Polyculture of carps using over-wintered fingerlings under different stocking densities

An on-farm trial was undertaken in twelve earthen ponds (1200-1600 m') to evaluate the growth and production of over-wintered fingerlings of rohu (Labeo rohita), catla (Carla catla) and mrigal (Cirrhinus rnrigala) in polyculture at three stocking densities. The stocking densities were 2,250; 3,250 and 4,250 fish/ha in treatment-1, treatment-2 and treatment-3, respectively. Fish in all ponds were fed with rice bran and mustard oil cake at the ratio of 3:1. Fish production obtained in three treatments were 2325±74.75, 2620±49.66 and 2982±171.52 kg/ha. The results demonstrated higher mean growth in T-1 than in T-2 and T-3. However, the highest production as well as net benefit was obtained in treatment-3.

Alternative phosphorus sources for formulated fish feed

An experiment was conducted to evaluate the possibility of using inorganic fertilizer triple super phosphate (TSP), inorganic fertilizer 16:20 (a 16:20 grade fertilizer contains 16 percent N and 20 percent P20 5), rice-bran and duck-manure as phosphorus sources in formulated fish feed for Nile tilapia ( Oreochromis niloticus). Experiment was conducted for a period of 2 months in net-cages suspended in fertilized earthen ponds and all male sex-reversed Nile tilapia (9.39- 10.37 g) were used in the experiment. Seven treatments including one non-feed treatment were used in this experiment. Treatment 1 (non-feed), treatment 2 (-P) where fish fed with phosphorus non-supplemented diet acted as control 1 and treatment 3, 4, 5, 6 and 7 where fish fed with 3% di-calcium phosphate (DCP), 3% triple supper phosphate (TSP), 7% 16:20 inorganic fertilizer, 30% rice-bran and 30% duck-manure supplemented diet, respectively. Results showed that the TSP and 16:20 grade inorganic fertilizer supplementation in diets as phosphorus sources were equivalent to DCP (Di-calcium phosphate) supplementation in terms of growth performance, feed utilization efficiency and final body composition of Nile tilapia. Ricebran and duck-manure were not found as good phosphorus sources.

Culture of green algae Chlorella ellipsoidea in inexpensive media

The culture of the of green alga Chlorella ellipsoidea was conducted under natural conditions at the same place simultaneously in five different media, viz., medium-I (inorganic medium), medium-II (powdered whole-pulse medium), medium-III (medium of pulse bran), medium-IV (mixed medium = 50% inorganic medium + 50% whole-pulse powder medium), medium-V (mixed medium = 50% inorganic medium + 50% pulse bran medium). The culture was done in 500 ml conical flask. Growth rates of C. ellipsoidea in five different media were different and reached maximum cell densities of 0.63 x 10^6 cells per ml in 8 days in medium-I, 4.02 x 10^6 cells per ml in 10 days in medium-II, 3.62 x 10^6 cells per ml in 9 days in medium-III, 4.38 x 10^6 cells per ml in 11 days in medium-IV and 4.36 x 10^6 cells per ml in 11 days in medium-V. The range of air temperature was 20 to 33°C and that of culture media was 24 to 32°C and light intensity was 2000 to 7000 lux during the culture period. The inexpensive culture media were found to be significantly useful for algal culture.

Seed production and culture techniques of Genetically Improved Farmed Tilapia (GIFT) in brackishwater environment

