Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8496564 | Aquaculture | 2007 | 9 Pages |
Abstract
This study investigated the effects of two levels of feeding (1 or 4% BW dayâ 1), two levels of stocking densities (3 or 10 female mâ 2) and two levels of water-flow rates (0.06 ± 0.00 or 0.35 ± 0.04 L sâ 1) on the fecundity, relative fecundity, spawning frequency and egg quality of Nile tilapia, Oreochromis niloticus (L.) with the goal of improving hatchery seed production. Males and females, 125 days of age, were stocked in recirculating concrete tanks. Eggs were collected every four days directly from the mouths of incubating females. Fecundity (eggs spawnâ 1), body weight gain (g dayâ 1) and egg diameter (mm) and weight (mg), percent protein and lipid, fertilization and hatchability were measured over 120 days. Higher eggs kg femaleâ 1 dayâ 1 (312 ± 36) was observed in treatments with lower levels of stocking density (3 female mâ 2) and water-flow rate (0.06 ± 0.00 L sâ 1) under both feeding rates. The rate was 2 to 4 fold higher than the others. Overall, high feeding level (4% BW dayâ 1) increased growth (g dayâ 1) by 35% and eggs spawnâ 1 by 18% and did not affect eggs kg femaleâ 1 dayâ 1, spawn femaleâ 1 and eggs mâ 2 dayâ 1. Higher stocking density (10 female mâ 2) lowered eggs spawnâ 1 by 19%, eggs kg femaleâ 1 dayâ 1 by 52% and spawn femaleâ 1 by 40%. Higher water-flow rate (0.35 ± 0.04 L sâ 1) increased growth (g dayâ 1) by 33%, and lowered eggs kg femaleâ 1 dayâ 1 by 51%. The variables also did not affect percent egg fertilization, hatchability, crude lipid and protein or egg diameter (mm). However, egg weight (mg) was higher in groups fed a lower ration (1% BW dayâ 1) with higher stocking density (10 female mâ 2) and higher water-flow rates (0.35 ± 0.04 L sâ 1). Feeding levels interacted with water-flow rates in improving growth (g dayâ 1) while stocking density interacted with water-flow rates in lowering eggs kg femaleâ 1 dayâ 1 and spawn femaleâ 1. The eggs kg femaleâ 1 dayâ 1 obtained in this study from the best treatments is comparable with the highest egg production rates reported by others for O. niloticus. This suggests that lower feeding level (1% BW dayâ 1), lower stocking density (3 female mâ 2) and lower water-flow rate (0.06 ± 0.00 L sâ 1) could be adopted as a management strategy to improve current tilapia hatchery seed production, although, optimum water flow-related stocking density needs further investigation.
Related Topics
Life Sciences
Agricultural and Biological Sciences
Aquatic Science
Authors
Getinet G. Tsadik, Amrit N. Bart,