Effects of fish stocking density on growth and survival of Silver carp (Hypophthalmichthys molitrix) fry in Jashore, Bangladesh

The experiment was operated in 9 consecutive weeks in nine earthen nursery ponds having the same area (0.09 acre) and depth (0.8 m). Seven days old fries of Silver carp (Hypophthalmichthys molitrix) were stocked at 4000, 5000 and 6000 fries/decimal in three treatments with three replications as T-1, T-2 and T-3, respectively to observe the growth and survival. At stocking, hatchlings were the same batch-rearing with an average length and weight of 0.44 ± 0.05 cm and 0.14 ± 0.05 mg, respectively. Wet mustered oil cake and commercial nursery feed containing 30% crude protein were given by two weeks interval, initially according to the bodyweight; the feeding rate was 14% in the first two weeks, gradually reduced to 12, 10 and 8%, respectively in the following week intervals. Water quality parameters and plankton sufficiency were observed every 15 days interval and was found within the acceptable range. Growth performance (6.458 g), survival rate of fingerlings (85.76%) and total production (22151g/decimal) were found highest in T-1 followed by T-2 and T-3. The study concluded that expect better production of fry up to fingerlings, proper stocking density should be maintained in pond fish culture in Jashore region of Bangladesh.

Production performance of stinging catfish (Heteropneustes fossilis, Bloch) in monoculture at two different locations

An on-farm mono culture experiment was conducted for a period of four months from May to September 2014 to compare the growth and production of stinging catfish, Heteropneustes fossilis, at two different environmental conditions. Two locations were one in Gazipur Sadar (AEZ 28)and the other in Narsingdi Sadar (AEZ 9).At each location, there were five ponds of almost similar size and water depth. The stocking density was 500 fry per decimal for each location. Pre-stocking and post-stocking management were similar in both locations. There were considerable variations in most of the water and soil qualities between two locations. After four months of rearing, significantlyhigher (p<0.05) mean harvesting weight of H. fossilis (48.10±7.12 g) was observed in Narsingdi, as compared to that of Gazipur (23.18± 6.24 g).

Effect of background color on the growth pattern and coloration of guppy (Poecilia reticulata)

A study was carried out to investigate the effects of background color on the growth, skin pigmentation and breeding performances of guppy, Poecilia reticulata. Guppy fish was reared in tanks with four different colors as treatments such as T0 (transparent), T1 (red), T3 (blue) and T4 (green) for 5 months. There were significant differences in growth and coloration among the treatments. The growth performance was found significantly higher in transparent background compared to the other treatments. The results showed that the highest mean weight (0.259 ±0.018 g), mean length (3.067±0.208 cm) and SGR (0.165±0.012) of the fish were significantly higher in T0. Least mean weight (0.167± 0.025 g), mean length (2.53±.0.058 cm) and SGR (0.104±0.017) were observed in T1 indicating association of red color with slower growth performance of guppy, compared to other treatments. Study showed significant influence of background color in skin pigmentation. Fishes reared in transparent tanks showed the highest value of carotenoid (0.00175±0.00004mg/g) and fishes reared in the red tank showed the lowest value of carotenoid (0.00092±0.000035 mg/g). Green background enhanced red orange color on fish skin and provided high amount of carotenoid value (0.00143±0.000046 mg/g) than that with blue (0.00095±0.000025 mg/g). These results suggest significant influence of background color on growth and skin pigmentation patterns of Guppy.

First record of two marine fish species from the northern Bay of Bengal, Bangladesh

The present study reports a new record of two marine fishes Filimanus similis (Feltes 1991) and Naso unicornis (Forsskål 1775) from Bangladesh waters. The specimens were collected from Saint Martin’s Island and Cox’s Bazar fish landing canter, Bangladesh. The specimens were diagnosed by analyzing their morphometric characters and DNA barcoding. The study also reports Naso as the first species of the genus ever recorded in the marine waters of Bangladesh.

Bacteriological study of bottom soil of three extensive fish farm ponds

The study was conducted for bacteriological assessment of pond bottom soil (sediment) from three selected fish ponds of Bangladesh Agricultural University. Samples were collected both in winter and summer seasons to see the seasonal variations of some bacterial genera. Physicochemical parameters of the pond water and sediment were also estimated monthly. Sediment samples were collected from the shore and middle zone of the ponds. All sediment samples were acidic. The total viable count of bacteria in pond sediment ranged from (8.5×106) to (4.9×109) cfu/g and bacterial count were higher in summer than in winter. A total of 16 bacterial genera were identified from the sediments. The predominant microflora consisted of Aeromonas, Flavobacterium, Cytophaga, Escherichia, Bacillus, Micrococcus, Staphylococcus, Aerococcus, Acinetobacter, Pseudomonas and Moraxella while the first five listed the greatest abundance. Aeromonas was the most dominant organism. Bacterial diversification was found higher in summer than in winter.