Effects of different levels of salinity on survival, growth and gonadal development of Genetically Improved Farmed Tilapia (GIFT) were studied under laboratory conditions in glass aquarium, for a period of ten weeks. The initial individual size of the GIFT was 20.23±4.45 and the salinity levels tested were 0, 5, 10, 15 and 20 ppt. The highest survival of 87.5% was found in 0 ppt and the lowest 60.5% in 20 ppt. Though the survival decreased progressively with increased salinity, there were no significant differences (P>0.05) among 0, 5, and 10 ppt. Similar to what has been observed in survival, the specific growth rate (SGR %/day) also decreased as of 1.30, 1.24, 1.08, 0.90 and 0.71, respectively, with the increased salinity of 0, 5, 10, 15 and 20 ppt. The gonadal development was highest in 0 ppt with a GSI value of 3.75 and lowest of 2.01 in 20 ppt. In the second experiment, gonadal development and seed production performance of GIFT in brackishwater condition were investigated for a period of three months. Each of the three fine meshed hapas of 20 square meters made from nylon net was placed in a freshwater (0 ppt) and in a brackish water (10-15 ppt) pond of the Brackishwater Station (BS). GIFT of 65 g average weight from a single cohort were stocked into three hapas at a rate of 2 per m. The male vs female ratio was 1:3. The development of gonad was faster with the higher gonadosomatic index (GSI %) of 3.85 % in freshwater condition than that of 2.73 % in brackish water. Within three months of the study period, a total of 70,510 and 44,250 GIFT fry were produced respectively, in freshwater and brackishwater conditions. Finally under third experiment, a participatory on-farm trial was carried out to evaluate the production performance of GIFT in monoculture and in polyculture with silver barb in coastal freshwater pond conditions. Nine ponds were selected for three treatment combinations of GIFT monoculture (T1), GIFT and silver barb polyculture (T2), and silver barb monoculture (T3). The ponds have been stocked in April, 05 at a density of 25,000 fry per ha. Fishes were fed with rice bran at the rate of 6% bw per day. In one month culture period, GIFT attained an average weight of 16.27 g in monoculture and 17.23 g in polyculture, against an average stocking weight of 0.37 g. Silver barb reached an average weight of 16.62 g in polyculture with GIFT and 10.01 g in monoculture, against an average stocking weight of 3.79 g.

On farm trial of Bangladesh Fisheries Research Institute (BFRI) evolved two aquaculture technologies

Two BFRI evolved aquaculture technologies - integrated rice fish farming and carp polyculture with over-wintered fingerlings under different stocking densities were tested during 2003-04. The study was coordinated with two local NGOs namely NICHAITA and JNDP, Muktagacha, Mymensingh. Integrated rice fish farming technology was demonstrated in 9 plots each having an area between 60-100 dec. during boro season. Fifteen days after transplantation of rice seedlings, fingerlings of rajpunti (Barbodes gonionotus) of 7-10 g of individual weight were stocked in the rice fields at the density of 3,000 (T1), 3,750 (T2) and 4,500/ha (T3). The corresponding final weight of fish after three and half months in treatments 1, 2 and 3 were 110±14.21, 101±16.55 and 86±22.28 g, respectively. The mean weight of fish in treatments 1 and 2 was significantly higher than treatment 3. Fish production obtained from treatments 1, 2 and 3 were 218.16±18.29, 239.70±25.11 and 236±24.66 kg/ha, respectively. On-farm demonstrations of carp polyculture using over-wintered fingerlings rohu (25-28 g), catla (24-26 g), mrigal (21-26 g) and grass carp (20-24 g) under different stocking densities were undertaken in nine earthen ponds (1,200-1,600 square meters) for a period of six months at three different stocking densities. The stocking densities of treatment 1 (T1), treatment 2 (T2) and treatment 3 (T3) were 2,000, 3,000 and 4,000/ha, respectively. Fish were fed with rice bran and mustard oil cake (3:1). Soft green grass and banana leaves were provided mainly for grass carp. At harvest, the production obtained in treatments 1, 2 and 3 were 2,325±74.75, 2,620±49.66 and 2,982± 171.52 kg/ha, respectively. The results demonstrated higher growth of fish in treatment 1 than those of treatments 2 and 3. However, treatment 3 contributed relatively higher production than those of treatments 1 and 2, whereas, highest net benefit was received from treatment 2.

