6,793 research outputs found

    Seminar on Potential Marine Fishery Resources - Proceedings and Recommendations

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    The seminar was organized by the Central Marine Fisheries Research Institute at Cochin on 23rd April 1986, marking the occasion of the Institute's moving into its own permanent building. The objective of the seminar was to find ways and means of bridging the gap between the estimated potential marine fishery resources of the country and the present level of actual yield from the exploited stocks. Considering the increasing demand for marine fish and the potential for export of marine products, critical information on the presently exploited stocks and those identified as under-exploited or unexploited resources is vitally essential for suggesting management and other measures to obtain optimum yields from these resources

    Analysis of gas absorption to a thin liquid film in the presence of a zero-order chemical reaction

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    The paper presents a detailed theoretical analysis of the process of gas absorption to a thin liquid film adjacent to a horizontal rotating disk. The film is formed by the impingement of a controlled liquid jet at the center of the disk and subsequent radial spreading of liquid along the disk. The chemical reaction between the gas and the liquid film can be expressed as a zero-order homogeneous reaction. The process was modeled by establishing equations for the conservation of mass, momentum, and species concentration and solving them analytically. A scaling analysis was used to determine dominant transport processes. Appropriate boundary conditions were used to solve these equations to develop expressions for the local concentration of gas across the thickness of the film and distributions of film height, bulk concentration, and Sherwood number along the radius of the disk. The partial differential equation for species concentration was solved using the separation of variables technique along with the Duhamel's theorem and the final analytical solution was expressed using confluent hypergeometric functions. Tables for eigenvalues and eigenfunctions are presented for a number of reaction rate constants. A parametric study was performed using Reynolds number, Ekman number, and dimensionless reaction rate as parameters. At all radial locations, Sherwood number increased with Reynolds number (flow rate) as well as Ekman number (rate of rotation). The enhancement of mass transfer due to chemical reaction was found to be small when compared to the case of no reaction (pure absorption), but the enhancement factor was very significant when compared to pure absorption in a stagnant liquid film. The zero-order reaction processes considered in the present investigation included the absorption of oxygen in aqueous alkaline solutions of sodiumdithionite and rhodium complex catalyzed carbonylation of methanol. Present analytical results were compared to previous theoretical results for limiting conditions, and were found to have very good agreement

    Strandings of whales along Gulf of Mannar and Palk Bay

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    Whale strandings occurred frequently along the southeast coasts of India along Gulf of Mannar and Palk bay during Dec 2005 and August 2006

    Bioaccumulation of heavy metals in sea turtles from the west coast of India

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    Sea turtles are widely distributed in the tropical, sub-tropical and temperate waters. Recent reports have indicated that their populations are threatened by the problem of marine pollution . (Stroelli et al., 1998). Heavy metals are one of the major pollutants and have the nature to concentrate in the tissues of animals and their concentrations vary according to biological process such as age, sex, reproduction and migratio

    Local polynomial method for ensemble forecast of time series

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    We present a nonparametric approach based on local polynomial regression for ensemble forecast of time series. The state space is first reconstructed by embedding the univariate time series of the response variable in a space of dimension (<i>D</i>) with a delay time (&tau;). To obtain a forecast from a given time point <i>t</i>, three steps are involved: (i) the current state of the system is mapped on to the state space, known as the feature vector, (ii) a small number (<i>K</i>=&alpha;*<i>n</i>, &alpha;=fraction (0,1] of the data, <i>n</i>=data length) of neighbors (and their future evolution) to the feature vector are identified in the state space, and (iii) a polynomial of order <i>p</i> is fitted to the identified neighbors, which is then used for prediction. A suite of parameter combinations (<i>D</i>, &tau;, &alpha;, <i>p</i>) is selected based on an objective criterion, called the Generalized Cross Validation (GCV). All of the selected parameter combinations are then used to issue a T-step iterated forecast starting from the current time <i>t</i>, thus generating an ensemble forecast which can be used to obtain the forecast probability density function (PDF). The ensemble approach improves upon the traditional method of providing a single mean forecast by providing the forecast uncertainty. Further, for short noisy data it can provide better forecasts. We demonstrate the utility of this approach on two synthetic (Henon and Lorenz attractors) and two real data sets (Great Salt Lake bi-weekly volume and NINO3 index). This framework can also be used to forecast a vector of response variables based on a vector of predictors

