A preliminary report on the gonadal development of adult milkfish, Chanos chanos, reared in tank

Abstract

Milkfish is one of the most important food fishes in Taiwan. There are more than 16,000 ha of culture area and over 160 millions of fry are needed for milkfish farming industry every year. The fry are collected from the sea and also imported from other countries. However, due to several environmental factors, there is unpredictable fluctuations in the occurrence of these wild fry. In recent years, the demand for milkfish fry has gone up considerably owing mainly to the fast-growing populations, the natural resources being so limited that there is insufficient supply of stocking materials of this important foodfish.

To solve the problem of shortage of milkfish fry, Tungkang Marine Laboratory started the preliminary work on artificial propagation of milkfish in 1970. In addition to capturing wild spawners, the Laboratory has also been raising the adult milkfish in tanks for this objective. After being reared for six years, one male and one female were dissected on 11 April 1976. The male had ripe sperms; the testes weighing 4.63 g with the GSI of 0.12. The gonad of the female weighed 21.20 g with the GSI of 0.66 and part of the ovarian oocytes was found to be at the oil droplet (yolk vesicle) stage. Judging from the condition of maturity of the above female, the feasibility of raising tank-reared spawners was ensured. It is believed that this is the first attempt on the world and is the prelude to successful artificial propagation by using tank-reared milkfish as spawner.