Problems associated with hormonal induction of gonad development in milkfish (Chanos chanos)
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Recent developments in milkfish breeeding include succesful induced spawning of wild1,2 and captive3-5 fish and spontaneous spawning of broodstock.6 Gravid spawners, however, are available only during the wild or are reared in captivity. The seasonal and uncertain supply of wild fry is a major constraint in efforts to increase production of this important food fish in the Philippines, Indonesia, and Taiwan. Gonad devepolment can be induced in some fish by hormone administration. This has been recently reviewed by Lamp7 and other workers.8,9 Induced gonad development using purified salmon gonadotropin have been reported in Salmo gairdneri,10 Oncorhynchus gorbuscha,11,12 and Mugil cephalus.13,14 Hormones are usually administered by injection at frequent intervals in these studies. To reduce stress from frequent handling, a slowrelease hormone cholesterol pellet was with success in Salmo auratus and Ophicephalus striatus.16 Recent literature suggests that vitellogenesis in fish (at least yolk granule or gobule formation) is under control of estrogen and a pituitary factors. Estrogen stimulates the liver to produce vitellogenin, while the incoporation of vitellogenin into oocytes requires a pituitary factor which may not be the glycoprotein (Con A II) gonadotropin.7 In the light of this information and in anticipation of a synergistic role of thyroid hormone ,17 a combination of fish pituitary extract, estrogen and thyroxin was used in some of our experiments. Our attempts to induce gonad development in sexually immature milkfish and rematuration of regressed fish have not been sucessful to date. This paper presents the experiments done and discusses factors possibly contributing to the negative resp[onse in this fish.
Lacanilao, F., Marte, C. L., & Lam, T. J. (1985). Problems associated with hormonal induction of gonad development in milkfish (Chanos chanos). In B. Lofts & W. N. Holmes (Eds.), Current Trends in Comparative Endocrinology. Proceedings of the 9th International Symposium in Comparative Endocrinology, 7-11 December 1981, Hongkong (pp. 1247-1253). Hong Kong: Hong Kong University Press.
PublisherHong Kong University Press
- Conference Proceedings 
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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).
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.
BookER Cruz-Lacierda, EG Estante, EGT de Jesus-Ayson & VL Corre Jr. - 2015 - Aquaculture Department, Southeast Asian Fisheries Development CenterThis monograph provides updated information on diseases of marine and brackishwater cultured milkfish in the Philippines. The information presented here is largely based on the results of a three-year research project on milkfish at the University of the Philippines Visayas funded by the Department of Science and Technology (DOST). The project involved surveillance and monitoring of hatchery, nursery and grow-out operations for occurrence of diseases as well as on disease diagnosis, prevention and control. Previously documented reports in the Philippines and in other documents, both published and unpublished, are also included in this monograph. The diseases are discussed on a culture phase basis, that is, disease problems encountered in hatchery-reared larvae and fry are listed first, followed by diseases observed in fingerlings and juveniles grown in nursery and grow-out culture areas, and adult stages maintained in broodstock facilities. Information regarding the causative agent, diagnostic procedures, and methods of prevention and control for each disease are provided, if available.