The effect of various salinity levels and stocking density manipulation methods on the survival of milkfish fry (Chanos chanos Forsskal) during storage

Results of the study indicate that the survival rate and increase in body weight did not differ significantly at different salinity levels or at different stocking density manipulation methods. A significant interaction between salinity and stocking density manipulation could not be demonstrated statistically. There apparently is no need to reduce the salinity of the water used in storing milkfish Chanos chanos fry in order to attain higher survival as commonly believed. Sufficient food and maintenance of good water quality are more important than salinity for higher survival of fry during storage

Preliminary notes on the salinity preference of milkfish, Chanos chanos, fry

Vertical salinity gradient columns were used to investigate the salinity preference of milkfish fry. Newly captured fry showed a preference for 32‰ salinity. Fry which had been in captivity for one to five days, at 12 or 22‰ salinity, had no salinity preference between waters of 12, 22 or 32‰ salinity

A guide to induced spawning and larval rearing of milkfish Chanos chanos (Forsskal)

The techniques for the artificial propagation of milkfish (Chanos chanos ) developed at SEAFDEC are presented. These include: 1) capture and transport of spawners; 2) determination of sex and weight and maturity of fish; 3) induced spawning (preparation of injection, males, females); 4) fertilization and incubation; 5) larval rearing; and 6) mass production of larval food.The study as well as the publication of this guide was supported in part by a grant to the Aquaculture Department of the SEAFDEC by the International Development Research Centre of Canada under Project No. 3-P-74-0146 (Phase I), No. 3-P78-0033 (Phase II) and No. 3-P81-0171 (Phase III).1st Ed

Broodstock management and seed production of the rabbitfish Siganus guttatus (Bloch) and the sea bass Lates calcarifer (Bloch)

This paper reviews results of studies conducted on the rabbitfish, Siganus guttatus (Bloch) and the sea bass Lates calcarifer (Bloch) at the Aquaculture Department of the Southeast Asian Fisheries Development Center. Studies include broodstock development and management, induced breeding, effect of handling stress and diet on egg quality, early life history, food, feeding strategy, weaning to artificial diets, effect of stocking density and salinity on egg development, larval growth and survival, and advancement of metamorphosis in sea bass by using thyroxine. A seed production technique had been developed for rabbitfish with survival rates ranging from 5-35% while the seed production technique for sea bass developed in Thailand had been modified to suit local conditions. Based on results from recent morphological and physiological studies, the stocking density, water management, and feeding scheme for the production of rabbitfish and sea bass fry had been modified to reduce cannibalism and improve survival

The commercial production of green grouper fingerlings, Epinephelus suillus, from wild caught fry - an industry experience

Wild-caught fry of the green groupers, Epinephelus malabaricus and E. suillus ranging in standard lengths (SL) from 1.5 to 3.0 cm were bought from different fry dealers all over the Philippines. These were reared from 1.0 to 2.5 months in 10 to 40 m3 (small) concrete tanks, in 240 m3 (large) concrete nursery tanks with sandy bottom, in 10 m3 hapa nets installed either in large nursery concrete tanks with sandy bottom or in 0.8 to 1.0 ha earthen ponds. The initial stocking density was 33-150/m3. When the fingerlings reached 5 to 7 cm SL, these were harvested and stocked in cages. The wild fry were fed adult brine shrimps for the first few days and later, trash fish. Rearing water in small concrete tanks was changed daily while that in large nursery tanks and hapas was changed only when dissolved oxygen level was about 4 ppt or lower. Survival rates ranged from 3% to 64%. Although survival rates varied, rearing grouper fry in hapa nets installed in earthen ponds were found to be the most suitable for the commercial production of grouper fingerlings to a size suitable for stocking in cages. The large variation in survival rates is attributed mainly to the quality of wild fry bought from different fry dealers all over the country and the occurrence of diseases during the culture period. The problems encountered in the commercial production of fingerlings are discussed

Milkfish culture in the Philippines

In the Philippines, the level of intensity of Chanos chanos culture is categorized into traditional and extensive management. Pond types for different culture systems, stocking practices, acclimation practices, water management, growout culture and harvesting are discussed. Fish pen culture and management are also briefly considered

Yolk and oil globule utilization and developmental morphology of the digestive tract epithelium in larval rabbitfish, Siganus guttatus (Bloch)

The purpose of this study was to find out how yolk and oil globule absorption in Siganus guttatus proceed as the digestive tract develops, in order to determine the probable causes of early larval mortality. Yolk and oil globule absorption in the rabbitfish were compared with the same processes in the more sturdy seaperch larvae during the first 10 days of larval life under identical rearing conditions in 32‰ sea water at 27°–30°C. The rapid decline of yolk in both species coincided with the rapid development of the digestive system within 24 h from hatching, indicating that most of the yolk was used for organogenesis. Whereas yolk was depleted in both fish in 3 days, the oil globule persisted in the rabbitfish only for 4 days and in the seaperch for 7 days. Oil globule depletion in the rabbitfish coincided with a negative mean length increment, implying an energy deficit even when the larvae had already started to feed. Ultrastructural observations of the gut epithelia of the rabbitfish revealed pinocytosis in the hindgut cells immediately after ingestion of rotifers, well in advance of complete yolk and oil globule absorption. Therefore, starvation due to exhaustion of the endogenous energy reserves in addition to the physical inability to feed were ruled out as major causes of larval mortality in rabbitfish

Use of hormones in breeding cultivated warm-water fishes with special reference to milkfish, Chanos chanos (Forskal)

The role of hormones in the controlled reproduction of a few test fishes is well documented. However, information on the mechanisms of endocrine regulation of ovulation in cultivated warm-water fishes is very meagre. Hormones, especially the gonadotropic hormones of piscine origin, are increasingly being used in modern aquaculture to produce the seed of many important cultivated fishes. While chorionic gonadotropin and other exogenous mammalian hormones are used in spawning the channel catfish, fish pituitary hormones are usually needed to induce spawning in the difficult-to-spawn Asiatic carps. In mullets, however, either homoplastic pituitary gland or human chorionic gonadotropin (HCG) or a mixture of HCG and a threshold dose of the former is ordinarily injected to precipitate spawning. Of late, semi-purified salmon gonadotropin (SG-G100) has been used to induce spawning in several species of food fishes. While several marine fishes have been artificially bred by administration of hormones, induced spawning of the milkfish, C. chanos has been tried with little success. The milkfish is a widely distributed food fish extensively cultivated in ponds in Southeast Asia. Recently, significant results have been obtained in spawning mature milkfish captured from the wild by hormone injections. The experiments conducted on induced breeding of milkfish leading to the successful fertilization and hatching of milkfish eggs are briefly described

Biological evaluation of phytoplankton (Chlorella sp., Tetraselmis sp. and Isochrysis galbana) as food for milkfish (Chanos chanos) fry.

Contribution No. 142 of the SEAFDEC Aquaculture Department.Phytoplankton cultures of Chlorella sp., Tetraselmis sp. and Isochrysis galbana were used alone as feed to rear separate batches of newly caught milkfish (Chanos chanos) fry (about 21 days old). Ultrastructural studies of fry hepatocytes and pancreatic acinar cells indicated that they cannot directly utilize Chlorella, which has a rigid cell wall. The fry can directly utilize Tetraselmis and Isochrysis, but neither is nutritionally adequate for growth and survival if used as the only feed. Tetraselmis is nutritionally inferior to Isochrysis