Now showing items 68-79 of 79

    • Conference poster

      Seasonal abundance of Penaeid prawn seed in the Ennore estuary, Madras in relation to hydrography and lunar phase. 

      S Vasudevan & T Subramoniam - In Y Taki, JH Primavera & JA Llobrera (Eds.), Proceedings of the First International Conference on the Culture of Penaeid Prawns/Shrimps, 4-7 December 1984, Iloilo City, Philippines, 1985 - Aquaculture Department, Southeast Asian Fisheries Development Center
      An estimate of seed resources in the coastline, estuarine, and backwater bodies is an important prerequisite for developing prawn farming. A one-year (1983) survey on penaeid seed, based on tide and lunar periodicity, indicates the following species: Metapenaeus dobsoni, Penaeus indicus, P. japonicus, M. monoceros, P. semisulcatus and P. monodon in order of their abundance. P. indicus and P. japonicus are predominant in February and March (77.5 and 82.06% of total seed, respectively) when the average salinity ranges from 33.6 to 35.1 ppt followed by M. dobsoni. A second peak of P. indicus is observed in June when M. dobsoni showed its highest peak (47.35%) with continued abundance up to December.

      During the northeast monsoon, when the average salinity fell to a lower range of 19.9 to 24.6 ppt, P. monodon and M. monoceros showed moderate abundance. As the site chosen is very near the bar mouth, most of the seed collected were postlarvae. In Penaeus and Metapenaeus genera, total size range is 7-15 mm and 3-4 mm, respectively. Afternoon collections showed greater abundance followed by forenoon and night collections. Low tide and Full Moon collections showed greater abundance than those made during high tide and New Moon. Differences in seasonality may reflect breeding intensity of the respective prawn species in the sea. Variations in hydrographic features may also significantly contribute to seasonal abundance. A strong correlation between salinity and seed abundance is seen. The seed potential of these prawns in Ennore estuary is discussed.
    • Conference poster

      Seasonal and local occurrence of adults and postlarval stages of Penaeus merguiensis and Penaeus indicus in Batan bay, Philippines. 

      VC Bañada - In Y Taki, JH Primavera & JA Llobrera (Eds.), Proceedings of the First International Conference on the Culture of Penaeid Prawns/Shrimps, 4-7 December 1984, Iloilo City, Philippines, 1985 - Aquaculture Department, Southeast Asian Fisheries Development Center
      Studies on seasonal and local occurrence of adults (spawners) and postlarval stages of Penaeus merguiensis and P. indicus in Batan Bay and Banate Bay, Aklan yielded the following results: 1) small-sized P. merguiensis and P. indicus dominated the rivers and interior bays, 2) P. merguiensis and P. indicus spawners appeared throughout the year with varying monthly abundance in Batan Channel and Banate shoreline, and 3) larval stages of penaeids were found in interior bays but were more abundant in the channel and offshore areas. Postlarval stages of penaeids are more abundant along the shoreline than in water edges of mangrove swamps which indicate that channels and offshore waters may be primary spawning grounds while interior bays and rivers are secondary spawning grounds. Moreover, size distribution of carapace length of P. merguiensis suggests that the channel and offshore areas are utilized as primary spawning grounds while the inner portions of the bay are nursery grounds and secondary spawning grounds.

      Lunar phase did not show a positive correlation with abundance of both spawners and postlarval P. merguiensis and P. indicus. The minimum size at sexual maturity for both male and female P. merguiensis is about 11 mm CL. Female P. indicus appear to become sexually mature at a smaller size (13 mm CL) than males (20 mm CL).
    • Conference poster

      Staggered harvesting as a method of increasing prawn production with supplemental feeding. 

      M Suemitsu, M Dimaano, E Jarabejo & JJ Canto - In Y Taki, JH Primavera & JA Llobrera (Eds.), Proceedings of the First International Conference on the Culture of Penaeid Prawns/Shrimps, 4-7 December 1984, Iloilo City, Philippines, 1985 - Aquaculture Department, Southeast Asian Fisheries Development Center
      Prawns, like any other animals, exhibit dissimilarities in growth rates. As they grow, a wide range of body weight distribution from the same population is observed. Staggered harvesting method is commonly practised in cultured animals having this characteristic. Selective or partial harvesting is especially useful in this type of management system. In this case, the larger shrimps are caught earlier than the small ones thus giving chance for the smaller ones to grow bigger.

