Effect of different sex ratios of ablated wild-stock Penaeus monodon Fabricius on maturation, fecundity and hatching rates

The study was conducted to determine other sex ratios of ablated wild-stock Penaeus monodon other than the most commonly practiced 1 male: 1 female. Four different sex ratios, 0:1, 1:1, 1:2, and 1:4 male: female were tested in four 4m diameter circular tanks for a period of 55 days. During the first run the 1 male: 2 females ratio gave: (a) the highest percentage of first (42.20%), second (30.00%) and third (33.33%) spawning; and (b) the highest total and average fecundity (3.9 million eggs and 300,692 eggs, respectively). The 1 male: 2 females ratio is recommended on the basis of highest percentage for the first, second and third spawners, total and average fecundity.

Co-management approach on fisher group: a case study on Ramsar site, Tanguar haor in Bangladesh

In Bangladesh, wetlands are managed through leasing system traditionally from time immemorial. Recently the Government accepted co-management approach for wetland fisheries management and this approach is being practiced in few wetlands for maximize revenue income. A study was carried out to evaluate trend and impact of co-management in Tanguar haor (a Ramsar site wetland) on fisheries resources and livelihood of resident people in the immediate vicinity of the wetland. In Tanguar haor, conflict between leaseholders and the local community was a common phenomenon in the past. Since 2003 the district administration of Sunamganj has been managing the vast wetland resources, however, local people participation was ignored in haor management system. Average monthly fish catch of fishermen increased by 17% after introduction of co-management system and 7 fish species reappeared after introduction of co-management. Average monthly volume of fish catch has increased from 70 kg to 87 kg. A well-defined management structure has been developed for integration of all people of Tanguar haor which would enable them to raise voice jointly and influence policy in their favour.

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.

Stock enhancement in Japan and Taiwan

Stock enhancement has been recognized as one of the essential strategies that can sustain and increase the resources of coastal fisheries. It has been practiced for over a century, with more than 100 species released to date in worldwide programs. Among the countries in Asia, Japan and Taiwan have already established the practice of stock enhancement. Details are given of the main species, number or seedstock produced and released in 1996 in Japan. The species released by the Taiwan Fisheries Research Institute 1976-1995 are also described.

The technology of milkfish hatchery in Indonesia

The culture of milkfish (Chanos chanos), which is the oldest fish cultured in Indonesia, has spread to almost all the provinces in the country. In order to answer the demand of milkfish fry, without decreasing production and wild fry supply, artificial fry production in big and small-scale hatcheries is being practiced. Details are given of the milkfish hatchery system, listing also the major criteria to be taken into account for site selection. Operation of the hatchery is described, outlining the following activities: broodstock rearing; hormone implantation; broodstock maintenance; egg production and harvest; and, larval rearing.

The Malaysian experience

Integrated farming has long been practiced in Malaysia, not only to provide protein requirements needed by the family, but also as a source of income. With fish being promoted on a larger scale, the Malaysian government is providing farmers with financial assistance and hands-on training on fish culture and rice production. Systems of fodder-fish integrated farming and fish-livestock farming in mine ponds are outlined.

Effects of cage fish culture on water quality and selected biological communities in northern Lake Victoria, Uganda

Growing of fish in cages is currently practiced in Uganda and was first introduced in northern Lake Victoria in 2010. An environment monitoring study was undertaken at Source of the Nile, a private cage fish farm, in Napoleon gulf, northern Lake Victoria. In-situ measurements of key environmental (temperature, dissolved oxygen, pH and conductivity) and biological (algae, zooplankton, macro-benthos) variables were made at three transects: Transect 1- the site with fish cages (WC); transect 2- upstream of the fish cages (USC-control) and Transect 3- downstream of the cages (DSC). Upstream and Downstream sites were located approximately 1.0 km from the fish cages. Environment parameters varied spatially and temporally but were generally within safe ranges for freshwater habitats. Higher concentrations of SRP (0.015-0.112 Mg/L) occurred at USC during February, September and at DSC in November; NO2-N (0.217- 0.042 mg/L) at USC and DSC in February and November; NH4-N (0.0054- 0.065 Mg/L) at WC and DSC in February, May and November. Algal bio-volumes were significantly higher at WC (F (2,780)=4.619; P=0.010). Zooplankton species numbers were consistently lower at WC with a significant difference compared to the control site (P=0.032). Macro-benthos abundance was consistently higher at the site with cages where mollusks and low-oxygen and pollution-tolerant chironomids were the dominant group. Higher algal biomass, concentration of low-oxygen/pollution-tolerant macro-benthos and depressed zooplankton diversity at WC suggested impacts from the fish cages on aquatic biota.