Input-output relationship and economics of pangas monoculture and carp-pangas polyculture in two districts of Bangladesh

An attempt was made to study the input-output relationships and economics of pangas monoculture and carp-pangas polyculture in Bangladesh. By analyzing the data collected from 50 pangas farms and 55 carp-pangas farms, the study has investigated the production systems of two technologies and the effects of fingerling stocking and applications of feed and fertilizer on fisheries income. The data were collected from the fishermen of Trishal and Bhaluka of Mymensingh district, and Kahaloo and Adamdighee of Bogra district during 2001-02. For pangas monoculture, the stocking density was 31,561 per ha while it was 55,017 per ha in carp-pangas polyculture. Most of the farmers used urea, TSP and lime before stocking. Rice and wheat bran happened to be the most common feed ingredients for both types of culture in general. Other important ingredients used were mustard oil-cakes, rice polish, wheat flour, fish meal, bone meal, soybean meal and poultry litter. In terms of quantities, rice bran and wheat bran dominated the farmers list. Rice and wheat bran together constituted about 60% of all studied feeds. Feed cost constituted 59.13% of total costs for pangas monoculture and 67.44% for carp-pangas polyculture. Per ha productions of pangas and carp-pangas in a single culture cycle were 15,508 kg and 19,745 kg, respectively. Per ha gross profits were estimated to be Tk 310,311 and Tk 464,418 for pangas monoculture and carp-pangas polyculture, respectively. Net profit appeared to be Tk 264,216 per ha for pangas monoculture and Tk 416,509 per ha for carp-pangas polyculture. The BCRs calculated were 1.46 and 1.68 for monoculture and polyculture, respectively. The break-even costs per kg of fish were estimated at Tk 36.93 for pangas and Tk 30.93 for mixed species which was much lower than the prices the producers received. Break-even productions were estimated at 10,702 kg per ha for pangas monoculture and 11,784 kg per ha for carp-pangas polyculture. Fingerling and feed cost, and pond size significantly explained the variation of income from pangas monoculture. These factors have significantly influenced the income from the crop. Functional analysis shows that 1% increase in the feed cost might increase 0.51% of pangas income and 0.41% in carp-pangas income. No other inputs had shown this much of responses to increasing income from a fish.

Suitable sites for sustainable aquaculture development in Mymensingh, Bangladesh: A GIS methodological perspective

A GIS study was carried out to find out the sites suitable for aquaculture in Mymensingh region. A number of criteria were selected for GIS modeling followed by the approach of Kapetsky (1994). The criteria were developed from a range of existing data sources such as, surface and underground water level, availability of feed ingredients and animal wastes, sources of fish fry, market facilities, extension support and communication facilities for aquaculture development. The data were located, collected and compiled from different GOs and NGOs located in the region along with primary data from the field survey wherever necessary and then prepared for computer analyses. Using the database, a series of GIS models were developed in order to ascertain and prioritize the most suitable areas for aquaculture development in the region. Out of total 407,528 ha available lands in the region, the study identified 99,415 ha very suitable and 302,754 ha moderately suitable for aquaculture promotion. Result of the study is indicative to the modeling power of GIS for aquaculture application and could be used to refine the models in future, particularly if it is supported with further detail field data. To get a more concrete and complete model, detailed study should be made available on the availability of mustard oil cake, rice bran, wheat bran, and usable animal and urban wastes that could be used as low-cost feed for sustainable aquaculture.

Monoculture of three native air breathing fishes in homestead ditches and plastic barrels

Six on-farm trials were conducted from 1 August to 23 November 2004 in two different environments such as homestead ditches (10 to 17 square meters) and plastic barrels (240 liters) to develop techniques for nonoculture [sic] of climbing perch, Anabas testudineus, stinging catfish, Heteropneustes fossilis and walking catfish, Clarias batrachus for poor and landless people who have no access to pond. Stocking density for ditch was 10 fry/square meter while that for barrel was 20 fry/cubic meter. The fishes were fed with 3-test diets viz. low-cost formulated feed (rice bran 20%, wheat meal 10%, mustered [sic] oil cake 35%, poultry offal 35%), live foods (chopped snails and clams), and a commercial feed (Saudi-Bangla feed, starter 3: first month and grower-1: subsequent two months) and designated as T1, T2 and T3, respectively. Feeding rate was the same in all the treatments viz. 10% of body weight (first two months), 8% (third month) and 6% (fourth month). T1 and T2 had three replications while T3 had two replications. Water temperature was recorded weekly while fish growth was monitored monthly. After 4 months' rearing, H. fossilis and C. batrachus in ditches and barrels attained higher average weight in T2 followed by T3 and T1 while A. testudineus in barrels also attained higher average weight in T2. The variation in net weight gain by A. testudineus in ditch fed test diets T2 and T3 was not significantly different (P>0.05) though the net gain in both T2 and T3 was significantly (P<0.05) higher than that of T1. The yield of climbing perch as obtained from T1, T2 and T3 was 988, 1136 and 1185 kg/ha, respectively while that stinging catfish was 395, 242 and 444 kg/ha and walking catfish was 1605, 2,099 and 1,654 kg/ha respectively. All the three species showed significantly lower growth rate in barrels than in ditches.

