Now showing items 37-56 of 79

    • 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.
    • Conference poster

      The influence of temperature and salinity on oxygen consumption of Penaeus monodon postlarvae. 

      S Licop - 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 salinity and temperature on oxygen consumption at different developmental ages of Penaeus monodon postlarvae (P5 to P60) was studied. The design was a 2 × 5 factorial, using two levels of temperature (15 and 30°C) and 4 levels of salinity (10, 15, 20 and 30 ppt). One-day old postlarvae (P1) were acclimated to various salinities prior to the start of the experiments. Oxygen consumption was determined after three hours using a YSI dissolved oxygen meter vis-a-vis Winkler titration method.

      Respiratory activity as affected by temperature and salinity varies, dependent on the postlarval stage tested. Statistical analyses showed that temperature did not significantly influence oxygen uptake at early stages (P5-P8) until P25-P28. Its effect started to become apparent when the postlarvae were P35-P38 and was most pronounced at P49-P52. general, the postlarvae consumed more oxygen at higher temperature and the variation in the oxygen consumption of the postlarvae under the two temperatures become less obvious as the postlarvae were older. Salinity seemed to affect the oxygen consumption of the young postlarvae, P5-P8 and P25-P28, more than temperature. Differences in rate of oxygen consumption at various salinities were greater in younger postlarvae (P5-P38) than in older postlarvae (P42_P60). The relationship between rate of oxygen consumption and body weight is nearly linear in the various salinity-temperature treatments. In all cases, the regression was significant at 1% level. P. monodon postlarvae behaved as respiratory con-formers in all the salinities tested at ambient temperatures.

      The least oxygen consumption rate was noted at salinities of 20 and 30 ppt at low temperature (15°C) and 20 ppt at high temperature (30°C). The importance of these findings is discussed and related to improvement of postlarvae transport methodology.
    • Oral presentation

      The integrated use of artemia in shrimp farming. 

      J Smets, P Leger & P Sorgeloos - 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 freshly hatched Artemia nauplii in penaeid hatcheries is a common practice, although a broader application of Artemia in shrimp farming is gaining more and more interest. In this regard, an integrated use of Artemia in shrimp culture is presented in this paper.

      Artemia booster in combination with Fleischmann yeast has been proven to be a suitable algal substitute and the early feeding of decapsulated Artemia cysts at protozoea I to II stages has been shown to improve larval growth. Freshly hatched Artemia nauplii may be introduced at protozoea II to III and the use of enriched nauplii from mysis stage on clearly improves postlarval production. Enriched nauplii, pre-adult and adult Artemia can be successfully used in a nursery phase in order to improve weaning success and performance in grow-out ponds. Furthermore, the use of adult Artemia in broodstock feeding has been shown to be effective for inducing maturation.

      All Artemia products mentioned can be purchased from commercial dealers but can be produced as well on the spot in most cases. Artemia cysts may be harvested from natural or inoculated populations occurring in adjacent salt works while decapsulation of the cysts can be done in the hatchery. Enrichment of Artemia nauplii can be done routinely using enriched formulated diets during hatching of the cysts or after separation of the nauplii. Pre-adult and adult Artemia can be produced either extensively in nearby salt ponds or intensively in flowthrough raceway systems using nutrient-rich effluent water from the hatchery.

      In this regard, an integrated use of Artemia in shrimp farming will not only increase postlarval production but will decrease costs as well by production on the spot of the most expensive and valuable live food: Artemia.
    • Conference paper

      Intensive culture and feed development in Penaeus japonicus. 

      K Shigueno - 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 economic feasibility of shrimp culture with high productivity of over 10 ton/ha/crop is still under evaluation in some research institutes. However, there is one exception. In a limited area in Japan, there are 63 tanks that are actually in operation and are commercially productive. One of the trials to grow Penaeus japonicus is herewith introduced to represent the intensive culture of penaeid shrimp. Tank design, feeding, growth, survival, water management, cost analysis and disease are described. In addition, an illustration of successful semi-intensive culture in earthen ponds is shown to help explain how to intensify and stabilize production.
    • Conference poster

      Intermediate culture of chinese prawn without feeding in nursery ponds. 

