Effect of towing speed on retention of zooplankton in bongo nets

Long-term time series of zooplankton data provide invaluable information about the fluctuations of species abundance and the stability of marine community structure. These data have demonstrated that environmental variability have a profound effect on zooplankton communities across the Atlantic basin (Beaugrand et al., 2002; Frank et al., 2005; Pershing et al., 2005). The value of these time series increases as they lengthen, but so does the likelihood of changes in sampling or processing methods. Sam-pling zooplankton with nylon nets is highly selective and biased because of mesh selectivity, net avoidance, and damage to fragile organisms. One sampling parameter that must be standardized and closely monitored is the speed of the net through the water column. Tow speed should be as fast as possible to minimize net avoid-ance by the organisms, but not so fast as to damage soft bodied zooplankters or extrude them through the mesh (Tranter et al., 1968; Anderson and Warren, 1991).

Effects of current speed and turbidity on stationary light-trap catches of larval and juvenile fishes

Light traps are one of a number of different gears used to sample pelagic larval and juvenile fishes. In contrast to conventional towed nets, light traps primarily collect larger size classes, including settlement-size larvae (Choat et al., 1993; Hickford and Schiel, 1999 ; Hernandez and Shaw, 2003), and, therefore, have become important tools for discerning recruitment dynamics (Sponaugle and Cowen, 1996; Wilson, 2001). The relative ease with which multiple synoptic light trap samples can be taken means that larval distribution patterns can be mapped with greater spatial resolution (Doherty, 1987). Light traps are also useful for sampling shallow or structurally complex habitats where towed nets are ineffective or prohibited (Gregory and Powles, 1985; Brogan, 1994; Hernandez and Shaw, 2003).

A High-Speed Fish Evisceration System (FES) for Bycatch and Underutilized Fish Stocks

Development of a high-speed and high-yield water-powered fish evisceration system (FES) to efficiently preprocess small fish and bycatch for producing minced fish meat is described. The concept of the system is propelling fish in a stream of water through an arrangement of cutting blades and brushes. Eviscerated fish are separated from the viscera and water stream in a dual screen rotary sieve. The FES processed head off fish, weighing 170–500 g, at the rate of 300 fish/min when used with an automatic heading machine. Yields of mince produced from walleye pollock, Theragra chalcogramma; and Pacific whiting, Merluccius productus; processed by the FES ranged between 43% and 58%. The maximum yield of minced muscle from fish weighing over 250 g was 52%, and the yield of 250 g was 58%. Test results indicated that surimi made from minced meat recovered from fish processed with the FES was comparable in quality to commercial grade surimi from conventional systems. Redesigned for commercial operation in the Faeroe Islands (Denmark), the system effectively processed North Atlantic blue whiting, Micromesistius poutassou, with an average weight of 110 g at a constant rate of 500–600 fish/min, producing deboned mince feeding a surimi processing line at a rate of 2.0 t/h. Yields of mince ranged from 55% to 63% from round fish. Surimi made from the blue whiting mince meat produced by the FES was comparable to surimi commercially produced from blue whiting by Norway and France and sold into European markets.

Comparison of model predictions and speed trial results for a group of 32' wooden trawlers

Speed trial results of six 32' wooden stern, trawlers built to the same design are analyzed to determine the EHP ship Froude number curves in each case and are compared with the model test results of the same design and for the corresponding, displacement, conditions.

In vitro phagocytic study of blood leucocytes and peritoneal macrophages of walking catfish Clarias batrachus ( Ham.) against Aeromonas hydrophila and Escherichia coli.

In observation of in vitro phagocytic activity against Aeromonas hydrophila isolate 34k (a virulent form) and Escherichia coli (an avirulent bacteria) of neutrophil- and monocyte-like cells of walking catfish Clarias batrachus showed phagocytosis. N eutrophils and monocytes phagocytized the avirulent form of bacterial isolate more than the virulent one. Other blood leucocytes did not show phagocytosis. Peritoneal macrophage of the fish were separated by glycogen elicitation and the macrophages were being adhered on plastic cover slips for studying their in vitro phagocytic activity. Most of the cells were alive after adherence and showed phagocytosis against the virulent and avirulent bacteria. The percent phagocytosis and phagocytic index were higher against the avirulent E. coli than the virulent A. hydrophila.

