Length-weight relationship and relative condition factor in Oreochromis mossambicus (Peters) of Bhima River

Oreochromis mossambicus (Peters), a common freshwater fish of Bhima river, has high economic value and considerable fishery importance. The length-weight relationship in the logarithmic way for this fish can be written as: Log W = - 4.50241627 + 2.884822741 log L. This is close to the cubic law indicating the isometric growth of the fish in its natural habitat. The correlation coefficient (r) was found to be 0.9865 which showed a good relationship between the two parameters. The mean relative condition factor (K sub(n)) was 1.00 suggesting the well-being of the fish.

Length-weight relationship and condition factor of Perna viridis (Linnaeus, 1758) and Meretrix meretrix (Linnaeus, 1758) from Mumbai waters

Length weight relationship of the two commercially important molluscs P. viridis and M. meretrix was found to be W=-0.40263L super(2.044719) & W=-0.04359L super(2.2315498) respectively. Condition factor was recorded to be less than 1.0 for most part of the year in P. viridis and for M. meretrix it ranged from 0.39 to 4.61. The present study reveals that there was allometric growth in both the species and the growth was not satisfactory since it showed lower K-value during most part of the year.

Length-weight relationship in freshwater cat fish Clarias batrachus (Linn.)

Clarias batrachus (Linn.), a common freshwater cat fish of Bhima River, has high economic value and considerable fishery importance. The length-weight relationship in the logarithmic way for this fish can be written as: Log W = 4.503717819 + 2.70681765 Log L. This is close to the cubic law indicating the isometric growth of the fish in its natural habitat. The correlation coefficient (r) was found to be 0.9824 which showed a good relationship between the two parameters.

Studies on equilibrium moisture content of canned prawn with particular reference to drained weight

Drained weight of canned prawn depends on moisture content of blanched meat and equilibrium moisture (EM) content of processed meat. The greater the difference between the two values the more is the fluctuation in drained weight. EM is a fixed value with particular reference to the species of prawn, which has been justified mathematically and by material balance of can contents before and after processing.

Effect of low cost feed on the production of walking catfish, Clarias batrachus in farmer's ponds

A feeding trial was conducted for six months in farmer's ponds to assess the performance of BFRI formulated catfish feed on the growth and survival of Clarias batrachus (L.). Nine interested farmers and their ponds (size range: 10-15 dec) in the Barera union of Mymensingh Sadar were selected. The ponds were divided into 3 treatments each with 3 replications. Among the three treatment diets, two diets - traditional (F1) and BFRI formulated (F3) were prepared by using low cost agro-based locally available ingredients and the commercial diets was Saudi-Bangla Grower-1 (F2). The diets were designed as F1, F2 and F3 for traditional (20.40% protein), Commercial (31% protein) and BFRI formulated (30.44% protein) diets respectively. The fingerlings of catfish (7.3 g) were collected from local fish vendors and stocked at the rate of 100/dec. Feeding rates were adjusted by weight after fortnightly sampling of fish. Feeding rate were 10 and 8% of the total body weight respectively for 1st, 2nd month and 5% for the rest of the experimental period. The range of some selected water quality parameters were as follows: dissolved oxygen 4.0 - 7.4 mg/l, temperature 24.0°- 33.9°C, pH 6.8 - 8.00, and transparency 17.0 - 32.00 cm. Which showed suitability of the ponds for rearing fish. At the end of the experiment, significantly highest gain (p<0.05) in weight (1210.96% ±87) and lowest gain in weight (865.25% ±90) were observed in the group of fish fed on diets F3 and F1 respectively. However, no significant differences in growth (p>0.05) was observed in fish fed on commercial diet (F2) and BFRI formulated diet (F3). The FCR value ranged between 2.00 and 2.80 with the traditional diet (F1) showing significantly lower FCR. The total production of fish ranged between 1398.08 and 2145.34 kg/ha with F3 diet resulting in the highest production and net profit. A simple economic analysis showed that fish fed with BFRI formulated (F3) diet resulted in the highest net profit in farmer's pond.

Eradication of uneconomical fishes with simple gill nets at Hirakud reservoir

Experiments with simple gill nets of mesh bar 25, 30, 35, 40 and 45 mm were carried out to determine the suitable mesh size for the eradication of the uneconomical fishes of Hirakud reservoir. Results show that net with 25 mm bar is more suitable particularly for Gudusia chapra (Ham), Rohtee cotio (Day) and Eutropichthys vacha (Ham).

Prediction of drained weight in canned prawn under commercial conditions

A general formula for the prediction of drained weight of canned prawn processed under laboratory condition has been worked out earlier (Chaudhuri et al., 1978). Attempts were made in this communication to modify the general formula to predict the drained weight under commercial conditions of processing particularly blanching, as the moisture content of meat depends on the quantum of heat received during blanching (Govindan, 1975).

Effect of weight of otter boards on the horizontal opening of trawl nets

The paper gives briefly the experiments carried out to determine the optimum weight of otter board that should be used for a trawl gear for better efficiency.

