Browsing by Author "Gaitan, Albert G."
ArticleEgg cannibalism by milkfish spawners in a circular floating net cage was investigated. The cage was lined with a fine mesh hapa net to retain spawned eggs and to prevent the entry of fish egg predators. Water samples were collected from the surface (0 m), middle (1.5 m), and bottom (3.0 m) of a 10 m diameter by 3 m deep floating net cage at the time of initial detection of spawning (0 min) and at 30, 60, 120 and 240 min thereafter. The mean number of spawned eggs at the surface significantly decreased (P<0.05) 60 min after spawning and very few eggs were recovered 240 min later. There was no significant difference (P>0.05) in the mean number of spawned eggs collected from the middle and bottom of the net cage at various times after spawning. Eggs were found in the digestive tract of all milkfish sampled (n=6) at about 5 h after spawning, indicating that captive milkfish eat their own eggs. It is recommended that spontaneously spawned milkfish eggs should be collected immediately after spawning to avoid loss by egg cannibalism.
BookAG Gaitan, JD Toledo, MT Arnaiz, EGD Ayson, JP Altamirano, RF Agbayani, ND Salayo & CL Marte - 2014 - Aquaculture Department, Southeast Asian Fisheries Development Center
Series: Aquaculture extension manual; No. 58A 42-pages extension manual describing the biology, fingerling production, site selection, cage design and construction, measurement & analysis of water & sediment quality parameters and economic analysis.
Nursery rearing of the Asian sea bass, Lates calcarifer, fry in illuminated floating net cages with different feeding regimes and stocking densities Successful rearing of hatchery-reared sea bass, Lates calcarifer, fry in illuminated floating cages was demonstrated in a 42-day experiment. Three feeding regimes, i.e. natural zooplankton (NZ) + minced fish flesh (MFF), NZ alone, or MFF alone and two stocking densities (600 and 1 200 individuals m2) were tested in a 3 × 2 factorial experiment. Fish reared in unlit cages and fed MFF alone during daytime served as the control. Results showed that no interaction existed between stocking density and feeding regime and that the two stocking densities used did not influence fish growth in terms of mean final body size. In general, sea bass reared in lit cages (NZ + MFF and NZ) grew and survived better than the control fish (MFF). However, fish reared under NZ + MFF feeding regime had the highest final mean total length (TL, 42.1 mm) and body weight (BW, 1 311.8 mg) followed by fish reared under NZ feeding regime (mean TL = 26 mm, BW = 415 mg). Fish in the unlit control cages exhibited the poorest growth (final mean TL and BW: 26 mm and 277.6 mg BW). Furthermore, specific growth rates (range: 5.7–8.5% day−1) of fish in lit cages were significantly better than those of fish in the unlit control cages (mean: 3% day−1). Percentage survival (38%) of fish stocked at 600 m−2 density and fed NZ was not significantly different from fish in the NZ + MFF feeding regime. However, increasing the density to 1 200 ind. m−2 tended to significantly decrease percentage survival (20%) of fish with NZ feeding. Fish reared in the unlit control cages had the poorest survival of 13–14%. The high percentage composition by number (CN, 88%) of copepods in the stomachs of sea bass fry fed on NZ alone and the equally high percentage feeding incidence (94%) indicated that fish fed sufficiently on natural zooplankton. Supplemental feed using minced fish flesh contributed about 43–59% of the fish diet in addition to natural zooplankton.
Studies on the nursery rearing of seabass, Lates calcarifer (Bloch) fry in illuminated floating net cages AC Fermin, MEC Bolivar & A Gaitan - In SA Al-Thobaiti, HM Al-Hinty, AQ Siddiqui & G Hussain (Eds.), Aquaculture Technology and Investment Opportunities. Proceedings of the First International Symposium on Aquaculture Technology and Investment Opportunities, 11-14 April 1993, Riyadh, Saudi Arabia, 1994 - Ministry of Agriculture and Water; King Abdulaziz City for Science and Technology; Riyadh Chamber of Commerce and IndustryThe feasibility of rearing seabass, Lates calcarifer, fry for fingerling production in illuminated floating nursery cages was determined. In experiment 1, seabass fry of 20.0 mm mean TL were stocked at 600 and 1200 in 1 m3 illuminated cages and reared without supplemental feeding. Control fish were stocked at same densities in non-illuminated cages and fed minced trash fish. After 42 days, fish held in illuminated cages at either density had higher specific growth rates (SGR) and percent survival (20-38%) than those of fish reared in non-illuminated cages. Mean number of zooplankton trapped inside the illuminated cages was significantly higher than those found in the non-illuminated cages which was dominated by Copepods such as the Calanoid, Cyclopoid and Harpacticoid and their nauplii. In experiment 2, minimum body size of seabass fry at stocking in illuminated cages was determined. Seabass fry of 7.35, 11.30, 18.73 and 20.71 mm total length (TL) were stocked at three replicates in illuminated cages and reared for 30 days. Percent survival was significantly higher for fish stocked at an initial size of 11.30 mm TL than the other size groups. Number of “shooters” (range = 6-9%) was significantly higher among fish with initial size of 7.35 mm and 20.71 mm than in other groups. SGR of 8.28%/day was highest for fish with mean stocking size of 7.35 mm TL. Feeding incidence (FI) ranging from 13.16 ± 6.7% to 54.9 ± 4.2% was similar for all size groups during the first week of rearing and significantly increased towards the end of rearing period except for fish stocked at 7.35 mm initial TL. Results showed that nursery rearing seabass fry in illuminated cages is feasible. Natural zooplankton were attracted into the cages by artificial illumination sufficiently served as food to fish. Minimum stocking size of seabass fry is from 10-15 mm TL for better survival. Early transfer of fry in nursery cages and availability of natural zooplankton through artificial illumination can be a cost-effective method of nursing seabass fry.