Effect of low cost feed on the production of walking catfish, Clarias batrachus in farmer's ponds

A feeding trial was conducted for six months in farmer's ponds to assess the performance of BFRI formulated catfish feed on the growth and survival of Clarias batrachus (L.). Nine interested farmers and their ponds (size range: 10-15 dec) in the Barera union of Mymensingh Sadar were selected. The ponds were divided into 3 treatments each with 3 replications. Among the three treatment diets, two diets - traditional (F1) and BFRI formulated (F3) were prepared by using low cost agro-based locally available ingredients and the commercial diets was Saudi-Bangla Grower-1 (F2). The diets were designed as F1, F2 and F3 for traditional (20.40% protein), Commercial (31% protein) and BFRI formulated (30.44% protein) diets respectively. The fingerlings of catfish (7.3 g) were collected from local fish vendors and stocked at the rate of 100/dec. Feeding rates were adjusted by weight after fortnightly sampling of fish. Feeding rate were 10 and 8% of the total body weight respectively for 1st, 2nd month and 5% for the rest of the experimental period. The range of some selected water quality parameters were as follows: dissolved oxygen 4.0 - 7.4 mg/l, temperature 24.0°- 33.9°C, pH 6.8 - 8.00, and transparency 17.0 - 32.00 cm. Which showed suitability of the ponds for rearing fish. At the end of the experiment, significantly highest gain (p<0.05) in weight (1210.96% ±87) and lowest gain in weight (865.25% ±90) were observed in the group of fish fed on diets F3 and F1 respectively. However, no significant differences in growth (p>0.05) was observed in fish fed on commercial diet (F2) and BFRI formulated diet (F3). The FCR value ranged between 2.00 and 2.80 with the traditional diet (F1) showing significantly lower FCR. The total production of fish ranged between 1398.08 and 2145.34 kg/ha with F3 diet resulting in the highest production and net profit. A simple economic analysis showed that fish fed with BFRI formulated (F3) diet resulted in the highest net profit in farmer's pond.

Nursery management system of stinging catfish, Heteropneustes fossilis and walking catfish, Clarias batrachus in Bangladesh

A total of four experiments were conducted to develop nursery management system for the two important native catfishes viz. stinging catfish, Heteropneustes fossilis and walking catfish, Clarias batrachus during 2003 and 2004. Two experiments were conducted in on-station condition to determine stocking density efficacy in hapa and in earthen mini ponds for H. fossilis. This was followed by on-farm trial on stocking density in earthen mini ponds. In hapa, the highest survival rate was 60% for H. fosssilis at stocking density of 100/square meter; followed by 54.5 and 50% at stocking densities of 150 and 200/square meter, respectively. Similarly, gain in weight and length was also better in lower stocking densities. Similar survival rate (45 to 55%) was observed in three densities in earthen mini ponds. However, gain in weight and length showed no significant (p<0.05) differences. H. fossilis, C. batrachus showed almost similar survival rates (57.5-59.0%) in all the three stocking densities (100, 150 and 200/square meter) in earthen mini ponds in on-station condition. In terms of gain in weight and length showed no significant (p<0.05) differences in pond conditions. Almost similar result was obtained in terms of growth and survival in on-farm condition.

Dietary protein and energy interations: an approach to optimizing dietary protein to energy ratio in walking catfish, Clarias batrachus

An 8 weeks feeding trial was conducted in a static indoor rearing system to investigate protein to energy ratio (PIE ratio) in walking catfish Clarias batrachus. Six fishmeal based diets of two protein levels (25 and 35%), each with three lipid levels (5, 10 and 15%) resulted in P/E ratios ranging from 13.57 to 21.97 mg protein kJˉ¹ gross energy (GE) were fed to 50 fish in triplicate. Fish were fed 6% of their body weight three times per day adjusted fortnightly. Significantly higher (p<0.05) growth rates in terms of weight gain, % weight gain and specific growth rate (SGR) were evident in fish fed with higher protein diet. The highest growth rate was found by fish fed 35% protein, 17.06 kJˉ¹GE with a P/E ratio of 20.55 mg protein kJˉ¹GE. Significantly better (p<0.05) feed conversion ratio (FCR) was also evident in fish fed with higher protein diet and best FCR was found by fish fed 35% protein, 10% lipid, 17.06 kJˉ¹GE with a P/E ratio of 20.55 mg protein kJˉ¹GE. Significantly indifferent (p>0.05) values of protein utilisation were found in between the both (higher and lower) protein diets. Higher lipid deposition (p<0.05) in whole body was observed with increasing dietary lipid level at each protein diet and as higher (p<0.05) for the lower protein diets. The study reveals that C. batrachus performed best the diet containing 35%, 17.06 kJ gˉ¹ and 20.55 mg protein kJ gˉ¹ GE protein, gross energy and P/E ratio respectively.