Abstract
Adult mackerel (Scomber scombrus) acclimated at 17.5 °C cleared their stomachs of silversides (Menidia menidia) at a constant rate. The time to complete emptying was approximately 28 h and did not seem to be affected by either ration size or body weight. Assimilation efficiency (calories) was 95%. Considerable ash was assimilated, probably in response to depletion of calcium reserves, after the shedding of spawning products.