Salmon & Steelhead Recovery Tracker

Alsea (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 7,375 2,400 31,900 23.0%
2015 6,185 1,632 16,500 37.0%
2014 25,733 7,388 36,400 71.0%
2013 9,283 2,140 31,900 29.0%
2012 8,470 1,934 31,900 27.0%
2011 28,337 8,794 36,400 78.0%
2010 9,688 2,133 36,400 27.0%
2009 14,638 4,864 36,400 40.0%
2008 13,320 3,439 31,900 42.0%
2007 2,146 1,240 16,500 13.0%
2006 1,972 942
2005 13,907 9,257
2004 5,233 1,541
2003 10,281
2002 9,073
2001 3,228
2000 3,363
1999 1,341
1998 108
1997 601
1996 1,060
1995 441
1994 828

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 16 19 84% 91%
2015 17 18 94% 91%
2014 11 11 100% 91%
2013 28 32 88% 91%
2012 29 30 97% 91%
2011 27 29 93% 91%
2010 24 27 89% 91%
2009 24 26 92% 91%
2008 19 22 86% 91%
2007 6 17 35% 91%
2006 6 12 50%
2005 5 6 83%
2004 17 23 74%
2003 18 19 95%
2002 11 12 92%
2001 15 21 71%
2000 7 12 58%
1999 6 19 32%
1998 1 18 6%

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 1,505 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
  • 2008
    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
2008 53.6 41.9 172 31.2%

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
2008 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 0.998 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 0.87
2015 0.91
2014 1.06
2013 1.13
2012 0.72
2011 2.25
2010 4.69
2009 7.84
2008 0.98
2007 0.46
2006 0.21
2005 1.57
2004 1.45
2003 3.32
2002 4.61
2001 1.93
2000 3.78
1999 0.88
1998 0.17
1997 0.52

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.