Technical documentation for EcoSim can be found at:
http://www.flenvironmental.org/pubs/index.html
Scroll to the end of the publication list to:
Bissett, W.P., DeBra, S., and Dye, D. 2004. Ecological Simulation (EcoSim) 2.0 Technical Description. FERI Technical Document Number FERI-2004-0002-U-D. p.27. August 10, 2004. Tampa, Fl.