      W Zhang & MR Li - 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 aim of the experiments is to find a new way to accomplish intermediate culture of the penaeid prawn in nursery ponds. Experiments have been carried out in prawn farms in Haiyang County, Shandong Province. Prawn fry were stocked at high density in a nursery pond. Commercial fertilizer was added to the nursery pond to fertilize the pond water as nutrients for the planktonic and benthic organisms. The prawn fry in the pond fed only on the available natural food organisms without any special feed supply and grew normally. The survival and growth rate of the prawn fry are discussed.
    • Oral presentation

      Larval growth and survival optima for four species of penaeids from Australia, as indicated by their distribution and abundance in the field. 

      PC Rothlisberg & CJ Jackson - 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
      Prawn catches from tropical northern Australia are dominated by four species of prawns: Penaeus merguiensis, P. semisulcatus, P. esculentus and P. latisulcatus. Three of the species (P. merguiensis, P. semisulcatus and P. latisulcatus) are widespread throughout the Indo-Pacific, while P. esculentus is endemic to northern and eastern Australia. The species appear, however, to have well defined and limited distribution on a smaller scale. Surveys of the larvae in the Gulf of Carpentaria, northern Australia, have shown both spatial and temporal heterogeneity in the abundance of all four of these species.

      Assessing the temperatures and salinities in which the larvae were caught may be a realistic indicator of conditions suitable for reproduction, as well as growth and survival of the larvae. Means of these distributions may be deemed optima and ranges indicate tolerances.

      Most of the larvae of all four species are found in water above 26°C and 31 ppt. However, the mean temperatures and salinities vary significantly between species. P. merguiensis has the lowest salinity optimum (31.8 ppt) and the highest temperature optimum (29.0°C). the other three species are similar for both temperature and salinity optima. P. latisulcatus has the lowest temperature optimum of 27.4°C compared with P. semisulcatus at 27.9°C and P. esculentus at 28.5°C. The salinity optima for these three species are almost indentical at approximately 33.2 ppt.

      While the ranges of temperatures of all four species are similar (21.5-30.6°C), the ranges of salinities in which the lar-vae are found coincide with the size of the biogeographic distribution of the species. The three widespread species have large salinity ranges: P. merguiensis, 26.2-34.9 ppt P. semisulcatus, 27.8-34.9 ppt: and P. latisulcatus, 28.6-34.9 ppt. The Australian endemic, P. esculentus, has the smallest and highest range, 30.1-34.6 ppt. This apparent inability of P. esculentus to tolerate low salinity water may restrict dispersal during the larval stages.
    • Conference poster

      Lecithin requirement of Penaeus monodon juveniles. 

      FP Pascual - 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 8-week feeding experiment was carried out to determine the lecithin requirement of Penaeus monodon postlarvae. Six shrimps with initial mean weight of 0.11 g were stocked in oval fiberglass tanks in a flowthrough system with 40 ℓ of seawater. There were 5 replicates or a total of 30 shrimps per treatment. Diets were similar for all treatments except for the source of lipid and levels (0, 1 and 2%) of added soybean lecithin. Cod liver oil (treatments 1 to 3), crude degummed soybean oil (treatments 4 to 6) and refined soybean oil (treatments 7 to 9) were the three sources of lipid.

      Differences in mean weight gain due to source among treatments were not significant after the fourth week of feeding but were significant after the sixth week. Mean survival rate was affected by source of lipid after the fourth and sixth weeks. Levels of lecithin significantly affected mean weight gain after the fourth and sixth week of feeding. Mean survival rate was significantly different among treatments after the sixth but not the fourth week. Although feed conversion or feed efficiency was generally poor, a trend is discerned. Feed conversion improved as dietary levels of lecithin increased from 0 to 2%. P. monodon juveniles need lecithin but the amount has yet to be defined.
    • Conference poster

      Lipids and essential fatty acids in the nutrition of Penaeus monodon larvae. 