The effect of various protein levels on the growth and survival rates of Penaeus monodon Fabricius

Postlarvae of tiger prawns, P. monodon , were fed with various protein levels of 0; 30; 40 and 50%, fish meal and rice bran were combined and pelletized for 16 wks. Prawns used had an average mean length of 1.2 mm and an average mean weight of 5.5 mg. Nitrite, ammonia, dissolved oxygen content, temperature and pH were monitored. After one month of feeding, growth increments of postlarvae fed with 30% protein diet were significantly different from those given 0; 40 and 50%. Survival rate of the group fed 40% protein was higher (81.7%) but was not significantly different from those fed 30% (68.0%). The highest feed efficiency was obtained from the 30% protein pellets (4.6). At the end of 16 weeks, growth increment of 40% protein level was significantly different from the 30% and 50% protein levels, but the survival rate was not signficantly different from the 30% protein level. Feed conversion for the 40% protein diet was 2.8.

Preliminary chemical and physical evaluation of some formulated feeds for P. monodon

The culture of Penaeus monodon has explicitly defined the need for diet formulations or supplementary feeds that would promote optimum growth and survival of the animal. A total of 28 feed combinations were developed for P. monodon. Fish meal, shrimp head meal, squid head meal, Ascetes spp. rice bran, and soybean cake were used as primary ingredients in these feeds. The commercial vitamin mix No. 22 was added to the dry ingredients. Gelatinized corn starch and wheat flour were used as binders. The pellets were extruded using a portable kitchen grinder with a diameter of 4 mm. The products were either sun-dried for 8 hours or oven-dried overnight at 50 degree C to stabilize moisture at 8-10%. The pellets were then kept in covered glass bottles and stored in the laboratory at room temperature. The cost of the feeds excluding labour were also computed. The pellets were analyzed for protein, fat, carbohydrate, crude fiber, ash, and moisture contents using standard procedures. They were also analyzed for water stability. To test the stability of pellets in water, 2-g samples were placed in plankton nets (mesh #40) and suspended in water for two, and six hours. The undissolved samples were then vacuum-dried and the moisture determined. Cost of the feeds ranged from P1.10 to P2.60 per kg depending on the feed ingredient. Squid and Ascetes spp. were rather expensive for use as basic ingredients. Proximate analysis of dry weight showed percentage protein content ranged from 20-63 g; fat, 8-20 g; carbohydrate (by difference), 11-36 g; ash, 8-28 g; moisture, 6-11 g; and crude fiber, 5 . 13 g. Stability tests showed that after two hours, 35-88% of solids remained intact and after 6 hours, 20-55% of the pellets remained undissolved. When a pellet disintegrates easily, pollution of the water occurs. Chances for the shrimp to feed on the pellet is minimized when the pellet is unstable. Thus, the search for a more compact feed pellet has to be continued.

