Feed utilization and wastage in semi-intensive pond culture of mahseer, Tor putitora. (Ham.)

Mahseer, Tor putitora with 12.75, 12.11, and 12.02g of initial weight were fou · J to attain a net weight gain of 12.0 kg, ll.5 kg, and 11.4 kg respectively in pond-1 (commercial feed), pond-2 (farm-made feed), and pond-3 (farm-made feed), respectively against 78.2 kg, 70.3 kg, and 68.1 kg feed fed. Gross energy contents in fish were 1359.3 Kcal/kg, 1281.5 Kcal/kg and 1266.6 Kcal/kg, respectively in pond-1, pond-2, and pond-3 against 3630.4, 3876.9 and 3570.5 Kcal/kg energy in the feed fed. Only 9.4%, 10.5% and 13.7% of the protein, and 8.9%, 3.4% and 3.3% of the lipid fed to fish were converted into muscle respectively in pond-1, pond-2 and pond-3. It was observed that the higher the protein content in feed, the lower the rate of conversion in muscle; the same was also true for lipid. It is supposed that feed derived wastes contribute potentially to water quality deterioration and eutrophication. Lower feed conversion, higher nitrogenous and phosphatic concentrations and higher plankton biomass in the ponds are all supportive to this observation.

Water quality of two semi-closed areas in the United Arab Emirates Coast along the Arabian Gulf:a comparative study

A comparative study was carried out between the two biggest creeks along the Arabian Gulf coast of the United Arab Emirates to evaluate impacts of sewage and industrial effluents on their hydrochemical characteristics. Surface and bottom water samples were collected from Abu Dhabi and Dubai creeks during the period from October 1994 to September 1995. The hydrochemical parameters studied were: temperature (21.10-34.00°C), salinity (37.37-47.09%), transparency (0.50-10.0 m), pH (7.97-8.83), dissolved oxygen (1.78-13.93 mg/l) and nutrients ammonia (ND- 13.12,ug-at N/1), nitrite (ND-6.66 ,ug-at N/1), nitrate (ND- 41.18 ,ug-at N/1), phosphate (ND- 13.06 ,ug-at P/1), silicate (0.68-32.50 ,ug-at Si/1), total phosphorus (0.26- 21.48 ,ug-at P/1), and total silicon (0.95- 40.32 ,ug-at Si/1). The present study indicates clearly that seawater of Abu-Dhabi Creek was warmer (28.l2°C) than Dubai (27.56°C) resulting in a higher rate of evaporation. Owing to more evaporation, salinity levels showed higher levels at Abu Dhabi (43.33%) compared to Dubai (39.03%) seawater. The study also revealed higher secchi disc readings at Abu Dhabi Creek (4.68 m) as compared to Dubai Creek (2.60 m) suggesting more transparency at Abu Dhabi Creek. Whereas, seawater of Dubai exhibited higher levels of pH (1.03 times), and dissolved oxygen (1.05 times) than Abu Dhabi seawater due to an increase in productivity. Meantime, seawater of Dubai showed higher tendency to accumulate ammonia (8.22 times), nitrite (10.93 times), nitrate (5.85 times), phosphate (10.64 times), silicate (1.60 times), total phosphorus (3.19 times), and total silicon (1.54 times) compared to Abu Dhabi seawater due to the enrichment of seawater at Dubai with domestic sewage waters which has distinctly elevated the levels of the nutrient salts particularly in inner-most parts of the creek leading to eutrophication signs. The changes occurred in the receiving creek water of Dubai as a result of waste-water disposal that have also reflected on the atomic ratios of nit: Effect of pollution rogen: phosphorus: silicon.

