The food and daily food consumption of lacustrine 0+ perch, Perca fluviatilis L.

SUMMARY.1  The diet and daily food consumption ( C t ) of 0+ perch were investigated in two shallow Scottish lakes. 2  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. 3  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. 4  Larvae fed during daylight hours with feeding maxima in midmorning and the evening. 5  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 C t 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).