Biology, Fishery, Conservation and Management of Indian Ocean Tuna Fisheries

The focus of the study is to explore the recent trend of the world tuna fishery with special reference to the Indian Ocean tuna fisheries and its conservation and sustainable management. In the Indian Ocean, tuna catches have increased rapidly from about 179959 t in 1980 to about 832246 t in 1995. They have continued to increase up to 2005; the catch that year was 1201465 t, forming about 26% of the world catch. Since 2006 onwards there has been a decline in the volume of catches and in 2008 the catch was only 913625 t. The Principal species caught in the Indian Ocean are skipjack and yellowfin. Western Indian Ocean contributed 78.2% and eastern Indian Ocean 21.8% of the total tuna production from the Indian Ocean. The Indian Ocean stock is currently overfished and IOTC has made some recommendations for management regulations aimed at sustaining the tuna stock. Fishing operations can cause ecological impacts of different types: by catches, damage of the habitat, mortalities caused by lost or discarded gear, pollution, generation of marine debris, etc. Periodic reassessment of the tuna potential is also required with adequate inputs from exploratory surveys as well as commercial landings and this may prevent any unsustainable trends in the development of the tuna fishing industry in the Indian Ocean

Measurement of B(D_s+ -> mu+ nu_mu)/B(D_s+ -> phi mu+ nu_mu) and Determination of the Decay Constant f_{D_s}

We have observed $23.2 \pm 6.0_{-0.9}^{+1.0}$ purely-leptonic decays of $D_s^+ -> \mu^+ \nu_\mu$ from a sample of muonic one prong decay events detected in the emulsion target of Fermilab experiment E653. Using the $D_s^+ -> \phi \mu^+ \nu_\mu$ yield measured previously in this experiment, we obtain $B(D_s^+ --> \mu^+ \nu_\mu) / B(D_s^+ --> \phi \mu^+ \nu_\mu) =0.16 \pm 0.06 \pm 0.03$. In addition, we extract the decay constant $f_{D_s}=194 \pm 35 \pm 20 \pm 14 MeV$.Comment: 15 pages including one figur

Survival characteristics of <i>Cercaria chackai</i> (Digenea: Transversotrematidae)

AbstractThe survival characteristics of Cercaria chackai, the larval form of the curious ectoparasitic digenetic trematode Transversotrema chackai, in sea water, sea water diluted with deionized water in different proportions, deionized water, pond water and tap water were studied. Naturally shed, fresh cercariae had the maximum life span of 20 h 40 min in pond water at salinity 17·8‰, pH 6·45, O2 5·76ml/l and temperature 31·5°C. With increase in salinities beyond 17·8‰, survival time was drastically reduced and beyond 23·58‰,, was restricted to a few minutes. In sea water with a salinity of 38·3‰, the maximum survival time was only 8 min. Below 17·8‰ salinity, although the survival time was less, the difference was not very marked and even in tap water with no salinity, the cercariae lived up to 19 h 50 min. In deionized water the maximum survival time was only 3 h 15 min. Since pond water at pH 6·45 allowed maximum survival time, it is presumed that the cercariae preferred a slightly acidic medium. As temperature was maintained constant and oxygen was available, neither of these two factors, apparently, affected the survival pattern. It is concluded that C. chackai is a typical freshwater form showing considerable tolerance to fluctuations in salinity although the family Transversotrematidae is considered to have a marine origin.</jats:p

<span style="font-size:15.0pt;font-family: "Times New Roman";mso-fareast-font-family:"Times New Roman";mso-bidi-font-family: Mangal;mso-ansi-language:EN-GB;mso-fareast-language:EN-US;mso-bidi-language: HI" lang="EN-GB">Stock assessment of Japanese threadfin bream, <i style="mso-bidi-font-style: normal">Nemipterus japonicus</i> (Bloch, 1791) from Veraval water</span>

519-527&nbsp;Fishery, population characteristics and stock estimates of <i style="mso-bidi-font-style: normal">Nemipterus japonicus was studied during 2006-2010 from Veraval water. Average annual landing was 5,577 t, which contributed to 4.49 % to the total trawl landings. Length-weight relationship showed growth was allometric for the species. L∞, K and t0 were estimated as 345.6 mm, 0.60/year and -0.1132 year. Total mortality rate (Z), fishing mortality rate and natural mortality rate (M) were estimated as 4.02/yr, 2.82/yr and 1.2/yr respectively. Exploitation ratio (E) was found to be 0.70 which showed overexploitation of the species. Length at capture and length at maturity were estimated as 165.47 mm and 180 mm respectively. Recruitment of the species was continuous with a peak in June. Thompson and Bell prediction analysis showed at present fishing level, there is depletion in the initial biomass, spawning stock biomass giving less revenue. Hence it is advisable to reduce the effort by 20%