Limnological conditions of naturally turbid ponds and its effects on fish growth

An experiment was conducted on six naturally turbid ponds in the village of Salakandi situated to the south-west corner of Bangladesh Agricultural University, Mymensingh for a period of three months from July to September '96. The experiment was performed by studying the physicochemical factors of water and soil, the biological factors such as densities of phytoplankton and zooplankton, and the growth of fishes. During the experimental period water turbidity varied among ponds. The highest value of turbidity was found to be 679±183.6 FTU in pond 1 and the lowest was 158±23.31 FTU in pond 4. The maximum and the minimum water transparency were recorded in the month of July and September respectably. The lowest net weight of fishes was found 28.8 kg/ha/year in pond 1 due to high turbidity and the highest was 35.8 kg/ha/year in pond 4 due to low turbidity. Most of the correlations between turbidity and transparency, phytoplankton, and zooplankton were significant at 1% and 5% levels.

Nutritional value of some small indigenous fish species (SIS) of Bangladesh

Twenty three small indigenous fish species (SIS) in the size range of 3-18 cm were analyzed for proximate composition and minerals (Ca and P) content to evaluate their nutritive value. The moisture content of different species ranged between 71.00 and 81.94%. In general, small sized fishes showed higher moisture content. The muscle protein content among the species varied widely (16.16-22.28%). In general, the muscle protein content of fishes showed higher value than the whole carcass protein content. The carcass lipid content varied between 1.87 and 9.55% and showed an inverse relationship with the moisture content. The gross energy content ranged from 19.51-27.30 KJ/g on dry matter basis. In the present study, the calcium and phosphorus contents ranged between 0.85-3.20% and 1.01-3.29% respectively. The calcium and phosphorus ratio (Ca/P) varied between 0.44 and 2.00. From the nutritional point of view, it shows that the SIS are good source of protein and minerals especially calcium and phosphorus

Colossal loss of shell and fin-fish larvae during collection of Penaeus monodon (Fab.) fry in the rivers of Satkhira

This study was conducted in five river-estuaries of Satkhira from January to December '96. It was found that during the collection of each Peneaus monodon) post larva (PL), about 45 larvae of other shrimps, 12 individuals of fin-fishes and 530 macro-zooplankters were mercilessly destroyed. It was also recorded that about 11.6 million of P. monodon PLs were harvested annually from the study area. The sh1dy implies that colossal loss of shell and fin-fishes and other plankton resources is done by tiger shrimp fry collectors, and such massive destruction adversely affect the natural productivity and ecological balance of the coastal environment.

Development of a new model of feeding strategy analysis of fish incorporating resource availability and use data

A feeding strategy model is proposed using stomach content and resource availability data as a modification to Costello (1990) and Amundsen et al. (1996). Incorporation of feeding electivity index (E) instead of the prey-specific abundance signifies the importance of resource availability in prey selection as well as the predator's ability to specialize, generalize or avoid particular prey items at the individual and population level.

Domestication of an endangered fish species Nandus nandus (Ham.). Pt. 1. Laboratory rearing of young fish up to sexual maturity

An experiment was conducted for rearing of Meni, Nandus nandus in laboratory condition for seven months with the objective to select appropriate feed for the species and to develop a rearing technique of the species up to the stage of sexual maturation. Different trials were conducted using artificial feed (35.5% protein), dead fresh kachki (Carica soborna), dead fresh prawn (Macrobrachium lamarrei) and live prawn (Macrobrachium lamarrei). The provision of bottom sediment did not significantly influence the growth of fish. Between dead fresh kachki and dead fresh prawn, the fish preferred dead fresh prawn. The fish was found to be reluctant to take dead fresh kachki and prawn as food unless they became very hungry. The fish was found actively feeding on live prawn. The FCR of the prawn as food for N. nandus was found to be 2.5. From the study, it was observed that in laboratory rearing N. nandus preferred live prawn as food than artificial feed, dead fresh kachki and dead fresh prawn. The fish fed on live prawn became sexually matured (eggs or white milt extruded by gentle pressure on the abdomen of the fish) in the laboratory at the end of the experiment.

Population dynamics of the ribbon fish, Lepturacanthus savala (Cuvier 1829) from the north-eastern part of the Bay of Bengal

Population parameters of Lepturacanthus savala from the trawl catches in the north-eastern part of the Bay of Bengal, Bangladesh were investigated based on length frequency data, using complete ELEFAN computer program. The asymptotic length (Lα) and growth constant (K) were estimated to be 106.50 cm (total length) and 0.80/year respectively. Based on these growth parameters, the total mortality (Z) was estimated to be 1.89. The estimated values for natural mortality (M) and fishing mortality (F) were 1.08 and 0.81 respectively. The estimated value for the exploitation rate (E) using the length converted catch curve was 0.43. The recruitment pattern showed two peaks per year. The estimated sizes of L. savala at 25, 50 and 75% probabilities of capture were 57.49, 60.39 and 63.28 cm respectively. The estimated length weight relationship for combined sex was W=0.00093 TL(super)2.97

Preservation of fish by freezing and glazing. Pt. 1. Bacteriology of fresh, frozen and glazed fish

Microbiological investigation of fresh and frozen fishes such as pomfret, surmai and mackerel was carried out under various conditions of preservation. Glazing, block-freezing and preservation in gunny bag were affected. Determination of bacterial load and isolation, identification and classification of the resistant bacteria were made. Spore-formers of Subtilis mesentericus group were found to be resistant to freezing as well as glazing by ascorbic acid, citric acid and sodium nitrite except a mixture of sodium chloride and glucose. Bacterial load was reduced to a good extent and maintained low till the end of frozen storage period.

