Land-based mass production of prawn (Penaeus monodon Fabricius) spawners

The first spawnings were obtained 12 days after ablation with 4 spawners yielding 784,000 eggs and a harvest of 250,000 P SUB-10 fry. Survival of females after 1 month was approximately 30%. Mortalities were mostly due to handling stress during the regular ovarian samplings as well as disease frm the accumulated excess feeds on the bottom of the tank. Male survival could not be recorded because of transfers to other tanks and addition of new stocks. Development seemed to peak 3 weeks after ablation. The average number of eggs per ablated spawner was 120,000. However, many of the partially spawned females were removed from the spawning tanks the following day so that remaining eggs released in the next 2 to 3 days could not be recorded. Estimate of the average number of eggs per ablated spawner is 120,000-150,000 in contrast to 500,000 per wild spawner. However, the low production cost more than compensates for the difference. Fry reared in the Wet Laboratory were used for experiments, mostly on feeding. Therefore, survival at harvest is not to be taken as a reflection of stock quality. Although fewer in number, larvae from ablated prawns are as healthy in terms of vigor in swimming and feeding as those from wild females. Most mortalities are due to inability to molt caused by lower water temperatures and inadequate feeding.

Relationship between diet composition and growth rate of the zoeal and mysis stages of Penaeus japonicus Bate

Diets containing Chaetoceros gracilis plus Artemia nauplii artificially prepared diet, Diet-B, and two commercial feeds Tapes and mysid meals, were fed to larvae of P. japonicus. Highest survival rate was obtained when larvae were fed with Diet-B. The results show that the early larval stages of P. japonicus can be reared on artificially prepared diets. Since the chemical composition of the diet is known, it can be used as supplemental data for larval feeding development and nutritional requirement studies for the early larval stages of Penaeus japonicus and/or other penaeids. Information is tabulated on feeds and feeding rates used, composition of the artificial diet, fatty acid composition of lipids of the different diets, and of the sterols of the different diets.

Effect of different feeding regimes on reproduction and survival of ablated Penaeus monodon Fabricius

Results of experiments conducted on ablated Penaeus monodon, fed with 4 different feeds (pellet-pellet, mussel-mussel, mussel-pellet and squid-pellet), on survival, spawning, fecundity and hatching rate are given and discussed.

Feeding behavior and food preference of Penaeus monodon Fabricius with scrap tilapia

The time of day during which P. monodon feeds at different depth levels in earthen ponds, and its preference for three types of tilapia feeds (dry, fresh and fermented) were determined. It was observed that P. monodon concentrated at the bottom beds during the day and along the periphery of dikes during night-time, with a slight tendency to swim and feed towards the surface as darkness increased. P. monodon showed special preference for dried tilapia compared to fresh and fermented tilapia. P. monodon also showed adaptability to the platform method of feeding, especially during night-time.

Effects of dietary vitamin E on the growth and breeding performance of Ompok pabda

A 90 day feeding trail was conducted to investigate the effect of vitamin E on the growth and breeding performance of Ompok pabda. A total of 84 healthy female brood fish (41.10±0.44g) were divided into 4 treatments i.e. treatment T1 T2, T3 and T4 having three replications each. The fish were fed twice a day with a standard feed (40% protein) having 4 doses of vitamin E viz. 0 (served as control), 50, 100 and 150mg vitamin E/kg feed. At the end of the feeding trial, the brood fish were induced to breed with PG extract to observe the effect of vitamin Eon feed. After rearing for 90 days with the experimental feeds, it was found that weight gain and specific growth rate of brood fish fed with 100mg vitamin E/kg feed (treatment T3) was the highest (14.78±0.38g and 2.99±0.11) while 150mg vitamin E/kg feed (treatment T4) fed fish gave the poorest result (2.97±0.89g and 1.21±0.32). There was no significant difference in terms of length gain of brood fish among the different treatments. The brood fish were induced to breed with equal dose of PG extract (18 and 12mg PG/kg body weight for female and male respectively) to observe the dietary effect of vitamin E on breeding performance. The highest ovulation, fertilization and hatching rate of eggs were found to be 81.48±6.41%, 84.04±3.53% and 68.59±5.03% respectively in the brood fish of treatment T1 while the poorest (33.33±00%, 52.35±5.02% and 45.70±7.24% respectively) were found in the brood fish under treatment T4. The results suggest that inclusion of 100mg vitamin E/kg feed is best for enhancing the breeding performance of O. pabda brood fish indicating that vitamin E content has a positive impact on reproduction of fish. The present results also imply that inclusion of higher level of vitamin E exerts an antagonistic effect in terms of growth and breeding performance of this species.

