Now showing items 21-40 of 79

    • Oral presentation

      Effect of various levels of squid protein on growth and some biochemical parameters of Penaeus japonicus juveniles. 

      LC Suarez, J Guillaume & AV Wormhoudt - 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 unknown growth factor previously suspected in squid meal was found in the protein fraction of squid (Loligo vulgaris). It is clearly different from hydro-alcohol-soluble feed attractants that are also present in squid meal. This squid protein fraction (SPF) improves the growth of Penaeus japonicus juveniles when added either in a semi-purified or in a more complex mixed diet. This growth-promoting effect does not seem to be related to the amino acid composition of SPF. In order to obtain more information on its action, several levels (1.5 to 16.0%) of SPF were added to a mixed diet. The diets were isoproteic (59% D.M.), isolipidic (8.5% D.M.), supplemented with vitamins, cholesterol, glucosamine, etc. They were fed as wet pellets to 3 replicates of 15 shrimp; blue mussel was used as the control. The growth of shrimp increased with the SPF level and attained a plateau above 6%. Body weight was significantly higher than that of the control group at this level. RNA content and RNA:DNA ratio increased with the SPF level indicating that growth was improved more by hypertrophy than by hyperplasy of the cells.

      The hepatosomatic ratio remained unchanged. The assay of two digestive enzymes, proteases and amylases, showed no clear effect of SPF on protease or amylase activities. More experiments are needed to explain the effect of the unknown growth factor of SPF.
    • Conference poster

      Effects of diet on reproductive performance of ablated Penaeus monodon broodstock. 

      OM Millamena, RA Pudadera & MR Catucatan - 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
      Four practical diets were compared for their effects upon ovarian maturation and spawning of ablated Penaeus monodon broodstock. Diets were formulated based upon the fatty acid profile of wild P. monodon. Diets 1 and 3 were cod liver oil-based while Diets 2 and 4 were soybean oil-based. Experimental treatments consisted of each of the formulated diets given in combination with natural food (squid, mussel, and annelids). An all-natural diet served as control. The fatty acid composition and total lipid content of the diets and of P. monodon fed with these diets were assessed.

      Reproductive performance was evaluated in terms of number of spawnings, fecundity, egg and nauplii production and hatching rate of eggs. Broodstock response was best in Diet 1 and comparable with the control, followed by Diets 3 and 4, and was poorest in Diet 2.

      Broodstock performance appeared to be related to the fatty acid pattern of the diet. All pelleted diets contained similar levels of total lipids. However, there were differences in amounts of important polyunsaturated fatty acids (PUFA): 20:4ω6 (arachidonic), 20:5ω3 (eicosapentaenoic) and 22:6ω3 (docosahexaenoic) acids. The fatty acid profiles of Diets 1 and 3 more closely resemble the profile of maturing ovaries of wild P. monodon; the PUFA content of these diets and ω3/ω6 ratios were higher compared to Diets 2 and 4. Diet 2, showing the poorest profile among the diets, was low in ω3/ω6 ratio and contained minimal levels of PUFA.
    • Oral presentation

      The effects of manures and pelleted feeds on survival, growth and yield of Penaeus stylirostris and Penaeus vannamei in Panama. 

      GI Garson, RM Pretto & DB Rouse - 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
      Brackishwater ponds (0.8 m deep and 600 m2) on the Pacific Coast of Panama were stocked at 5/m2 with post-larval shrimp (1 cm, 0.05 g) collected from the wild. Species composition at stocking was 56% Penaeus vannamei, 33% P. stylirostris and 11% P. occidentalis. Experimental treatments received different nutrient inputs consisting of cow manure (4,500 kg/ha dry wt.), chicken manure (4,500 kg/ha), 25% protein pelleted feed (790 kg/ha) and a control (no nutrient input), each replicated five times, in random order. Water was exchanged 5 to 10% per day and the production period was 120 days during the 1982 rainy season.
    • Conference poster

      Effects of some water-soluble vitamins on the growth of Penaeus monodon juveniles. 

