Salmon & Steelhead Recovery Tracker

Siltcoos (Independent Population)

Analyses of viability criteria (adult abundance, persistence, productivity, distribution, diversity and habitat) are presented for each independent population. Trends in adult abundance and habitat condition are presented for dependent populations.

Oncorhynchus kisutch

Abundance

Annual estimates of the abundance of naturally-produced spawners for each population.

Spawning Year Nat. Origin Spawners 95% Confidence Interval Abundance Goal Proportion of Goal
2016 2,421 22,700 11.0%
2015 1,558 11,800 13.0%
2014 7,178 25,900 28.0%
2013 3,797 22,700 17.0%
2012 3,945 22,700 17.0%
2011 6,354 25,900 25.0%
2010 7,678 25,900 30.0%
2009 5,197 25,900 20.0%
2008 3,873 22,700 17.0%
2007 1,447 11,800 12.0%
2006 5,452
2005 4,364
2004 7,998
2003 6,628
2002 4,636
2001 5,104
2000 3,835
1999 2,756
1998 3,122
1997 2,653
1996 4,707
1995 4,415
1994 1,302

Evaluation Thresholds

Pass -the observed spawner abundance is > the marine survival-specific escapement target at least six times in any 12-year period.

Fail - the observed spawner abundance is > the marine survival-specific escapement target 5 times or less in any 12-year period.

Distribution

The manner in which adults (spawners) are distributed within the freshwater portion of a population's home range.

Metrics

1. The percentage of random, spatially balanced surveys that have more than 4 wild adult spawners/mile (percent occupancy)

2. Comparison of the spatial pattern of potential spawning distribution to that observed using SVB or other spatial statistics.

Spawning Year Sites Occupied Sites Total Percent Occupied Occupancy Goal
2013 12 20 60% 100%
2012 6 8 75% 100%
2011 17 17 100% 100%
2010 17 20 85% 100%
2009 9 9 100% 100%
2008 16 16 100% 100%
2007 7 10 70% 100%
2006 4 4 100%
2005 1 1 100%
2004 5 5 100%
2003 2 2 100%
2002 3 3 100%
2001 2 2 100%
2000 3 3 100%
1999 3 3 100%
1998 6 6 100%

Evaluation Thresholds

Metric 1

Pass - the observed percent occupancy is greater than or equal to the marine survival-specific occupancy target at least six times in any 12-year period.

Fail - the observed percent occupancy is greater than or equal to the marine survival-specific occupancy target five times or less in any 12-year period.

Metric 2

Pass - the observed regularity ratio is not significantly different from a random distribution at least six times in any 12-year period.

Fail - the observed regularity ratio is significantly different from a random distribution at least six times in any 12-year period.

Diversity
  • 2007
    pass

Within-population diversity is the result of phenotypic differences among individuals. These differences provide the flexibility of the population as a whole to respond successfully to short-term environmental variations. They are also the basis by which populations are able to adapt and evolve as conditions within their home range go through changes that are more permanent.

Metric

The average of the 100-year harmonic mean of spawner abundance for each independent population, as forecast from a population viability model.

Analysis Year Harmonic Mean Goal
2007 5,118 1,200

Evaluation Thresholds

Pass - If 100-year harmonic mean of spawner abundance is greater than 1,200.

Fail - If 100-year harmonic mean of spawner abundance is less than or equal to 1,200.

Time Period Category Comment
2007 pass Goal met 1 of 1 years

Habitat

The amount of available high quality habitat for all freshwater life stages in each independent population, excluding the lakes populations.

Habitat condition is evaluated using population specific winter habitat surveys in the range of coho salmon. These surveys began in 2007 with the goal of surveying each independent population or dependent population group once every 5 years. Not all populations in the Coast Coho ESU have been surveyed for habitat at this time therefore some populations will display no habitat data.

Survey Year Miles Current 95% Confidence Interval Miles Goal Percent of Goal

Evaluation Thresholds

For a population to pass this criterion, the miles of high quality habitat (i.e. capable of producing > 2,800 smolts/mile) equals or exceeds the population-specific goals.

Persistence
  • 2007
    pass

The forecast probability of persistence for each independent population based on results from population viability analysis (PVA) models.

Analysis Year Average Probability Goal
2007 1.000 0.99

Discussion and Rationale

A persistence criterion of a 99% or greater probability of persistence significantly increases the likelihood that the ESU will remain viable under extreme marine survival conditions while providing substantial environmental, cultural, and economic benefits. Future analyses will be based on an average persistence value from the four PVA models developed by the TRT (Wainwright et al. 2008;Wainwright et al. 2006 poster).

Analysis

Because of the uncertainty of demographic effects at low population size, the TRT used two levels of "quasi-extinction" (1 and 50) to model persistence of the populations.

Evaluation Thresholds

For a population to pass this criterion it must have an average probability of persistence of 0.99 or greater as estimated by the four PVA models used by the TRT (Wainwright et al. 2008;Wainwright et al. 2006 poster).

Time Period Category Comment
2007 pass Goal met 1 of 1 years

Productivity

Annual estimates of the number of naturally produced recruits (progeny) per spawner (parent) (R/S) in the population.

Spawning Year R/S
2016 0.70
2015 0.54
2014 1.43
2013 0.63
2012 1.00
2011 1.86
2010 6.04
2009 1.08
2008 0.90
2007 0.20
2006 0.89
2005 0.96
2004 1.70
2003 1.88
2002 1.73
2001 1.69
2000 1.51
1999 0.62
1998 0.75
1997 2.05

Evaluation Thresholds

Pass - Over a 12-year period, R/S values, standardized to a spawner density equal to the spawner abundance goal for each marine survival category, are statistically greater than or equal to 1.0.

Fail - Over a 12-year period R/S values, standardized to a spawner density equal to the spawner abundance goal for each marine survival category, are statistically less than 1.0.