Southeast Alaska steelhead studies, 1998

Alternate Titles

• Situk River weir and surveys of regional index streams.
• Federal aid in sport fish restoration (Alaska)

Description

Regionwide monitoring of trends in steelhead Oncorhynchus mykiss spawning abundance in twelve index streams in Southeast Alaska was continued in 1998. Each of these index streams was surveyed weekly for steelhead abundance by a two- or three-person team using snorkel gear during April and May 1998. Peak steelhead abundance in these 12 systems declined 34% from 1997 to 1998. The Situk River produces the largest run of steelhead in Southeast Alaska. Between 4 May and 12 July 1998, 5,786 steelhead were counted as they emigrated downstream through a weir located 1.2 miles upstream of the Lower Landing on the Situk River. This count indicated a decline of 21% in the steelhead escapement from 1997. Float surveys on the Situk River downstream of Nine Mile bridge counted a maximum of 3,282 steelhead, 57% of the total counted at the weir. Situk River steelhead abundance survey counts and conditions were compared to weir counts during 1994 to 1998. Float survey counts averaged 78% (SD = 14%) of the steelhead counted upstream of the weir under the best survey conditions. Total river surveys (Situk LakeLower Landing) conducted under the best observation conditions, during 5 May through 21 May, averaged 73% (SD = 10%) of the annual weir count for these years. Lower Situk River float count surveys conducted under the best observation conditions, during 16 May through 27 May averaged 63% (SD = 10%) of the weir counts. The average total lengths of female and male steelhead from the Situk River were 776 mm (SE = 2) and 745 mm (SE = 4), respectively. Of the 1,136 fish sampled, 38 or 3% were =36 inches (914 mm) in total length; 21 of these were female and 17 were male. Length composition of samples taken early in the evening was similar to those taken late in the evening, but there were differences in sex composition.

Subjects

Series Statement

• Fishery data series -- no. 99-33.

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