    Underwater acoustic instrumentation for investigating deep scattering layer

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    The instruments used for the DSL studies were scientific echo-sounder for detection, Isacc's Kid Midwater trawl for sampling mesopelagics and the trawl sonde to lower the IKMT to the exact depth at which the DSL appeared. Opening of the IKMT and the temperature of the seawater at which the DSL appeared was also recorded on the trawl sonde system. The echoscope connected to the echosounder showed the DSL in different colours depending upon its density. The continuous monitoring on echogram revealed that the DSL observed at surface during night and at 600 m depth during day

    Preliminary report on a reconnaissance survey of the major coastal and marine ecosystems in Gulf of Kutch

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    The region of Gulf of Kutch was possibly more an arid zone in the pleistocene, almost approaching to a desert condition, than what it is at present. The gulf is believed to be the result of a wide indentation or subsidence that allowed encroachment of the sea in the geological past. The whole area is still supposed to be seismically unstable. The Gulf of Kutch covers an area of circa 7,350 sq. km with a maximum depth of 60 m. The tidal range varies from 3.06 to 5.89 m with an average of 4 m. The intertidal zones are sandy and muddy or with sandstones of vast expanse and prolonged exposure

    Influence of salinity on hatching rate, larval and early juvenile rearing of sea cucumber Holothuria scabra Jaeger

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    The fertilized eggs, auricularia larvae and one month old juveniles of Holothuria scabra, obtained from induced spawning were used for various experiments to assess the effect of salinity on hatching rate and larval and early juvenile growth. The experiments were conducted for two days on hatching rate of fertilized eggs, for ten days on larval survival, growth and development and for 30 days on juvenile’s growth rate. The maximum hatching of 39% at 35 ppt, followed by 32% at 33 ppt indicated the suitability of an ambient salinity of 33 to 35 ppt for effective hatching of fertilized eggs. High survival, growth rate and fastest development of auricularia were obtained at salinity between 33 and 35 ppt. The maximum growth rate in length and weight, was at 30 ppt, which may be the optimum for juvenile rearing. The one way ANOVA on differences in the hatching rate, larval growth and survival rate and juvenile growth rate at different salinities indicated high level of significance (p<0.001 )

    Stock enhancement of seacucumbers - a solution for the depletion of natural stocks of Holothuria scabra along Gulf of Mannar

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    Sea cucumbers form a valuable source of income for the poor fisherfolk along Gulf of Mannar and Palk Bay areas of South-east-coast of India. Owing to the high demand in international market and inadequate fishery management practice, the commercial sea cucumber species have been over-exploited leading to the extinction of sea cucumber populations in several habitats. The "Convention on International Trade in Endangered species of Wild Fauna and Flora" (CITES) has recommended inclusion of sea cucumbers in the list of endangered animals and cited the reasons as limited mobility, late sexual maturity, density depended reproduction, low rates of recruitment and ease of collections for their overexploitation and subsequent resource depletion. The releasing of hatchery produced juveniles of commercial sea cucumber species to their natural habitat, a process called restoration, restocking or reseeding is gaining momentum world wide, as the only way for replenishing the depleted stock of sea cucumbers

    Dial variations in temperature, salinity and dissolved oxygen from the neritic waters off Cochin during April (peak summer)

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    Dial variations of important hydrographic parameters were studied continuously for 7 days at a 100 m depth station off Cochin. The frequency of observations varied from 1-3 hourly intervals. In surface waters, the ranges in temperature, salinity and dissolved oxygen values recorded during 10-17 April were 30.64°-32.36°C, 34.56- 34.68 X lO''' and 4.06-4.65 ml/1 respectively. Tlie STD profiles in the diurnal study revealed clearly the premonsoon warming (30°-31°C) in the upper 0-30 m depth zone. In the water column up to 50 m depth, mean salinity values ranged from 34.6 to 35 X 10 while dissolved oxygen values were above 4 mI/1. Time series observations on the production and utilisation of dissolved oxygen revealed wide fluctuation from hour to hour. Vertical gradients in the diurnal study indicated the existence of thermocline around 60 m depth with sharp decline in temperature and dissolved oxygen and increase in salinity below 60 m. The diurnal variation on the distribution of temperature and dissolved oxygen exhibited significant rhythmic tidal impulse of a semi-diurnal wave pattern which was more prominent in the bottom layer below 60 m
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