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 the performance of three locally available feeds on the seed production of Nile tilapia (Oreochromis niloticus). Three hundred and sixty female Nile tilapia (mean weight +/- SE, 91.5 +/- 2.3 g) with the same numbers of male (123.4 +/- 2.1 g) were stocked in each of 12 large nylon hapas suspended in two fertilized earthen ponds. An estimated 16 million eggs and yolk-sac fry were collected from the mouths of incubating females using hand nets at 5-day intervals. Broodfish were fed near to satiation twice daily. The female groups 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 herbivorous diet. Seed outputs from the catfish pellet-fed fish were 138 +/- 6 and 141 +/- 5 seed m(-2) day(-1), respectively, while that from herbivorous feed was 108 +/- 2 seed m(-2) day(-1). Broodfish consumed the small catfish 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 gram of feed was significantly higher (P < 0.05), which resulted in the lowest production cost when the females were fed with the large catfish pellets as compared to the females that received the smaller catfish pellets and the 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 longer periods. (C) 2001 Elsevier Science B.V. All rights reserved.