Genetic tools and techniques for fish improvement

Abstract

The Indian continent is a rich source of marine, freshwater, brackishwater and cold water species of fishes of which more than 2900 species have been documented so far. India is blessed with a long coastline of 8129 kms, inland water bodies like rivers and reservoirs, lakes etc. Fisheries and aquaculture in our country contribute about 1.5 % to the GDP. In addition to providing food and nutrition security to millions of people, about 14 million people are directly or indirectly employed in this vibrant sector. Response to selection for body weight in first is higher because of existence of high genetic variability. The fecundity is also very high in fish/shellfish thereby allowing for a higher selection intensity.External fertilization offers a great opportunity for production of family as per choice. Fisheries research especially related to genetics had been initiated by the ICAR in a very systematic manner. Genetic characterization of candidate species has also been undertaken in a major way since 2008. Microsatellites and mitochondrial genes ATPase 6/8, Cytochrome oxidase I, 12S rRNA and 16S rRNA are also being used for genetic characterization. Individual selection is still considered the best choice although family selection could also play a vital role in retaining genetic variability. ICAR-Central Institute of Freshwater Aquaculture, Bhubaneswar along with the Norwegian Agency for Development Cooperation (NORAD) initiated the selective breeding programme on the carp-Labeo rohita in 1992. This is the first genetic improvement programme on fishes in our country and till date is in vogue with substantial genetic gains in growth. In 2007, at the same institute, genetic improvement programmes in the giant freshwater prawn Macrobrachium rosenbergii and recently on another carp Catla was initiated. Fish genetics study at ICAR-Central Institute of Brackishwater Aquaculture, Chennai and ICAR-Central Institute of Fisheries Education, Mumbai in collaboration with the NORAD on the tiger shrimp Penaeus monodon revealed that growth has moderate to high heritability and individual selection is the preferred choice for eliciting maximum response. Additive genetic variances have been exploited to control some diseases, whereas in White Spot Syndrome Virus disease in shrimp, the additive genetic variance is negligible, thereby making selection ineffective. Presently, a genetic improvement programme on the fgreshwater catfish Clarius magur has been initiated at ICAR-CIFE at Balabhadrapuram near Kakinada