The highest number of strays in the 2020-2022 period were from one group of Mokelumne River hatchery smolts released in 2018 to Half Moon Bay on the coast south of San Francisco.\u00a0 The next highest group of strays are from American and Feather hatchery smolt releases to San Francisco Bay.\u00a0 The trucked hatchery smolts do very well during drought years and thus tend to bias high the Yuba returns from drought years.\u00a0 That is to say, drought effects on the natural Yuba run are even worse than indicated in escapement estimates.<\/p>\n
I categorize the decade-long decline as a \u201ccrash\u201d based on the population spawner-recruit (S\/R) relationship (Figure 2).\u00a0 The S\/R \u201ccurve\u201d generally reflects a positive logarithmic relationship between spawner and recruitment numbers.\u00a0 The more eggs spawned generally leads to more adult returns three years later.\u00a0 The S\/R ratio, at least in the Central Valley salmon populations, also reflects drought or habitat conditions wherein recruits are generally depressed from density-independent habitat factors like droughts.\u00a0 The six drought years in the last decade shown in Figure 2 as red dots have led to escapement levels in the lower-left quadrant of the S\/R curve \u2013 a pattern often referred to as a population crash.<\/p>\n
Often it is difficult for a population to recover from that situation because there are not enough spawners (eggs) to get the population out of the hole<\/em>.\u00a0 It would take a lot of good years in sequence to make that happen, unless certain actions are taken to accelerate the recovery.\u00a0 For some suggestions on how this can be accomplished, see my past post<\/a> on the subject.<\/p>\n Because of the supplementation of recruitment from other rivers and resulting mixed bag of spawners, the Yuba run is not threatened with extinction.\u00a0 However, in its present state, its poor contribution to the commercial and recreational fisheries is a problem.\u00a0 The Yuba is a magnificent salmon river that should contribute more salmon.<\/p>\n Figure 1. Yuba River Fall-Run Chinook salmon escapement estimates 1953-2024.<\/p><\/div>\n Figure 2. Yuba River Fall-Run Chinook salmon spawner-recruitment relationship wherein recruits are related to recruits three years earlier. Red dots represent escapement years where two years earlier it was a drought year during rearing and outmigration.<\/p><\/div>\n The Yuba River Fall-Run Chinook salmon population \u201ccrashed\u201d in the last decade.\u00a0 Yuba River escapement ranged only from 2000-5000 spawners counted per year (Figure 1).\u00a0 Such low escapements were last encountered only during the Central-Valley-wide crash during the 2007-2009 drought. … Continue reading ![\"\"](\"https:\/\/calsport.org\/fisheriesblog\/wp-content\/uploads\/2026\/03\/image1-1-1024x683.png\")
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