Sustainable Production of Shrimp in Thailand

Abstract

World production of farmed shrimp is focused on a few species. At present, the Pacific whiteleg shrimp Litopenaeus (Penaeus) vannamei tops the list, followed by the black tiger shrimp Penaeus monodon and a few others. The former attains the market size between 15 and 25 g within three months in culture, while P. monodon requires at least four months to reach the marketable size of ~25 g and larger. It is therefore desirable to produce stocks of P. monodon with a fast-growth-rate trait, either through selective breeding or via other modes of scientific invention. Among others, chromosome manipulation of P. monodon that confers three sets of chromosomes (3n) to the shrimp, a condition called triploidy and a feat that was achieved through a non-GMO technique, could be the answer. Thermal chromosome set manipulation for triploid induction is considered as a safe and environmentally friendly technique to produce sterile offspring for genetic protection, and prevent genetic pollution from aquaculture stocks in the wild. The black tiger shrimp can be induced to yield a high percentage of triploid offspring with abnormal reproductive histology. Two studies applying different induction methods briefly at the very early stage of embryo formation—one from Australia (chemical shock) and another from Thailand (cold shock) have reported successful results. The triploid shrimps produced from chemical shock method had reduced growth rate, while that from cold shock displayed higher growth rate compared to shrimp with the natural double set of chromosomes. Gender distribution of the triploid P. monodon induced by cold shock was skewed towards females, the larger size of the two sexes and hence is favored more in aquaculture. Because of the favorable results of the cold shock method, it is currently pursued to produce triploid P. monodon for commercial purposes. The production is accomplished through an automatic cold-shock induction system, consisting of spawning detection and cold shock treatment sections. This triploid induction project is an extension of the ongoing selective breeding program of a specific pathogen -free P. monodon that has already been commercially launched, and is part of an initiative to promote sustainable genetic stock improvement protocols for this shrimp species.