Towards More Environmentally Responsible Grow-out Systems in Aquaculture
By Dr. J.H. Primavera, SEAFDEC Aquaculture Department
Tigbauan, Iloilo 5021, Philippines

Abstract

Aquatic plants, molluscs, crustaceans and fish are grown out in a variety of ponds, pens, cages, trays, and rafts from low-density, low-input extensive systems to high-density farms with artificial feeding and water circulation. Asian aquaculture, mainly in the tropics and subtropics, contributed around 80% of global output, and freshwater fish (44%) and macroalgae (22%) the bulk of production in 1999. But increasing focus on high-value carnivores like shrimp and salmon and their culture in intensive ponds and pens/cages has caused negative ecological impacts associated with resource utilization (e.g., mangrove conversion) and waste production (causing eutrophication, sedimentation and salinization). Grow-out systems need to reduce and mitigate such impacts and become more environmentally responsible through the development and/or wider dissemination of available onfarm technologies (e.g., recyling), integration of aquatic species (pond polyculture of freshwater Chinese/Indian carps, and brackishwater tilapia/fish and shrimp), and of aquaculture with agriculture/ silviculture (e.g., vegetable-poultry/livestock-fish in freshwater ponds). Brackishwater culture can redress past environmental damage and become mangrove-friendly by adopting silvofisheries (or aquasilviculture where crabs/fish/shrimp are reared at low density in mangrove ponds and pens) or integrating mangrove as filters adjacent to intensive fish/shrimp ponds. All these require a paradigm shift from the short-sighted "common" exploitation of water, mangroves and other resources to the ecological footprint approach incorporating not only inputs such as feed and seed, but also outputs, e.g., effluent treatment facilities.