Prospect of fishery, utilisation and culture of crabs in India

Investigations on the fishery, utilization and development of the crabs in Indian waters have been reviewed. Various factors relating to the improvement of fishery, keeping quality of the crab meat and possibilities for an integrated farming of commercially important crabs are discussed.

Formulation, stability and keeping quality of three pelleted feeds used in carp culture

Three dry pelleted feeds incorporating fish meal, fish silage or a mixture of colocasia leaf powder and fish meal were formulated for use in carp culture. The diets formulated were tested for water stability and also for changes in their quality parameters over storage of three months. The different pellets showed satisfactory water stability. The variations recorded in the proximate composition during the period of storage did not bring about any drastic change in the overall keeping quality of the feeds. Therefore, the three formulated feeds are considered suitable for use in the culture of carps.

Fish farm technology. 1 - Brackishwater fish culture based on "aquafeed"

A method has been evolved to enhance the production of natural feed in brackish water fish farms by providing substrates for bio-growth ('aquafeed' production) which is a biomass complex consisting of sedentary and associated organisms of plant and animal species. The seasonal fluctuations of the aquafeed production over different substrates ranged as: 787-1830g/coconut leaf (6m²)/45 days, 16.0-072.9g/glass panel (2x10x10cm²)/30 days, 52-230g/nylon mat (2x25x25cm²)/30 days and 18.6-123.1g/wooden block (6x10x10cm²)/30 days. The average dry weight composition of the major components of aquafeed obtained in the present study was sand-silt-clay 40%, protein 22%, carbohydrate (water soluble) 1.8% and fat 3.35% (water content 85%). Mugil cephalus of 1.85 cm reared in a 0.01ha pond and fed on aquafeed attained a size of 23 cm length and 146.73g weight during one year. Survival rate was 54% at a density of 1000/ha. Salinity and temperature of the pond during the culture period ranged between 1.4 and 32.8‰ and 28.1 and 36.5°C respectively.

Hydrobiological studies of an irrigation tank with reference to the culture of large murrel, Channa marulius (Hamilton) and striped murrel Channa striatus (Bloch)

The importance of selection of species for culture according to the ecological niches and fish food organisms is highlighted with respect to the Fox Sagar, an irrigation take. The tank was infested with submerged vegetation as well as minnows and weed fishes, which rendered the tank unsuitable for the culture of Indian major carps. The tank was stocked with 8000 fingerlings of Channa marulius and C. striatus during 1981 by the local fisherman co-operative society. Only partial harvest was possible during 1982 because of high water level. The final harvest was in April-May, 1983. The yield obtained was 3640 kg during the culture period of about 20 months.

Identification and culture of common diatoms as possible feed for Penaeus monodon

Diatoms were collected from Buyuan Bay, and from the hatchery tanks at Tigbauan, to determine the commonly occurring species, the feasibility of culturing these species, and the potential of these selected species as food for larval P. monodon. The commonly occurring diatoms were identified as Chaetoceros calcitrans, Navicula grimmei, Nitzchia seriata, Nitzchia closterium and Amphiprora sp. These diatoms were isolated and unialgal cultures prepared. Protein content analysis using the micro-Kjildahl method gave the following result: C. calcitrans, 11 . 78%; Nitzchia seriata, 25%; Nitzchia closterium, 30 . 5%; Navicula grimmei, 9 . 06% and Amphiprora sp. 8 . 96%. Feeding experiments were conducted to determine acceptability of the different diatom species and percentage survival of larval stages Z SUB-1 -M SUB-2 . Larvae were placed in 4-l capacity plastic containers with a stocking density of 10/l. The results of several feeding trials using the different mass-produced diatoms are summarized. From the data gathered, C. calcitrans appears to be the most promising candidate as feed for zoea and mysis stages of P. monodon. The average percentage survival of C. calcitrans was 63 . 76% for the 3 trials, and as high as 82 . 22% in the third trial. Comparatively high percentage survival of larvae was also recorded when Nitzchia seriata (48 . 17%) and Nitzchia closterium (67 . 6%) were given as feed, while both Amphiprora sp. and Navicula grimmei gave 0% survival. The poor results with Amphiprora sp. and Navicula grimmei may be due to their low protein content (8 . 96% and 9 . 06%, respectively) and the inability of the larvae to ingest them. Navicula and Amphiprora were observed to cling to the appendages of the larvae and to settle down in the medium making them unavailable to the larvae. Low survival was also noted when frozen C. calcitrans was used (14 . 25%). This may be due partly to the effect of the floculating agent (ALSO SUB-4 . 25 g/l) used in concentrating the diatoms. When protein contents of C. calcitrans, N. seriata and N. closterium are compared, the 2 Nitzchia species have relatively higher protein contents than C. calcitrans and, therefore, could be the more desirable feed candidates. However, few feeding trials were made using Nitzchia so that additional investigations will have to be done on this aspect.

Organic pollution in culture water resulting from excess feed and metabolite buildup

Penaeus monodon postlarvae were subjected to increasing feed concentrations and their growth and survival rates were recorded. Measurements were made of dissolved organic matter, and ammonia and nitrite-nitrogen concentrations. Survival was highest at the lowest feeding level and decreased as feed concentration increased. It is concluded that although organic matter enriches the food supply for P. monodon postlarvae, at higher concentration levels it can pollute the culture water, which in turn leads to mass mortality of the postlarvae. Secondly, the survival rate of P. monodon postlarvae is directly related to dissolved organic matter concentration, oxygen tension, and ammonia-nitrogen concentrations in the culture water. Even at sublethal levels these adverse environmental conditions decrease the survival rate.

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.