Preliminary studies of factors affecting the feeding rhythm of milkfish (Chanos chanos Forskal).
1986
Chiu Y.N. | Macahilig M.P. | Sastrillo M.A.S.
Milkfish raised in brackishwater fishponds have been observed to be daytime feeders. Feeding activity is characterized by a single peak, which correlates with the intensity of sunlight, the levels of dissolve oxygen (DO) and water temperature and the activity of digestive enzymes. Three experiments were conducted to investigate the effects of DO, artificial feed and light on the feeding rhythm of milkfish. Fish were reared in covered and uncovered circular canvas tanks supplied with water flowing through at different rates from an adjacent ponds and were either fed or not fed with artificial feed. Varying flow rates resulted in different DO patterns, with the dawn DO differing by at least 2 ppm. Fish were sampled at regular intervals for 24 hours and feeding index (FI = wt of intestine with content/wt of fish x 100) determined. The three experiments consistently demonstrated feeding behavior patterns: (1) regardless of any of the experimental parameters, peak feeding occurs during the day and the gut is completely devoid of food between 10 p.m. and 2 a.m., (2) in the presence of both natural and artificial food, natural food is preferred during the light hours while artificial feed is preferred during dark, suggesting preference for photosynthesizing algae; (3) below a certain limiting DO of about 1.5 ppm, milkfish stop feeding and, (4) the feeding activity of milkfish is not completely dependent on the presence of light or completely correlated with temperature and DO levels.
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