Fisheries managers are increasingly using creel limits, season closures, protected areas, and restrictive length limits to curb exploitation rates and protect the age and size structure of populations. Often, it would be informative to predict the effects of management measures before they are implemented or to use models to guide the choice of a particular management measure (for example, to choose the minimum size limit that will maximize yield). Milne Technologies can build and analyze simulation models that are specific to your population or system of interest.

Example simulation model of a smallmouth bass fishery. After 50 years of no fishing, a recreational fishery is opened and after another 50 years a minimum size limit is implemented.

Management measures tested can include:
   •  minimum length limits
   •  effort reductions
   •  slot limits
   •  season closures
   •  protected areas and sanctuaries
   •  creel limits

Data used in a model can include:
   •  life-history variables such as growth rate, maturation age and size, and gonado-somatic index
   •  stock-recruitment relationship
   •  relationship between population abundance and growth rates (i.e., to include density-dependent growth)
   •  natural mortality rates
   •  fishing mortality rates
   •  angler dynamics, for example, the relationship between quality of the fishery and effort
   •  size-selectivity of the fishery

Which of the above data are needed for the model will depend on the population and on the specific purpose of the model. If some of the above data is missing for a particular population, data on similar populations or species can be substituted or assumptions made which are subsequently tested with sensitivity analyses. Your knowledge of the system is important and we are very happy to develop the model in close dialogue with you, ensuring that key features of the system are included and that tested management measures are relevant and realistic.

Click here for a brief description and to see the results of an example model used to predict the effectiveness of alternative length limits in a smallmouth bass fishery.

Already have a particular model in mind?
Milne Technologies can build models from the ground-up in consultation with you in order to meet your specific needs. However, if you already have a particular model in mind that you would like to use for your system, Milne Technologies can parameterize and run the model and provide detailed analyses and results. Examples of existing models include those from the primary literature (e.g., Post et al. 2003, NAJFM 23:22), the Fishery Analysis and Simulation Tools FAST (http://www.ag.auburn.edu/fish/peaks-of-excellence/fast/fast.htm), and Ecopath with Ecosim (http://www.ecopath.org/).