Larval development of a semi terrestrial mangrove sesarmine crab Chasmagnathus convexus (Crustacea: Decapoda: Brachyura: Grapsidae) reared in laboratory

Four zoeal stages and one megalopal stage were identified in laboratory reared semiterrestrial mangrove sesarmine crab Chasmagnathus convexus. At an average salinity and temperature of 20±1% and 19.2±0.2°C, the megalopa was attained 24 days after hatching. Morphologically, the first zoae of C. convexz1s is very similar to those of other species of the genus Chasmagnathus as well as species of the genus Helice, in that view all share the following characteristics: lateral spine on the carapace, three pairs of setae on the posterior margin of the telson furca, one plus five setae on the endopod of the maxillule, and two plus two setae on the endopod of the maxilla. The differences between the first zoea and megalopa of and those of its congeners are discussed.

Culture potentials of bata, Labeo bata under semi-intensive management system

Small indigenous fish species (SIS) provide food, nutrition, subsistence and supplemental income to a great majority of the people particularly the poor and disadvantaged people of Bangladesh. To date nobody explored the possibilities of culturing these species in combination with the indigenous major carps viz. catla, Catla catla; rohu, Labeo rohita, and mrigal Cirrhinus cirrhosus and grass carp, Ctenopharyngodon idellus. An experiment on the polyculture of carps with a popular SIS, bata (Labeo bata) was carried out to evaluate the production performance of carp-SIS culture in on-farm condition during 15 March to 15 September 2003. Three treatments each having three replications with different stocking densities of bata were tested keeping the carp species combination and stocking density similar in all the treatments viz. treatment 1 (T1), bata (5,000/ha) + catla, rohu and mrigal (5,000/ha at the ratio of 1:1:1) + grass carp (250/ha); treatment 2 (T2), bata (7,500/ha) + catla, rohu and mrigal (5,000/ha at the ratio of 1:1:1) + grass carp (250/ha); and treatment 3 (T3), bata (1 0,000/ha) + catla, rohu and mrigal (5,000/ha at the ratio of 1:1:1) + grass carp (250/ha). After six months rearing, the production obtained were 2,466±77, 2,395±85 and 2,074±72 kg/ha from T1, T2 and T3, respectively. The highest production was obtained from T1, where the stocking density of bata was the minimum (5,000/ha) while the lowest production was obtained from T1 [sic], where the stocking density of bata was maximum (10,000/ha). Significant difference (P<0.05) exists in the production levels as obtained from different treatments. The contribution of bata to total production was 10.31%, 13.96% and 14.38% in case of T1, T2 and T3, respectively.

Active steering of a tractor-semi-trailer

This paper develops a path-following steering control strategy for an articulated heavy goods vehicle. The controller steers the axles of the semi-trailer so that its rear end follows the path of the fifth wheel coupling: for all paths and all speeds. This substantially improves low-speed manoeuvrability, off-tracking, and tyre scrubbing (wear). It also increases high-speed stability, reduces 'rearward amplification', and reduces the propensity to roll over in high-speed transient manoeuvres. The design of a novel experimental heavy goods vehicle with three independent hydraulically actuated steering axles is presented. The path-following controller is tested on the experimental vehicle, at low and high speeds. The field test results are compared with vehicle simulations and found to agree well. The benefits of this steering control approach are quantified. In a low-speed 'roundabout' manoeuvre, low-speed off-tracking was reduced by 73 per cent, from 4.25 m for a conventional vehicle to 1.15 m for the experimental vehicle; swept-path width was reduced by 2 m (28 per cent); peak scrubbing tyre forces were reduced by 83 per cent; and entry tail-swing was eliminated. In an 80 km/h lane-change manoeuvre, peak path error for the experimental vehicle was 33 per cent less than for the conventional vehicle, and rearward amplification of the trailer was 35 per cent less. Increasing the bandwidth of the steering actuators improved the high-speed dynamic performance of the vehicle, but at the expense of increased oil flow.

