Shading Influenced Water Quality and Seed Production of Nile Tilapia (Oreochromis niloticus L.) in the Hapa-within-Pond System During Warm Months

Abstract

This study evaluated the influence of shading designs on water quality and Nile tilapia seed production in hapa-within-pond system. Metal frames were installed in three 200 m2 ponds and covered with greenhouse nets. Treatments were: no shading (NoS); top portion of frame covered (TopS); half of top and side portions of frame covered (HalfS); and top and sides of frame covered (TotalS). Twenty-four conditioned breeders (6♂:18♀) were bred on each hapa (1 m x 2 m x 1 m) installed in the ponds. Seeds were collected after 14 days. In both trials, significant differences in water temperature at 1500 h were observed among all treatments, with the lowest recorded in the TopS. The spawning rates of NoS (18.1±10.5%; 2.8±5.6%) were significantly lower than those of TopS (72.2±12.0%; 65.3±10.5%), HalfS (56.9±22.4%; 58.3±13.2%) and TotalS (66.7±23.6%; 65.3±10.5%). TotalS (8,563+3769 fry) and TopS (7,305+2491 fry) had significantly higher total seed production (TSP) than that of NoS (1,219+1150 fry) during the first trial, while TSP of HalfS (5,200+3051 fry) was comparable to those of the other treatments. During the second trial, shaded treatments had comparable TSPs but were significantly higher than NoS. For economic reasons, maximum reduction of water temperature, and optimum seed production during summer, the TopS design is recommended.