Induced breeding and larval rearing experiments with milkfish Chanos chanos (Forskal) in the Philippines
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Salmon pituitary homogenate was used alone or in combination with human chorionic gonadotropin, to induce spawing in captive and wild adult milkfish at ambient temperature (26–30°C) and salinity of 34%.. Healthy or slightly injured females having oocytes with a minimum mean diameter of 0.66 mm could be induced to spawn in captivity using a total dose of 20 mg SPH/kg + 3000 IU HCG/kg given in two injections. Badly injured females did not respond readily to the hormone and required more than two injections to induce ovulation. Milkfish larvae were reared successfully to metamorphosis using only Chlorella-fed rotifers during the first 10 days. Survival rates were greatly improved when, aside from Chlorella and Chlorella-fed rotifers, Isochrysis galbana and Tetraselmis chuii were added to the rearing tanks.
CitationJuario, J. V., Duray, M. N., Duray, V. M., Nacario, J. F., & Almendras, J. M. E. (1984). Induced breeding and larval rearing experiments with milkfish Chanos chanos (Forskal) in the Philippines.
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Conference paperLV Benitez - In RD Fortes, LC Darvin & DL de Guzman (Eds.), Fish and crustacean feeds and nutrition : Proceedings of the seminar-workshop on fish and crustacean feeds and nutrition held on 25-26 February 1985 at UPV, Iloilo City, 1989 - Philippine Council for Aquatic and Marine Research and DevelopmentThis paper reviews recent work on milkfish nutrition. Substantial progress had been made towards understanding the digestive physiology of milkfish. Major enzaymes envolved in the digestions of carbohydrates, protein and lipids had been detected in the pyloric caece, intestines and pancreas of milkfish. The most active carbohydrates were involved in the hydrolysis of α - glocosidic bonds. Intestinal amylase activity consistently reached the peak at about noon when milkfish gut was full. This confirms that milkfish is s daytime feeder. No cellulase activity was detected in any region orf the digertive treat although the fish relies heavily algae and other plant source for food. Trypsin, chymotrypsin and general proteases were also detected in milkfish digestive tract. A powerful milkfish trypsin inhabitor was detected in the filementous algae, Chaetomorpha brachygona which is predominant species in lumot. Lipass in the pancreas and intestines had two pH optima, suggesting a physiologic versatility for lipid digestion in milkfish. There is a limit information on the nutrient requirement of milkfish. Most studies showed that milkfish fry has a dietary requirement of 40% protein, and 7-10 lipid. Studies on the protein-energy requirement of fingerlings suggested that 30-40% protein, 10% fat and 25% carbohydrates are required. Subsequent studies showed an optimum protein energy to total metabolizable energy ratio of 44.4%. Amino acid test diets for milkfish had been formulated to contain white fish meal, gelatin and approprate amino acid mix.
Lactate dehydrogenase isozyme patterns during the development of milkfish, (Chanos chanos (Forskal)) PD Requintina, LM Engle & LV Benitez -
Kalikasan, The Philippine Journal of Biology, 1981 - University of the Philippines at Los BañosPolyacrylamide disc gel electrophoresis was done to determine the lactate dehydrogenase (LDH) isozyme patterns for fry (5-3 mg), fingerling (6-12 g), pond-size (150-250 g) and adult (6-9 kg) milkfish. The patterns were tissue specific; the different tissues examined, viz., eye, liver, heart, and skeletal muscle had different expressions of LDH isozymes. The resolved patterns appeared to be products of LDH gene loci A, B, and C. Subunits A and B were present in all tissues. A4 and B4 were predominant in skeletal and heart muscle, respectively; the two associated non-randomly in vivo and formed only the heteropolymers A3B and AB3. A liver band, L4, was most conspicuous in the fingerling, pond-size, and adult; it was assumed to be coded by locus C. A negatively charged band, X4, was detected in fully developed ovary and in fry homogenized as whole individuals, but it could not be resolved in tissues of fingerling. Six-mo old stunts and 3-mo old fingerlings had similar LDH patterns for all tissues examined. The patterns for 11-mo old stunts and fingerlings also were similar but the one for the eye of the former was the same pattern resolved for the eye of adults. There was no change in the LDH isozyme patterns of milk fish stunted for 6 mo under different salinity levels (0-5, 15-20, 32-35 ppt).
Evaluation of different supplemental feeds for milkfish (Chanos chanos) reared in brackishwater ponds The effects of supplemental feeding on milkfish growth, production, survival, water quality, and economic benefits in brackishwater ponds were evaluated by comparing a rice bran diet, containing 11.3% protein, and two pelleted diets, containing 22.0% and 27.4% protein, with an unfed control. Four 800-m2 tide-fed ponds, subdivided into quarters, were used. Each treatment was replicated in four random pond compartments. Milkfish with initial average weight of 1 g were stocked at 8000/ha and feeding commenced when the average weight and standing crop were 57 g and 417 kg/ha, respectively. All supplemental feeds significantly (P<0.05) increased growth and production over the unfed control. Feeding diets containing 22.0% and 27.4% protein resulted in 35.3% and 46.7% higher net profits, respectively, whereas feeding rice bran resulted in a 34.4% lower net profit when compared to the unfed control. The growth of milkfish became significantly slower (P<0.01) than those fed the 27.4% protein diets when the standing crop of unfed and rice bran-fed fish reached 535 kg/ha and fish fed the 22.0% protein diet reached 972 kg/ha. Survival was not significantly different among the treatments. The concentration of metabolites in the culture water for all treatments was low but a significant increase (P<0.05) in level of total carbon dioxide and nitrite-nitrogen was observed as biomass increased.