Semi-supervised video segmentation using tree structured graphical models

We present a novel, implementation friendly and occlusion aware semi-supervised video segmentation algorithm using tree structured graphical models, which delivers pixel labels alongwith their uncertainty estimates. Our motivation to employ supervision is to tackle a task-specific segmentation problem where the semantic objects are pre-defined by the user. The video model we propose for this problem is based on a tree structured approximation of a patch based undirected mixture model, which includes a novel time-series and a soft label Random Forest classifier participating in a feedback mechanism. We demonstrate the efficacy of our model in cutting out foreground objects and multi-class segmentation problems in lengthy and complex road scene sequences. Our results have wide applicability, including harvesting labelled video data for training discriminative models, shape/pose/articulation learning and large scale statistical analysis to develop priors for video segmentation. © 2011 IEEE.

Culture potentials of climbing perch, Anabas testudineus (Bloch) under different stocking densities at semi-intensive management

Anabas testudineus was cultured at different stocking density for the period of five months from May to September. Three stocking densities such as 50,000 (Treatment-1, T1), 56,250 (Treatment-2, T2) and 62,250/ha (Treatment-3, T3) were tested with three replications. After five months rearing, the mean weights of koi were 46.74±2.59, 40.44±2.98 and 37.27±3.01 in T-1, 2 and 3, respectively. The calculated production of native koi in T1 T2 and T3 were 1,916±314, 1,774.31 ±260 and 1,431 ±297 kg/ha, respectively which were significantly different (p<0.05) from each other.

On the use of combined compact scheme for numerical solution of the two-layer oceanic shallow water equations

Many types of oceanic physical phenomena have a wide range in both space and time. In general, simplified models, such as shallow water model, are used to describe these oceanic motions. The shallow water equations are widely applied in various oceanic and atmospheric extents. By using the two-layer shallow water equations, the stratification effects can be considered too. In this research, the sixth-order combined compact method is investigated and numerically implemented as a high-order method to solve the two-layer shallow water equations. The second-order centered, fourth-order compact and sixth-order super compact finite difference methods are also used to spatial differencing of the equations. The first part of the present work is devoted to accuracy assessment of the sixth-order super compact finite difference method (SCFDM) and the sixth-order combined compact finite difference method (CCFDM) for spatial differencing of the linearized two-layer shallow water equations on the Arakawa's A-E and Randall's Z numerical grids. Two general discrete dispersion relations on different numerical grids, for inertia-gravity and Rossby waves, are derived. These general relations can be used for evaluation of the performance of any desired numerical scheme. For both inertia-gravity and Rossby waves, minimum error generally occurs on Z grid using either the sixth-order SCFDM or CCFDM methods. For the Randall's Z grid, the sixth-order CCFDM exhibits a substantial improvement , for the frequency of the barotropic and baroclinic modes of the linear inertia-gravity waves of the two layer shallow water model, over the sixth-order SCFDM. For the Rossby waves, the sixth-order SCFDM shows improvement, for the barotropic and baroclinic modes, over the sixth-order CCFDM method except on Arakawa's C grid. In the second part of the present work, the sixth-order CCFDM method is used to solve the one-layer and two-layer shallow water equations in their nonlinear form. In one-layer model with periodic boundaries, the performance of the methods for mass conservation is compared. The results show high accuracy of the sixth-order CCFDM method to simulate a complex flow field. Furthermore, to evaluate the performance of the method in a non-periodic domain the sixth-order CCFDM is applied to spatial differencing of vorticity-divergence-mass representation of one-layer shallow water equations to solve a wind-driven current problem with no-slip boundary conditions. The results show good agreement with published works. Finally, the performance of different schemes for spatial differencing of two-layer shallow water equations on Z grid with periodic boundaries is investigated. Results illustrate the high accuracy of combined compact method.

Notes on the larval rearing scheme at SEAFDEC/AQD

For tiger shrimp, milkfish, and sea bass, larval rearing starts with the hatching of artificially spawned eggs. The eggs are stocked in larval rearing tanks, hatched, and metamorphosed larvae are fed and reared with good water management. Fry are harvested after about 30 days.