Salmon & Steelhead Recovery Tracker

Nehalem (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 7,549 3,668 72,900 10.0%
2015 3,079 1,376 37,800 8.0%
2014 30,577 11,643 83,300 37.0%
2013 4,539 2,303 72,900 6.0%
2012 2,963 1,267 72,900 4.0%
2011 15,322 3,864 83,300 18.0%
2010 32,215 8,426 83,300 39.0%
2009 21,753 7,732 83,300 26.0%
2008 17,205 11,909 72,900 24.0%
2007 14,033 7,548 37,800 37.0%
2006 11,614 3,551
2005 10,451 3,048
2004 18,736 4,231
2003 32,517
2002 17,164
2001 21,928
2000 14,462
1999 3,555
1998 1,206
1997 1,187
1996 527
1995 1,700
1994 2,844

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
2016 11 19 58% 77%
2015 9 15 60% 77%
2014 12 13 92% 77%
2013 14 27 52% 77%
2012 8 21 38% 77%
2011 25 34 74% 77%
2010 30 33 91% 77%
2009 11 13 85% 77%
2008 5 6 83% 77%
2007 11 15 73% 77%
2006 19 22 86%
2005 24 30 80%
2004 44 61 72%
2003 51 56 91%
2002 51 65 78%
2001 41 56 73%
2000 39 58 67%
1999 17 43 40%
1998 16 62 26%

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 2,926 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
  • 2007
    fail

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
2007 149.8 83.2 393 38.1%

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.

Time Period Category Comment
2007 fail Goal met 0 of 1 years

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 0.996 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 1.82
2015 1.23
2014 2.34
2013 0.17
2012 0.16
2011 0.98
2010 2.31
2009 1.87
2008 1.68
2007 0.85
2006 0.38
2005 0.61
2004 0.91
2003 2.42
2002 4.34
2001 18.08
2000 5.95
1999 0.89
1998 0.34
1997 0.24

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.