Crab Energy Balance: Overview

The energy balance of crabs, like clams, is modeled using grams wet weight. Let the mass of the crab at time $t$ (including stomach contents, but excluding eggs) be given by $G$ (g) and the amount of food in the stomach of the crab by $G_{\text{stom}}$ (g). Mass balance dictates that:

$$\frac{\delta G}{\delta t} = G_ - G_ - G_ - G_ - G_ - G_ .$$ (A.30)

That is, the rate of change in the mass of a crab over each update time, $\delta t$, is governed by the change in the mass of food ingested minus the mass egested, in addition to the mass expended for respiration and excretion, movement, molting, and reproduction. How each of these terms is modeled is described below. The way in which crabs forage and feed (Appendix A.5.6) provides the necessary background information for understanding how ingestion (Appendix A.5.7) and egestion (Appendix A.5.8) are modeled.