THE FOOD AND DAILY FOOD-CONSUMPTION OF LACUSTRINE 0+ PERCH, PERCA-FLUVIATILIS L

SUMMARY.  The diet and daily food consumption (Ct) of 0+ perch were investigated in two shallow Scottish lakes.  The first food comprised the rotifer Keratella sp., Volvox sp., copepod nauplii and stage I copepodites of Cyclops strenuus abyssorum Sars. Larger copepodites and adults of C. s. abyssorum and Diaptomus gracilis Sars were consumed as larvae grew and cladocerans were also eaten by larvae >11 mm. The diet of juveniles included a wider range of cladocerans and benthic invertebrates. Cannibalism was not observed among 0+ perch.  The range of food items taken by larvae increased with length, and the size of food particles ingested was governed by jaw gape which was linearly related to fish length.  Larvae fed during daylight hours with feeding maxima in midmorning and the evening.  The arithmetic (constant) rate of evacuation R of the digestive tract of larvae was 0.59—1.16% of body weight h−1 and exponential R was 0.21–0.33% h−1. Daily Ct calculated using an arithmetic model was 14.2–23.4% body weight at water temperatures of 12.5–18.2°C, and 23.9–40.3% utilizing an exponential method. For larvae of 9 mm. this was 46 μg dry weight day−1 and 148 by an exponential model. Food conversion efficiency was 37–72% (arithmetic model) and 21–45% (exponential model). Copyright © 1990, Wiley Blackwell. All rights reserved