M. Kailasam

Diversity of Sulfur-Oxidizing Bacteria in Greenwater System of Coastal Aquaculture

Reduced sulfur compounds produced by the metabolism are the one of the major problems in aquaculture. In the present study, herbivorous fishes have been cultured as biomanipulators for secretions of slime, which enhanced the production of greenwater containing beneficial bacteria. The genes encoding soxB which is largely unique to sulfur-oxidizing bacteria (SOB) due to its hydrolytic function has been targeted for examining the diversity of SOB in the green water system of coastal aquaculture. Novel sequences obtained based on the sequencing of metagenomic clone libraries for soxB genes revealed the abundance of SOB in green water system. Phylogenetic tree constructed from aligned amino acid sequences demonstrated that different clusters have only 82–93% match with Roseobacter sp., Phaeobacter sp., Roseovarius sp., Sulfitobacter sp., Ruegeria sp., and Oceanibulbus sp. The level of conservation of the soxB amino acid sequences ranged from 42% to 71%. 16S rRNA gene analyses of enrichment culture from green water system revealed the presence of Pseudoxanthomonas sp., which has 97% similarity with nutritionally fastidious Indian strain of Pseudoxanthomonas mexicana—a sulfur chemolithotrophic γ-proteobacterium. Our results illustrate the relevance of SOB in the functioning of the green water system of coastal shrimp aquaculture for oxidation of reduced sulfur compounds, which in turn maintain the sulfide concentration well within the prescribed safe levels.

Gonadal development and steroid hormone profile of wild caught grey mullet (Mugil cephalus)

The grey mullet Mugil cephalus is one of the popular and fast growing fishes being cultured in tropical and subtropical regions. In the present study, histological observation of gonadal development and corresponding changes in sex steroid levels from different maturity stages of wild caught male and female were studied. In female, testosterone and 17β-estradiol increased with the advancement of maturation and reached peak (17β-estradiol, 323 ± 13 pg/ml; testosterone, 938 ± 7.87 pg/ml) in mature stage, whereas the level of progesterone was maximum (488 ± 4.9 pg/ml) during ripe stage. Vitellogenin level in serum showed a similar trend as 17β-estradiol. In case of male, the testosterone level in serum increased gradually with advancement of maturation and was maximum (1820 ± 40.25 pg/ml) during ripe stage, whereas significant decrease in 17β-estradiol and progesterone was noticed with advancement of maturation. The fundamental information from this investigation would be useful for developing protocol for accelerating maturation and spawning under captive condition.

Recent Advances in Rotifer Culture and Its Application for Larviculture of Finfishes

Global production of fish from aquaculture has grown substantially in the past decade reaching 52.5 million tonnes in 2008, compared with 32.4 million tonnes in 2000. Aquaculture continues to be the fast-growing animal food-producing sector and currently accounts for nearly half (45.6 %) of the world’s food fish consumption compared with 33.8 % in 2000. The value of world aquaculture, excluding aquatic plants, is estimated at US

Controlled Breeding, Seed Production and Culture of Brackishwater Fishes

98.4 billion in 2008. A forecast indicates that aquaculture food fish production is expected to be 57.2 % million tonnes in 2010 (FAO 2010). Asian countries are dominating the world in aquaculture production due to the favourable tropical climatic conditions and the availability of suitable sites and natural water resources such as bays, rivers, estuaries and brackishwater lagoons.

Optimization of feeding frequency of Asian seabass (Lates calcarifer) fry reared in net cages under brackishwater environment

Aquaculture in marine/brackishwater ecosystems in coastal ponds, open sea cages and pens is assuming greater significance in recent years. Out of the total fish production of about 147 million tonnes, the contribution through culture has become half the mark, sharing annual increase between 8 and 10 %. Considering the capture fisheries’ stagnations and the growing demand for fish as animal protein source, aquaculture plays an important role in augmenting production. In India, the contribution through aquaculture is 80 % in the freshwater sector and around 160,000 tonnes through coastal aquaculture. Aquaculture has developed rapidly over the last three decades and has become an important growing industry for generating the revenue, providing employment and nutritional security for the millions of people. The ever-increasing population and the rising demand for animal protein are causing pressure on fishery development globally. Fish and fishery products contribute around 15 % of the animal protein supporting the nutritional security. In the global fish production, Asian countries occupy the top eight, where India stands second position after China. China has produced 70 % of the global production which formed 50 % in value, whereas India is a distant second with 5 % production and 4 % in value. The global average per capita consumption of fish is around 15 kg. The present average per capita consumption in India is around 9 kg. In countries like Japan and some of the Southeast Asian countries, the average per capita consumption is more than 100 kg. Reaching the global average of 15 kg, taking into consideration that 50 % of the Indian population will be fish consumers, by 2020 the domestic requirement itself will be in the order of 9 million tonnes. By 2020, the coastal aquaculture in India is expected to support the tune of around 350,000 tonnes, from the current production of around 150,000 tonnes. This implies that a quantum jump has to be made in the ensuing years. Out of this, shrimp is expected to contribute around 250,000 tonnes and the rest has to come through fishes and other nonconventional groups.