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Okanagan River sockeye spawner enumeration and biological sampling 2005

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by Audy, Natasha
[ Books ] Authors: Walsh, Michelle | Okanagan Nation Alliance--Fisheries Dept. | Public Utility District No. 1 of Douglas County (Wash.) | Okanagan Nation Alliance--Fish Water Management Steering Committee | Natasha Audy and Michelle Walsh Published by : ONA (Westbank, BC, Canada) Physical details: iv, 27 p. ill. 28 cm. Year : 2006 Books Item type : Books
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EXEC. SUMMARY: Sockeye migrated to the spawning grounds from their holding in Osoyoos Lake with the first fish counted on September 13th. Counts from Wells Dam indicated that 53,218 sockeye passed the dam's ladder. The peak counts of live and dead sockeye in the index section (Reaches 1 through 3) is 23,565. This count occurred on October 19th 2005. The date when 10% of the count run is dead which is considered the time when the peak of the run has been passed also occurred October 19th. The peak counts of live kokanee occurred on October 13th with 19 kokanee counted. The peak counts of live chinook occurred on October 16th with 16 chinook counted. the peak count of sockeye redds was 3,281. A peak count of 714 live sockeye were found in the VDS section (Reach 4) on October 22ne. Another high live count occurred on October 13th, this may have occurred because of medium fish visibility and because the crew had changed. The peak count of kokanee occurred on October 13th with 451 counted. A total number of 315 sockeye were sampled this year for length, weight, age (otilith [sic] and scales), and fecundity of 21 green females. Chinook were also sampled non-lethally, this information is to be presented in a different report. Of the 315 sockeye sampled, 289 were sampled by beach seining in the Okanagan River, the remaining 26 were gill netted in Osoyoos Lake. Of the 289 sampled in the Okanagan River, complete results exist for 274 fish. Of the 147 male spckeye sapled, 95.2% were 4-years-old (4-2 Gilbert-Rich) and had average lengths of 50.0 cm. Of the 151 females 97.4% were 4-year-old with an average length of 49.5 cm. The average fecundity of sockeye this year is 2316, which is smaller by comparison to last years 3234 for 4-2 age fish. A number of methods were used this year to estimate the ratio of male to female sockeye and determine the best method for future years. Of the three methods, gillnetting, beach seining and dead counts, we found varied ratios. Ratio of male to females for gillnetting was 1:0.71, and similarly for beach seining a ratio of 1: 0.47 was found. These methods are known to favour the capture of males. In contrast the ratio from the dead counts was 1:1.7 in favour of females. It is recommended that we continue, and preferably increase, our number of dead counts by stream walks to more accurately estimate the sex ratio.

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