Artificial fertilization of eggs and early development of the milkfish Chanos chanos (Forskal) H. Chaudhuri, J. Juario, Jurgenne H. Primavera, R. Mateo, R. Samson, Erlinda Cruz, E. Jarabejo, and J. Canto Jr. Abstract Hydrated eggs obtained from a female milkfish were artificially fertilized with the milt collected from a male injected with acetone-dried pituitaries of salmon. The fertilized eggs (1.1 to 1.25 mm in diameter) developed normally in seawater in basins and Petri dishes at a salinity of 30-34 ppt and successfully hatched in 25 to 28½ hours at a temperature of 26.4-29.9°C. The yolk was completely absorbed in about 2½ days and at this period many postlarvae died. A few larvae were reared up to 5 days but all died within 6 days. Effects of feeding the postlarvae from the third day with freshly hatched trochophore larvae of oysters obtained from eggs artificially fertilized in the laboratory could not be ascertained. Introduction The milkfish Chanos chanos (Forskal) is an important food fish and is extensively cultured in brackishwater ponds in Southeast Asia, particularly in the Philippines, Indonesia, and Taiwan. Since it does not attain maturity or breed in captivity, the only source of its seed is the coastal waters from where milkfish fry are collected during the spawning season. While the milkfish industry is rapidly expanding, the present supply of fry is inadequate to meet the growing demand. Thus, the urgent need to develop a dependable source of seed is now being realized as fishery scientists in a number of countries are engaged in research in inducing maturation and spawning in both pond-grown and wild milkfish by hypophysation. Our knowledge on milkfish, especially on parameters such as spawning habits and spawning grounds, nature of eggs and the characters of early larvae, is meager. Since Delsman's description (1929) of probable milkfish eggs, there was hardly any information until Senta et al. (1976) reportedly collected a few eggs from a spawning ground near Batbatan island off Antique province in the Philippines. Preliminary experiments carried out in Taiwan to induce maturation in tank-reared milkfish (Liao and Chang, 1976) have been partially successful. Earlier attempts made in the Philippines to gather information on mature milkfish from the wild and induce them to spawn by hormone injections were not successful (Angeles, 1968; Inland Fisheries Project Technical Report, 1974; Delmendo and Angeles, 1975). More recently, experiments carried out at the Oceanic Institute in Hawaii (Nash and Kuo, 1976) and at the SEAFDEC Aquaculture Department, Philippines (Vanstone, et al., 1976a) to induce spawning in adult milkfish captured from the wild by injections of semipurified salmon gonadotropin (SG-G100) resulted in the release of hydrated eggs from the injected females. These eggs, however, were not fertilized. *Contribution No. 12 of the Aquaculture Department, Southeast Asian Fisheries Development Center, P.O. Box 256, Iloilo City 5901, Philippines.