Comparison of two hormone preparations on the reproductive performance of air breathing catfish Clarias batrachus (Lin.)

Two hormone preparations viz. Human Chorionic Gonadotropin (HCG) and pituitary gland (PG) suspension were compared for their comparative efficacy on the breeding performance of a air breathing catfish Clarias batrachus. It was found that HCG induced fish gave better ovulation response than PG. Both fertilization and hatching of eggs were significantly (p

Investigation of air-core vortex at hydraulic intakes

Hydrodynamic properties of the surface vortex have been investigated. Based on the Navier-Stokes equations, three sets of the new formulations for the tangential velocity distributions are derived, and verified against the experimental measurements in the literature. It is shown that one modification greatly improves the agreement with the experimental data. Physical model experiments were carried out to study the intake vortex related to the Xiluodu hydropower project. The velocity fields were measured using the Particle Tracking Velocimetry (PTV) technique. The proposed equation for tangential velocity distribution is applied to the Xiluodu project with the solid boundary being considered by the method of images. Good agreement has been observed between the formula prediction and the experimental observation. © 2010 Publishing House for Journal of Hydrodynamics.

Monoculture of three native air breathing fishes in homestead ditches and plastic barrels

Six on-farm trials were conducted from 1 August to 23 November 2004 in two different environments such as homestead ditches (10 to 17 square meters) and plastic barrels (240 liters) to develop techniques for nonoculture [sic] of climbing perch, Anabas testudineus, stinging catfish, Heteropneustes fossilis and walking catfish, Clarias batrachus for poor and landless people who have no access to pond. Stocking density for ditch was 10 fry/square meter while that for barrel was 20 fry/cubic meter. The fishes were fed with 3-test diets viz. low-cost formulated feed (rice bran 20%, wheat meal 10%, mustered [sic] oil cake 35%, poultry offal 35%), live foods (chopped snails and clams), and a commercial feed (Saudi-Bangla feed, starter 3: first month and grower-1: subsequent two months) and designated as T1, T2 and T3, respectively. Feeding rate was the same in all the treatments viz. 10% of body weight (first two months), 8% (third month) and 6% (fourth month). T1 and T2 had three replications while T3 had two replications. Water temperature was recorded weekly while fish growth was monitored monthly. After 4 months' rearing, H. fossilis and C. batrachus in ditches and barrels attained higher average weight in T2 followed by T3 and T1 while A. testudineus in barrels also attained higher average weight in T2. The variation in net weight gain by A. testudineus in ditch fed test diets T2 and T3 was not significantly different (P>0.05) though the net gain in both T2 and T3 was significantly (P<0.05) higher than that of T1. The yield of climbing perch as obtained from T1, T2 and T3 was 988, 1136 and 1185 kg/ha, respectively while that stinging catfish was 395, 242 and 444 kg/ha and walking catfish was 1605, 2,099 and 1,654 kg/ha respectively. All the three species showed significantly lower growth rate in barrels than in ditches.

Baroclinic waves in an air-filled thermally driven rotating annulus.

In this study an experimental investigation of baroclinic waves in air in a differentially heated rotating annulus is presented. Air has a Prandtl number of 0.707, which falls within a previously unexplored region of parameter space for baroclinic instability. The flow regimes encountered include steady waves, periodic amplitude vacillations, modulated amplitude vacillations, and either monochromatic or mixed wave number weak waves, the latter being characterized by having amplitudes less than 5% of the applied temperature contrast. The distribution of these flow regimes in parameter space are presented in a regime diagram. It was found that the progression of transitions between different regimes is, as predicted by recent numerical modeling results, in the opposite sense to that usually found in experiments with high Prandtl number liquids. No hysteresis in the flow type, with respect to variations in the rotation rate, was found in this investigation.

Estimation of yield of dry air bladders from eel fish

The findings are presented of a study conducted to determine a method for the calculation of the yield of dried air bladders of eel from the weight of the whole fish.