      M Catacutan & A Kanazawa - 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 response of Penaeus monodon juveniles (ave. wt.= 0.076 g) in terms of survival and growth rates to vitamin test diets was observed in a 35-day feeding experiment. The prawns were reared in 60-ℓ oval tanks containing filtered seawater in a flowthrough system of ambient temperature and salinity. The treatments consisted of a control (complete vitamin mix), a vitamin-free diet and nine other diets, each lacking one of the vitamins in the mixture. At the end of the feeding trial, the survival rates in all treatments ranged from 80 to 100%, while weight gain ranged from 74 to 40%. Significantly lower weight gains were obtained from choline chloride-free diet (P<0.05) and vitamin-free and inositol-free diets (P<0.01) than from control.
    • Oral presentation

      The effects of stocking densities on growth and survival of Penaeus vannamei in cow manure-enriched ponds. 

      CS Lee, JN Sweeney & B Richards - 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
      Ecuadorian Penaeus vannamei were stocked in eight dirt ponds (approximately 163 m2) at four different types of density, i.e., 5 shrimp/m2, 10 shrimp/m2, 15 shrimp/m2, and 20 shrimp/m2. The initial body weight ranged between 1.1 and 3.8 g. No commercial feed was given to the shrimp. The only input to the pond was 30 kg of cow manure/week. Shrimp were sampled either weekly or bi-weekly for body weight measurements. Water quality parameters, such as temperature, pH, DO and turbidity were recorded twice daily; nutrients (nitrite, nitrate, ammonium and phosphate) and BOD were measured twice weekly. The chemical composition of the cow manure was analyzed. After 14 weeks' experiment, the shrimp were harvested, weighed and counted. Survival and total yield were compared among treatments.

      The results showed negative correlation between stocking density and growth. The weekly growth of shrimp was between 0.7 and 1.0 g. There was no relationship between stocking density and survival. Survival averaged 68%. The most suitable stocking density should be judged by profit. However, the total yield of shrimp was higher in the higher stocking density.
    • Conference poster

      Environmental physiology of the prawn Penaeus (melicertus) latisulcatus. 

      A Ramasamy & AP Pandian - 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
      There are a number of intrinsic and extrinsic factors which affect the normal routine activity of the prawn. The present study attempts to elucidate the optimum levels of various environmental factors for the culture of prawns.

      The salinity tolerance capacity of Penaeus (Melicertus) latisulcatus was estimated in 13 different test salinities from 0 to 60 ppt (at 5 ppt increments). The prawns can tolerate a wide salinity range of 20-50 ppt. Maximum survival, however, was between 25 to 45 ppt. The extreme low (0-10 ppt) and high (60 ppt) salinities were highly lethal to the prawns. The change in acclimation temperature from 30 to 35°C increased the upper incipient lethal level from 38.5 to 39.5°C. The prawns acclimated to 30°C tolerated 42°C for 275 sec and 45.5°C for 13 sec, while prawns acclimated to 35°C tolerated 42°C for 505 sec and 46.5°C for 11 sec.

      Prawns were acclimated to a salinity of 26 ppt and oxygen consumption was measured at 5, 15, 26, and 38 ppt in a continuous water-flow method. The total oxygen consumption showed an inverse relationship with weight. Oxygen consumption declined with increase in salinity. The resistance of prawns to hydrogen sulphide was tested in 18 different concentrations of sodium sulphide mixed with seawater. The prawns tolerated sodium sulphide concentrations up to 20 mg/ℓ. The dissolved oxygen in the water was found to be reduced to very low levels with the increase in the concentration of sodium sulphide (from 5.9 ml O2/ℓ to 0.54 ml O2/ℓ). This may cause heavy mortality of the prawns.
    • Conference poster

      Evaluation of artificial feeds for shrimp (Penaeus monodon) production in brackishwater ponds. 

      NS Tabbu, P Kungvankij, G Taleon, I Potesta & M Bautista - 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 experiment was conducted in fifteen 500-m2 brackishwater ponds to determine the response of Penaeus monodon juveniles fed with various artificial diets. Five treatments with three replicates each were: two commercial feeds containing 45% and 40% crude protein (treatments I and II), two experimental diets formulated to contain 35% crude protein (treatments III and IV) and control, without feeding (treatment V). Shrimp were fed twice daily at feeding rates based on shrimp consumption.

