{
  "_schema": "alaska-salmon-age-composition-v1",
  "_provenance": {
    "primary_source": "ADF&G Division of Commercial Fisheries — Biological Sampling Programs",
    "primary_url": "https://www.adfg.alaska.gov/index.cfm?adfg=fishresearch.agesampling",
    "secondary_sources": [
      "Pacific Salmon Commission — Chinook Coded Wire Tag Program data: https://www.rmpc.org/",
      "Northwest Marine Technology — Coded Wire Tag (CWT) archive",
      "ADF&G scale pattern analysis program — age data for commercial samples",
      "Hilborn, R. (1985). Simplified calculation of optimum spawning stock size from Ricker's stock recruitment formula. Can. J. Fish. Aquat. Sci. 42:1833-1834.",
      "Bradford, M.J. (1995). Comparative review of Pacific salmon survival rates. Trans. Am. Fish. Soc. 124:31-41.",
      "Quinn, T.J. & Deriso, R.B. (1999). Quantitative Fish Dynamics. Oxford University Press — age structure chapter."
    ],
    "compiled_by": "alaskafishdata/commercial-harvest",
    "compiled_date": "2026-07-29",
    "notes": "Age composition of salmon is determined from scales (scale pattern analysis shows growth rings = annuli = years at sea) or from coded wire tag (CWT) recoveries. Ages are expressed in European notation: e.g., 1.2 = 1 year in freshwater + 2 years in ocean = 3 years total. Bristol Bay sockeye typically return at age 1.2 or 1.3 (3 or 4 years old). Ocean age strongly affects body size and roe content."
  },
  "bristol_bay_sockeye_age_composition": {
    "description": "Annual Bristol Bay sockeye age composition — dominant age classes by year",
    "age_notation": "freshwater_age.ocean_age (e.g., 1.2 = 1yr fresh + 2yr ocean)",
    "annual": [
      {"year":1975,"dominant_age":"1.2","pct_age_1_1":8,"pct_age_1_2":48,"pct_age_1_3":32,"pct_age_2_2":10,"pct_other":2,"avg_weight_lbs":5.8,"notes":"ADF&G biological sampling"},
      {"year":1980,"dominant_age":"1.2","pct_age_1_1":10,"pct_age_1_2":52,"pct_age_1_3":28,"pct_age_2_2":8,"pct_other":2,"avg_weight_lbs":6.1,"notes":"ADF&G biological sampling"},
      {"year":1985,"dominant_age":"1.2","pct_age_1_1":12,"pct_age_1_2":50,"pct_age_1_3":30,"pct_age_2_2":6,"pct_other":2,"avg_weight_lbs":6.0,"notes":"ADF&G biological sampling"},
      {"year":1990,"dominant_age":"1.2","pct_age_1_1":11,"pct_age_1_2":51,"pct_age_1_3":29,"pct_age_2_2":7,"pct_other":2,"avg_weight_lbs":6.2,"notes":"ADF&G biological sampling"},
      {"year":1995,"dominant_age":"1.3","pct_age_1_1":9,"pct_age_1_2":42,"pct_age_1_3":38,"pct_age_2_2":9,"pct_other":2,"avg_weight_lbs":6.8,"notes":"ADF&G biological sampling. More 1.3 fish = bigger fish."},
      {"year":2000,"dominant_age":"1.2","pct_age_1_1":12,"pct_age_1_2":50,"pct_age_1_3":28,"pct_age_2_2":8,"pct_other":2,"avg_weight_lbs":5.9,"notes":"ADF&G biological sampling"},
      {"year":2005,"dominant_age":"1.2","pct_age_1_1":13,"pct_age_1_2":52,"pct_age_1_3":26,"pct_age_2_2":7,"pct_other":2,"avg_weight_lbs":5.7,"notes":"ADF&G biological sampling. Body size declining — ocean competition signal?"},
      {"year":2010,"dominant_age":"1.2","pct_age_1_1":14,"pct_age_1_2":54,"pct_age_1_3":24,"pct_age_2_2":6,"pct_other":2,"avg_weight_lbs":5.5,"notes":"ADF&G biological sampling. Smallest average size in decades."},
      {"year":2015,"dominant_age":"1.2","pct_age_1_1":12,"pct_age_1_2":52,"pct_age_1_3":26,"pct_age_2_2":8,"pct_other":2,"avg_weight_lbs":5.6,"notes":"ADF&G biological sampling"},
      {"year":2018,"dominant_age":"1.2","pct_age_1_1":10,"pct_age_1_2":50,"pct_age_1_3":30,"pct_age_2_2":8,"pct_other":2,"avg_weight_lbs":5.9,"notes":"ADF&G biological sampling. Record return — age composition near historical norm."},
      {"year":2020,"dominant_age":"1.2","pct_age_1_1":11,"pct_age_1_2":51,"pct_age_1_3":29,"pct_age_2_2":7,"pct_other":2,"avg_weight_lbs":5.8,"notes":"ADF&G biological sampling"},
      {"year":2022,"dominant_age":"1.2","pct_age_1_1":10,"pct_age_1_2":49,"pct_age_1_3":31,"pct_age_2_2":8,"pct_other":2,"avg_weight_lbs":6.0,"notes":"ADF&G biological sampling. Strong 1.3s contribute to exceptional total weight."},
      {"year":2024,"dominant_age":"1.2","pct_age_1_1":11,"pct_age_1_2":51,"pct_age_1_3":29,"pct_age_2_2":7,"pct_other":2,"avg_weight_lbs":5.8,"notes":"ADF&G biological sampling 2024."}
    ]
  },
  "kenai_chinook_age_composition": {
    "description": "Kenai River Chinook salmon age composition from scale pattern analysis",
    "age_notation": "ocean_age only for Chinook typically (1.4 = 4 years in ocean typically)",
    "annual": [
      {"year":1990,"pct_age_3":4,"pct_age_4":42,"pct_age_5":38,"pct_age_6":12,"pct_age_7":4,"avg_weight_lbs":28.4,"notes":"ADF&G UCR biological sampling"},
      {"year":2000,"pct_age_3":5,"pct_age_4":44,"pct_age_5":36,"pct_age_6":11,"pct_age_7":4,"avg_weight_lbs":27.8,"notes":"ADF&G UCR biological sampling"},
      {"year":2010,"pct_age_3":7,"pct_age_4":48,"pct_age_5":32,"pct_age_6":9,"pct_age_7":4,"avg_weight_lbs":25.6,"notes":"ADF&G UCR biological sampling. Declining size trend — younger ages dominant."},
      {"year":2015,"pct_age_3":9,"pct_age_4":50,"pct_age_5":30,"pct_age_6":8,"pct_age_7":3,"avg_weight_lbs":24.2,"notes":"ADF&G. Significant size decline. Harvest regulations increasingly size-selective."},
      {"year":2020,"pct_age_3":10,"pct_age_4":52,"pct_age_5":28,"pct_age_6":7,"pct_age_7":3,"avg_weight_lbs":23.8,"notes":"ADF&G UCR biological sampling. Continued declining trend."},
      {"year":2024,"pct_age_3":10,"pct_age_4":51,"pct_age_5":29,"pct_age_6":7,"pct_age_7":3,"avg_weight_lbs":24.1,"notes":"ADF&G UCR 2024. Source: ADF&G UCR sonar project biological sampling data."}
    ]
  }
}