      OM Millamena & ET Quinitio - 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 lipid levels and fatty acid distribution during larval development of Penaeus monodon were determined. Larvae were cultured utilizing standard rearing procedures and feeding schemes adopted by the Crustacean Hatchery of SEAFDEC Aquaculture Department in Tigbauan, Iloilo, Philippines. At each developmental stage (spawned egg, nauplius, protozoea, mysis, postlarva), samples were collected for biochemical analysis.

      Lipid content decreased with developmental stage (from egg to postlarva), indicating utilization of lipids as energy source during larval development and metamorphosis. The major fatty acids in the egg lipid were 16:0 (palmitic), 16:1 (palmitoleic), 18:0 (stearic), 18:1 (oleic), 18:3 (linolenic), 20:4 (arachidonic), 20:5 (eicosapentaenoic), and 22:6 (docosahexa-enoic acids. As the larvae developed, levels of 16:1 and 18:1 fatty acids decreased with a corresponding increase in polyunsaturated fatty acids (PUFA), particularly 20:5ω3 and 22:6ω3. These indicate the importance of PUFA as dietary components.

      Comparison was made between fatty acid changes during larval development and the fatty acid constituents of commonly used larval feeds (algae, rotifer, brine shrimp, egg yolk) for P. monodon. The algae and zooplankton were found to contain 20:5ω3, while egg yolk was high in total lipids but low in polyunsaturates. Most larval diets were deficient in 22:6ω3 fatty acid.

      Crustaceans have been shown to have a limited capacity to biosynthesize long-chain PUFA; these have to be provided in their diet. These essential fatty acids must be available in appropriate amounts to ensure successful larval development and survival.
    • Conference poster

      Molt staging in adult Penaeus monodon. 

      Pudadera R., J Llobrera, R Caballero & N Aquino - 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
      Changes and formation of cuticular layers and setae bordering the uropods and endopodites of the pleopods of adult Penaeus monodon were examined under a light microscope. Observations and photographs were made at 0, 12 and 24 hours after molting and every 24 hours thereafter until second molting occurred. Results show that the internal structures of the setae and cuticle undergo marked changes throughout the molt cycle. It was possible to identify the molt stages A, B, C and D. Rapid examination of the molt stages allows the proper timing of eyestalk ablation to induce ovarian maturation.
    • Conference poster

      Morphometric studies on three Penaeid shrimps, Penaeus japonicus, P. vannamei and P. marginatus in Hawaii. 

      CS Lee & JN Sweeney - 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
      Penaeus japonicus, P. vannamei and P. marginatus cultured at the Oceanic Institute in Hawaii, were sampled and measured. The shrimps sampled ranged from 1 to 15 g in body weight. The measurements included carapace length (CL), body length (BL), total length (TL) and body weight (BW). The results showed significant linear relationships between TL and CL, BL and CL. The relationships between CL and BW, BL and BW, TL and BW are well expressed by exponential curve. These relationships were found for all three species. However, P. japonicus has more similar morphometric characteristics to P. marginatus than P. vannamei. The carapace portion in P. vannamei is smaller than either P. japonicus or P. marginatus. In other words, P. vannamei has a greater edible portion than P. japonicus and P. marginatus. Equations for length-weight relationships can provide means of converting one characteristic into another.
    • Oral presentation

      A new approach in intensive nursery rearing of penaeids. 

      Aquacop - 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 need for a nursery phase between the hatchery and the growing pond to avoid mortalities of young postlarvae, and provide a better assessment of stocked animals is general in crustacean aquaculture.

      The Centre Oceanologique du Pacifique recently developed a new culture technique using strong aeration, no water exchange and no external filter or artificial substrates. The technique relies on the development of a phytoplankton and bacterial medium with both nutritive and purifying qualities. Early postlarvae (PL3) are grown for a month or less up to 0.1 g mean weight, in 10 to 100 m3 tanks, at densities of 1 to 10 individuals/ℓ. The mean daily growth rates are around 20% for Penaeus indicus, P. stylirostris and P. vannamei and only 12-15% for P. monodon. For all species tested, density has little or no influence on growth. The final survival rates are generally high.
    • Conference paper

      Nutrition of penaeid prawns and shrimps. 