      Highest mean harvest weight was attained in treatment I (23.47 g) > III (19.25 g) > II (18.86 g) > IV (11.29 g) > V (9.27 g). Statistical analysis showed that differences in growth were significant at 5% probability level. However, growth in treatments I, II and III are comparable, also growth in treatments II, III and IV. Growth in treatments I, II, III and IV was significantly different from treatment V. Highest mean survival was attained in treatment III (91.82%) > I (88.93%) > II (86.95%) > IV (83.62%) V (82.62%). Statistical analysis showed no significant differences among treatments at 5% probability level.

      Projecting on a hectare basis, mean yield for each treatment was: I (628.37 kg) > II (496.35 kg) per crop in 120 days culture. Good yield was attributed to provision of formulated feeds, use of pumps in addition to tidal change for water exchange and control of predators, and pest eradication through proper pond preparation.
    • Conference paper

      Extensive and semi-intensive culture of prawn and shrimp in the Philippines 

      FD Apud - 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
      Various farming systems for prawn and shrimp are compared, with emphasis on the extensive and semi-intensive culture of tiger prawn Penaeus monodon and white shrimp Penaeus indicus in monoculture or in polyculture with milkfish (Chanos chanos). The bases of comparison include pond design characteristics, stocking density, food supply, water management, average production, technical, and other major input requirements. Common factors that may influence production for each system are also discussed.

      It is observed that prawn and shrimp production has been mainly characterized by the extensive system. Of the 200,000 ha of brackishwater fishponds in the Philippines, about 25% (50,000 ha) are stocked with prawns and shrimps in monoculture or in polyculture with milkfish. Only a relatively small portion (less than 500 ha) of the area is utilized for semi-intensive culture. The dramatic increase in area utilization for extensive prawn production in recent years can be attributed to high market demand, increased hatchery-bred fry production, minimum technical requirements, and lower production cost and risks.

      The trend towards intensification among existing large fishfarms is hampered by rising capital costs for fishpond improvement and increasing operational expense and risks. However, intensification is gaining some attention and progress in limited areas, primarily to maximize utilization and production to avoid high investment cost of land for expansion. Further development and progress in the industry will be dependent on such factors as market price, availability of fry and feed at reasonable cost, supply of trained technicians, technical problems, financial situation, and economic viability of the operation.
    • Oral presentation

      Factors affecting maturation and spawning of Penaeus esculentus in the laboratory. 

      PJ Crocos - 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
      Adult tiger prawns Penaeus esculentus were held in laboratory tanks under varying conditions of tank size, density, temperature and photoperiod for assessment of ovarian maturation and spawning. Both eyestalk ablated and intact females were studied. Maturation and spawning of intact females was favored by conditions of warm temperature (26°C) and long days (14.5 hr), whereas ovary maturation did not occur at lower temperature (20°C) and short days (12 hr). Tank size was a critical factor with intact females as maturation and spawning required a large tank (4 m2). Spawning did not occur in small tanks (1 m2) despite ideal temperature and photoperiod conditions. Unilaterally ablated females matured and spawned under both short day-cold temperature conditions and in small tanks, but the success rate was greater under long day-warm temperature conditions in large tanks. Intact females required 40-60 days before onset of ovary maturation, whereas ablated females showed maturation to ovary stage III approximately 20 days after ablation. Mating success was severely limited under small tank conditions but occurred normally in the large tanks.
    • Oral presentation

      Floating cage nursery culture system for Penaeus monodon. 

      D de la Peña, AT Young & OQ Prospero - 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 use of floating cages as nursery for Penaeus monodon postlarvae was tried at the Batan, Aklan Substation of the SEAFDEC Aquaculture Department. The cages were made of bamboo and measured 2 × 5 × 1.5 m (effective volume 10 m3) with cement-coated styrofoam sheets as floats. Two nets were installed inside a cage. The outer net (3 mm mesh size) protects the inner net (0.5 mm mesh size) from floating debris in the bay. The cages were installed offshore where water depth was at least 2 m during the lowest tide, and were attached to bamboo posts by metal rings. Postlarvae were stocked at ages ranging from PL5 to PL16. Feed consisted of raw ground fish paste applied to a feeding net which also served as substrate. Average survival based on 25 production runs was 40.98% after 2 to 3 weeks of culture. Stocking density ranged from 4,000 to 16,895 PL/m3.

