Determination of Dichlorodiphenyltrichloroethane Residues Levels in Commercial Marine Dry Fish from Different Regions of Bangladesh

Dichlorodiphenyltrichloroethane (DDT) residual levels are available several commercially dry fishes. So, these fishes were detected and determinate the contamination status of dichlorodiphenyltrichloroethane (DDT). The most popular dry fish-Ribbon fish (Lepturacanthus savala), Chinese pomfret (Pampus chinensis), Bombay duck (Harpodon nehereus) and Shrimp sp. (crustaceans) were selected for this study and these dry fishes were collected from nine different markets (three from each of Khulna, Chittagong and Cox's bazar district) of Bangladesh during December-March in 2013. A total number of 36 samples were selected for analyzing in the laboratory by using gas chromatography-mass spectrometry electron captured (GC-ECD) detector. The ranges of DDT in all samples were 2.81 to 877.82ppb. The ranges of DDT in the samples of Bombay duck, Chinese pomfret, Ribbon fish and Shrimp were 13.7-874.35ppb, 2.81-877.82ppb, 3.73-253.68ppb and 4.27-585.97ppb respectively. The mean concentrations of DDT were found highest amount from retailer markets while compared to that from the producer’s markets. Results indicated that the concentration of DDT in dry fish from Bangladesh are higher and may cause chronic disease and potential long-term risk for human health

Effects of spirulina Spirulina platensis meal as a feed additive on growth performance and immunological response of Gangetic mystus Mystus cavasius

The aim of this study was to investigate the effects of dietary Spirulina platensis supplementation on the growth and immunity of Mystus cavasius. Fish were fed on the experimental diets, where the fish meal was replaced with S. platensis meal at 0%, 2.5%, 5.0%, 7.5%, and 10% levels, respectively. Triplicate groups of fish were fed with each diet twice a day near satiation and reared for 10 weeks. After the trial, serum lysozyme levels, whole-body composition, feed utilization, growth performance, and blood characteristics were examined. The pathogenic Aeromonas hydrophila was administered intra-peritoneally to 10 fish from each group and monitored for daily mortality rate. Metagenomics analysis was used to investigate the gut microbiota. When more than 7.5% of fish meal in the diet was replaced with S. platensis meal, the body weight, and specific growth rate were higher than in the control diet. The protein efficiency and feed conversion ratio were also positively affected by dietary S. platensis meal supplementation. The replacement of 7.5–10% fishmeal with S. platensis increased the whole-body protein and ash contents more than the control. The red blood cells, white blood cells, hemoglobin, hematocrit, and mean corpuscular hemoglobin levels of M. cavasius rose when fish were fed 7.5–10% S. platensis compared with the control. The serum lysozyme test result showed an increase in the lysozyme value as dietary S. platensis supplementation was gradually increased. The abundance of bacterial composition was found to be higher with gradually increasing S. platensis supplementation, especially up to 5–10% supplementation level. The total mortality of fish was decreased with higher inclusion of S. platensis when challenged by A. hydrophila. These findings suggest that dietary S. platensis has positive effects on the growth and immune system of M. cavasius, and maintaining dietary replacement of 7.5–10% fish meal with S. platensis can be suggested for feed formulation of M. cavasius

Dietary manganese requirement of stinging catfish Heteropneustes fossilis

The study was aimed to determine the optimal dietary manganese (Mn) requirement by evaluating the effects of various dietary Mn levels on the growth performance, whole-body chemical composition, bone mineralization, and haematology of juvenile stinging catfish Heteropneustes fossilis. Five isonitrogenous purified diets containing graded levels of supplemental Mn from MnSO4.H2O (0, 5, 10, 15 and 20 mg Mn kg−1) were formulated, and referred to as Mn0, Mn5, Mn10, Mn15, and Mn20, respectively. Fish (mean weight of 1.24 g) were stocked in 15 glass aquaria (40 fish per aquarium) each of 180 L water capacity. Each diet was hand-fed twice a day (9.00 and 16.00 h) to apparent satiation to triplicate groups of fish, 7 days a week for 10 weeks. Results indicated that significantly (P < 0.05) the highest % weight gain (186.65 ± 6.59 g) and specific growth rate (1.59 ± 0.13 % day−1) were observed in the fish fed with Mn10 diet supplemented with 10 mg Mn kg−1 diet. The fish feed with Mn10 diet had significantly the lowest (1.80 ± 0.16) feed conversion ratio (FCR). Incorporating dietary Mn up to 10 mg kg−1 was reported to boost whole-body protein; however, subsequent increases in dietary Mn inclusion level did not result in any changes. The whole-body moisture and lipid contents of stinging catfish dropped significantly (P < 0.05) when fed with 10 mg kg−1 Mn (Mn10) supplemented diet. The concentration of Mn in muscle and bone rose linearly (P < 0.05) up to the dietary intake of 10 mg Mn kg−1 diet and then it remained stable. The amount of iron (Fe) in bone and muscle was found to decrease as dietary supplementation level of Mn increased. Increasing dietary Mn levels up to 10 mg kg−1 was found to increase haemoglobin (Hb), red blood cells (RBC), white blood cells (WBC), and mean corpuscular haemoglobin (MCH); however, further increase in dietary Mn levels caused these values to decrease. The amount of dietary concentration between 7.99 and 10.38 mg Mn kg−1 diet was revealed to be acceptable for culture stinging catfish by applying the second-order polynomial regression analysis. It is concluded that better growth and physiological status of stinging catfish can be ensured by using optimum Mn levels in the diet. The results of this study will also motivate further research into the dietary Mn requirements of other species