Salmon & Steelhead Recovery Tracker

Siuslaw (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 Broad Sense Goal Proportion of Goal
2021 38,031 15,922 107,600 35.0%
2020
2019 5,881 2,447 48,900 12.0%
2018 6,635 2,240 94,200 7.0%
2017 7,129 3,698 94,200 8.0%
2016 9,141 3,584 94,200 10.0%
2015 10,352 2,884 48,900 21.0%
2014 38,896 13,149 107,600 36.0%
2013 14,118 4,596 94,200 15.0%
2012 11,946 3,677 94,200 13.0%
2011 28,082 5,812 107,600 26.0%
2010 25,983 8,180 107,600 24.0%
2009 30,607 9,347 107,600 28.0%
2008 17,491 10,515 94,200 19.0%
2007 3,552 1,217 48,900 7.0%
2006 5,869 3,193
2005 16,907 6,633
2004 8,729 2,222
2003 29,003
2002 55,445
2001 10,606
2000 6,532
1999 2,980
1998 1,020
1997 501
1996 7,234
1995 6,161
1994 3,159
1993 4,600
1992 3,554
1991 2,808
1990 2,269

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 Total Sites Visited Occupied Sites Percent Total Occupied Sites Percent Wild Occupied Sites Proportion of Goal Wild Sites Broad Sense Goal
2020 12 87%
2019 22 10 46% 46% 52% 87%
2018 20 13 65% 65% 75% 87%
2017 23 13 57% 57% 65% 87%
2016 15 11 73% 73% 84% 87%
2015 14 12 86% 86% 99% 87%
2014 12 9 75% 75% 86% 87%
2013 32 23 72% 72% 83% 87%
2012 24 19 79% 79% 91% 87%
2011 24 21 88% 88% 101% 87%
2010 25 22 88% 88% 101% 87%
2009 36 27 75% 75% 86% 87%
2008 9 8 89% 89% 102% 87%
2007 22 13 59% 59% 68% 87%
2006 24 10 42%
2005 39 35 90%
2004 37 23 62%
2003 41 38 93%
2002 44 34 77%
2001 41 27 66%
2000 46 29 63%
1999 38 16 42%
1998 36 3 8%

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

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 Broad Sense Goal

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.

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 Broad Sense Goal Percent of Goal
2007 172.0 85.4 508 33.9%

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

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

Analysis Year Average Probability Broad Sense Goal

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).

Productivity

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

Spawning Year R/S Broad Sense Goal
2020 1.0
2019 0.75 1.0
2018 0.73 1.0
2017 0.20 1.0
2016 0.70 1.0
2015 1.10 1.0
2014 1.58 1.0
2013 0.64 1.0
2012 0.50 1.0
2011 1.70 1.0
2010 7.54 1.0
2009 5.16 1.0
2008 1.03 1.0
2007 0.46 1.0
2006 0.22
2005 0.32
2004 0.89
2003 4.83
2002 18.26
2001 7.95
2000 10.10
1999 0.28
1998 0.15
1997 0.11

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.