Study on the growth and survival of Channa striatus (Bloch) postlarvae using live feed

Feeding experiments were conducted on the postlarvae of Channa striatus with two different live feeds - a copepod (Thermocyclops decipiens) and cladocerans (Moina micrura and Ceriodaphnia comuta) individually and in mixture. Food was provided at the rate of (500±50 Ind/L) and the experiments were carried out in 100 litre capacity tanks for 30 days. Results indicated better weight gain (951.85±28.77%) and survival (92.00<%) of postlarvae fed with mixed live food than individual live feed organisms.

Suitability of commercially available Bacillus probiotics on growth, survival and production of black tiger shrimp (Penaeus monodon Fab.)

Different forms of Bacillus probiotics was assessed in the earthen ponds on tiger shrimp (Penaeus monodon) culture. The experiment was designed with three different treatments depending on the mode of application (T1=oral probiotics; T2=spreading probiotics and T3=oral+ spreading probiotics). The shrimp was cultured for 120 days with the stocking density of 6-PL/m².Oral probiotics in the respective ponds were supplied with feeds. Whereas, spreading probiotics was applied to the pond water during pond preparation at 30, 60 and 90 days of culture period. Results of the experiment revealed that, all forms of Bacillus probiotic had effective role to keep the culture environment friendly in terms of mineralization of organic matter, nitrogen and phosphorus content in bottom sediment; holding of water transparency in a congenial state, increasing the density of planktonic biomass and boosting the THB-Vibrio ratio in water and sediment with insignificance (p>0.05) difference between different treatments. Whilst, spreading form of Bacillus pro biotic showed higher weight gain (27.58±1.18g), survival rate (70.75±8.54%) and production (1167.66±109.62 kg/ha) and expected lower FCR (1.81 ±0.06) values with significant difference (p<0.01) with others methods of application, indicated its superiority in tiger shrimp culture.

Effects of supplemental feed and fertilizer on growth and survival of Macrobrachium rosenbergii (de Man) post larvae in pond nursery system

The study was conducted to compare the performance of different nursing practices of giant freshwater prawn (Macrobrachium rosenbergii) post-larvae (PL). Three treatments such as only fertilizers (T1), fertilizers with 5% supplementary feed (local feed) (T2), and 10% commercial feed (T3) were applied in the nursing system of prawn PLs in earthen pond. An earthen pond (315m²) was divided into nine equal small ponds by fine meshed nylon nets. Feeds were used once daily on a tray placed near the pond bottom. There was a significant difference (p<0.05) in some water quality parameters like pH and total alkalinity, but all measured water quality parameters viz. water temperature, transparency, dissolved oxygen and ammonia-nitrogen were within the acceptable range for nursing of prawn PL. The results showed that the mean final lengths of prawn post-larvae were 6.3±0.07 cm, 7.12±0.22 cm and 8.17±0.16 cm in T1, T2 and T3, respectively. There were significant difference (p<0.05) in mean final length of prawn PL among the treatments. Significantly higher (p<0.05) average daily weight gain was observed in T3 (0.071 ±0.007 g) than in T2 (0.052±0.006 g) and T1 (0.031 ±0.002 g). The specific growth rate (SGR) of T3 (8.81±0.26) was found significantly higher (p<0.05) than T2 (8.35±0.22) and T1 (7.42±0.11). Survival rate (%) was also significantly higher (p<0.05) in T3 (66.24±1.58) than in T2 (60.52±1.64) and T1 (53.86±2.71). Therefore, it may be concluded that the growth and survival in prawn nursery was better in commercial feed than only fertilizers and fertilizers with local feeds.

