Layer 1Population Model First the population model computes the essential

Layer 1population model first the population model

This preview shows page 6 - 9 out of 10 pages.

Layer 1—Population Model: First, the population model computes the essential population factors such as stock abundance, mortality, growth, reproduction, and movement for each year, typically during the past several decades. Layer 2—Observation Model: Next, the observation model creates predictions from the population model of data that have been measured, including survey abundance index, catch, fish size and age composition, and others as available. Layer 3—Statistical Model: Finally, the statistical model compares the data predictions to the data observations and adjusts the factors in the population and observation model to achieve the best possible match to all the data. Hundreds of factors may be needed in complex situations with multiple stock areas, several fishing fleets, and lengthy time series data. In the end, how closely a fish stock assessment model fits the actual data indicates the reliability of the historical estimates and future predictions for a fish stock. Many modern assessment models use graphical interfaces to help standardize assessments and make it easier for scientists to work together on projects and compare their work. Page 6
Image of page 6