Preliminary biological evaluation of some formulated feeds for P. monodon

Rice bran is widely used by fish farmers as supplementary feed while soybean cake is used both as feed and as fertilizer in fishponds. Both fish meal and shrimp head have been found acceptable as feed ingredients. However, not much is known of the acceptability and efficiency of a mixture of these ingredients as feed for Penaeus monodon larvae. Ninety 127-day old P. monodon were measured for length and weight and were randomly divided into nine aquaria each containing 20 liters of water. These were fed 'lampirong' for two months previous to the study. There were three replications for each treatment. Length, weight, and survival rates were used to compare the efficiency of the diets. Weighed amounts of pellets equivalent to 100% of the body weight were fed during the first three days and reduced to 50% thereafter. A stopwatch was used to determine the length of time that elapsed before the shrimps would approach the pellet. Ten shrimps approximately 4 months in age were placed in 10 liters of water in a 25-liter aquarium. Two grams of each pellet type were placed simultaneously on opposite sides of the aquarium. The time that elapsed from the moment the pellets sunk to the bottom up to the time that any one shrimp approached the pellets was recorded. The group fed the imported pellets gained the most. Those fed FP-2s-77 elongated faster than those fed FP-1s-77. Survival rate of those fed FP-2s-77 was 37% while those fed imported pellets was 73%. Both 1s and 2s pellets disintegrated in water easily but the imported pellets were stable even after six hours in water. The attractability test for the pellets showed that the prawns were more readily attracted to the pellets 1s and 2s than to the imported pellets.

Minimum dissolved oxygen tolerance of four different sizes of milkfish

Four size groups of milkfish were tested, 4-18 g, 20-34 g, 35-95 g and 200-300 g. A number of fish from each group were placed separately in identical 1.2 m2 wooden tanks containing seawater filled up to 30 cm depth. The aggregate weight of fish per size group was approximately 1 kg. The fish were held for 72 h, fed with lab-lab and provided with continuous aeration to allow recovery from stress during transport and handling. After the recovery period, aeration was stopped and 200 g of the fine rice bran was spread over the water in each tank creating a film of bran particles on the water surface. This was designed to speed up depletion of dissolved oxygen considering the combined effects of the screening-off of sunlight, the reduction of air-water interface and the breakdown of the bran particles. It is probable that stress on milkfish in brackishwater ponds could start when oxygen level drops to about 1.4 ppm. A further decrease to 0.04 ppm could produce a total kill of all specimens above 4 grams with marketable size and bigger size fish dying first.

Culture experiments on the copepod, Tisbintra elongata MORI, and evaluation of that species as food organism for milkfish larvae

Five types of food were used to culture T. elongata: rice bran, cow dung, bread, cow dung, bread yeast, fermented fish solubles and Spirulina. Bread yeast was found to give the highest densities. An evaluation was also made of the effectivity of rice bran and fermented fish solubles for the outdoor mass culture of T. elongata . A comparative study on the growth and survival rate of milkfish fry (Chanos chanos) fed with T. elongata and Artemia showed there to be no significant differences between the diets.

Effects of increased stocking density and supplemental feeding on the production of milkfish fingerlings

Experiments were conducted to determine the effects of increased stocking density and supplemental feeding on survival and growth of milkfish (Chanos chanos ) fry to fingerling stage and also to evaluate the profitability of supplemental feeding in the milkfish fry nursery. Results showed that increased stocking density from 50 to 75 fry/m super(2) increased net income and is profitable. Survival was further increased through supplemental feeding with rice bran, which is cheap and easily obtainable.

The effect of various protein levels on the growth and survival rates of Penaeus monodon Fabricius

Postlarvae of tiger prawns, P. monodon, were fed with various protein levels of 0; 30; 40 and 50%, fish meal and rice bran were combined and pelletized for 16 wks. Prawns used had an average mean length of 1.2 mm and an average mean weight of 5.5 mg. Nitrite, ammonia, dissolved oxygen content, temperature and pH were monitored. After one month of feeding, growth increments of postlarvae fed with 30% protein diet were significantly different from those given 0; 40 and 50%. Survival rate of the group fed 40% protein was higher (81.7%) but was not significantly different from those fed 30% (68.0%). The highest feed efficiency was obtained from the 30% protein pellets (4.6). At the end of 16 weeks, growth increment of 40% protein level was significantly different from the 30% and 50% protein levels, but the survival rate was not significantly different from the 30% protein level. Feed conversion for the 40% protein diet was 2.8.