The feasibility of relating recruitment to environmental variation depends on the development of a model defining this relationship. A recruitment-environment model would need to contain components relating to both to the ecosystem "engine" and various sensors or gauges to measure its performance. Trophic transactions are an important component of the ecosystem engine. This study describes a gauge capable of measuring the probability of these transactions as they are affected by motion, irradiance, and temperature. The method in principle considerably shortens the causal linkages that need to be examined and thereby materially increases the feasibility of developing a predictive model on trophic energy exchange in the sea.