Chinook Escapement Monitoring

Chinook Escapement Monitoring

Helicopter used for Chinook salmon monitoring over the Nechako River.Since 1988, Nechako River Chinook have been monitored annually in relation to the Conservation Goal (NFCP Chinook Escapement Report). Spawner enumeration has been carried out using Area-Under-the-Curve (AUC) methodology since 1988; prior to then, spawner counts were obtained by DFO Fishery Officers using less rigorous methods.

The AUC method uses both periodic helicopter counts of spawner numbers during fall Chinook spawning and estimates of the time female spawners spend on the redd (residence time) in the calculation of the spawner population size.

Refinements to escapement monitoring were implemented based on sensitivity analysis of the estimates to the frequency and timing of helicopter overflights, number of locations for residence time estimates and the use of a long-term mean residence time estimate.

During 2015 the Technical Committee decided to transfer the responsibility for adult Chinook monitoring to Fisheries and Oceans Canada as part of their routine stock assessment activities in large BC Chinook rivers. The rationale was documented in a report that reviewed trends in Nechako Chinook adult escapement over 26 years of NFCP monitoring. The evaluation considered 2 monitoring periods: 1) 1988 - 2002, covering the data set analysed during the 2005 Technical Data Review (TDR), and 2) 2003 - 2014. The intent was to determine whether the conclusions in the TDR remained valid by comparing the respective escapements in the two periods. Results showed that Chinook escapements in the recent period increased on average by 61% compared to the earlier period, thus supporting the earlier conclusions contained in the TDR.

In view of the documented increase of the Nechako Chinook population between 2005 - 2014, the Technical Committee concluded that adult Chinook escapement monitoring could be further streamlined. A decision was taken to reduce the helicopter overflight frequency from 5 flights to 2 flights. It is intended that this survey design be followed for the foreseeable future.

More is available regarding Nechako Chinook and sockeye salmon conservation in the Nechako River.