Marine Survival Time Series

Summary

There were 2,009 steelhead smolts enumerated at the fence in 2016. This is in the 32nd percentile of smolt abundances since 1977 and lower than both the overall mean smolt abundance (3,962) and the mean smolt abundance since 1990 (2,570). Smolts per wild female spawner estimates are 79.8 and 27.1 for the 2011 and 2012 brood years respectively (with 5-year smolts from 2012 brood yet to be sampled next year). The 2013 brood year has produced 24.3 smolts-per-female to date, with four-year-olds to be enumerated in 2017.

 

Marine survival in 2013 was 4.9%, a decrease from 6.0% in 2012. Recent marine survival (2009 to 2013: mean = 5.6%, range = 3.8 - 8.6%) remains higher than historical lows (1.8% in 2002 and 2.3% in 2005). However marine survival estimates remain low compared to the 1977-1990 mean (14.9%).  Partial returns from 2014 (3.0%) are similar to the previous three years, and will be adjusted upwards as the majority of migrants from the 2014 cohort return as ocean-age-three and four steelhead in the 2017-2018 year.

 

Coho smolt (O. kisutch) abundance was 91,582 individuals. This is higher than the overall average of 67,449 smolts (1977-2014) and follows several years of high smolt production that appears to be unrelated to adult spawner escapements.

Figures 

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Steelhead Smolts
Figure 1. Keogh River steelhead smolt abundance enumerated at the lower river fish fence from 1977 to 2016.
Steelhead Smolts
Figure 6. Estimated steelhead smolts per wild female spawner.
Adult Steelhead
Figure 11. Mark-recapture estimates for wild adult steelhead at the Keogh River 1976-2016.
Coho Smolts
Figure 13. Coho smolt abundance at the Keogh River 1977-2016. Line indicates running three-year average.
Coho Adults
Figure 18. Estimated adult coho abundance at the Keogh River 1998- 2015.
Coho Adults
Figure 19. Estimated coho marine survival at the Keogh River 1998- 2015.
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Full Report

J.M.S. Harding.  2016.  Adult steelhead trout (Oncorhynchus mykiss) and salmonid smolt migrations at the Keogh River, BC, during winter 2015 and spring 2016.  BC Ministry of Forests, Lands and Natural Resource Operations, Victoria, BC.

©2017 by Keogh River Research

Steelhead Smolts

Figure 6. Estimated steelhead smolts per wild female spawner.