      Unlike nursery tanks, this system is easier to manage and needs no aeration and pumping, thus reducing operational costs. Floating nursery cages should be located in protected areas; they can also be installed inside fishponds.
    • Oral presentation

      Genetic changes during development of penaeid shrimp. 

      JL Lester - 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
      As penaeid shrimp grow from the earliest naupliar stages, through protozoeal and mysis stages, to postlarvae, they develop greater morphological and behavioral resemblance to the adults. Electrophoretic analysis of cytoplasmic enzymes from nauplii, protozoea, mysis, postlarvae, and adults show that each stage has a unique pattern of gene activity. Thirteen enzyme stains and a general protein stain have been used on larval samples from Penaeus stylirostris, P. vannamei and P. aztecus. Some enzymes, such as phospho-glucose isomerase, are produced in the same isozymic form during all of the stages. Other enzymes exhibit changes in the number and position of isozymic bands during development, e.g. glutamate dehydrogenase. Some of these differences among developmental stages can only be explained by changes in the number and/or identity of the genes that are active at each stage. This finding suggests larval and adult responses to selection may be relatively independent.
    • Oral presentation

      Growth and productivity of juvenile banana prawns, Penaeus merguiensis in natural and laboratory systems. 

      DJ Staples, DJ Vance & DS Heales - 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
      Growth and survival of Penaeus merguiensis juveniles were measured over four years in the Norman River estuary, south-eastern Gulf of Carpentaria. Growth in carapace length for the first 8-9 weeks after settlement was essentially linear and averaged 1.2 mm/week in summer at 29.5°C and 0.45 mm/week in winter at 19.5°C. A comparison of different cohorts under varying temperatures and salinities indicated that growth was temperature- but not salinity-dependent. Survival of newly settled postlarvae varied seasonally and was highest in spring (October-November).

      In the laboratory, a study of moulting rate and moult increment at 15, 20, 25, 30 and 35°C demonstrated that the optimal temperature for growth was 25-30°C. Survival of juveniles was also highest at intermediate temperatures. Effects of salinity and food ration amounts are discussed.
    • Conference poster

      Growth and survival of Penaeus monodon postlarvae with different feeding regimes and stocking densities in earthen brackishwater nursery ponds. 

      NS Tabbu - 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 effect of different stocking densities (50, 100 and 150/m2) and two feeding regimes (natural food, consisting mainly of lablab, and natural food plus artificial diet) on the growth and survival of Penaeus monodon postlarvae (PL4 to PL5) were evaluated in eighteen 40 m2 earthen brackishwater nursery ponds using tidal water exchange for a period of 45 days.

      Results of the experiment indicated that the effect of different stocking densities was highly significant (P<0.01) on growth but not on survival for the two feeding regimes. Likewise, no interaction effect was discerned. Shrimps given artificial feed (Treatments II, IV and VI) obtained higher mean weight gains of 1.55, 1.17 and 1.05 g, respectively, than those that were not given artificial feed (I-1.44 g, III-0.92 g, and V-0.66 g). Similarly, those reared with artificial feed attained better survival of 41.62% (II), 67.44% (V) and 52.14% (VI) compared to shrimp that were not given artificial feed (I-42.53%, III-54.61% and V-46.90%).

      An exploratory economic study showed that the nursery operation gave promising results in all treatments. High rate of investment (ROI) was obtained to give a safe margin for the risk involved in this kind of business. Among all treatments, treatment V had the highest ROI of 693% and shortest payback period of 0.19 years.
    • Oral presentation

      The growth of a bialgal culture and its use as food for shrimp larvae. 

