Techniques in finfish larviculture in Taiwan

Abstract

Taiwan now has over 90 finfish species in which larviculture is possible. Billions of finfish fry can be produced annually. The use of modern and advanced techniques in larviculture has won Taiwan a leading position in the world. This achievement can be attributed to: (1) successful broodstock management, including broodstock collection and cultivation, maturation and spawning, and egg collection and incubation, (2) complete larval rearing using outdoor and indoor systems, and (3) establishment of techniques of live food preparation for larval feeding. Cannibalism, difficulties in water quality control, and disease outbreak often cause mass mortality in the rearing larvae. However, the obstacles that hinder the development of larvae at their later stages are being overcome. Through a systematic understanding of the complex behavioral patterns of finfish larvae, cannibalism can somewhat be controlled under larviculture conditions. Control strategies often involve physical manipulations such as grading and feeding adjustments. For water quality and disease control, an indoor larval rearing system has recently been established. It adopts ozone or chlorine to disinfect fertilized eggs, the rearing water, and facilities. Additionally, utilization of the green water technique in rearing larvae and of ozone-disinfected recirculating water in weaning larvae has improved the hygiene of the systems. For instance, the average survival rate in the fry of grouper used to be less than 0.1% until they attained a size of about 2 cm. With the improved system, grouper fry grow from 3 to 10 cm with almost no mortality or viral infection, with a feed conversion rate of 0.7–0.9 and a daily weight increase rate of 4–27%. Application of live food enrichment techniques with selected nutrients for short and long terms has proven beneficial to larval growth. Studies determining the optimal environmental requirements of larvae have been essential towards successful larviculture. This paper mainly discusses developments and advanced techniques of finfish larviculture in Taiwan.