This study investigated the effects of dietary fatty acids and water salinity on fatty acid composition and expression of the fatty acid desaturase (fads)-like and elongase (elovl)-like genes of red sea bream Pagrus major. Sequence and phylogenetic analyses revealed that the fadslike and elovl-like genes isolated in this study encoded fads6 and elovl5, respectively. There was no significant difference in growth performance or proximate composition of fish fed diets formulated with 100% fish oil (FO) (FO diet) or with 67% of FO substituted with canola oil (VO diet). Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) contents were significantly higher in liver of fish reared at 15 and 20 ppt than those at 33 ppt. The liver fatty acid desaturase gene transcript was detected by reverse-transcription polymerase chain reaction (RT-PCR) in liver of fish fed the VO diet at 15 ppt, but not at either 20 or 33 ppt. The elovl5 gene was clearly expressed in liver for all treatments. These results suggest that red sea bream could synthesize EPA and DHA from their precursors in liver and that EPA and DHA biosynthesis potency was stimulated at lower salinity.

This present research was conducted to assess the bioaccumulation of toxic heavy metals in fish before and after six months feeding with synthetic feed. Here in concentrations of eight toxic heavy metals such as chromium (Cr), copper (Cu), cadmium (Cd), lead (Pb), nickel (Ni), zinc (Zn), iron (Fe) and manganese (Mn) were determined by atomic absorption spectrophotometric (AAS) method. Before feeding, the concentrations in fish were found to be 19.5 ppb, 61.8, 30.5, 35.3, 123.3, 121.9, 197.7 and 543.2 ppb, respectively. And after feeding with synthetic feed, the concentrations were found to be 22.1 ppb, 101.5, 37.7, 102.0, 147.6, 214.1, 175.8 and 508.0 ppb, respectively. Contents of the trace metals in the feed, fresh water and the water after addition with synthetic feed were also evaluated. The Labeo rohita locally known as "Rui fish" has been selected for this study since it is a very popular fish in the rural as well as in urban peoples of Bangladesh. The accumulation of beneficial elements i.e., Cu, Zn, Fe and Mn were found to be within the permissible limit in both the fishes of before and after feeding with the synthetic feed. Concentrations of potential toxic metals i.e., Cd, Pb and Ni (37.7 ppb, 102.0, and 147.6 ppb, respectively) accumulated in the fish after six months feeding were found to be much higher than that of the recommended permissible limit. Concentrations of Cd, Pb and Ni (21.6 ppb, 102.0 and 114.0 ppb, respectively) in the synthetic feed used for feeding were also found to be much higher than the WHO/EU recommended value. Considering the potential health risk issues, it is recommended that the use of natural feed should be encouraged for feeding despite the synthetic feed in the fish firming project.

This study describes the diets and feeding habits of Cyprinus carpio in integrated rice-fish farming system in the Agronomy Field Laboratory of Bangladesh Agricultural University, Mymensingh, Central Bangladesh during May 1999 to August 1999. Percentage of frequency of occurrence and percentage in number methods were applied for the qualitative and quantitative estimation of plankton. The water quality parameters recorded during the study were within the suitable range for optimal fish growth and plankton populations were also abundant in the water of the rice plots. The phytoplankton population recorded from the gut contents of C. carpio was under 4 groups (viz., Chlorophyceae, Euglenophyceae, Cyanophyceae, Bacillariophyceae) and the zooplankton under 3 groups (viz., Rotifera, Cladocera, Copepoda). Bacillariophyceae and Chlorophyceae were the dominant phytoplankton group while Rotifera was the dominant zooplankton group in the gut contents of C. carpio. This study also revealed that, gut contents of C. carpio was composed of 48.47% phytoplankton and 51.53% zooplankton indicating omnivorous nature of the fish. The availability of plankton population in the rice plots and the food and feeding habits of C. carpio suggest that, this fish could be a vital candidate for integrated rice-fish aquaculture.

No abstract

Fisheries are a prospective sector of Bangladesh contributing 5.7% of the total export earning and 4.92% to the GDP (BBS 2003(BBS -2004. But this sector has been facing serious problems due to unplanned water development structures. The water development structures (dam, polder, sluice gate etc.) block the movement of fish to and from the floodplain, which serves as the spawning and nursery ground for fish and throw thousands of fishermen out of work (Kabir and Sharmin 2003). Fish pass is a structure which helps to overcome this problem by facilitating upstream or downstream migration of fish. Sariakandi fish pass was established in 2001 at Sariakandi upazila under Bogra district to facilitate fish migration between the Rivers Jamuna and Bengali. The field study was conducted at Sariakandi, Fish pass of Bogra, Bangladesh during the first part of 2007 to know the impacts of the fish pass on fish diversity of Bengali river, socio-economic condition of fishermen and ecological condition near the fish pass area. To perform this study interview, case study, structured questionnaire and eye observation methods were used. (Henderson) are available. Now the fishermen capture more fish from the Bengali river and earn more money (about 200-300 Tk/day). They are making semi-paka and paka house and they are using sanitary latrine. The number of school and college-going children of the fisherman family are also increasing. The ecological condition near the fish pass area is degrading year after year. The connecting part of the Jamuna River to the fish pass is becoming high land due to heavy siltation during the rainy season.From the study we may conclude that the fish pass has positive significance on fish diversity and socio-economic development of the fishermen. But the fish pass is going to be inactive due to siltation. So this study recommends overcoming the siltation problem near the fish pass area in future.

Optimum feeding schedule is one of the main things for the proper growth of fish and other animals. A study was conducted to optimize the effects of different feeding frequencies on growth performance and production of Rui (Labeo rohita) under pond cage culture system in Rajshahi, Bangladesh. Labeo rohita with an average weight of 302.23±4.07g (mean ± SD) were randomly stocked in 9 cages at 30 fish/cage in all the treatment. Fish were fed (4% of body weight) a commercial floating feed with three different feeding schedules: feeding of fish thrice daily in T1treatment; twice in T2 treatment and once in T3 treatment. Water quality parameters were measured during the study period. The physico-chemical parameters of pond water were within suitable ranges for fish culture in cages. The obtained values of the water quality parameters were temperature 28.26 to 28.46°C, pH 6.91 to 6.94, DO 5.04 to 5.33 mg/l, CO2 2.95 to 3.02 mg/L. The mean final weight gain was significantly highest in T1 (345.05 g) a followed by T2 (324.66 g) and T3 (257.82 g). The Specific growth rate (SGR) value were significantly higher in T1 treatment (0.91% bwd-1; Body weight per day) than T2 (0.87% bwd-1) and T3 treatment (0.73% bwd-1). The feed conversion ratio (FCR) value was significantly lower in T1 fish group (2.72) than other two T2 (2.84) and T3 (3.44) treatments. The fish productions were 18.13, 17.55 and 15.67 kg/cage/cycle in T1, T2 and T3 respectively. The highest net profit was found (Bangladeshi Taka, BDT 1445.38) in T1 compared to T2 (BDT 1329.24) and T3 treatment (BDT 937.99). The cost benefit ratio (CBR) was significantly higher in T1 (0.57) than T2 (0.53) and T3 (0.37). The feeding schedule three times in a day was most suitable than other two schedules.

No abstract