Canada — Department of Fisheries and Oceans Lab

Last modified on Apr 11, 2019

Department of Fisheries and Oceans Canada (DFO) Schlerochronology Lab has an extensive training program, because they provide age data for hundreds of Chinook stocks (MacLellan and Gillespie, 2015) in Canadian waters. For their program, acceptable expertise can be learned in one to two seasons, but it takes several years and review of thousands of scales to be considered an expert.

Training and development system

DFO trainers develop a written training plan with input from the trainee and supervisor. A training plan provides goals and expectations for both the trainer and trainee. DFO examines quality and quantity of reads to measure a trainee's age estimation skills. Quality is assessed by measuring precision and accuracy. Productivity is measured by comparison with established target rates (# fish/hour). Comparative tests against self, experienced readers, and known-age (CWT) fish assess a trainee's precision and accuracy. Trainees are expected to meet agreement targets of >80%. To become an expert reader, a novice must develop good judgment and decisiveness.

Example Training Plan

Goals & Expectations: To participate in production aging of Chinook stocks using scales.

  • Consistently meet target of >80% agreement with expert readers to become a first reader.
  • Read 40-80 fish/hr (average of 60 fish/hour) on samples with 5 scales/fish.

Stage 1:

  • Review scales from 200-500 Chinook to become familiar with growth patterns.
    • Produce similar ages (60-70% agreement) to experienced readers with access to age data.
  • Age ~500 previously-aged Chinook scales from 2-3 stocks without age data.
    • Discuss differences in age estimations with trainer.
    • If agreement is >80%, trainee ready for next stage.

Stage 2:

  • Examine scales from 500-1,000 challenging samples, including poorly-defined annuli, prominent checks, varying life history types, and resorbed margins.
    • Trainee examines previously-aged samples, then independently ages ~500 fish.
    • Goal is >80% agreement.
  • Trainee first reads easy samples as well as those requiring more interpretation.
    • Samples second read by experienced Chinook reader, and if agreement >80%, only 20% of sample reviewed.
    • If agreement is <80%, entire sample second read by experienced reader.
  • Meet target of >80% agreement. Most reader agreement is >90%.

Stage 3:

  • May require 500-1,000 more fish before trainee allowed to test other readers.
  • Meet production goals of 40-80 fish/hour (samples of 5 scales per fish).
  • Trainee expected to meet quality (>80% agreement) and quantity (40-80 fish/hr) targets.

Productivity standards

Experienced readers are expected to meet productivity targets. Ranges were produced because not all samples and readers are the same. Rate can be affected by: species, stock, sample, life history, scale pattern clarity, number of scales per fish, scale resorption and/or age composition. Generally, experienced Chinook scale readers spend about one minute determining the age of a single fish.


MacLellan, S., and Gillespie, D., 2015. Chinook Salmon (Oncorhynchus tshawytscha) scale age determination procedures. Canadian Technical Report of Fisheries and Aquatic Sciences 3123, 69.