DAILY RATION AND SPECIFIC DAILY RATION OF THE CHAETOGNATH SAGITTA-ENFLATA

Digestion time, obtained directly from laboratory feeding, were used in conjunction with a day/night series of field samples to estimate the daily ration and specific daily ration of S. enflata Grassi, the most abundant chaetognath in the Gulf Stream near Miami, Florida (USA), during winter and early spring. Feeding was independent of time of day and increased with increasing chaetognath size from 1.7 prey/day for the 11.5 mm size class to 2.9 prey/day for the 21.5 mm class. The diet of S. enflata consisted of 94.8% copepods having a mean weight of 21.8 .mu.g, and 5.2% prey chaetognaths estimated to be 2/3 the length of the predators. The daily ration of S. enflata from 12.5-20.5 mm in length increased from 48.3-143.3 .mu.g prey dry wt and from 18.5-48.1 .mu.g prey C. The specific daily ration declined from 0.12-0.08 dry wt basis, and from 0.26-0.14, C basis, over the same size range. Prey chaetognaths contributed as much as 51% of the ration on a C basis.