstract

Hubbard Glacier is expected to dam Russell Fiord and cause glacial flooding of the lower 20 km of the Situk River near Yakutat, Alaska. To determine probable effects of the flooding on juvenile salmonids Oncorhynchus spp., two rotary‐screw traps were used to estimate smolt yield inside and outside the predicted flood zone. Traps were fished from April to mid‐August 1990: one at the predicted upstream limit of flooding and the other 3 km upstream from the river mouth. Every week, a sample of each salmonid species was tattoo‐marked and released 1 km above each trap; recaptures were used to expand catches to estimate smolt yield. Trap efficiency ranged widely among species, from 3% for steelhead O. mykiss to 24% for chinook salmon O. tshawytscha. Estimated total smolt yields were 900,000 sockeye salmon O. nerka, 213,000 coho salmon O. kisutch, 67,000 chinook salmon, and 26,000 steelhead; only sockeye salmon (34% of this species' smolts) originated in the flood zone. Estimated mortality between traps was 8% for coho salmon, 13% for chinook salmon, and 16% for sockeye salmon. Our study demonstrated that upriver and downriver rotary‐screw traps and mark‐recapture techniques can partition smolt yield, but mortality between traps and mark recognition must be considered.

Kootenai River Fisheries Investigations; Rainbow and Bull Trout Recruitment, 1999 Annual Report.

“…We used a rotary-screw trap to capture juvenile trout out-migrating from Boundary Creek from March 16 to August 23, 1999(Thedinga et al 1994Kennen et al 1994). The trap was located in the SW ¼ of Section 11, Township 65 N., Range 2 W, just downstream of the United States Geological Survey (USGS) gauging station.…”

“…These fish were then marked with a caudal clip, moved 250 m upstream of the screw trap, and released to estimate trap efficiency (Thedinga et al 1994). All other species were weighed and measured and released downstream of the trap.…”

Emigration of Natural and Hatchery Naco x (Chinook salmon; Oncorhynchus tshawytscha) and Heeyey (Steelhead; Oncorhynchus mykiss) Smolts from the Imnaha River, Oregon from 5 October 2006 to 21 June 2007, Annual Report 2007.

“…Solutions Inc., Corvallis, Oregon, was used to capture migrating salmonids (Figure 3). Similar traps have been used to capture migrating juvenile salmonid species in New York and Alaska (Kennen et al 1994;Thedinga et al 1994). The screw trap used in the spring and fall consists of a 2.1 m diameter-trapping cone supported by a metal A-frame and two six-meter pontoons that provided flotation.…”

Investigations into the Early Life-history of Naturally Produced Spring Chinook Salmon and Summer Steelhead in the Grande Ronde River Basin, Annual Report 2001.

“…Variance of each weekly $ N was estimated by the one-sample bootstrap method (Efron and Tibshirani 1986;Thedinga et al 1994) with 1,000 iterations. Preliminary analysis indicated that when there were less than 10 recaptured fish in a week, bootstrap variance estimates were greatly expanded.…”

“…Variance for at each trap during systematic sampling was estimated by the onesample bootstrap method (Efron and Tibshirani 1986;Thedinga et al 1994) …”