Coastal Aquaculture and Mariculture (2+1)

Unit 5 - Finfish culture systems

5.4.1. Biology and Seed supply

Biology

• Groupers are carnivorous fish associated with reefs.
• They are found both in marine and brackishwaters.
• Feed on small fish and shrimp.
• Distributed primarily in South East Asian countries.
• They are protogynus hermophrodites – mature as females and convert to males as they grow larger.
• In Epinephelus tauvina sex reversal begins at the age of 6 years and the proportion of males increases thereafter.
• Most fish become males after the age of 9 years.
• For hatchery production of fish males can be got younger by hormonal sex reversal.
• Functional males of E. tauvina could be obtained by feeding methyl testosterone for 14 days @1mg/kg fish per day.

Seed supply

• Both wild and hatchery reared seed are used. Survival rates of larvae in hatchery is still poor.
• Hence majority of the seed is from the wild. Fry measuring 3.5-5 cm are available during the breeding season.
• Fishermen collect them with small seines and transport them for sale to fishermen.