Effects of DHA-enriched live food on growth, survival and incidence of opercular deformities in milkfish (Chanos chanos)
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The use of commercial enrichers to improve the nutritional quality of live food in larviculture of milkfish was investigated. Fish were either fed rotifers cultured on Chlorella sp. and newly hatched Artemia nauplii (Control, Trt I) or rotifers and Artemia given DHA enrichment diets (DHA-treated, Trt II). Results showed survival was significantly better (P<0.05) in the DHA-treated fish than in the untreated fish after 25-day culture period. Although growth was not statistically different (P>0.05) between the control and DHA-treated fish during the hatchery phase, extensive rearing of the postlarvae (fry) in nursery ponds for another 60 days showed that DHA-treated fish exhibited significantly better (P<0.05) growth than the untreated fish. Opercular deformities in 85-day old milkfish juveniles were also significantly lower (P<0.05) in the DHA-treated fish than the control. Survival after nursery culture, however, was high for both treatments but not significantly different (P>0.05). The lack of a viable and reliable method of mass culturing copepods as live food in the hatchery makes the use of off-the-shelf commercial enrichment diets for rotifers and Artemia a practical option in the larval culture of milkfish.
CitationGapasin, R. S. J., & Duray, M. N. (2001). Effects of DHA-enriched live food on growth, survival and incidence of opercular deformities in milkfish (Chanos chanos).
The authors acknowledged the financial support of SEAFDEC/AQD under the study code Nr-12-F90T.
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The length-weight relationship, food habits and condition factor of wild juvenile milkfish in Sri Lanka Wild juvenile milkfish (Chanos chanos) were obtained from Negombo lagoon in September 1984. Thirty-one specimens (92–186 mm FL) had a fork length-body weight relationship of log W = −5.6083 + 3.2598 log L. These fish were caught in the early morning and had empty guts. The mean condition factor (K) was 8.7. The intestine length to fork length ratio (I) was 3.7. Two large specimens (245 mm and 340 mm FL) caught around mid-day from the ocean off Negombo had full guts. Food was mostly blue-green algae, diatoms and detritus, with a number of copepods and nematodes. These fish had K values of 11.7 and 13.6 and I values of 8.1 and 8.5. The age and the month of spawning of these fish were back-calculated using known milkfish growth rates. It seems that in Sri Lanka, milkfish spawn from January to at least November.
Milkfish (Chanos chanos) fingerling production in freshwater ponds with the use of natural and artificial feeds Milkfish fry were reared to fingerling size in freshwater ponds. For the first experiment, fish were fed the blue-green algae Oscillatoria inoculated and grown in the ponds, Oscillatoria supplemented with a fishmeal-based formulated diet, and the formulated diet alone. Twelve 50-m2 earthen ponds were prepared to enhance growth of the indigenous natural foods. Acclimated wild milkfish fry were stocked randomly at 90/m2 and were fed for 6 weeks. Milkfish fed the formulated diet alone had a significantly higher (P<0.05) mean weight gain (1.314±0.201 g) than milkfish given the combination of Oscillatoria and formulated diet (0.882±0.230 g). Growth was lowest for fish fed Oscillatoria alone. The feeding treatments in the second experiment were: combination of Spirulina powder and formulated diet, formulated diet alone, and rice bran alone. The stocking rate was equivalent to 91.5–92.5 fry/m2 and feeding lasted for 7 weeks. All feeds promoted some growth but the milkfish fed the formulated diet alone invariably had the highest weight increment (1.504±0.167 g), followed by fish given the feed combination (0.881±0.140 g). Rice bran alone gave the lowest growth response. For both pond experiments, growth trends of the young milkfish were similar to those grown under laboratory conditions. Although survival rates were significantly different in one aquarium experiment, survival rates of milkfish in ponds did not differ significantly (P>0.05) among treatments.
Conference paperMN Duray - In CL Marte, GF Quinitio & AC Emata (Eds.), Proceedings of the Seminar-Workshop on Breeding and Seed Production of Cultured Finfishes in the Philippines, Tigbauan, Iloilo, Philippines, 4-5 May 1993, 1996 - Aquaculture Department, Southeast Asian Fisheries Development CenterIn the past, larviculture of milkfish depended entirely on the use of rotifers and brine shrimp nauplii and rearing trials were done under roofed facilities. Since the dietary value of live food varies according to culture and feeding conditions, rotifers were enriched with SELCO, a lipid emulsion containing high levels of highly unsaturated fatty acids (HUFA) prior to feeding the larvae. Alternatively, a microbound larval feed (Nosan R-1) was given as a supplement to rotifers during the first two weeks of culture. Larval growth was enhanced and survival was significantly improved when rotifers were enriched or supplemented with these diets. All rearing trials were conducted in 5-10 tons concrete circular/rectangular outdoor tanks. Verification runs on the use of HUFA-enriched rotifers to milkfish larvae were tried in two nearby private hatcheries. Results from mis collaborative work are presented.