The potential of mixed culture of freshwater giant prawn Macrobrachium rosenbergii de Man and tiger shrimp Penaeus monodon Fab. at Khulna region, Bangladesh

The freshwater giant prawn (golda), Macrobrachium rosenbergii and tiger shrimp (bagda), Penaeus monodon were stocked together with or without fin fishes at different stocking rates in semi-saline waters at Khulna region and their growth, survival, yield and costreturn analysis were made. Survival rate of golda and bagda ranged from 23.0 to 36.8% and 8.2 to 24%, respectively. The both species were significantly affected by their own stocking density. The average final weight of golda and bagda ranged from 62.4 to 73.3 g and 32.0 to 66.4 g. The bivariate analysis of average final weight of both golda and bagda revealed that golda positively and bagda negatively influenced by the total stocking density. However, the results of the individual sizes of both golda and bagda showed an increase in the proportions of smaller animals and a decrease in the proportion of larger ones with increasing stocking rates. The harvesting weights of all animals in the experimental ghers were in marketable sizes although their prices varied with the individual size. The total production comprised of both golda and bagda ranged from 514.6 to 952.8 kg ha·1, over a culture period of 10 months. Return on investment ranged from 51.0 to 125.7%

The potential of periphyton-based aquaculture production systems

Key words : Periphyton; Biofilm; Artificial substrates; Pond productivity; Tropical aquaculture; Monoculture; Polyculture; Fertilization; Proximate composition; Stocking ratio; Stable isotope ratio; Nutrient efficiency; Production economics; Indian major carps; Catla catla ; Labeo rohita ; Labeo gonius ; Labeo calbasu . The overall objective of this study was to determine the technical and economical performance of periphyton-based aquaculture systems in Bangladesh. It thus addressed one of the key constraints for the poor to benefit from fish culture - limited access to resources such as fertilizers and feeds - while trying to maximize the conversion of these resources into fish. The suitability of four locally available substrates for periphyton growth was evaluated and the optimal fertilization regime determined. The production and growth of four indigenous species, rohu Labeo rohita (Hamilton), catla Catla catla (Hamilton), kalbaush L. calbasu (Hamilton) and gonia L. gonius (Linnaeus), was evaluated under single species and polyculture conditions. The species were selected on the basis oftheir feeding behaviour, ease of culture and high market demand. The periphyton production rate was around 2.5 g of ash free dry matter m -2d -1. Considering the total periphyton substrate area in the pond, this rate can support an estimated fish production of 5,000 kg ha -1y -1. Periphyton production effectively doubled the autotrophic C production, while no trade-off in production between phytoplankton and periphyton communities was observed. The nutritional quality of periphyton was adequate to support the dietary needs of the experimental fish. Nitrogen retention in fish in substrate-based systems was about 1.6 times higher than in control systems without substrate. As periphyton substrate, bamboo ( Bambusa sp.) proved better than hizol branch ( Barringtonia sp.), bamboo side shoot or jute stick ( Corchorus sp.) in terms of nutritional quality and periphyton productivity. Jute stick, however, provided better economical returns. In single species culture, fish yields of rohu and kalbaush increased on average 80% compared to control systems without substrate, whereas with gonia, no significant production increase was observed. In periphyton-based polyculture systems, 70-180% greater fish production compared to controls was obtained. A three species periphyton-based polyculture technology was developed. Using the 75 m 2experimental freshwater ponds, provided with a substrate surface area approximately equal to the pond water surface area and stocked at the rate of 6,000 rohu, 4,000 catla and 1,500 kalbaush (total 11,500 juveniles) per hectare, a fish production of 2,306 kg was achieved within a 90-days culture period.A pilot scale trial in an extended number of household ponds, distributed over different agro-ecological zones of the country, has been proposed before dissemination of this technology for wider use as a means of poverty alleviation and nutritional security in Bangladesh and elsewhere in the region.</p

Optimisation of stocking density of Thai silver barb (Barbodes gonionotus Bleeker) in the duckweed-fed four species polyculture system

The optimisation of stocking density of Thai silver barb (Barbodes gonionotus) in the polyculture with Labeo rohita, Catla cat/a and Cyprinus cmpio was investigated in seasonal ponds. Three different stocking densities of Thai silver barb i.e., 5,000, 6,000 and 7,000 fingerlings ha-1 were tested with stocking density of carps fixed at the rate of 10,000 fingerlings ha-1 Duckweed was applied to all ponds supplemented with rice bran and oil cake. There were no significant variations on either water quality parameters or abundance of planktonic organisms due to the different stocking densities of silver barb. A significantly higher fish production (p<O.OS) was recorded in the ponds in which medium stocking density of Thai silver barb was maintained

Effects of periphyton grown on bamboo substrates on growth and production of Indian major carp, rohu (Label rohita Ham.)

The effects of periphyton, grown on bamboo substrates, on growth and production of Indian major carp, rohu, Labeo rohita (Hamilton), were studied in 10 ponds during July to October '95 at the Bangladesh Agricultural University, Mymensingh. Five ponds were provided with bamboo substrates (treatment I) and the rests without bamboo substrates (treatment II). It was revealed that there had been no discernible difference in the water quality parameters between treatments. A large number of plankton (30 genera) showed periphytic nature and colonized on the bamboo substrates. The growth and production of fish was significantly (p<0.05) higher in the ponds with bamboo substrates as compared to the ponds without substrates. The net production of rohu in treatment I was about 1.7 times higher than that of treatment II. Fish production was as much as 1899 kg/ha over a culture period of 4 months in the periphyton-based production system

The effects of artificial substrates on freshwater pond productivity and water quality and the implications for periphyton-based aquaculture

As a first step in assessing the viability of periphyton-based fish production in South Asian pond aquaculture systems, the effects of artificial substrates on development of periphyton and on water quality were evaluated. Earthen ponds (10 x 7.5 m) were provided with an artificial substrate constructed from poles of either bamboo, kanchi or hizol tree branches (1.0 m2 artificial substrate per m2 pond surface). Higher periphyton biomass, in terms of dry matter (DM) (4.9 mg cm–2) and chlorophyll a (11.5 g cm–2) developed on hizol and bamboo, respectively. Periphyton ash content was higher on hizol (41€than on the other two substrate types (29Ž Protein content of the periphyton growing on bamboo (38 f ash-free dry matter (AFDM)) was 50 igher than that on the other two substrate types. Maximum periphyton productivities of 1.01, 1.38 and 1.03 g C m–2 d–1 were obtained for bamboo, hizol and kanchi substrates, respectively. Taxonomic composition of periphyton showed a rapid development of a relatively stable community with few differences between the substrate types. In total, 56 genera of algal periphyton and 35 genera of phytoplankton were identified. Based on a periphyton productivity estimate of 2.2–2.8 g AFDM m–2 d–1, periphyton alone can sustain an estimated fish production of 5000 kg ha–1 year–1 through the addition of a substrate area equivalent to 100 f the pond surface area

Electrical, optical and gas sensor properties of chloroaluminium (ClAlPc)

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