Modifications to the Chum Genetic and Environmental Management Model (ChumGEM), a run reconstruction computer model

A ChumGEM beta version was developed utilizing a growing genetic data set, historic catch data, escapement estimates and migration assumptions for boundary area Chum stocks. That project was funded in 2013 and completed in 2015. This proposal would support the required improvements and modifications to that beta version identified in our model evaluations over the last year.

Objectives of this work will be:

– Change model structure so that swim speed, diversion rate, and proportions of fish designated to each migration route are not fixed outside the model.

– Change the model structure so that multiple years are fit simultaneously. Sharing information across years could improve model fit significantly. Variables controlling timing of arrival, swim speed, diversion rates, and migration proportions are likely consistent across years.

– Review priors on arrival timing- are the current model inputs realistic?

– Data verification – this model takes a large diversity of data, further evaluation of this is required.

– Review infill procedures especially for escapement, catch and GSI data.

– Identify plausible chum Genetic Unit (GU) specific diversion rates.

– Identify GU-specific variances in observation errors on escapement.

– Incorporation of age specific data when available.

– Investigate why several small stocks are not showing up in GSI data. Are we not seeing these fish, or are they not being recognized separately from larger stocks? Do we need to include them?

– Investigate methods for filtering the GSI data.