Effect of delayed icing on quality changes and shelf-life of some freshwater fish from Bangladesh

The quality and shelf-life of three freshwater fish species of Bangladesh, catla (Catla catla), magur (Clarias batrachus) and tilapia (Oreochromis niloticus) stored at room temperature and ice were evaluated. Live fishes were killed by cranial spiking and stored at room temperature (27-30 °C), ice stored immediately after death, 5 hr after death and 10 hr after death. The shelf-life and quality of the fishes were evaluated by organoleptic method, rigor-mortis studies and bacteriological assessment. Fishes kept at room temperature became organoleptically unacceptable within 16-20 hr duration. Ice stored fishes showed considerable differences in their shelf-life when icing was delayed for different duration. Shelf-life of catla ice stored immediately after death was 20 days but shelf-life reduced to 12 days when icing delayed for 10 hr after death. Similar trend was observed for two other fish species magur and tilapia. Rigor-index of the fishes stored under different conditions also considerably varied among the three fish species, particularly effect of delayed icing was very much evident. Bacteriological study showed patterns of Aerobic Plate Count (APC) at the end of shelflife study when fishes became organoleptically unacceptable were more or less similar for all the three fish species stored under different conditions. No definite pattern was observed in the generic distribution of bacteria in different fish species under different storage conditions. Micrococcus, Coryneforms, Pseudomonas and Achromobacter were the dominant groups of bacteria isolated from the fishes spoiled at room temperature and ice stored condition.

Ecology and production in two sandy beaches of Goa. Part (A) Distribution of bacteria in Colva and Siridaon in relation to certain environmental parameters

Qualitative and quantitative studies on the bacterial flora of two beaches viz., Colva and Siridaon at high tide, mid-tide and low tide levels during the pre-monsoon period were made. Estimations of important nutrients, like inorganic phosphates and nitrates and organic carbon have been made and correlation with the bacterial counts is being attempted. Definite correlation between bacterial population and organic carbon is seen however, no correlation is observed between bacterial counts and other physicochemical parameters.

Cholesterol content in the eggs of some freshwater teleosts

The authors report the distribution of cholesterol in the ripe, unspawned eggs of 10 spp of teleost (carps, catfish and murrels) together with values for egg diam. The egg, with its relatively abundant yolk, is shown to be fairly rich in cholesterol, though values differ from sp to sp. The lowest value (700 mg/100 g) was recorded from Wallago attu, and the highest (1537 mg/100g) from Heteropneustes fossilis. In general the levels are lowest in carp eggs. No definite relationship could be established between lipid and cholesterol contents, or between egg diam and total cholesterol. The role of cholesterol in physiology of fish is discussed; it is noted that the carnivorous fish tended to have higher levels of cholesterol in their eggs.

Studies on smoke curing of tropical fishes

Fresh mackerel (Rastrelliger kanagurta), catfish (Tachisurus dussumeri) and sole (Cynoglossus dubis) were gutted, cleaned, washed, brined, and smoked. Though it contributes to the quality of the smoked products, salt does not appear to prevent bacterial growth or spoilage at low concentration. In heavily salted products, salt is found to have a definite preservative action. Smoking lasted roughly 5 hrs for mackerel and 4 hrs for sole. Increasing the smoking time gave the product an unpleasant taste. Fish were then sun-dried to 20% moisture. The fish had been prepared in three groups, (1) turmeric-treated, (2) propionate-treated and control. Turmeric treated samples had a very attractive appearance, especially sole. The course of spoilage, as measured by following changes in total volatile nitrogen content, is tabulated. All controls were spoiled within 3 months; the others remained in good condition for 6 months. Turmeric is considered to be an ideal preservative.

Effect of starvation on the biochemical composition of Clarias batrachus (Linn.)

Marked changes were observed in different chemical constituents of C. batrachus during starvation. The N and protein fractions showed a definite pattern of variations. The highest values of these were recorded on 10th day of starvation and thereafter values declined gradually. On the other hand, the acid soluble phosphorus exhibited a reverse trend, increasing gradually from the first to the 30th day of starvation. These changes have been attributed mainly to the energy and metabolic demands of the starving fish.

