Length-weight relationship and relative condition factor in Daysciaena albida (Cuv.) and Gerres filamentosus (Cuv.)

The length-weight relationship of Daysciaena albida and Gerres filamentosus were calculated separately for indeterminants, mature males and mature females. The logarithmic regression equation obtained for D. albida - males: log w = -1.5055 + 2.8618 log l; females: log w = -0.9260 + 2.4089 log l; indeterminants: log w = -l.7188 + 3.0616 log l. The regression co-efficients between males and females, males and in determinants and female and in determinants showed significant differences. In G. filamentosus the relationship can be expressed as males: log w = -1.3224 + 2.8740 log 1; females: log w = -1.2874 + 2.8381 log l; indeterminants: log w = -0.8167 + 2.2558 log l. The difference in regression co-efficients between male and female are insignificant at 5% level whereas significant differences were observed between males and indeterminants and females and indeterminants. The relative condition factor (Kn) was calculated for the above two species. In D. albida the reasons for the fluctuations of Kn values can be attributed to both spawning cycle as well as feeding intensity whereas in G. filamentosus it synchronies mainly with spawning cycle.

Isolation and culture in artificial media of Lagenidium from Penaeus monodon larvae

Fungal infection of P. monodon larvae is a problem in hatchery operations. The fungus, which attacks the nauplius to postlarval stages and causes up to 100% mortality, has been tentatively identified as belonging to the genus Lagenidium . This pathogenic organism has recently been isolated and cultured. A description is given of the fungus, and features of its biology and pathology are discussed.

Use of aspirator for aeration in fish culture

A description is given of the use of an aspirator in fish culture and hatchery water management in order to solve the problem of dissolved oxygen depletion. Trials show that a single aspirator can be used efficiently when using 1,000 litres of water for bioassays, breeding experiments, or hatchery management work with continuous flow or recirculating systems.

Ferrocement buoys for mussel culture

A method is described for culturing mussels (Mytilus smaragdinus) using ferrocement buoys, which may be used in the construction of a raft house or a flotation system for nets and cages.

Culture experiments on the copepod, Tisbintra elongata MORI, and evaluation of that species as food organism for milkfish larvae

Five types of food were used to culture T. elongata: rice bran, cow dung, bread, cow dung, bread yeast, fermented fish solubles and Spirulina. Bread yeast was found to give the highest densities. An evaluation was also made of the effectivity of rice bran and fermented fish solubles for the outdoor mass culture of T. elongata . A comparative study on the growth and survival rate of milkfish fry (Chanos chanos) fed with T. elongata and Artemia showed there to be no significant differences between the diets.

A statistical index of growth condition in an aquaculture experiment

A simple statistical index, for evaluating the condition of growth in an aquaculture experiment and indicating the extent of effect of any plausible rival hypothesis, is presented.

Culture of the mud crab, Scylla serrata (Forskal) at different stocking densities in brackishwater ponds

The mean weight percentage survival, relative growth increment, net production and feed conversion value of S. serrata stocked in monoculture at different stocking densities are presented.

Culture of grey mullet, Mugil cephalus, Linnaeus in brackishwater ponds at two stocking densities

The culture potential of hatchery-produced grey mullet (Mugil cephalus, Linnaeus) stocked with average weight of 3.7 g and at 2,500 (treatment I) and 3,000 (treatment II) fingerlings/ha in six 350m brackishwater ponds following the lab-ab method of culture was studied.

Some observations on the growth and cyst production characteristics of the brine shrimp Artemia sp. (Gujarat strain) in pond culture and its potential for import substitution

Experimental culture of the brine shrimp Artemia sp. (Gujarat strain) and production of cyst is discussed. The qualitative and quantitative aspects of the cyst and its economic potential for import substitution are highlighted.

Integrated cage-cum-pond culture systems with high valued climbing perch (Anabas testudineus) in cages and low-valued carps in open ponds

An on-farm trial was conducted over 150 days to determine appropriate stocking ratio, growth and production of climbing perch (Anabas testudineus) in cages and carps in open water of ponds in eighteen farmers' ponds from Haluaghat Upazila at Mymensingh district of Bangladesh. One or two 1 m super(3) cage was suspended in each of 12 earthen ponds and other 6 ponds served as control without cages. Climbing perch of 2-3 g in size were stocked in cages while fingerlings of silver carp (Hypophthalmicthys molitrix), catla (Catla catla), rohu (Labeo rohita), mirgal (Cirhinus cirrhosus), rajputi (Puntius sarana) and common carp (Cyprinus carpio) were stocked at 1 fish/m super(2) with a species ratio of 5:4:4:4:2:1 in open water of all ponds to give cage to open-pond fish ratios of 1:1 (T sub(1:1)) and 2:1 (T sub(2:1)) and 0:1 (T sub(0:1)) as three treatments with six replicates each. Survival of climbing perch was higher in T sub(1:1) (61.67%) than that of T sub(2:1) (29.5%) and was significantly different (p>0.05) between the treatments. Stocking of small size climbing perch fry increased the mortality rate in cages. The net yields of Thai koi were 0.13±0.01 (t/ha) and 0.10±0.01 (t/ha) in treatments T sub(1:1) and T sub(2:1), respectively and both were significantly different (p>0.05). Survival of-open-pond carps was high, ranging from 50 to 91.67% with significantly lower in T sub(0:1) than that of T sub(1:1) and T sub(2:1) treatment. Net and gross yield of each carp species were significantly higher in the T sub(1:1) and T sub(2:1) treatment than that in T sub(0:1) treatment. Net revenues were positive but low in all treatments. Therefore, bigger size climbing perch with lower stocking ratio (T sub(1:1)) is suitable for integrated cage-pond culture of climbing perch and carps. However, more on-farm trials in different ecosystem with scientific interventions are necessary to develop the technology for further dissemination among the rural farmers.

