Farming of Seabass (Lates calcarifer) in net cages in Negombo Lagoon, Sri Lanka: Culture practices, fish production and profitability

Shrimp farming is the main coastal aquaculture activity and sea bass cage farming also recently started in Sri Lanka. Information pertaining to culture practices, fish production, financial returns and costs involved in respect of seabass cage farms operate in the Negombo lagoon were collected through administering a questionnaire. The survey covered 13 farms of varying sizes. The number of cages operated by an individual farmer or a family ranged from 2 – 13. Almost all the farmers in the lagoon used floating net cages, except for very few farmers, who use stationary cages. Net cages used by all the farmers found to be of uniform in size (3m x 3m x 2m) and stocking densities adapted in cages are also similar. Production of fish ranged between 300 to 400 Kg per grow-out cage. All seabass farmers in the Negombo lagoon entirely depend on fish waste/trash fish available in the Negombo fish market to feed the fish. Availability of these fish waste/trash fish at no cost to the farmers has made small scale seabass farming financially very attractive.

Increase of cage farms in the Negombo lagoon has led to conflicts between seabass farmers and other resource users and need of taking adequate precautionary measures to avoid potential conflicts are stressed. The main constraints for the development, sustainability and expansion of seabass farming in Sri Lanka are unavailability of low cost effective diets and irregular and inadequate supply of seabass seeds. Recommendations made include importance of determination of optimum number of fish cages, that can be established in a water body based on carrying capacity assessments to prevent uncontrollable increase of cage farms.

Keywords: seabass farming; farming in cages; culture practices; carrying capacity assessments.