Hatchery and sea cage production of brown croaker, Miichthys miiuy: A new fish species in coastal aquaculture in Korea

Abstract

Brown croaker had been known as a high valued food fish traditionally both in Korea and China. At present, by resources decrease, necessity of aquaculture of this species is serious. However the aquaculture production of this species has been hindered by difficulty in production of good quality of fertilized eggs. In this study, we developed methods for successful production of good quality of fertilized eggs and subsequent seed production.Ten days after brooder stocked, fertilized eggs were observed in brooder tank. Presumably, fertilization occurred 7:30 p.m. The total amount of eggs collected were 2,000 ml during three consecutive days. Mean egg diameter ranged from 1.028 mm to 1.045 mm and 64.4% of eggs had a single oil globule. The time to hatch was inversely related to incubation temperature, ranged from 24.0h at 22 oC to 16.5h at 28 oC. Mortality was negligible in three test temperature regimes. Just hatched larvae measured 2.45 mm (S.D. 0.17 mm) in TL, had a single oil globule located at the posterior margin of the yolk sac. The larvae were fed with the rotifer, Brachionus sp. at 3 days after hatch (3.62 mm in TL) and absorption of the oil globule was completed by day 4 at 28 oC temperature regime. When larvae reached 6.25 mm in TL, they were fed freshly hatched Artemia nauplii and micro-encapsulated artificial feed. After the 6 months of seed production trial period, seeds (6.07cm in TL, 1.50g in BW) were transferred to sea cage located in coastal area southern part of Korea peninsula. In sea cage, the mean specific growth rate was 1.24 compared to 0.49 in land based tanks. The above results of the first attempt to production of fertilized eggs by induction of natural mating with temperature treatment and seed production showed a possibility of commercial culture of this species as a new fish species in coastal aquaculture in Korea. As there are some technical problems (e.g. mechanical damage causes mass mortality), in further study, more sophisticated ma