      The study was conducted in four one-ha ponds. Recommended pond preparation was followed. Partial harvesting was employed in experimental ponds by using 2-4 units of 8 knots selective pound nets once a week commencing after three months culture until final harvest. Control ponds were harvested only once at the end of the culture period.

      The results show a mean production value of 506 kg from control ponds and 639 kg from experimental ponds. Average survival rate for experimental ponds was higher (92.90%) than for control (77.65%). Final average body weight was higher for experimental ponds (21.8 g) than for control (20.5 g).

      Size-wise, production of big size group (30-35 g) is 578.0 kg compared to 434.6 kg for small size group (13.1-13.4 g) from both control ponds with over-all production of 1,012.6 kg. On the other hand, production from the two experimental ponds for big and small size groups is 872.2 and 405.8 kg, respectively. The means of the total weights of marketable size Penaeus monodon from control and experimental ponds are 289.0 and 436.1 kg, respectively. That is, 43.5% of the stock reached marketable size in ponds with staggered/partial harvest method compared to only 27.5% from control ponds.
    • Oral presentation

      Studies on the artificial insemination and fertilization of grass shrimp, Penaeus monodon. 

      MN Lin & YY Ting - In Y Taki, JH Primavera & JA Llobrera (Eds.), Proceedings of the First International Conference on the Culture of Penaeid Prawns/Shrimps, 4-7 December 1984, Iloilo City, Philippines, 1985 - Aquaculture Department, Southeast Asian Fisheries Development Center
      The culture of grass shrimp, Penaeus monodon has become a fast-growing enterprise in Taiwan since formulated shrimp feed was successfully developed in 1978. In 1983, the total postlarval production for stocking reached 600 million at the price of 12.5 U.S. cents each. This high price of the postlarvae resulted from (1) limited availability of wild gravid females, (2) undesirable spawnings obtained by using the method of eyestalk ablation, manifested by a low average hatching rate of 20%, and (3) high demand from grow-out farms. The eyestalk ablated females induced to spawn were often found unmated which partly explained the poor spawnings and low hatching rates. Consequently, re-use of ablated females was not practised by farmers in the past.

      The present paper describes the results of artificial insemination and fertilization of wild or pond-reared females whose gonadal development was induced by eyestalk ablation. The hatching rates from unmated soft-thelycum females implanted with two spermatophores are 84.7% and 43.7% while those implanted with only one spermatophore, 74.1% and 16.8%, for the first and subsequent spawning, respectively. These results positively confirm that the unmated condition of ablated females is the main reason for low hatching. Through artificial insemination, the spawning and hatching can be improved and ablated females can be re-utilized. For unmated hard-thelycum females, artificial fertilization was done by releasing spermatozoa into the spawning tank right before spawning. Out of 15 attempts, three were successful with hatching rates of 63.1, 52.3, and 49.9%.

      Induced maturation of pond-reared shrimps was attempted by manipulation of temperature and salinity. Under constant temperature of 22±2°C, salinities ranging between 25 and 37 ppt were experimented. The best results with 67% success were obtained at salinities of 30 and 35 ppt. Continued efforts will be made to improve spawning performance through the technique of artificial insemination under controlled conditions.
    • Conference poster

      Study on the larval rearing of Penaeus merguiensis. 

      N Ruangpanit, S Maneewongsa, T Tattanon & P Kraisingdeja - In Y Taki, JH Primavera & JA Llobrera (Eds.), Proceedings of the First International Conference on the Culture of Penaeid Prawns/Shrimps, 4-7 December 1984, Iloilo City, Philippines, 1985 - Aquaculture Department, Southeast Asian Fisheries Development Center
      Nursing postlarvae of Penaeus merguiensis in the same tank as rearing always results in low survival rates, around 30%. One reason is that stocking density for P1 is too high for postlarvae grown to P20 size. Another reason may be that it is impossible to sufficiently clean a tank containing culture stock. In order to overcome the first constraint and to test whether the second is valid, rearing of nauplii to early postlarval stage was done in one tank, then early postlarvae were moved to another tank for nursing to P20.

