Contribution of natural food and supplemental feed to the gut content of Penaeus monodon Fabricius in a semi-intensive pond system in the Philippines
Juvenile Penaeus monodon were stocked in grow-out ponds and fed a compound diet at high rates for 19 weeks under semi-intensive conditions. At three stages of the rearing period (weeks 6, 11 and 16), the gut content of the shrimp was analysed microscopically at every hour of the day. Additionally, possible sources of natural food (lablab, lumut, zoobenthos, etc.) were analysed microscopically and where possible for proximate composition. At week 6, the gut content consisted of 28.9% supplemental feed, 42.3% plant materials (other than from the pelleted diet), 1.8% crustacean parts and 27.0% diverse detrital matter. For week 11, the percentages (same order) were 47.5%, 21.1%, 22.8%, 8.6% and for week 16, 21.7%, 34.3%, 31.7% and 12.9%, respectively. Food preference did not change with time of the day. At week 6, most feeding activity occurred at night, later, feeding activity shifted to day-time. Reduction of the maximum gut content at dissolved oxygen levels below 4 mg l<sup>−1</sup> at night indicated a cessation of feeding in which case shrimp fed during the day-time, when dissolved oxygen levels were higher.
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