      A de la Cruz, E Alfonso & S Leal - 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 cultivation of the microalga Tetraselmis chuii with the protection of the extracellular products of Chlorella kessleri, grown in a bialgal culture, allows its development in outdoor tanks without special conditions of sterilization or aeration. Fish meal and agricultural inorganic compounds are used as fertilizers. The growth of the mixed species is analyzed comparing it with monoalgal cultures. The best fit of growth data to a logistic curve is performed and the whole curve is compared using a covariance analysis. The stratification of T. chuii in the tank favors its harvest at high concentration. A bialgal culture (based on T. chuii at 50 cells/mm3) as food for the larvae of the shrimps Penaeus notialis and P. schmitti, together with hard boiled egg yolk and rotifers, achieves good development and survival.
    • Conference poster

      Hepatopancreas cells as monitor cells for the nutritional value of prawn diets in aquaculture 

      G Vogt, FP Pascual & ET Quinitio - In Y Taki, J 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 hepatopancreas is considered to be the central organ of metabolism in decapod Crustacea. It is a system of blind tubules consisting of four cell types. The E-cells at the summits of the tubules develop into R-cells (for resorption of nutrients), F-cells (for production of digestive enzymes) and B-cells (function unknown).

      The ultrastructure of Penaeus monodon R-cells changes largely after starvation and feeding different diets. B-cells show slight reactions, while F- and E-cells are rather constant. Thirteen day-starvation results in a large decrease of the cell size and in a significant reduction of all cell organelles. After seven days starvation and four days refeeding with various extreme diets, the R-cells develop completely different food-specific ultrastructures. A distinct proliferation of the endoplasmic reticulum is characteristic of protein diets. Large fat drops are the main feature after refeeding with cod liver oil. Sucrose feeding results in "empty" cells with only few organelles. The most diversified ultrastructure with fat droplets and a high amount of all cell organelles is obtained by feeding a mixed diet.

      The study indicates that R-cells are very sensitive to the application of different diets. They could be used as monitor cells for the nutritional value and the availability of a diet for prawns. Particularly poor or badly formulated feed could be detected early by electron microscopy. This method may be very helpful for the development of artificial prawn diets in aquaculture, especially if natural sources will be used as food components.
    • Oral presentation

      Heterotrophic bacteria associated with eggs and larvae of Penaeus indicus in a hatchery system. 

      I Singh, P Laksmanaperumalsamy & D Chandromohan - 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
      Total viable aerobic heterotrophic bacteria (THB) associated with egg, nauplius, zoea, mysis and postlarva of Penaeus indicus and seawater in a hatchery system were estimated for three years from 1981 to 1984. The bacterial population varied from 1.3 × 104 to 8.72 × l07/g in egg, 1.5 × 104 to 6.17 × 107/g in nauplius, 4 × 103 to 3.14 × 107/g in zoea, 1.35 × 106 to 1.25 × 108/g in mysis, 1.6 × 105 to 8.44 × 106/g in postlarva. Water contained a THB population of 1.2 X 105 to 2.8 × 108/100 ml.

      Species of Vibrio, Pseudomonas, Aeromonas, Acineto-bacter, Moraxella, members of the family Enterobac-teriaceae, Micrococcus, Bacillus, and Coryneform group were encountered. Gram-negative bacteria were found to be dominant in all stages and showed an increase from egg (81.3%) to postlarva (92.7%). However such an increase was not recorded in the respective water samples even though gram-negative bacteria were found to be dominant. Vibrio spp. were found in high numbers in postlarvae and it was to be increasing from egg (10.4%) to postlarva (80%). The number of larvae in culture pools gradually declined as the nauplii metamorphosed to postlarvae through zoea and mysis. In general, coincidence of higher percentage of Vibrio spp. and larval mortality was recorded. Physico-chemical factors such as salinity, temperature, pH, oxygen, inorganic phosphorus, organic phosphorus, inorganic nitrogen and organic nitrogen of water did not show much variation in the same set of pools. Relationship between the physico-chemical parameters, bacterial population and the number of larvae is discussed.
    • Oral presentation

      Imperatives for the future development of prawn culture in the Cochin backwater system (Kerala, India). 

