Trawl fisheries sector account more than 50% of the marine fisheries production of India. Annual average fish landing from trawlers was 17, 21, 000 t (2008-2011), which formed around 51 % of the marine fish landing of the coast. In this about 51% of the catch was contributed by the west coast and remaining by the east coast of India. Recent studies of the trawl fishery in India have shown that incidental catches/low value bycatch (LVB) landing and utilization has increased over the period of time. The present study is based on the data collected from major trawl landing centres along the coast of India during the period 2008-2011.The estimated landing of low value bycatch (LVB) in trawl fisheries, increased from 14 % in 2008 to 25 % in 2011, which is reflected as reduction in discard volume by trawlers. On an average the highest quantity of LVB landed was in Veraval (50,000 t) and in Mangalore, LVB landing increased from 3% in (3000 t) in 2008 to 26 % (12,000 t) in 2011.In Mumbai, the percentage of trash fish landed remained around 5% during the study period. In Calicut, the LVB landed in 2011 contributed 26% to the total landings by the trawl. In Kochi, Kerala the total LVB landed in 2011 was 1,992 t forming 7.2 % of the total landing. In Chennai, Tamilnadu, the LVB landing which was 13 % in 2008 increased to 17% in 2011, while in Visakhapatanam, Andhra Pradesh, LVB landing showed a steady increase from 2% in 2008 to 21% in 2011. The landing centre price for LVB showed an increasing trend due to increased demand for trash fish for the production of fish meal and fertilizer. The dominance of finfishes in LVB found to increase the value of LVB and the value realized for 30,000 t of LVB in Mangalore in 2011 ( Rs.280 million) was more than that realized for 50,000 t of LVB in Veraval (Rs.200 million). A disturbing trend observed from the studies in Mangalore was that, the sardines in trash fetches higher price in some seasons (upto Rs.16/kg) compared to a lower price when landed in fresh form, and the percentage of sardines in LVB is found to be very high (24% in 2010). This trend may cause a severe threat to the protein availability to the rural poor. Looking at the trend of trawl landing during 2008-2012, it is seen that even though the trawl landing showed an increase over the period of time, the edible portion of the trawl landing did not show any significant increase rather showing general declining trend. Study on the bycatch from different centres along the coast of India showed that as many as 237 species / groups of marine fauna with juveniles of commercially important fishes were landed as LVB. Increase in utilization of LVB (which was discarded earlier) from trawl fishery, a trend which is market driven and its implication on the ecosystem and marine fisheries production of the country is discussed in this paper.

An experimental study was carried out to evaluate the efficacy of three commercially available probiotics P1, P2 and P3 consisting of mainly Bacillus spp. and nitrifying bacteria against Vibrio loads in mass culture tanks of the rotifer Brachionus plicatilis. Triplicate tanks were maintained for each of the probiotic treatment as well as for control group. All the tanks were inoculated with 50 rotifers ml -1 and were fed with Nannochloropsis oculata at a density of 1 x 10 7 cells ml -1 . Every alternate day, all the experimental tanks were treated with probiotics at a concentration of 1 x 10 4 cfu ml -1 and the experiment was carried out for one week. The study showed a significant increase in rotifer density (p<0.05) in all the tanks treated with the probiotics and a maximum density of 400 nos. ml -1 was observed in the tanks treated with P3. After 5 th and 6 th day of culture, total elimination of Vibrios was also recorded in the tanks treated with P3 and P2 respectively. The study revealed that P3, with a combination of Bacillus, Thiobacillus, Acetobacter and Paracoccus supplemented with enzymes, was found to be most effective in the enhancement of rotifer density and also in the elimination of Vibrios in rotifer mass culture tanks.

(Linnaeus, 1766) in relation to the water and sediment quality of marine farm at Karwar for two consecutive crops (2012-13 and 2013-14) were analysed. No significant variation was observed in the specific growth rate (SGR) of both the species between the crops. But within a crop, variations were observed in the SGR and absolute growth rate (AGR) of both the species (p<0.05). Specific growth rate of cobia was 0.75 and 0.78 % day -1 in 210 days of culture for the years 2012-13 and 2013-14 respectively. Physico-chemical parameters of water at cage and reference sites did not vary significantly, except for ammonia-nitrogen and nitrate-nitrogen levels at cage site between and within the crops. No significant variation was observed in total bacterial and Vibrio loads of water in cage site between the crops but significant variation was observed within the crop. The results revealed that temperature (r = +0.61 for 2012-13 and +0.63 for 2013-14) and salinity (r = +0.6 for 2012-13 and +0.5 for 2013-14) played a major role on SGR of cobia during both the crops with higher AGR recorded during summer months. In case of Asian seabass, no significant impact of temperature and salinity on SGR was noticed during the experimental period.

Effect of marine microalgal diet on filtration and ingestion rates of Brachionus plicatilis was studied. Marine microalgae viz., Nannochloropsis oculata, Isochrysis galbana, Chaetoceros calcitrans and a combination of N. oculata and I. galbana (Nanno+Iso) at different cell concentrations were selected for the experiment and triplicates were maintained for each feed. Significant difference (p<0.05) was observed in the filtration and ingestion rates of B. plicatilis, between the treatments. Peak filtration rate of 12.2x10-5 cells ml -1 ind -1 min -1 was recorded in B. plicatilis fed with Nanno+Iso, followed by I. galbana. Ingestion rate was found to be significantly high (p<0.05) for those fed with C. calcitrans, followed by Nanno+Iso. Filtration rate was significantly high (p<0.05) in rotifers stocked at an initial density of 50 nos. ml -1 fed with Nanno+Iso. The results indicated that a combination of Nanno and Iso is the best suitable microalgal diet for rotifer with peak filtration (12.2x10 -5 cells ml -1 ind -1 min -1 ) and ingestion (5.4x10 -3 cells ml -1 ind -1 min -1 ) rates during the first 60 min.

Investigations were carried out on the bacterial flora of water and the quality of rotifers in outdoor mass culture tanks. Brachionus plicatilis and B. rotundiformis were cultured in 10 numbers of 1 tonne tanks and the physico-chemical parameters and microbial loads of water, and total bacterial and Vibrio loads of microalgae and rotifers, during the period 2014-15, were studied. The study revealed a significant variation of the ammonia levels and total bacterial loads with different diets (P < 0.05). A positive correlation was observed between the total bacterial loads of algal concentrations and loads of rotifers, but no correlation was observed between Vibrio loads of water and rotifers. The prevalence of Vibrio loads of rotifers was low in tanks fed with Nannochloropsis oculata and maximum Vibrio loads were recorded in Chaetoceros calcitrans fed rotifers. The Vibrio loads significantly varied with days of culture and also with the algal diets. A positive correlation was observed between the total Vibrio loads of water and rotifers.