Thai pangus polyculture with carps has been increasing for its high potential, however very few attempts were made to compare its growth using different types of feed. A research was undertaken to assess the effect of three types of feed on growth of Thai pangus (Pangasius hypophthalmus) and rohu (Labeo rohita) in polyculture system for 11 months from 15 May 2005 to 15 April 2006 in Khulna. Growth performance using Hand-made Feed (F 1 ) was compared with two commercial fish feed, Sunney Feed (F 2 ) and Saudi-Bangla Feed (F 3 ) in three respective treatments of T 1 , T 2 and T 3 . All treatments were carried out in triplicate at 24700/ha for Thai pangus and 4940/ha for rohu. Average initial weight of Thai pangus and rohu were 4.5 and 33.5g respectively. Growth performance was influenced by feed type. Average final weight of Thai pangus and rohu were 820 and 710; 846 and 770; and 872 and 717g with specific growth rate 1.58 and 0.93; 1.59 and 0.95 and 1.60 and 0.93 % day -1 in T 1 , T 2 and T 3 respectively. Feed conversion ratio was estimated 2.3 in T 1 , 2.1 in T 2 and 1.96 in T 3 . The result showed a typical increasing trend of final weight and specific growth rate of Thai pangus along with the increasing of feed protein level. But rohu showed highest growth in T 2 where protein level was 26-30% which was lower than that of T 3 (Protein level 28-32%). The study suggests that suitable protein level and quality feed is required for adequate growth of fish.
Plankton population of shrimp and shrimp-GIFT (Genetically Improved Farmed Tilapia) culture ponds were studied. The present study was carried out to estimate phytoplankton and zooplankton abundance and diversity in mono and polyculture systems. A total of 13 phytoplankton genera of cyanophyceae, chlorophyceae, bacillariophyceae, euglenophyceae, rhodophyceae and dinophyceae were recorded from the monoculture ponds while 12 phytoplankton genera were measured from shrimp-tilapia mixed culture ponds. Six genera of zooplankton under copepod, rotifer, cladocera, ostracoda were identified in monoculture system and 7 genera were found from polyculture ponds. The numbers of phytoplankton and zooplankton species were recorded to be significantly (p<0.05) higher in monoculture, compared to the polyculture system. In both culture systems, cyanophyceae of phytoplankton and copepod of zooplankton were the dominant groups.
While the increase of the yield of commercially trendy farmed fishes are of special priority in aquaculture, a number of handy technologies are indispensable to realize the surplus production aiming to feed the growing population. As a genetic means of doing this, hybridization technology has been being used for years, because it can produce hybrid vigor through inducing heterosis. Similar attempt was made in mrigal, Cirrhinus cirrhosus, by crossing the hatchery strain with the riverine strain to investigate the heterotic effect in the progeny the species could generate through such intra-specific hybridization. Mean fertilization and hatching rates in hybrids were found to be lower by 7% and 4% respectively than that in purebreds, which envisioned to be trivial to impact the purpose of crossing. Comparative growth test between purebreds and hybrids showed significant differences (p< 0.05) in weight and length, and resulted 30.51% heterosis in hybrid mrigal. This experiment can be considered as a preliminary investigation to motivate the application of strain crossing in mrigal farming and the result found thereof can be used as a clue to optimize this growth boosting technique for the species through further research.
This review synthesizes the available information on the climate variability, fisheries resources and aquaculture activities in the Sundarbans. The article also focuses on the possible impact of temperature and sea level rise, salinity intrusion, impaired freshwater supply, precipitation variability, acidification, and tropical storm surges on the fisheries and aquaculture in and adjacent areas of the Sundarbans as well as dependent fisher-folk communities. It prescribes some adaptation and mitigation measures as well. The synthesis implies that the distribution, abundance, and spawning habit of the Sundarbans fisheries stock of more than 227 species and their recruitment processes needs to be changed. The sea level rise (0.30-1.5m by 2030) and salinity intrusion (16% by 2050) may open door for marine fisheries of euryhaline type and crustacean species, and coastal-aquaculture (e.g. farming of sea-bass, mullet, shrimp, and mud crab). Nevertheless, stenohaline fish species may extinct. The frequent tropical cyclone and flood in recent years resulted in the alteration of the Sundarbans ecosystem, loss of biodiversity and damages to aquaculture farms, and thus livelihood of fisher-folks are at risk. Breeding protocol and adaptive farming technology of suitably saline tolerant fisheries species, reforestation, river restoration, integrated protected area management, and the resilience capacity of the fisher-folk communities must be developed for sustainable fisheries and aquaculture in the Sundarbans and adjacent areas.
Freshwater prawn farming has become an important component in the livelihood of marginal farmers in the freshwater interface of Southwestern coastal Bangladesh. This prawn farming has been integrated with rice and/or vegetable either simultaneously or sequentially. In an attempt to assess the status of integrated prawn-agriculture gher farming in the area, 20 farms at Fakirhat Thana, Bagerhat were surveyed during August-October, 2005. Farmers were interviewed with questionnaire on the production and economics of such integrated farms. Stocking of prawn PL was done at the densities 0.5 to 2.0 PL m-2 during February-March in simultaneous culture and at the densities 3.0 to 7.0 PL m-2 during June-July in sequential system. This integrated prawn farming has beneficial impact on the income of the farmers. Net profit was calculated to be Tk 20,395 ha-1 from a cycle (5-6 months) of simultaneous culture and Tk 35,457 ha-1 from sequential system, and Tk 127,000 ha-1 from rice + prawn + vegetable farming.
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