Some aspects of freezing and frozen storage of pomfrets

It has been observed that a better frozen product can be obtained by freezing good quality pomfrets transported in insulated containers with sufficient quantity of ice. To enhance the keeping quality and to prevent dehydration and discoloration, a dip in B H A (0.005%) for 15 minutes and subsequent storage in polythene lined gunny bag at -15°c to -I8°c can be recommended. The products treated in the above manner can be stored well over six months. Periodical glazing at an interval of 3 weeks will also prevent the dehydration to a greater extent.

Postmortem changes in hilsa fish. Pt. 2. Studies on physical and bacteriological changes in iced and frozen stored hilsa fish (Tenualosa ilisha Ham.)

Studies were conducted to evaluate the quality of hilsa fish during icing and freezing storage at -20°C by determining organoleptic and bacteriological aspects. The fishes stored in ice were organoleptically in acceptable condition 2 for 20 days. The bacterial load in muscles of 4 days ice stored fish was 2.5x10² CFU/g which gradually increased up to 1.8x10⁵ CFU/g after 20 days when the fishes were organoleptically in acceptable condition. The keeping qualities of different days of ice stored fishes were also evaluated during their subsequent frozen storage at -20°C. Both 4 and 7 days of ice stored fishes were organoleptically in acceptable condition up to 48 weeks but the highest degree of freshness was found for fish stored in ice for 4 days before freezing at -20°C. The result indicates that the longer is the duration of ice storage before freezing, the shorter is the shelf life of the fish. The initial bacterial load prior to freezing of the 4 and 7 days of ice stored samples were 2.5x10³ CFU/g and 3.8x10⁴ CFU/g, respectively which reduced to 2.21x10² CFU/g and 2.38x10² CFU/g, respectively at the end of the 24 weeks of frozen storage. However, after 40 weeks the bacterial load in the frozen stored sample fell below the detection level.

Study on the intestinal bacteria of Labeo rohita (Ham.)

The quantitative and qualitative aspects of intestinal bacteria of rohu fish (Labeo rohita) showed that total viable count of bacteria ranged from 9.9 x 106 to 1.4 x 107 CFU/g of intestine in different age groups of fish. The bacterial load was highest in the month of July and lowest in January. The genera of the isolates from intestine included Coryneform, Micrococcus, Flavobacterium, Cytophaga, Achromobacter, Aeromonas Enterobacteriaceae and Vibrio. Coryneform was the dominant group throughout the study period followed by Micrococcus and Enterobacteriaceae. Marked variations in the bacterial load and generic composition of intestinal bacteria were evident during the study period in different age groups of rohu fish.

Some aspects of population dynamics of juvenile hilsa shad (Tenualosa ilisha Ham.) from the Meghna river, Bangladesh

Population dynamics of the juvenile hilsa shad (Tenualosa ilisha) in the nursery ground of the Meghna River have been studied on the basis of the length cohort analysis of 8023 specimens. The growth parameters viz; asymptotic length (Lα), curvature character (K) and initial time (t0) were found to be 30.69 cm, 1.2 yrˉ¹ and 0.45 yrˉ¹ respectively. Curvature parameter indicates that jatka is a fast growth performer. The natural, fishing and total mortality were found to be 1.37 yrˉ¹, 1.41 yrˉ¹ and 2.78 yrˉ¹ respectively. Survival rate (S) was found to be 6.2%. A small difference was found between the age at first capture (Tc) and the recruitment age (Tr). Stocks of jatka seem to be overexploited and need to be conserved.

Technological aspects of processing of edible mussels, clams and crabs. Pt. 1. Spoilage during ice storage

Rate and pattern of spoilage of some of the economically important edible species of shell fishes Mytilus edulis (Mussel), Villorita cornucopia (Clam), Neptunus pelagicus (Crab) and Scylla serrata (Crab) have been discussed in this communication. Chemical indices used for objective evaluation of quality were water extractable nitrogen (WEN), non-protein nitrogen (NPN), free α-amino nitrogen (α - NH2 -N), glycogen, lactic acid and inorganic phosphorus in addition to the subjective tests. No significant difference in the spoilage pattern of the species during ice storage was observed and these species could be preserved in ice in organoleptic acceptable condition up to 8 days, 9 days, 8 days and 11 days respectively.

