Breeding biology and monosex male seed production of Genetically Improved Farmed Tilapia (GIFT) strain of Oreochromis niloticus L. in Bangladesh

A study on the breeding biology of the GIFT strain of Nile tilapia, Oreochromis niloticus, was conducted for a period of five months. The sex ratio of the parent individuals was optimized for performance in spawn production, where the best results were obtained with a sex ratio of female to male of 4:1 compared to those of 3:1 and 2:1. The diameter of eggs obtained from the GIFT stock had major and minor axes of 2.19±0.09 and 1.72±0.07 mm, respectively, with no significant differences between the treatments. The average number of eggs produced was 392±22 per female, with fertilization and hatching rates ranging between 94-96% and 85-88%, respectively. No significant variation was observed between the treatments. Breeding frequencies per female in the three treatment groups ranged between 10-40 days and the highest value was obtained at a female to male sex ratio of 4: l. In an other experiment, l7 aMethyltestosterone (MT) was applied orally to the fry at their first feeding stage with treatments- 1, 2, 3 and 4 at the dosage of 100, 80, 60 and 40 mg/kg feed respectively, for the period of 28 days. The mean percentage of males obtained in treatments, 1, 2, 3 and 4 were 98, 97, 95 and 68, respectively. Treatments-1, 2 and 3 did not differ significantly (P>0.05) from each other but treatment 4 showed significant variation (P<0.05) from other treatments. The results showed that MT-100, 80 and 60 mg/kg feed administered for 28 days produced close to cent percent male population of the GIFT strains in aquaria.

Studies on geo-morphology, ecology and fish production of the 92 rivers of Rajshahi Division, Bangladesh

Geo-morphology, ecology and fish production of the 92 rivers of Rajshahi division have been presented in this paper. Fifteen rivers are dead and 11 rivers have severe erosion problem. Siltation has increased in 66 rivers and depth has decreased in 11 rivers. Sixty nine rivers are suffering from low flow conditions. Fish diversity has decreased in 20 rivers while fish production has declined in 75 rivers. A total of 31 fish species have extinct, 25 species are under threat of extinction and 43 species have low production. Siltation and pollution are the major causes of fish habitat loss. Recommendations are made to protect and conserve fish habitat and riverine fisheries of Rajshahi division.

Pond production of Artemia in Pakistan

Currently our government and the private sectors are very much interested in the establishment of marine aquaculture. For the successful operation in aquaculture of finfishes and shellfishes, the basic requirement is the suitable diet, apart from proper environment. For the larvae, juveniles and adult stages of the culturing organisms the live Artemia is the ideal food. The aquaculturists the worldover are using live food for their culturing organisms, as the live food played an important role in the dietary management of aquaculture of finfishes and shellfishes (Sorgeloos and Kulasekarapandian, 1984), particularly during larval stages. The live nauplii of Artemia are used in aquaculture of finfishes and shellfishes due to being nutritionally balanced, non polluting, economically bearable, viable and readily acceptable to the culturing species. The adult Artemia is also used for feeding the aquarium fishes particularly so when there is a clear abundance of this resource which is cheaper and can economically compete with alternative artificial diet. By the use of Artemia the aquaculturists may obtain optimum growth and survival rate of the organisms. The life cycle of Artemia is very short, which is completed within two weeks especially during dry season in highly saline waters, the two weeks old Artemia starts producing cysts. These cysts become ready to harvest within a week.

Effect of stocking density on the production of common carp (Cyprinus carpio Lin.) in cages at Kaptai lake, Bangladesh

Growth, survival and food conversion ratio (FCR) of Cyprinus carpio in cages at different stocking density were studied in Kaptai lake. Fingerlings of common carp (12.47 ± 4.29 g) were stocked at 25/m2 , 50/m2 and 75/m2 each with replication in six floating net cages each of Sm x Sm x 4m and reared for 240 days. The growth rate was inversely related to the stocking density with the mean weights of 325.5 ± 11.74 g, 268.99± 8.44 g and 167.0 ± 11.66 g at low, medium and high densities, respectively. At harvest, standing crop biomass averaged 7 .82, 12.83 and 11.58 kg with the survival of 98.9%, 97.6% and 94.4% and food conversion ratios of 4.51, 3.82 and 4.21 for the above three densities, respectively. Weight gain and production at density 25 fish/m 2 were significantly different (p< 0.01) from other two densities. Water quality was not affected in the cages having different stocking densities.

Production of freshwater giant prawn using over-wintered juveniles for enhancement of farm income and reduction of rural poverty in Bangladesh

Freshwater giant prawn, Macrobrachium rosenbergii fry produced during late season can not withstand low temperature thus the prawn culture programme during winter is hampered. To overcome this problem, late season (August-September) prawn juveniles (0.9-6.8 g) were stocked at a density of 1.43 to 3.57/square meter in 350-476 square-meter ponds in Pabna and Mymensingh districts during October 2000 and cultured till May 2001. Monthly average water temperature during the winter months (December-February) varied from 16 to 22 °C and gradually increased to 32 °C in May. The prawn fry showed fast growth rate and attained an average weight of 60-70 g within eight months including three winter months. Growth compensation was observed during summer months. Survival rate was 60-79%. After extrapolation of the present growth rate more than 1,600 kg/ha production can be achieved in better-managed ponds. Extrapolated cost of production was Tk. 268,000 and 200,000 Tk./ha in two best ponds, sale value was Tk. 644,9146 [sic] and 528,466 and gross profit was Tk. 376,000-410,000, suggesting a higher economic feasibility of farming freshwater prawn with over-wintered juveniles.

