Selection of a commercial feed for Nile tilapia (Oreochromis niloticus) broodfish breeding in a hapa-in-pond system

A 95-day trial was conducted on a commercial farm in Thailand to compare th e performance of three locally available feeds on the seed production of Ni le tilapia (Oreochromis niloticus). Three hundred and sixty female Nile til apia (mean weight +/- SE, 91.5 +/- 2.3 g) with the same numbers of male (12 3.4 +/- 2.1 g) were stocked in each of 12 large nylon hapas suspended in tw o fertilized earthen ponds. An estimated 16 million eggs and yolk-sac fry w ere collected from the mouths of incubating females using hand nets at 5-da y intervals. Broodfish were fed near to satiation twice daily. The female g roups fed with large and small catfish pellets produced 27% and 30% more (P < 0.05) seed, respectively, as compared to those females that were fed a h erbivorous diet. Seed outputs from the catfish pellet-fed fish were 138 +/- 6 and 141 +/- 5 seed m(-2) day(-1), respectively, while that from herbivor ous feed was 108 +/- 2 seed m(-2) day(-1). Broodfish consumed the small cat fish pellets more readily than the large catfish pellets and grew faster on this diet. These results showed that excess energy enhanced somatic growth rather than the reproductive output of the fish. The number of seed per gr am of feed was significantly higher (P < 0.05), which resulted in the lowes t production cost when the females were fed with the large catfish pellets as compared to the females that received the smaller catfish pellets and th e herbivorous feed. Overall seed yield and the clutches started to decline after the second month of the experimental period regardless of the type of feed given, showing quadratic relations. it indicated that an appropriate feed with a sound feeding strategy is required to minimize hapa fouling and maintain good water quality, and thereby produce high seed yield for longe r periods. (C) 2001 Elsevier Science B.V. All rights reserved.