Introduction to stock assessment
Unit 2.5: Model-free stock assessments
For some stocks, models may not be used for stock assessment. There are several model-free methods that can be used for data-limited stocks that do not require intensive computations. These approaches instead look for patterns in the data using time series. This allows for tracking stock changes to estimate how it will respond to different management actions.
Photo credit: Gregory Puncher, DFO
Model-free stock assessments often use time series of relative abundance or biomass as the basis for stock assessment instead of complex models that estimate absolute abundance. Model-free stock assessments may also estimate average biomass over time or the average fishing mortality rate that did not lead to stock decline over time.
Time series of relative biomass can support the identification of reference points. For example, the lowest biomass from which a stock has recovered is sometimes used as a way to identify the limit reference point. The average relative biomass over time may be used to estimate the upper stock reference. Recommended harvest levels can also be set based on relative fishing mortality over time.
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