On the optimum buoyancy-weight relation for a bottom trawl

Comparative fishing operations were carried out with 0.55; 0.75 and 1.00 buoyancy-weight relations of bottom trawl in order to find out the optimum relation. Two nets, 18.26 m. (60') two seam nylon and 16.16 m. (23') two seam cotton trawls, were used for the experiment. The results showed that the total catch per trawling hour with 0.75 B-W relation was 16.5% and 32.08% more than that with 0.55 and 1.00 B-W relation for nylon net used. A similar trend was noticed with cotton trawl also as the catch rate with 0.75 B-W relation was 13.89% and 25.78% more than that with 0.55 and 1.00 B-W relations. However, the analysis of catch composition indicated that the off bottom fishes like lactarius, upenoides sp., synagris sp. etc., were of more percentage with 1.00 B-W relation, near bottom fish like saurida, sciaenids etc., were more with 0.75 B-W relation, while the bottom fishes like soles, prawns, skates and rays etc., were more with 0.55 B-W relation.

A statistical study on weight loss in frozen prawns

This paper deals with an extensive study conducted to estimate the extent of weight loss in frozen prawns. The weight Joss varied from 7 to 12% in peeled and deveined (PD), 5 to 7% in headless (HL) and about 7% in cooked and peeled (CP) prawns from the date of processing to the date of inspection, normally within two weeks. To compensate the weight loss nearly 11% of excess material is being added with every frozen block resulting in an average annual loss of Rs. 2.68 crores in foreign exchange. The relevant data pertain to the period 1971 to 1973 and the annual average loss was estimated for the ten years ending 1973.

Length-weight and tail length-total length relationship in Panulirus homarus Linnaeus on the south-west coast of India

Length-weight relationships of Panulirus homarus caught from the Kanniyakumari coast was found to be W=0.000566 L super(2-50). The relationship between tail length and total length was also investigated and compared with that of Panulirus polyphagus. Same relationship did not hold good for the two sexes as in the case of P. polyphagus. For a given tail length, the head length, the total length and the weight appear to be relatively larger for females of small sizes of P. homarus.

Relation between weight and linear measurement of shell in C. madrasensis (Preston)

Relation of weight to height, length and breadth in the Indian backwater oyster Crassostrea madrasensis (Preston) is reported. The relative importance of the variables on weight was found to be height, length and breadth in their order of preference. The multiple regression V = -0.4017 + 0.46743 X + 0.8278 Y + 0.1130 Z can be used to estimate the meat weight (logarithm) for given dimensions of length, height and breadth (all in logarithms). An exponential relation between weight and height is also observed.

A simple method of tagging prawns

The recognition of individual animals is crucial to many aspects of research. Prawns (Penaeus monodon) present unique difficulties in this respect since they molt regularly. Thus, almost all tagging and marking methods developed for prawns so far have proven inadequate. Some tags or marks are lost during molting; others cause injury to the prawns. A new and efficient method has been developed at the Igang Seafarming Station of the Aquaculture Department. Rectangular brass tags measuring 5 mm by 20 mm and numbered consecutively are used. The prawn is held gently but firmly at the base of the carapace with the left hand while the right hand slips the brass tag around the stalk of the unablated eye and presses the tag gently. All tagging must be made under water to avoid stress. From May 29 to September 7 1977 to a total of 348 unilaterally-ablated adult female prawns were tagged on the unablated eyestalk in 5 batches to enable individual observations on gonadal maturation, molting, and growth. Periodic examinations were made four times a month to coincide with the different phases of the lunar cycle. On each examination, survival and recovery rates were recorded. The data included death due to immediate mortality during ablation and loss to cannibalism for the duration of the experiments. In all five tagging experiments, most of the prawns recovered had their tags intact. These included even dead and molting animals. The eyestalk tagging method is suitable for prawns because the tags can be attached without causing injury and has no effect on the rate of growth, maturity, molting and behavior of the animal. The tags are identifiable and permanent; they remain attached to the animal even after death.

The propagation of the mud crab Scylla serrata (F.) de Haan

The mud crab Scylla serrata is an important commercial species found in many brackish areas in the Philippines. During spawning and hatching, the berried females migrate to the sea. Seeds for pond stocking are obtained from the wild. Because of the unpredictability of seed supply, there is a need to propagate the species artificially. Thus, spawning, larval rearing, maturation, and rematuration of the species are being studied. The first attempts at hatching S. serrata were successful with rates varying between 75% and 90%. Two out of three trials on larval rearing yielded a few megalops. The first zoeal stages were fed diatoms, rotifers, Artemia salina, and bread yeast. Overfeeding programs were implemented during the critical premolting periods to prevent weakening of the larvae and lessen cannibalism. Larval weakening during the premolt makes them susceptible to attacks by fungi like Lagenidium and ciliates like Vorticella. S. serrata larvae survived salinity levels as low as 15 ppt until the 14th day of rearing. Other larvae were able to survive in salinities of 30-32 ppt for 8 to 13 days. Zoeal molting was hastened by lowering the salinity to 25-27 ppt. Artificial broodstocking of juveniles and adult crabs has been made possible using a simple refuge system made of three-compartmented hollow blocks. This system has been helpful in minimizing fighting among crabs. Remarkable growth rates have been observed with feeds like mussel meat and trash fish. Average growth increments of 11 mm carapace length and 20 . 35 g body weight have been observed every fortnight. A newly spent spawner could gain additional weight of 22 . 5 g in only 6 days. Feeding rates of juveniles and adult crabs have been established based on the average body weight from an experiment using mussel meat. Crabs feed more at night. In another experiment, eyestalk ablation was found to be effective in inducing growth and mating. Aside from hastening the molting process, copulation is induced even among the small crabs (average carapace length = 55 mm). Natural mating lasts about 26 hr. A copulation which lasted for seven days with a break in between was observed.