Demonstration of some selected aquaculture technologies under farming system research in Jessore and Santahar, Bangladesh

BFRI evolved some selected aquaculture technologies viz. polyculture of carps in perennial ponds, monoculture of short cycled fish species (BFRI super strain) in seasonal ponds and prawn seed production through backyard hatchery system have been demonstrated under Farming System Research (FSR) component in Jessore and Santahar regions. Both polyculture of carps and monoculture of short cycled fish species technologies were tested in farmer's ponds in Kaium Kula village near Jessore town. In polyculture trials, seven species comprising of silver carp (Hypophthalmichthys molirrix), catla (Catla catla), rohu (Labeo rohita), grass carp (Ctenopharyngodon idellus), common carp (Cyprinus carpio), mrigal (Cirrhinus cirrhosus) and silver barb (Barbonymus gonionotus) were stocked @ 9,500 (ratio 6:2:4:2:1:5:5); 10,750 (ratio 6:2:4:2:1:5:5) and 12,000 (ratio 6:2:4:2:1:5:4) fish/ha respectively in ponds of T1, T2 and T3 having three replications of each. The mean highest fish production was 3,148 kg/ha in T3, followed by 2,899 kg/ha in T1 and 2,875 kg/ha in T2. Production of T3 was significantly different (P<0.05) than both T1 and T2, while there was no significant differences (P>0.05) between the production of T1 and T2. In case of trial of short cycled fish species, two treatments were tested: T1 (comprising of BFRI super strain of Nile tilapia, silver carp, common carp and silver barb; ratio 3:5:1:1) and T2 (having only BFRI super strain of Nile tilapia). Stocking density in both the treatments were same (20,000 fish/ha). In this trial average production was higher in T1 (2,743 kg/ha) than that of T2 (2,369 kg/ha) but the production figure in these two treatments was not significantly different (P>0.05). Demonstration of backyard prawn hatchery technology was tested at Santahar region of Bogra district, North-west part of Bangladesh. This hatchery consisted of three main components i) bio-filter, ii) rearing tank unit (chari) and iii) air blower/air pump unit. Plastic drum of 200-250 l capacity and cemented chari of 200-250 l capacity were used as bio-filter and larval rearing containers respectively. A 0.5 hp air blower with 6 aquarium air pump were used to operate the aeration system in the hatchery. Diluted sea water (10-12 ppt) made from brine solution (200-250 ppt) collected from salt-bed was used in the backyard hatchery system of hatching of eggs and rearing of larvae. Rearing of first stage zoea-larvae was reared in three rearing tanks following the stocking densities of 40, 50 and 60/l of water respectively. Production of post-larvae were 20±0.82, 22±1.12 and 28±1.63/liter of water in treatments I, II and III respectively in 38, 40 and 39 days rearing period.

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.

Biology and farming of the green mussel Mytilus smaragdinus

Biological investigations were carried out in Sapian Bay, Capiz from November 1975 to December 1976 with samplings conducted fortnightly. Histological studies on the gonad reveal a high percentage of ripe and spent females during the month of April and May, and ripe to near ripe during November to December. However, larval counts were highest on February 25, 1976 with 253 mytilid larvae per haul compared to 0-79 per haul during all other months. The high larval count was followed by the highest spat settlement during the next sampling period two weeks later, with the spat collector set in the water during the February 25 sampling. The four materials tested, blue polypropylene fiber rope, black polypropylene fiber, and coir rope, all had their highest spat counts during this period with an average of 471 spats per standard 10 cm rope piece. The range during the other time periods is 2-283 spats. Of the 4 materials tested, the black fibrillated polypropylene film had the highest larval counts in 15 out of a total of 25 sampling periods. The blue rope was the poorest spat collector. Coconut husk was tested later on and it proved to have a very high catchability, with spats completely enveloping the husk surface. Growth monitored from one cohort in Sapian Bay averaged 10 mm per month. 50-60 mm is considered marketable size. Trial growth experiments with transplanted mussels were also conducted at Igang Bay in Guimaras Island, Makato River in Aklan, and a milkfish pond in Leganes, Iloilo. Survival in Igang was less than 50% after the second week, and the condition of the surviving mussels can be described only as 'watery' with the mantle completely transparent. Mortality was minimal in Makato but the growth rate was only 30% that of Sapian Bay. The pond experiments were terminated due to severe crab predation.

Year-round and rotational freshwater prawn, Macrobrachium rosenbergii and paddy farming: soil quality, production and economics

A study was carried out at five upazillas (Dumuria, Fakirhat, Pirojpur sadar, Gopalgonj sadar and Kalia) of five southern districts of Khulna, Bagerhat, Pirojpur, Gopalgonj and Narail to understand the comparative production performance and any effect on soil quality in case of year-round golda (Macrobrachium rosenbergii), alternate prawn-paddy and year-round paddy farming. A direct interview of 55 farmers was taken, using pretested questionnaire, and soil samples were taken from selected farms before and after each crop. Among the five upazillas, farmers in Gopalgonj sadar and Kalia are not practicing year-round golda. Rotational golda-paddy farming has been recorded to result in maximum profit, with the highest of Tk. 310,912/ha/year in 2003 at Dumuria. Only paddy farming is less profitable than other two cropping patterns, irrespective of study sites. The nutrient status of soil in rotational golda and paddy farming has been found improved, compared to that of only golda or paddy farming.

Environmental assessment of shrimp farming in relation to livelihoods in the south-west coastal Bangladesh

The study was designed to assess the environmental impact of shrimp farming and implications on local livelihoods at the south-west coastal area of Bangladesh. All the stakeholders reported that shrimp farming negatively affected on the environment at the coastal area. The soil and water, fish habitation, agricultural cropland, grazing land, indigenous fish, household vegetations, trees and plants, land fertility and mangroves are affected negatively by the shrimp farming in the coastal area. About 44% of stakeholders agreed that mangroves were destroyed by the extension of shrimp farming in the study area. In the case of positive impact of shrimp farming on environment about 16% of stakeholders agreed that the household vegetations increased due to alternate rice and shrimp-prawn farming.

Farming seaweeds at SEAFDEC/AQD

The article presents the practices that have been developed or documented by SEAFDEC Aquaculture Department for farming seaweeds. These practices are: the cage culture of Kappaphycus, and the ‘rice planting’ method for cultivating Gracilaria. The seaweed gathering practices in coastal communities in western Visayas is also presented.

Oyster and mussel farming

The article discusses the oyster and mussel culture practices in western Visayas, Philippines. Spat collection, culture methods and management, and harvesting technique are discussed. The article also discusses mussel culture in New Zealand.

Offshore fish farming

The article discusses offshore fish farming, which is commonly practiced in some countries in Asia, North and South America, and Europe. Environmental factors such as the exposure of the cage to wind and waves, and its management are also discussed.

Farming the seaweed Kappaphycus

Seaweed farming is the top foreign exchange earner for the Philippines. Kappaphycus constitutes 80% of the Philippine seaweed export. It is sold in both fresh and dried forms; although dried seaweed has a greater demand, fresh seaweed is highly prices in restaurants. The 3 main seaweed products marketed are agar, alginate and carrageenan. A brief outline is given of farming operations and investment costs and returns.