The Guts to Estimate Fish Daily Ration

Abstract

We compared daily ration values estimated using the Elliott and Persson and the Eggers models implemented with field-derived variations in stomach and complete digestive tract (CDT) contents of fish. Stomach evacuation rate (0.31∙h−1) was 2.8 times greater than that of CDT (0.11∙h−1). Daily rations obtained using both models and sections of the digestive tract estimated at 2-h intervals averaged 0.84 (Trial 1), 2.56 (Trial 2), and 2.41 g dryl∙100 g wet−1∙d−1 (Trial 3) and never differed by more than 23.6% within trials (average = 11.4%). Variances in daily ration values from the Elliott and Persson model were, on average, 3.4 times larger than variances derived using Eggers model. Variances associated with daily rations on stomach contents were, on average, 5.9 times larger than variances based on CDT contents. Sampling frequencies (from 2- to 4-, 6-, 8-, and 12-h intervals) had no significant influence on mean daily ration values but, on average, caused a 3.6-fold increase in variances. The precision and robustness of daily ration values appeared more directly influenced by the section of digestive tract used than by the estimation model chosen; the Eggers model implemented with CDT contents appeared to be the most efficient combination.