Effects of stocking density on growth and production of GIFT (Oreochromis niloticus)

The study was carried out to assess the effects of stocking density on growth and production of GIFT for a period of 100 days. Three stocking densities were used 150, 200 and 250 fish/decimal; designated as treatment T1, T2 and T3 respectively having two replicates for each. Commercial pellet feeds were fed at the rate of 30% body weight up to first 10 days and then gradually it was readjusted to 22%, 18%, 15%, 12%, 10%, 8%, 6%, 5% and 4% respectively after every 10 days interval. The result showed that the fish in the treatment T1 stocked with the lowest stocking density (150 fish/dec) resulted in best individual weight gain (148.65g) followed by those in treatment T2 and T3 respectively. The specific growth rates (SGR) at every 10 days were ranged from 6.59 to 1.11 in different treatments during the experimental period. The food conversion ratio (FCR) values ranged between 1.82 to 2.03 with treatment T1 showing the lowest FCR. The survival rate ranged between 84 to 92%. Treatment T1 and treatment T2 showed significantly higher survival than Treatment T3. The fish production rate in treatment T1, T2 and T3 were 18.58, 23.87 and 26.78 kg/decimal respectively.

A comparative ecological study on internationally important wetlands of Khoor-e-Kolahy and Tiab

Ecological study on Kolahy and 'flab estuaries were carried out during 1996-1997. Water and sediment sampling was done seasonally. In order to study the physical and chemical characteristic of the water, various animal fauna from different material niches including planktons and fish from water, benthousi from the sediment , and surface living animal such as Arthropod (Crabs) and Waterbirds were identified. I he result shoved, that water salinity of both estuaries was the same as the general salinity existing its the Persian Gulf water, and its variation is same IN those waters Minimum water salinity in both estuaries are seen during Bahairdan or early winter mooth(Jaa.), which is about 31ppt and Maximum is during .rirldlun.) or summer mouth at about 19 ppt. Dissolved otygen and pH are slime as the general Persian Gulf waters., Dissolve Oxygen being directly associated to temperature and its fluctuation is between 7- Sing/I and pH between 7.5-LS. The animals of both estuaries are almost similar having a sal factory species diversity . The birds of the region are often seasonal migrants , the maximum population of which occurs in winter season and the minimum during summer month. Nam coverage is richer in Tiab than Kolahy estuary, where in Kolahy a signal Mangrove tree is in exigence. 'Ile total coverage of Mangrove forest in Tiab is estimated about -29 hec.Both estuaries are included with in the international Ramsar Convention sites in 1971. Due to national importance of these estuaries inproviding refugee for various birds species and also hinting grounds and access traffic for local fishing vehicles, Actiog as an important access for various inhabitancy living with these area of the Persian Gulf. Due to importance or prawn aquacultur for the economical well being of local inhabitance, these areas provide a suitable grandees for prawn production. I-test statistics show, there are no significant difference among various invertebrate and vertebrate animals. In over all out look 21) phytoplankton genera, 21) zeoplankton genera 17 miafauna and 32 roaerofauna genera , 11 different species Carcineacearions and 119 species of walerbirds were identified with in the Tiab and Kolahy estuariesregioos. The X statistic show that the animal density is directly associated to season. Where density of miofauna and maerofauna in both estuaries are in maiticrourn during summer and the minimums existing during the winter season. In addition the bentic invertebrate population density in closlly association to birds population density since , the later, feeds on the former animals. Where the increasing in bird population density during the winter season, the bentic invertebrate animal population density decreases. The over all trend of animal population density in winter tend to increased towards the summer seasons, which this is due to climatic conditions of the region. The bird population on the contrary to other animals of both estuaries tend to increase from summer towards the winter seasons and which this bird population density is in maximum in winter with in the region.

