Effect of different feeding regimes on growth in juvenile Atlantic cod, Gadus morhua L.

Abstract

Different feeding regimes (fasting/re-feeding and reduced feeding) were tested in a 131day trial with 1400 juvenile (mean±SE, 132g±1) Atlantic cod (Gadus morhua) in order to see if a compensatory growth response could be elicited, and if hyperplastic growth was stimulated during the compensatory growth phase. The Atlantic cod was fed in compliance with the following five feeding (F) fasting (S) schedules: the control group (Cont) was fed 100% according to a commercial growth table every day, the second group was fed 50% for two weeks and 100% for four weeks (S50), the third group was fed 100% every secondday and 0% the following day (ALT), the fourth group was fasted one week and fed 100% two weeks (S1W), and the last group was starved two weeks and fed 100% four weeks (S2W). At the termination of the experiment, the body mass of the fish in the control, ALT and S50 groups were significantly higher than the fish in S1W and S2W groups. The shorter fasting treatment groups (ALT and S50) consumed significantly less feed (42.9 and 37.5% less feed, respectively) compared to control whereas final weight did not differ between these three groups. Growth rate was highest in the S50 group (0.78%day−1), and lowest in the longer fasting period groups (S1W, 0.59%day−1 and S2W, 0.57%day−1). White muscle fibre diameter, white muscle fibre density and the percentage of small fibres below 25μm was measured in the control and S2W group and did not differ at any sample point during the experiment. There were minor differences between the groups in percentage distribution of fibre diameter classes. The results demonstrate that feeding costs can be drastically reduced without compromising biomass growth by using feeding on alternate days or by periodically fasting and re-feeding juvenile cod.