{"id":1127,"date":"2023-11-20T20:36:03","date_gmt":"2023-11-21T01:36:03","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/eweguide\/?post_type=chapter&p=1127"},"modified":"2024-10-22T12:50:34","modified_gmt":"2024-10-22T16:50:34","slug":"ecopath-input","status":"publish","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/eweguide\/chapter\/ecopath-input\/","title":{"raw":"Ecopath Input","rendered":"Ecopath Input"},"content":{"raw":"

The first task in building an ecosystem model is to clearly define the question(s)<\/a> that the model is to answer. Once this is in place, it becomes much clearer what the model structure should be like. Assuming that is done, you can go ahead with the practical aspects of getting your model defined in EwE. That's what this chapter deals with.<\/p>\r\n

Before entering data, you are encouraged to read the introductory material on the mass balance approach to ecosystem modelling for information about how the input parameters are used in the model.<\/p>\r\n

Be aware that generally, leaving an input blank on a data entry form implies it is unknown. For some required parameters defaults are supplied and leaving such in place means accepting the default values. This is for instance the case for biomass accumulation, detritus import, landings, discards, migrations and prices (for all of which the default value is 0). You should be aware that opting for default values is as much a modelling decision as setting values \u2013 default values will not necessarily be appropriate for your model. \u00a0But one upside is that you generally don't have to explain the EwE default values when publishing your model.<\/p>\r\n\r\n

Model Parameters<\/h1>\r\nThe\u00a0Ecopath > Input > Model parameters\u00a0<\/em>form is used to define some basic settings and record basic information about your model.\r\n

Model<\/h2>\r\nThis descriptive part is for recording some basic information, including the model area (in km2<\/sup>). All model stock sizes and flow rates are expressed per unit area (km-2<\/sup>), and stock and flow calculations in Ecopath, Ecosim, Ecospace and Ecotracer are all expressed per that unit area. There is, however, one exception. The value chain analysis works with quantities, so it, e.g., sums of how much the landings (in t km-2<\/sup> year-1<\/sup>) are for the ecosystem in question and then multiplies this with the model area (km-2<\/sup>) to get the quantity (t year-1<\/sup>). The value chain will then work with these quantities for all calculations. It makes sense, once the seafood is landed, the quantity is what matters, not how big the area was it came from or what the densities were in that area.\r\n\r\nThe spatial extent (N, S, W and E) can also be entered here. If this is done, the area will be known in Ecospace where it is used to calculate the cell dimensions considering the model latitude.\r\n

Classification<\/h2>\r\nIf values are selected here from the drop down listings, the information can be used by the ecosystem model collection in Ecobase<\/a>, Related, when you \u00a0have published an Ecopath model, you are strongly encouraged to submit it to Ecobase. This can be done from the menu File > Export model > To Ecobase<\/em>. Ecobase models are available at www.ecobase.ecopath.org<\/a> and can also be downloaded directly from\u00a0File > Import model > From Ecobase.<\/em>\r\n

Basic Input<\/h1>\r\nWe provide only a cursory introduction and explanations for the various input fields as many are self-explanatory.\r\n

Define Groups<\/h2>\r\n

You must define whether a functional group is a primary producer, consumer or detritus by checking the appropriate box.<\/p>\r\n\r\n