Energy transformations by the sargassum fish, Histrio histrio (L.)

Ingestion, egestion, growth, and respiration measurements were made in the laboratory on three size-classes of the Sargassum fish, Histrio histrio (L.). Comparison of three size-classes showed changes from high growth and low respiration and assimilation in small Histrio to reduced growth and increased respiration and assimilation in larger fish. A high assimilation and growth efficiency suggest that Histrio is adapted to a food-limited environment (Sargasso Sea). Energy requirements of the smallest size-class (10–29 mm) were compared to the energy provided by their dominant food source, the Sargassum shrimp Latreutes fucorum (Fabricius) and Leander tenuicornis (Say). The annual energy requirement per individual was 1.4 times greater than the food energy available. This discrepancy is attributed to the difficulty in extrapolating laboratory studies to the field and the difficulty in obtaining adequate population size measurements of the Sargassum community fauna.