Candidate species for open ocean aquaculture： the successful case of cobia, Rachycentron canadum in Taiwan

Abstract

Cobia, Rachycentron canadum, is an idea species for open ocean aquaculture. Reproduction in captivity is relatively easy and sexual maturity is attained at the begining of the second year. If water temperature is maintained at 23-27℃, spontaneous spawning occurs year-round with a peak in spring and autumn. Fry can be mass-produced in outdoor ponds at relatively low cost. Weaning of fry from 20 d old onward (from a total length of about 6 cm) to pellet feeds is easy. Fry size of 8-15 cm can be attained in 45 d with survival rates ranging from 5-20% from fertilized eggs. Nursery from 30 g until 1 kg can be done either in outdoor ponds or cages near the coast. From 500 g, cobia reachs 1 kg within 2 mo in grow-out cages; thereafter cobia may gain as much as 1 kg every month until about 10 kg or before sexual maturity. Cobia intended for the Japanese market are harvested at 6-8 kg while those for the domestic Taiwan marlet at 8-10 kg. The meat is of excellent quality, containing high levels of fat, EPA, DHA, and vitamin E. The ratio of edible portion is about 60%. In Taiwan, over 80% of the 1,500 open ocean cages are devoted for cobia aquaculture. Compared with other marine finfish, the competitive traits of cobia for open ocean aquaculture are the relatively inexpensive mass fry production, ease in weaning to pellet feeds, fast growth rate, tolerance to high stocking densities, resistance to ectoparasutes, and excellent meat quality.