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Gmacs: mastering a modeling framework to assess Crustacean species

Welcome

This is the online version of “Gmacs: mastering a modeling framework to assess Crustacean species,” a user guide book currently under development and that aims to merge and synthesize all the current and past work done by the Gmacs development team since the inception of this project.

Statistical catch age models have several advantages over simple production type models in that age and size composition data can be used to better inform structural features such as recruitment variability, growth variability and total mortality rates. There are a number of generic age-structured models in use today (e.g., Stock Synthesis, CASAL, …), but there are very few generic size-based, or staged-based models that are used in stock assessment.

The Generalized Model for Assessing Crustacean Stocks (GMACS) is an integrated analysis modelling framework designed to develop size-structured stock assessment models for crustacean species.

Crab stocks of Alaska are managed by the North Pacific Fishery Management Council (NPFMC). Some stocks are assessed with integrated size-structured assessment models of the form described in Punt et al. (2013). Currently, most of these stocks are assessed using a stock-specific assessment model (e.g. Zheng and Siddeek (2014)). In this context and with the aim of uniform the assessment process of these species, the Gmacs project aims to provide a software that will allow each stock to be assessed independently but using a single flexible modelling framework.

This book is designed to take you from knowing nothing about Gmacs and its utilities

Structure of the book

  • Chapter 1: What is Gmacs - How to get it installed
  • Chapter 2: File Organisation
  • Chapter 3: Data file description
  • Chapter 4: Control file description
  • Chapter 5: Projection file description
  • Chapter 6: A set of functions to help the user to fill/modify input files (have to be developed)
  • Chapter 7: Running Gmacs and using the gmr package to plot results
  • Chapter 8: Building your first stock assessment using Gmacs
  • Chapter 9: Producing stock assessment documents
  • Chapter 10: Frequently Asked Questions

License

The Gmacs project has been and is still funded by the National Marine Fisheries Service and the Bering Sea Fisheries Research Foundation. This product is currently hosted by the Nation Oceanic and Atmospheric Administration (NOAA).