The overall model consists of four main components: (1) environmental variables including salinity, temperature, depth and dissolved oxygen; (2) clams; (3) background prey; and (4) individual crabs. The environmental variables, clams and background prey are all modeled at the scale of individual fine-level triangles, crabs are modeled as individuals and move from triangle to triangle. While the first three model components are updated every 24 hours, individual crabs are updated on average once per hour and even more frequently if crabs interact. Since environmental variables alter habitat variables (clams and background prey), and since all of these are relevant to crab response in the estuary - environmental, habitat, and crab density all vary spatially and temporally.
To represent the spatial variation in the environmental and habitat variables, the overall model domain is discretized into small triangles (Appendices A.2 and A.3). The clam and background prey models operate within the environmental conditions of each of these triangles (Appendix A.4) while individual crabs respond autonomously to the above conditions (Appendix A.5). This appendix focuses on providing and justifying the particular implementation assumptions made. The model is implemented using the object-oriented language C++. All parameter values (and associated references used to justify them) are summarized in Table C1.