Impact of common carp, Cyprinus carpio (L.) and Nile tilapia, Oreochromis niloticus (L.) on arthropods population, zoobenthos and weeds in rice-fish culture

An experiment was carried out in the fields of the Agronomy Field Laboratory, Bangladesh Agricultural University, Mymensingh, Bangladesh to determine the impact of common carp (Cyprinus carpio) and tilapia (Oreochromis niloticus) culture on arthropod population, zoobenthos and weeds of rice field. The treatments were: (1) rice combined with mono sex tilapia, (2) rice combined with common carp, (3) rice combined with a mixed culture of mono sex tilapia and common carp and (4) rice alone. It was observed that tilapia significantly reduced the number of arthropods, green leafhoppers and white leafhoppers in the rice-fish production systems. Benthos analysis revealed significant effects of fish culture on the abundance of molluscs, oligochaete worms and chironomid larvae. Lowest number of benthos was obtained in the treatments with common carp and significant reduction of the weed biomass was observed, especially in the tilapia containing plots. Based on the results of the study it can be suggested that common carp may play an important role in controlling of benthic organisms, while tilapia might be more effective to control terrestrial arthropods and weeds.

Polyculture of carp with small indigenous fish, bata, Labeo bata (Ham.) at different stocking densities

Small indigenous fish species (SIS) play very important role in the diet of the people of Bangladesh. Until recently, the possibilities of culture them in consideration with the Indian major carp yet to be explored. In view of the above, an experiment on the polyculture of carps with SIS, bata (Labeo bata) was carried out to evaluate their production performance in the on-farm condition during 15 March to 15 September 2003. Three different stocking densities of bata with carp species were given. After six months of rearing, the productions obtained were 2,466±98 kg/ha, 2,395 ±88 kg/ha and 2,074±94 kg/ha from treatments-1, 2 and 3, respectively. The highest production was obtained from treatment-1, when compared with treatments-1 and 2. The contribution of bata in terms of production was 10.31% in treatment-1, while it was 13.36% and 14.38% in treatments-2 and 3, respectively.

Culture potential of Amblypharyngodon mola with carps in polyculture in farmers' pond of northern regions of Bangladesh

To assess the culture potential of mola (Amblypharyngodon mola) along with carps in polyculture systems, an experiment consisted of three treatments each with five replications was conducted for 4 months in two villages of Parbatipur upazilla under Dinajpur district. In the first treatment (SS), catla, rohu, mrigal, grass carp, Thai punti, common carp and a higher density of silver carp (8 per 40m²) were stocked. In the second treatment (SM), stocking density of silver carp was reduced to half and mola was added at a stocking density of 12,500/ha with all other fishes used in SS. In the third treatment (MM), no silver carp was stocked and mola was added at a stocking density of 25,000/ha with all other fishes used in SS. All treatments were subjected to the same regime of feed and fertilizers. The yields of large carps were 2035 kg/ha, 1757 kg/ha and 1326 kg/ha for treatments SS, SM and MM, respectively. Catla, grass carp and carpio showed better growth and production performance in presence of mola at a higher density, while rohu, Thai punti and mrigal showed better performance when stocking density of mola was relatively low. Mola yield was almost two times higher (184 kg/ha) in absence of silver carp (MM) than (62 kg/ha) in presence of silver carp (SM). The result showed that there was a significantly (p<0.01) lower total fish production in treatment MM. But there were no significant difference in total production between treatment SS and SM.

Culture potentials of climbing perch, Anabas testudineus (Bloch) under different stocking densities at semi-intensive management

Anabas testudineus was cultured at different stocking density for the period of five months from May to September. Three stocking densities such as 50,000 (Treatment-1, T1), 56,250 (Treatment-2, T2) and 62,250/ha (Treatment-3, T3) were tested with three replications. After five months rearing, the mean weights of koi were 46.74±2.59, 40.44±2.98 and 37.27±3.01 in T-1, 2 and 3, respectively. The calculated production of native koi in T1 T2 and T3 were 1,916±314, 1,774.31 ±260 and 1,431 ±297 kg/ha, respectively which were significantly different (p<0.05) from each other.

Effects of fish and prawn culture on physico-chemical parameters of water and rice yield in rice fields

An experiment was conducted with five treatments i.e. rice combined with fish having regular urea fertilization (T1), rice combined with prawn having regular urea fertilization (T2), rice combined with fish with supplementary feeding (T3), rice combined with prawn with supplementary feeding (T4) and without fish and prawn (T5) was kept as control. The dissolved oxygen values obtained in treatments with fish both in morning and afternoon were lower than the values of prawn containing treatments and control. The values of nitrate-N, ammonia-N, phosphate-P and chlorophyll-a were higher in fish containing treatments than the prawn containing treatments and control. Between the two fish containing treatments the higher gross (539.44 kg/ha) and net (440.14 kg/ha) yield were obtained in T3 with supplementary feeding and the lower gross (424.88 kg/ha) and net (314.32 kg/ha) yield were recorded in T1 without supplementary feeding. Again, between two prawn containing treatments the higher gross (108.69 kg/ha) and net (81.92 kg/ha) yield were obtained in T4 with supplementary feeding and lower gross (64.32 kg/ha) and net (30.98 kg/ha) yield were recorded in T2 without supplementary feeding. The highest yield of rice grain (3.45 mt/ha) and straw (6.37 mt/ha) were obtained in T1 with fish having urea fertilization without feeding.