Some aspects of the biology of Otolithes cuvieri (Trewavas) and Johnius glaucus (Day) from Veraval

The length-weight relationship in O. cuvieri and J. glaucus can be described by the equations log W=-5.27997+3.13225 log L and log W=-4.93431+3.02556 log L respectively. The length at first maturity in O. cuvieri is estimated as 256 mm and in J. glaucus as 180 mm. Empty stomachs occurred in high percentage in both the species. A study on composition of food items revealed that O. cuvieri feeds on a variety of organisms while J. glaucus a selective feeder.

Some aspects of the biology of Tachysurus tenuispinis Day from Veraval

The regression coefficients in length-weight relationship of males and females of Tachysurus tenuispinis differ significantly. The relative condition factor was calculated for females in relation to various lengths and months. The sex ratio in the catch varied widely in the different months. The number of eggs ranged from 72 to 89 for the fish of length 394 to 570 mm. Empty stomachs occurred in a very high percentage (63.5%) of the total stomachs examined. This is a bottom carnivorous feeder. The main food items found in the guts in order of preference were crustaceans, polychaetes, molluscs, fishes and echinoderms.

Switching aspects of hybrid semiconductor power devices

A hybrid semiconductor power device has been designed which combines IGBT switching and thyristor on-state characteristics. A single gate signal controls the switching and triggers the transitions between an IGBT and a thyristor mode of operation. This paper discusses aspects of the switching behaviour of this and of similar devices. Simulation results of an example structure are presented and conceivable developments in the switching characteristics of hybrid devices are discussed.

Eyes on their fingertips: some aspects of the arts, science, technology and culture of the fisherfolk of Trivandrum, India

Eyes on Their Finger Tips deals with the traditional marine wisdom of a set of people and the rarest of rare experiences they have had at sea. Through these numerous chapters he takes us into the seas of the fishers. It is a voyage which we cannot make in reality. But through the heroic deeds of his father, the riddles of oldman Sebesti, the shark story of brother Kamalappan, and the rituals of his mother, we get a fascinating peep into the wisdom of the watery world of the small-scale fishers of Trivandrum, Kerala, India.

Fault-tolerant aspects of MPC

The architecture of model predictive control (MPC), with its explicit internal model and constrained optimization is presented. Since MPC relies on an explicit internal model, one can imagine dealing with failures by updating the internal model, and letting the on-line optimizer work out how to control the system in its new condition. This aspects rely on assumptions such that the nature of the fault can be located, and the model can be updated automatically. A standard form of MPC, with linear inequality constraints on inputs and outputs, linear internal model, and quadriatic cost function.

Fault-tolerant aspects of MPC

The various aspects of fault-tolerant control systems that have the ability to survive major equipment failures or damages are discussed. Model predictive control (MPC) offers a promising basis for fault-tolerant control. Failures can be dealt with by updating internal models and letting the on-line optimizer control the system in its new condition. Fault detection and isolation (FDI) and the management of complex models are two emerging technologies in this field.

Switching aspects of hybrid semiconductor power devices

A hybrid semiconductor power device has been designed which combines IGBT switching and thyristor on-state characteristics. A single gate signal controls the switching and triggers the transitions between an IGBT and a thyristor mode of operation. This paper discusses aspects of the switching behaviour of this and of similar devices. Simulation results of an example structure are presented and conceivable developments in the switching characteristics of hybrid devices are discussed.

Some aspects of fisheries of the Sylhet basin, Northeast Bangladesh

A comprehensive study on the fisheries aspect was done in the Sylhet basin, Bangladesh during 1994 through 1998. Maximum fishing effort was engaged in the period of April to September while the bulk catch came during the September-January, when less effort was exerted. Barbs comprised 19%, catfishes 18% and major carps 16% of the total catch. Chatla beel, a three years pile, showed the highest fish production. Nine types of nets, four types of hooks and five types of traps were found in operation in the basin. The highest daily mean catch was recorded in glzer jal (26.5 kg/day) and the lowest in the clzandi jal (2.5 kg/day). Behundi jal was the most efficient (0.89 kg/man/h) while chandi jal was the worst (0.12 kg/man/h) gear. Gill net (/ash jal) seems to be the best selective gear. Actual catch/effort always remained less than the projected catch/effort. Maximum economic point of effort lies around 7.0 mandays/km2 and the fishery is gradually moving towards over-fishing. Income of professional fishermen was comparatively high than that of non-professional subsistence groups.