Diversity of fishing gears and crafts used for harvesting the Asian seabass, Lates calcarifer along the Bay of Bengal, Bangladesh coast

Though Asian Seabass, which is locally known as "Koral"/"Vetki," is a vital species in terms of its popularity and price, little is known about the location of breeding and nursery ground, peak breeding season, peak harvesting season, population dynamics, harvesting operation (gears and crafts used for harvesting) of this species in Bangladesh. An investigation was carried out to enlist the group of crafts and gears that are being operated on the Bay of Bengal coast by the fishermen for Asian seabass harvesting. The survey was based on interviews with the local fishermen and secondary data collected from the regional fisheries offices. The study revealed a total of 10 distinguishing fishing gears, including seven nets and two types of hook and lines were used for harvesting this fish. Some are selective for harvesting Seabass, but most of them are involved in multi-species exploitation. Four types of motorized and two types of non-motorized traditional boats are being used for harvesting the seabass in Bangladesh. The seabass fishery extends almost throughout the year at different life stages. The Koral net, Mela Barshi (Single Hook and line), and Push net were found to be effective for catching adult, pre-adult, and juvenile Asian seabasses, respectively. The Sampan boat and Mela barshi were reported for the first time as fishing boats and fishing gear in Bangladesh.

Comparative assessment of dried fish quality collected from market and drying centre at Kuakata in Patuakhali, Bangladesh

The study identified the quality differences of dried Chinese pomfret (Stromateus chinensis), Bombay duck (Harpodon nehereus) and ribbon fish (Trichiurus haumela) from market and drying center at Kuakata, Patuakhali. The sensory, nutritional and microbial quality of collected dried samples were evaluated following organoleptic quality index, standard AOAC and aerobic plate count methods, respectively. Organoleptically no significant difference found between the samples from market and drying center. The highest moisture content value was obtained in Bombay duck (29.78%) from the market and lowest value in Chinese pomfret (20.06%) from drying center. The highest and lowest protein content was in Chinese pomfret (60.73%) and Bombay duck (47.9%) from drying center and market, respectively. The lipid and ash content varied from 2.85% to 7.20% and 13.98% to 19.57% for all the dried fish species collected from both sites. Microbiologically, higher aerobic plate count (APC), total E. coli count (TEC) and total Salmonella count (TSC) were found in Chinese pomfret at 1.96×106 CFU/g, 3.98×105 CFU/g and 1.62×105 CFU/g from market and lowest count found in Bombay duck at 5.05×105, 2.22×105 and 0.81×105 from drying center, respectively. In ribbon fish no Salmonella sp. was found. Based on the sensory and nutritional quality the study conclude that among three species and two sites studied, the dried Bombay duck from the fish drying center had better quality characteristics than the counter parts. However, higher microbial load especially pathogenic TSC and TEC suggests to improve hygiene and sanitary practices, better market distribution and storage facilities need to be followed by the producers for safe and quality dried fishery products.

Effects of attractants inclusion on the growth and survival of Channa striata

An experiment was conducted to evaluate the efficacy of different natural and artificial attractants in the diet of stripped snakeheads Channa striata. The experiment was conducted into two phases- Nursery and Grow-out. There were four treatments TC (Control), TG (Glycine), TA (Alanine) and TN (Nappi) for each phase with three replicates. In phase-1, the fry/fingerling were fed three times daily for four months; in phase-2, the fish were fed twice daily in the morning and afternoon for six months where the effects of formulated diets were compared with control (TC) which is locally available as commercial feed. In phase-1, significantly (p<0.05) lower FCR (1.58±0.13), higher individual weight gain (91.90 g), higher SGR (2.47±1.79 %/day), higher survival (90%), and higher feeding efficiency (57.60±5.54%) were found in the control (TC) compared to all other treatments. On the other hand, in phase-2, significantly (p<0.05) lower FCR (1.63±0.06), higher individual weight gain (299 g), and higher feeding efficiency (45.96±1.63%) were found in Nappi (TN) supplemented diet whereas significantly (p<0.05) higher survival (93.33%) and higher SGR (0.90±0.17 %/day) were found in Glycine (TG) supplement diet compared to the control (TC). Therefore, domestication and then the addition of natural and artificial attractants in formulated feeds may enhance the efficacy of formulated feeds for better growth and survival of the carnivorous fish like stripped snakeheads especially in grow-out phase. Hence, this finding will help to culture C. striata using protein-rich formulated feed adding attractants rather than depending on any live feed or formulated feed which is not commercially feasible.

Heavy metal concentration in some freshwater fishes during autumn and winter in Mymensingh district of Bangladesh

Study was conducted to determine the heavy metal concentration in 5 freshwater fishes Heteropneustes fossilis, Clarias batrachus, Anabus testudineus, Oreochromis niloticus, and Mystus gulio during autumn and winter. Most widely eaten five freshwater fish species were selected for this purpose. These fish species were Among the heavy metals estimated in this study (Cd, Cr, Pb, Cu, Zn) the Cd, Cu, Zn were within the acceptable level but Cr and Pb concentration was above the maximum allowable limit. The Cd, Cr, Pb concentration in the fish muscle was higher in winter as compared to that of autumn but the Cu and Zn concentration was higher in autumn when compared to that of winter. Result of the present research indicates that the heavy metal concentration in fish muscle significantly varies with season. Some heavy metal were within the acceptable level in autumn season but above the maximum allowable limit in winter season. In H. fossilis, C. batrachus, and O. niloticus, heavy metal concentration was within the acceptable level but in A. testudineus and M. gulio heavy metal concentration was above the maximum allowable limit. So heavy metal concentration varied with season as well as with species of fish.