Preservation of fish by freezing and glazing. Pt. 2. Keeping quality of fish with particular reference to yellow discolouration and other allied organoleptic changes on prolonged storage

Organoleptic observations of quick, slow and block frozen, glazed and stored fish were recorded at regular intervals. Glazing was renewed at intervals of four weeks. Development of yellow discolouration in the case of white pomfret was followed. Keeping quality of glazed fish was better than unglazed frozen fish. Yellow discolouration could be controlled by ascorbic acid for 42 months and by a mixture of sodium chloride and glucose for 52 months.

Preservation of fish by freezing and glazing. Pt. 3. Effect of freezing, glazing and frozen storage on the B-vitamins and essential minerals present in the fish flesh

The changes occurring in moisture, thiamine, riboflavin niacin, phosphorus, iron and calcium in pomfret, surmai and frozen mackerel, glazed with ascorbic acid, citric acid, sodium chloride, glucose, sodium nitrite and kept under frozen storage were studied up to 6 months and results reported.

A small scale fish meal dryer

A batch type rotary drum dryer for the production of fish meal suitable for operation in the fishing villages of India has been designed, fabricated and operated successfully. The dyer can be used for production of fish meal from whole lean fish or press-cake from fish body oil extraction plants. The time taken to reach a moisture level below 10% is 5-8 hours depending upon the type of material fed into the dryer.

Preliminary observations on the effect of electrical seine on fish catch

Forty-six experiments were done with the electric seine in 24 tanks with a.c. and interrupted a.c. The source of electrical energy was a 3 Kw a.c. generator of water-cooled diesel engine. A control seining without applying electricity was conducted for every experiment with electric "seine" to have a comparison for the efficiency of electric "seine" over control ones. Electric seine was found to have an increased catch over control seining both in numbers and in weight. Electric seine with two electrodes was found to have better effect over three electrodes. Benthic fishes like Cirrhina mrigala, Notopterus notopterus, Cyprinus carpio, Glassogobius giuris, Ophicephalus sp. and Mystus sp. were found to be more sensitive in electric "seine". Increased catch of small fishes like C. mrigala, N, notopterus and Ophicephalus sp. has been observed in electrical "seine" in addition to larger ones.

Pattern of cutaneous wound healing in a live fish Clarias batrachus (L.)(Clariidae, Pisces.)

Incisional wounds of the same length and depth were made on skin between dorsal fin and the lateral line canal of Clarias batrachus and the pattern of wound closure has been studied histologically. Following infliction, a marked change in the colour of the skin surrounding the wound was observed which lasted for about 30 h and restored thereafter. Mucus and blood cells plugged the wound gap shortly after infliction. The epidermis surrounding the wound was found to be detached from the basement membrane. Mass movement of epidermal cells was observed from both side of the wound gap. The epidermal cells at the margin of the wound became hypertrophied. The epidermis became normal by 32 days. The dealing of sub-epidermal tissue indicated degenerative and regenerative changes of muscle fibres. The mucus and blood cells were accumulated in the wound gap and later fine blood vessels were formed. Gradually granulation tissue was formed and fibroblasts and myoblasts appeared. Myoblast differentiated into muscle bundles. The epidermal repair was completed within 35 days.

Nutritional characteristics of the two fermented fish products: Hentak and Ngari of Manipur

Proximate composition and nutritional characteristics of the two fermented fish products Hentak and Ngari of Manipur (India) were evaluated. Percentage of moisture, protein, lipid and ash contents in Hentak and Ngari were respectively: 36.30 versus 36.03; 33.33 versus 38.38; 13.60 versus 13.34 and 11.43 versus 5.49. Digestibility values in feeding trials in laboratory rats for 28 days were 82.37% for Hentak 89.46% for Ngari and that of Casein was 92.69%. The biological value, food conversion ratio and protein efficiency ratio (PER) of Hentak were 96.94, 4.83 and 1.8 respectively and that of Ngari were 97.83, 3.17 and 1.8 respectively. The α amino nitrogen of Hentak and Ngari in Pepsin + Trypsin phase were 28.40 and 28.92 respectively. The TBA number, peroxide value and TVBN were within the acceptable limits.

Effect of fertilizer carbamide on proteolytic enzymes of fish Labeo rohita

Specific activities of acid, alkaline and neutral proteases in liver, muscle, brain, and gill of fish exposed to 50 ppm ambient carbamide for 15, 30 and 60 days and in control were estimated. It was observed that carbamide even at low concentration of 50 ppm inhibited proteolysis and favoured protein synthesis.

Studies on paddy-cum-fish culture under different land situations

Paddy fields can be broadly classified on the basis of land situations viz. Upland - Shallow water (10-30 cm), Medium land-medium deepwater (30-100 cm) and Low land-deepwater (above 100 cm). Three major systems of paddy-cum-fish culture, viz. (A) high yielding paddy varieties (H.Y.V) and air-breathing fish under Upland, (B) H.Y.V./local paddy and Tilapia/common carp under Medium land and (C) deepwater paddy and major Indian carps under Low land situations have been successfully investigated in the farmers' fields and at the Research Stations (1982-92). Effects of low-cost artificial feeding on growth, yield and management practices of different types of fish showed a considerable increase of rice and fish yields and a decrease in insect-pest incidence. Under Upland situation, short duration H.Y.V. in combination with fast-growing air breathing fish was studied thrice a year (summer, winter & autumn seasons). Combined rice and fish culture produced highest yields in all the seasons than in the control.