      Rearing was done in rectangular, concrete tanks (5 m × 5 m × 2m) of 50 ton capacity, with an initial stocking density of 20-40 nauplii/ℓ. Chaetoceros sp. at a density of 3-4 × 104 cell/ml, or Tetraselmis sp. at 1-3 × 104 cell/ml were fed to zoea stage, then rotifer was given when the larvae metamorphosed to mysis stage. Within 8-10 days, when all of the larvae metamorphosed to postlarval stage, they were transferred to the nursing tank. Postlarval nursing was done in rectangular, concrete tanks with a capacity of 12 or 30 tons. The stocking rate was 12 postlarvae/ℓ in the 12-ton tanks and 8 postlarvae/ℓ in the 30-ton tanks. The early postlarvae were fed constantly with brine shrimp, and the older postlarvae were fed 4-5 times daily with squid meat. Fifty to seventy percent of seawater was exchanged, and siphoning of food remnants was done daily. The postlarvae grew to an intermediate size (1.0-2.5 cm total length) for stocking in grow-out ponds within 12 to 20 days.

      The results of rearing in 50-ton tanks with an initial stocking density of 20-25 postlarvae/ℓ, 25-30 postlarvae/ℓ and 30-40 postlarvae/ℓ produced survival rates of 74.3%, 63.6% and 47.6%, respectively. The survival rate for nursing in 12-ton tanks, with stocking density of 12 postlarvae/ℓ was 85.0% and for 30-ton tanks with stocking density of 8 postlarvae/ℓ was 61.7%. These results seem to indicate that the rearing and nursing of shrimp would be more efficient if carried out in separate tanks.
    • Conference poster

      Survival, growth and production of white shrimp Penaeus indicus in brackishwater ponds. 

      FD Apud, D Javellana & R Jomen - In Y Taki, JH Primavera & JA Llobrera (Eds.), Proceedings of the First International Conference on the Culture of Penaeid Prawns/Shrimps, 4-7 December 1984, Iloilo City, Philippines, 1985 - Aquaculture Department, Southeast Asian Fisheries Development Center
      This study was conducted in 4 one-ha ponds, 70-100 cm deep and 2 two-ha ponds, 40-70 cm deep to evaluate the survival, growth and production of white shrimp, Penaeus indicus stocked at 50,000/ha and cultured within a period of 90 days with supplementary feeding.

      It was observed that mean survival and yield per ha obtained were significantly higher in deeper ponds, 70.36% and 343.2 kg/ha, respectively, compared with those in shallow ponds, 37.50% and 180 kg/ha, respectively (P < 0.05). There was no significant difference in mean body weight at harvest for deep ponds (9.80 g) and shallow ponds (9.55 g). Results suggest that white shrimp production is better in deeper ponds than in shallow ponds.
    • Oral presentation

      Thermal tolerance of larval greentail prawn Metapenaeus bennettae (Raced and Dall) a comparison with school prawn Metapenaeus macleayi. 

      T Murai - In Y Taki, JH Primavera & JA Llobrera (Eds.), Proceedings of the First International Conference on the Culture of Penaeid Prawns/Shrimps, 4-7 December 1984, Iloilo City, Philippines, 1985 - Aquaculture Department, Southeast Asian Fisheries Development Center
      The thermal tolerance of four larval stages of Metapenaeus bennettae was studied in the laboratory. Critical Thermal Maximum (CTM), One hour Median Lethal Temperature (lhLT50), and Median Resistance Time (MRT) were measured. Moulting rate of larvae and hatching rate of embryos were also monitored to study the delayed effect of thermal stress.

      Thermal tolerance was shown to be strongly dependent on acclimation temperature (TA) at all larval stages,which showed ontogenetic development of thermal resistance. Moulting of larvae was hindered at temperatures (37.2°C for nauplius when TA=25°C) well below lhLT50 (38.1°C for nauplius when TA=25°C). The embryonic stages were more susceptible to thermal stress than the larval stages. The salinity effects were also significant. Nauplius and protozoea stages showed their highest CTM values at the salinity in which they were spawned.When compared with another penaeid M. macleayi (offshore breeder), M. bennettae (estuarine breeder) was found to have higher thermal resistance, but was less adaptive to changes in acclimation temperature.
    • Conference poster

      The tolerance of Penaeus monodon eggs and larvae to fungicides against Lagenidium sp. and Haliphthoros philippinensis. 