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.

Pilot plant for production of fish ensilage and the economics of production

This communication describes the design aspect and functions of individual pieces of equipment of a pilot plant for the production of fish ensilage based on lactic acid fermentation process. Details about the equipment, process flow sheet and equipment layout of the pilot plant have been given. An attempt has been made to prepare an estimate of the cost of production of liquid ensilage and solid feed mix.

Nucleotide degradation and production of hypoxanthine in some Indian marine and freshwater fishes

Changes in nucleotides and production of hypoxanthine in rohu (Labeo rohita), mrigal (Cihhrina mrigala) and common carp (Cyprinus carpio) during storage at 2-4°C were examined. Differences were observed between common carp and others. Production of hypoxanthine in pomfret (Stromateus argenteus), cat fish (Arius macronotacanthus), shark (Scoliodon spp.), seer fish (Scomberomorus guttatus), ray fish (Dasyatis imbricata) and prawns (Parapenaeopsis stylifera) was examined during storage at 2-4°C and -28°C. At 2-4°C hypoxanthine increased regularly but at -28°C there was no increase during storage over 28 weeks.

Land-based mass production of prawn (Penaeus monodon Fabricius) spawners

The first spawnings were obtained 12 days after ablation with 4 spawners yielding 784,000 eggs and a harvest of 250,000 P SUB-10 fry. Survival of females after 1 month was approximately 30%. Mortalities were mostly due to handling stress during the regular ovarian samplings as well as disease frm the accumulated excess feeds on the bottom of the tank. Male survival could not be recorded because of transfers to other tanks and addition of new stocks. Development seemed to peak 3 weeks after ablation. The average number of eggs per ablated spawner was 120,000. However, many of the partially spawned females were removed from the spawning tanks the following day so that remaining eggs released in the next 2 to 3 days could not be recorded. Estimate of the average number of eggs per ablated spawner is 120,000-150,000 in contrast to 500,000 per wild spawner. However, the low production cost more than compensates for the difference. Fry reared in the Wet Laboratory were used for experiments, mostly on feeding. Therefore, survival at harvest is not to be taken as a reflection of stock quality. Although fewer in number, larvae from ablated prawns are as healthy in terms of vigor in swimming and feeding as those from wild females. Most mortalities are due to inability to molt caused by lower water temperatures and inadequate feeding.

Preliminary report on the first production of the crab stages of alimasag, Portunus pelagicus (Linnaeus)

An experiment was undertaken studying the early life history of Portunus pelagicus in order to obtain information of relevance to rearing techniques for crabs.

Mass production of Penaeus monodon Fabricius juveniles in earthen nursery ponds

Different culture techniques were tried for rearing larvae of Penaeus monodon, in order to obtain preliminary data on stocking density, water management, fertilization versus feeding and effect of different types of vertical substrate. The results of the experiments showed that: (1) older fry have greater chances of survival; (2) the traditional nursery pond designs and practices used for milkfish in the Philippines are applicable to prawn only at very low densities and give acceptable high survival rates only when used with the older postlarval stage.

Successful inoculation of Artemia and production of cysts in man-made salterns in the Philippines

The authors report on inoculation experiments of Artemia nauplii and young adults of the San Francisco Bay strains in earthen fish ponds. The test inoculated proved successful where water salinity ranges from 20 to 32 o/oo during the start of the rainy season in the Philippines.

Effect of substrate types on fecundity and nauplii production of ablated Penaeus monodon Fabricius

Experiments were undertaken to assess the survival, spawning, fecundity and nauplii production of ablated P. monodon females reared in flow-through broodstock tanks with white coralline and black sand substrate for 62 days. The similar trend observed in mortality rates in both substrates suggests that variation in substrate material for broodstock tanks is not a likely cause of prawn mortality. There were also no significant differences observed between rematurtion rates, i.e. number of spawnings, under the different treatments. Singnificantly higher nauplii production were observed in females in tanks with white substrates. At present, the land-based broodstock tanks in SEAFDEC utilize white coralline substrates due to higher hatching rate of eggs and nauplii production, convenience in siphoning out debris and excess food that tend to accumulte in the tank, and contrast provided by the white substrate during nightly observations of ovaries.

Survival, growth and production of Penaeus monodon at different stocking densities in earthen ponds with flow-through system and supplementary feeding

The survival, growth and production of Penaeus monodon in earthen ponds were observed. A significant effect of stocking density on the survival rate of prawns was observed. The final average weight obtained varied inversly with the stocking density and the production varied directly with stocking density and survival rates. The maintenance of a clear water environment is recommended as a preventive measure against Vorticella attack.

Survival, growth and production of Penaeus monodon and P. indicus at different density combinations with milkfish

Penaeus monodon and P. indicus juveniles were stocked and reared for about 3 months in earthen ponds at different density combinations with Chanos chanos. The presence of either Penaeus species at any density ratio did not affect significantly the C. chanos survival. Survival rates of the penaeids indicated that intraspecific and interspecific competition occurred and were reduced with the reduction in stocking rate. It is concluded that further studies on higher density ratios and feeding and economic consideration would be of help to the development of this kind of fishpond management system.