Counting prey is not counting available energy

Prey counts, biomass, potential energy, and predator benefit need not change in the same direction. This methods note combines forage-fish composition measurements, comparative cetacean evidence, and an ontogenetic consumption analysis to clarify the conversion among those quantities. Invented samples demonstrate a forty-percent decline in count alongside an eighty-percent increase in calculated energy, while additional examples expose wet-versus-dry-mass errors and conditional assimilation assumptions. The cited studies span subarctic and other marine systems; their fitted values are not treated as Arctic constants. The note does not estimate actual ingestion or predator fitness. It argues for retaining counts and biomass alongside energetic conversions, then asking whether a specified consumer can capture the relevant prey, at an appropriate season and life stage, for a useful net return.