An improved method for collecting naturally spawned milkfish eggs from floating cages
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Natural spawnings of captive milkfish (Chanos chanos Forsskal) held in floating cages were observed in 1980, 1981, 1983 and 1985. Frequency of spawnings increased from two in 1980 to 41 in 1985. Various collectors and collection methods were tried with only slight improvements in number of eggs collected. Although the number of eggs collected per spawning increased from 900 in 1980 to a maximum of 769 000 in 1985, the numbers were not sufficient for mass-scale fry production. The most urgent problem was egg predators inside the floating cages during the spawning season. This paper presents an improved method of egg collection using fine-mesh net cages ("hapa" nets, 1 mm mesh) which effectively prevented entry of egg predators. Before "hapa" nets were installed the number of eggs collected ranged from 3300 to 668 000. From 330 000 to 2 942 000 eggs were collected by using "hapa" net cages. With the new method mass-scale production of milkfish fry can be achieved.