Succession of bacterial genera during iced storage of three species of tropical prawns, Penaeus indicus, Matapenaeus dobsoni and M. affinis

The native bacterial flora of ocean fresh tropical prawns, Penaeus indicus, Metapenaeus dobsoni and M. affinis was more or less similar, mainly consisting of Pseudomonas, Acinetobacter, Moraxella and Arthrobacter. A definite succession of bacterial genera during iced storage was observed in these prawns. As the day of ice storage increased, the proportion of Acinetobacter and Moraxella also increased considerably and constituted 70-78% of the flora at the time of spoilage. Spoilage by Pseudomonas was very not significant in prawns under iced storage.

Effect of water washing on biochemical and gel characteristics of minced meat from croaker fish (Johnius gangeticus)

Quality of analog fishery products invariably depends on the gel characteristics and nutritional status of minced meat. With an objective to find out the effect of water washing on kamaboko gel, the minced meat from Croaker fish was washed for four times (5 minutes each) using chilled water at a temperature of 8-10°C. Results reflected noticeable improvement in folding test and SSN% of kamaboko with essential decrease in fat content, water soluble proteins, expressible water and quality parameters like NPN, VBN, TMA, FFA and PV denoting superior gel quality than control sample after repeated washing. The results indicated that there was a definite improvement in functional properties such as gel forming ability, expressible water content of the croaker minced meat essential decrease in fat content, water soluble proteins, expressible water and quality parameters after each wash, but two washes of 5 minutes duration each was necessary to achieve satisfactory results.

The effects of trawling on the fish stocks of Lake Victoria

Species composition for Lake Victoria can be divided into two major groups. Haplochromis includes at least four genera, the largest consisting of 120 major species, while the remaining species together number about eighteen. The fish species of this lake have been grouped into two for obvious reasons-Haplochromis forms at least 80 per cent, by weight, of the yield of the lake. When carrying out the survey, the lake was divided into thirteen sampling areas and, although there were variations, all the species were encountered throughout most of the sampling units, except that there were definite trends as one species moved as one from shallow water towards the centre of the lake. It was noted that there was a numerical decrease of species the nearer one got to the centre of the lake, and the catch rates of the species in deeper waters also tended to decrease. The species that were found most consistently throughout the whole lake included Haplochromis complex and Bagrus, and the species found to be confined almost entirely to the shallow waters was Tilapia, in particular Tilapia nilotica.

Relationship between the water levels and the fish catches in lakes Mweru and Mweru wa Ntipa, Zambia

The relationships between water level and catch per effort in two Zambian lakes are compared. In the relatively stable Lake Mweru, a positive correlation exists which can be used, with certain reservations, to predict the state of the fishery two years in advance. The cause of the relationship is probably the effect of water level on the marshy and swampy breeding areas, where at least the most common species in the commercial catch (Tilapia macruchir) has definite limits for the depth of water in which it will breed. For Mweru wa Ntipa, a consistant definite relationship does not exist, probably because the water level and extent of the lake fluctuate widely.

Determination of ecological sensitive areas of the coastal areas of Caspian Sea (Boujagh Wetland National Park) based on ecological carrying capacity and economical valuation region

The coastal districts, as an intersection of two perfectly different ecosystems of dry land and sea, is one of the most complicated and the richest natural system on earth. Considering these areas are constantly exposed to aggregation of water pollutants and also consequence resulting from construction and development activities, they are very vulnerable. Therefore, "sensitive Coastal areas" has become a common word in the related subjects to marine environment recently. The said title relates to the areas of the coastal lines which are vulnerable to the natural condition or human actions because of ecological, social, economic, educational and research importance, also they need particular supports. The southern coasts of Caspian Sea, In Iran prominent samples are of these sensitive areas which their environment are exposed to demolition and destruction intensely, due to increasing and uncontrolled development. The first stage of protecting and managing the coastal areas is identifying sensitive Coastal areas and broadening the Coasts. In this survey, we attempted to examine a definite area in the southern coasts of Caspian Sea. In Iran, by profiting from the world experiences and concluded researches in Iran especially the concluded studies by marine environment office and the Environment protection organization on the subject of determination criteria of the sensitive ecological districts. For this purpose (In Gilan Province) Boujagh national park district which is located in the mouth of sefidroud river and also is possessed of the special ecological and environmental features and distinctions. In this survey, first they said district is divided proportionally on the basis of using a grid system in order to identify the sensitive ecological districts and broaden the coast, and then the desired indices have been determined and scored by numeral valuation method in each unit and then analysis has been done by using of the geography information system (GIS) and final has estimated economic valuation of sensitive ecological areas that is presented in this essay.