| Abstract/Description or Keywords |
From 1988 to 2003, adult Chinook salmon (Oncorhynchus tshawytscha) were enumerated in both the Nechako and Stuart rivers. The number of Chinook salmon returning to spawn in the Nechako River each year is a key measure of the Conservation Goal identified in the 1987 Settlement Agreement (Anonymous 1987). The Stuart River portion of this study provided a control Chinook population as Stuart River flows are unaffected by flow regulation. Following 16 years of study, the Stuart portion was discontinued in 2003 as data gathered during the time series failed to show any appreciable deviation in results when compared to the Nechako River data. Chinook salmon continue to be enumerated on the Nechako River to gauge the returning population against the Conservation Goal identified in the 1987 Settlement Agreement (Anonymous 1987). Since 1988 the escapement of Chinook salmon to the Nechako River has been estimated based on aerial counts and residence time observations using standardized methodology. Residence times were estimated annually from 1989 to 2004, with estimates varying from 8.9 days in 1994 to 12.5 days in 2004 and a mean of 10.6 days (SD=1.03). Due to the relatively small variation in residence time estimates observed since 1988, the Nechako Fisheries Conservation Program Technical Committee (NFCP TC) decided to apply an average mean residence time of 10.6 days for AUC calculations for years when residence time studies were not conducted. A residence time study was also conducted in 2009, with an average value of 9.8 days During the reporting period of 2004-2012, peak total live counts varied between 1,123 and 4,608 fish. Applying Area-Under-the-Curve methodology yielded annual escapement estimates of 1,021 to 7,039 fish. During the 2004-2012 time series, annual escapements did not reach the lower limit of the 1987 Settlement Agreement target population range of 1700-4000 fish in two years (2007 and 2012), was within the target range twice (2005, 2009) and exceeded the range 5 times. The mean estimated Nechako Chinook escapement of 4,021 fish is slightly greater than the upper limit of the 1987 Settlement Agreement target escapement range. |