      GL Po & E Sanvictores - In Y Taki, JH Primavera & JA Llobrera (Eds.), Proceedings of the First International Conference on the Culture of Penaeid Prawns/Shrimps, 4-7 December 1984, Iloilo City, Philippines, 1985 - Aquaculture Department, Southeast Asian Fisheries Development Center
      The in vivo effect of mycostatic levels of fungicides against the fungi Lagenidium sp. and Haliphthoros sp. were tested on Penaeus monodon eggs and larvae. Hatching rate and survival of nauplii, zoeae, myses and postlarvae exposed to 10 mg/ℓ Benzalkonium chloride, 1 mg/ℓ Clotrimazole, 1 mg/ℓ Crystal Violet, 10 mg/ℓ 2,4-D, 10 mg/ℓ Daconil, 20 mg/ℓ laundry detergent, 1 mg/ℓ Econazole nitrate, 10 mg/ℓ Resiguard, 0.2 mg/ℓ and 10 mg/ℓ Treflan-R, 0.01 mg/ℓ and 0.2 mg/ℓ Trifluralin were monitored daily for 96 hr in a static bioassay in glass aquaria. Results showed that all test chemicals had no inhibitory effect on hatching rate but survival rate of hatched nauplii was significantly reduced in most treatments except that of 0.2 mg/ℓ Treflan-R. Tests with zoeae, myses and postlarvae indicated that 0.2 mg/ℓ Treflan-R and 0.01 mg/ℓ and 0.2 mg/ℓ Trifluralin did not adversely affect survival. In addition, Benzalkonium chloride caused no significant mortalities among exposed myses.
    • Conference poster

      The use of haptophyceae in rearing experiments on larval Penaeus orientalis. 

      MR Li, BZ Bian, L Ma & L Ma - In Y Taki, JH Primavera & JA Llobrera (Eds.), Proceedings of the First International Conference on the Culture of Penaeid Prawns/Shrimps, 4-7 December 1984, Iloilo City, Philippines, 1985 - Aquaculture Department, Southeast Asian Fisheries Development Center
      The food value of five clones of Haptophyceae, Coccolithus pelagicus, Dicrateria zhanjiangensis, Isochrysis galbana, Tahitian Isochrysis aff. galbana, and Pseudoisochrysis paradoxa were tested for larval Penaeus orientalis. The algae were semi-continuously cultured in 5,000 ml carboys with 4,000 ml of Guillard f/2 medium, under 2,000 lux continuous light and under aeration. The algal density was up to 1 × 107 cell/ml. Rearing experiments were conducted in round tanks with diameter of 45 cm. Algal density was controlled at 1 × 105 cell/ml in the course of the experiments. The larval density was 18 individual/100 ml; water temperature, 21-24°C; pH, 7.5-7.7; and sea water specific gravity, 1.019.

      The results showed that of five clones used, Tahitian I. aff. galbana and D. zhangjiangensis proved to be the best. It took 9-11 days for nauplius I to develop into mysis I with survival rate of 73.5% and 73.4%, respectively.
    • Oral presentation

      The use of microencapsulated feeds to replace live food organisms in shrimp hatcheries. 

      ED Scura, J Fischer & MP Yunker - In Y Taki, JH Primavera & JA Llobrera (Eds.), Proceedings of the First International Conference on the Culture of Penaeid Prawns/Shrimps, 4-7 December 1984, Iloilo City, Philippines, 1985 - Aquaculture Department, Southeast Asian Fisheries Development Center
      An adequate supply of hatchery produced shrimp fry is the major constraint to the intensification and growth of shrimp culture practices. If even 20% of the more than 500,000 ha of the world's existing tropical and sub-tropical brackishwater ponds were to stock at the relatively low density of 50,000 fry/ha/year, it would take thousands of new hatcheries to produce the 25 billion fry required. The availability of artificially produced diets to replace cultured live food organisms would alleviate many of the problems currently limiting shrimp hatchery production by: (i) reducing the level of technical skill required to operate a hatchery; (ii) assuring a reliable supply of a nutritionally balanced larval feed; (iii) reducing sources of contamination and larval disease; and (iv) simplifying hatchery design and capital cost requirements, thereby facilitating small scale hatchery development.