Evolution and management of the mukene (Rastrineobola argentea) fishery

Rastrineobola argentea locally known as mukene in Uganda, omena in Kenya and dagaa in Tanzania occurs in Lake Nabugabo, Lake Victoria, the Upper Victoria Nileand Lake Kyoga (Greenwood 1966). While its fishery is well established on Lakes Victoria and Kyoga, the species is not yet exploited on Lake Nabugabo. Generally such smaller sized fish species as R. argentea become important commercial species in lakes where they occur when catches of preferred largersized table fish start showing signs ofdecline mostly as a result of overexploitation. With the current trends of declining fish catches on Lake Nabugabo, human exploitation of mukene on this lake is therefore just a matter of time. The species is exploited both for direct human consumption and as the protein ingredient in the manufacture of animal feeds.

Changes in fish fauna and the impact of the introductions on fish yield

There have been considerable changes in fish species composition in Lakes victoria, Kyoga and Nabugabo since the Nile perch were introduced. Populations of most of the native species have declined and many species may have become extinct. The original decline in the fish stocks was due to overfishing but the recent and more drastic decline has been attributed to predation by the Nile perch. Nile perch feeds on invertebrates changing to a piscivorous diet with size. Haplochromine cichlids, which were the most abundant fish in Lakes Victoria just before the Nile perch populations started increasing rapidly have been depleted. As more suitable types of prey were depleted in the new habi tats, Nile perch switched to other prey types to the extent of feeding even on its own young. There are, fears that the Nile perch will overshoot its food supply, resulting in a reduction of its own population and subsequently a collapse in the fishery (FAD 1985).

A study of Rastrineobola argentea in the Ugandan lakes

Increased stocks of mukene Rastrineobola argentea and the subsequent interest in its fishery on Lake Victoria has been attributed to the poor performance of the endemic fishery as a result of introductions into this lake of foreign fish species Lates niloticus and Oreochromis niloticus. R. argentea now remains the only endemic fish species of economic importance ranking second to the Nile perch in this lake. Despite this importance, biological information on the species and knowledge of its fishery is scanty. Preliminary observations on the species in the Ugandan waters indicate that R. argentea feeds mainly on zooplankton (copepods) during daylight hours. Small quantities of aquatic insect larvae/pupae (chironomids and chaoborids) are also eaten mainly at night. These fishes breed just after the rainy seasons and the young eventually mature at between 43-44 mm standard length. Growth and population parameters show a rate of growth (K) of 0.92 with L of 64.5 mm S.L. Natural mortality (M) is given at 2.371 and total mortality (2) of 3.594. Two mesh size nets 10 and 5 mm are in use in the lake. The smaller mesh size which is more preferred by the artisanal fishermen however tends to capture many immature fishes. There is therefore need for a unified lakewide data collection on the species and its fishery in order to obtain more reliable biological information necessary proper management of this fast developing fishery.

The importance of quality fish feed and their proper management in ponds

The brochure explains the types of feeds needed by fish and how to detail with over feeding. Fish need to be provided enough nutritious food in order to attain big sizes in a short period of time under culture conditions.

Preliminary observations on cage culture of Tilapia esculenta Graham and Tilapia xillii (Gervais) in Lake Victoria waters, at the Freshwater Fisheries Institute, Nyegezi, Tanzania

Cage culture of Tilapia is not suggested as a substitute for any known techniques in fish culture, but as one of the various techniques of obtaining more fish under controlled conditions. This fact has been very well accepted in various countries. Whererever facilities exist, this line of fish culture should be vigorously explored as a possible avenue in increasing fish production. High density stocking, management under controlled conditions, easy technique of fabricating the cage at relatively low cost, having no demand on land area, absence of prolific and effective breeding and easy availability of fish when a person needs it are a few of the attractions of the technique. The studies indicate that it is desirable to have different meshes for the cages, such as, small meshed cages for rearing fry to fingerlings stages, and larger meshed cages for rearing fingerlings to table sized fishes. II' the meshes are small, the resistance will be more and less water wilt pass through. While feeding with powdered food material, because of brisk activity of feeding fish, a part of the feed appeared wasted. This can be easily overcome if we would resort to feeding fish with cheap pelleted feeds which will no doubt reduce wastage. Precaution has to be taken against damage of the net and thereby loss of fish and against poaching by unauthorised persons. In the present attempt has been demonstrated the possibility of utilizing locally available species of Tilapia for cage culture and obtaining moderately satisfactory growth rates.