      D Stephen - 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
      A traditional system of prawn culture practised in the Cochin Backwater System, the largest backwater system in Kerala State, has an estimated yield of 4,000 tons from about 4,500 ha. Governmental investments to encourage prawn production on a scientific basis continue to grow with the dual objective of improving the socio-economic conditions of fisherfolks and augmenting prawn exports. A geographic study of land and water uses and an assessment of environmental impact of these uses point to basic incompatibilities of city expansion and semi-intensive prawn culture. Population growth, urban expansion and industrial development projections for Cochin City and its surrounding areas support the view that water quality will deteriorate further making culture of prawns for export a difficult proposition. Functioning horizontal-communications between city and fisheries planning units are essential as are improvements in environmental protection than presently evident. Attention is directed towards examining other options for improving socio-economic conditions of fisherfolks and increasing prawn production and developing public policy for protecting prawn culture areas elsewhere.
    • Oral presentation

      An improved strategy for building brackishwater culture ponds with iron pyrite soils in mangrove swamps. 

      MP Yunker & ED Scura - 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 problems associated with acid sulfate soil limit the potential utilization of vast coastal areas of mangrove swamps for brackishwater aquaculture. There is an estimated 4.8 million ha of mangrove area in the ASEAN countries alone. Until recently, most attempts to build earthen ponds in these areas have yielded poor results.

      Aquatic Farms, as technical consultants for a 250 ha-prawn farm in Johore Peninsula, Malaysia, developed a construction technique that utilized the volcano-like burrow mounds of the mud lobster (Thalassina anomala) to cover and seal pond embankments that has minimized the culture problems usually experienced with iron pyrite soil. The strategy, pond design and construction technique are described. Pond dynamics and performance are discussed since the commencement of culture operations and these are compared with a nearby prawn farm that was constructed using conventional techniques. A cost benefit analysis is given in conclusion.
    • Oral presentation

      Induced ovarian maturation and rematuration by eyestalk ablation of Penaeus monodon collected from Indian ocean (Phuket province) and Songkhla lake. 

      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
      Because of the difficulty involved in maintaining a supply of sexually mature female shrimp for larval production in hatcheries, experiments on induced ovarian maturation in tiger shrimp, Penaeus monodon by eyestalk ablation were carried out from March to August, 1983. These shrimps were collected from two areas of Thailand: Phuket on the Indian Ocean and Songkhla Lake with entry to the Gulf of Thailand. Every female had one eyestalk pinched before being stocked together with males in various female-male ratios in 50-ton cement tanks with continuous water flow. The shrimp were fed 10% of their body weight daily with a diet of 90% green mussel (Mytilus edulis) and 10% cow liver.

      Results show that of those female shrimps collected in the Phuket area which is a natural spawning ground, 51% became gravid.However, of those collected in Songkhla Lake which is not a spawning area, only 19.51% became gravid. There was also a large difference in the number of days between eyestalk ablation and first spawning: 4-5 days for the Phuket samples and 20-30 days for those from Songkhla Lake. The survival rate of the larvae until P20 averaged 8.5% (total 732, 259) for the Phuket samples and 4.0% (total 300,000) for the Songkhla Lake samples. Results show mass mortality during the nauplius and mysis stages of shrimp from both locations which may indicate a greater susceptibility to bacterial and fungal infections in larvae produced from artificially matured females.

      Further studies should be undertaken to determine the proper nutritional diet for maximum production of gravid females, and to discover methods to increase sperm production in males from areas other than natural spawning grounds.
    • Oral presentation

      Induction to ovary maturation by ablation in the pink shrimp Penaeus notialis. 

      L Ramos - 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
      A partial unilateral ablation was carried out on immature females of the pink shrimp Penaeus notialis. They were maintained in 1,600 ℓ asbestos-cement tanks together with apparently mature males, not submitted to treatment, at a ratio of 2 females: 1 male. A quick development of the ovary was attained, which did not present significant differences in average diameter of the ovocytes in the anterior, median, and posterior lobes, and with similar histological characteristics to those described for naturally mature females. Viable spawnings were obtained three days after the treatment and onwards. The larvae obtained showed normal activity and development.