      Aquatic farms has been working with the Mars Microencapsulation Research Group (MMRG) to develop techniques for adapting current shrimp hatchery technology and design so that MMRG feeds can be used in existing hatcheries as a live feed replacement. Feeding trials have been conducted in commercial hatcheries in Hawaii, Malaysia and Thailand. The results of these trials and the techniques employed are discussed. Growth and survival of larvae fed microencapsulated diets as total or partial replacement of live foods was comparable to larvae cultured in control tanks using the standard operating procedures of the hatchery in which the trials were conducted. In trials to date, larval survival from nauplii to postlarvae has been as high as 70%.
    • Oral presentation

      Variation in tissue lipid content and fatty acid composition during ovarian maturation of unablated and ablated Penaeus monodon broodstock. 

      OM Millamena, R Pudadera & MR Catacutan - In Y Taki, JH Primavera & JA Llobrera (Eds.), Proceedings of the First International Conference on the Culture of Penaeid Prawns/Shrimps, 4-7 December 1984, Iloilo City, Philippines, 1985 - Aquaculture Department, Southeast Asian Fisheries Development Center
      The tissue lipid content and fatty acid composition in the hepatopancreas, tail muscle and gonad of unablated and ablated Penaeus monodon were determined. Females at various stages of maturity were collected from offshore spawning grounds in Tigbauan and Guimbal, Iloilo, Philippines. Ablated females were reared in captivity.

      The hepatopancreas showed the highest lipid content at 15.72 to 25.20% in unablated females and 22.47 to 34.90% in ablated females. Fresh lipid levels averaged 2.60% with no marked variation throughout the maturation period. Ovarian lipid increased from 5.80% (unablated) and 7.50% (ablated) in Immature Ovaries to more than two-fold in Early Maturing Ovaries coupled with a drop in hepatopancreatic lipid suggesting lipid mobilization to the ovaries. In ablated females, ovarian lipid progressively increased to a maximum of 21.90% in Fully Mature Ovaries with a corresponding rise in hepatopancreatic lipid. Both the ovarian and hepatopancreatic lipids declined in spent females. Fatty acid profiles of the tissues consistently showed the presence of polyunsaturated fatty acids (PUFA) 20:4ω6, 20:5ω3 and 22:6ω3. These fatty acids were reflected in the spawned egg. The lipid level in the hepatopancreas appeared to be inversely related to the total PUFA concentration in the ovaries. Lipid accumulation in ablated females was significantly higher than in unablated females.

      The findings suggest storage and subsequent utilization of lipids for maturation and spawning processes. The type of polyunsaturates present in the maturing ovaries is indicative of their metabolic and physiological importance in the reproductive process.
    • Oral presentation

      Water quality criteria for farming the grass shrimp, Penaeus monodon. 

      HC Chen - In Y Taki, JH Primavera & JA Llobrera (Eds.), Proceedings of the First International Conference on the Culture of Penaeid Prawns/Shrimps, 4-7 December 1984, Iloilo City, Philippines, 1985 - Aquaculture Department, Southeast Asian Fisheries Development Center
      Physiological and growth effects of pH, salinity, temperature, heavy metals, pesticides and others on juvenile grass shrimp Penaeus monodon have been investigated to

      determine the biologically safe concentrations. Optimal pH, salinity and temperature are found to be in the range of 8.0-8.5, 15-25 ppt, and 28-33°C, respectively. A dissolved oxygen concentration of 3.7 ppm seems to be the critical oxygen pressure to support the normal life of grass shrimp. To avoid poor survival and retarded growth, the recommended level for each pollutant are: heavy metals, 0.0025 ppm Hg, 0.1 ppm Cu, 0.15 ppm Cd, 0.25 ppm Zn; pesticides, 0.0004 ppb parathion, 0.001 ppb malathion, 0.008 ppb rotenone, 0.01 ppb Azodrin, 0.033 ppb Saturn, 0.01 ppb paraquat, 0.01 ppb Endosulfan, 1 ppb Butachlor; surfactants, 0.1 ppm Dunall OSE, 0.2 ppm BP 1100, 0.5 ppm Seagreen 805; and others, 0.033 ppm H2S, 0.1 ppm NH3.