      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
      Since Hudinaga succeeded in the artificial hatching and subsequent culture of larvae of the prawn, Penaeus japonicus, techniques for rearing this prawn from hatching to commercial sizes have been improved in Japan and applied to other penaeid species in Asian and other countries. The nutritional requirements of P. japonicus juveniles started to be investigated about 15 years ago. As a result, this prawn is found to require proteins, lipids, carbohydrates, minerals, and vitamins for normal growth, indicating the deficiency disease, poor growth, and high mortality when reared with diets lacking some nutrients. On the basis of this knowledge, compounded artificial diets are used practically for commercial production of P. japonicus as substitutes for traditional live food such as the short-necked clam and mussel.

      However, seed production of penaeids has depended on live food such as diatoms, Chlorella and Artemia. Mass culture of planktonic organisms not only requires much manual help and expensive equipment but also fluctuates with climatic conditions. Also, the nutritive value of planktonic organisms is occasionally variable and this makes the use of live food for mass culture restrictive. Therefore, the development of artificial diets for larval penaeids is one of the most important research areas in the field of penaeid culture. We have prepared microparticulate diets for larval penaeids for use both as substitutes for live food and for nutritional studies. In this presentation, I intend to deal with the overview of penaeid nutrition.
    • Oral presentation

      Nutritional value of marine yeast fed to larvae of Penaeus monodon in combination with algae. 

      EJ Aujero, E Tech & S Javellana - 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
      Saccharomyces cerevasiae and Rhodotorula aurantica, two marine yeast species, were fed to Penaeus monodon larvae (N6 to M1) singly and in combination with Tetraselmis sp. and Chaetoceros calcitrans in varying proportions. Larvae fed combination diets gave survival rates comparable to or higher than those fed algae or yeast alone. Chemical analyses show that the yeasts have low fat, moderate protein and high carbohydrate content. They also contain essential amino acids but are different in the fatty acids found to be essential for prawns. When used in combination with algae, the nutritional value of the yeasts seemed to have been improved.

      The use of marine yeasts in larval rearing could reduce economic and technological inputs in the production of natural foods for larval rearing. They are cheaper and easier to mass produce. They can be grown to very high densities using cheap carbon sources like molasses, brown sugar and coconut water with added nutrients in relatively shorter periods of time.
    • Oral presentation

      Observations on the nauplii production from wild, cultivated and mixed populations of the blue shrimp (Penaeus stylirostris) 

      RA Mendoza - 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
      Due to low nauplii production from cultivated broodstock and to minimize dependence on wild stock, an experiment was run in which four treatments, consisting of combinations of 400 adult blue shrimp (Penaeus stylirostris) from wild and cultivated (F6) populations, were applied (wild females and males, wild females and cultivated males, cultivated females and wild males, and cultivated females and males). Females were inspected every third day. Those observed with spermatophores were captured and transferred to individual 100-ℓ spawning tanks. Water was treated with EDTA and erythromycin phosphate. More than 300 individual spawns were evaluated within a 180-day period. To evaluate the nauplii production per female, an analysis of variance for a factorial arrangement (43 × 2) was conducted. The factors considered were: the abovementioned treatments, different ovarian maturation stages, adhesion of the spermatophore, and kind of spawning (complete or partial). The mixed populations had higher nauplii production than the cultivated broodstock. All the females were tagged around an eyestalk and examined for rematuration. Up to six rematurations per female were registered as well as a minimum of four days between successive spawnings for the same female. The effect of rematuration on the quantity of nauplii is discussed. Gonadosomatic index for wild and cultivated females is compared. Selective criteria for spawners are given.
    • Oral presentation

      Osmotic, total protein and chloride regulation in Penaeus monodon. 

      RP Ferraris, FDP Estepa, JM Ladja & EG de Jesus - 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 osmotic, total protein and chloride ion regulation in two size groups (10 and 30 g) of Penaeus monodon Fabricius was investigated. Preliminary experiments showed that osmolality, total protein and chloride concentrations tend to become stable 24 to 36 hours after molting.Thus,hemolymph values 36 to 240 hours after sampling were not significantly different from each other. Based on these results, only 36 hours (or more) postmolt animals were sampled after transfer from control (32 ppt) to five test salinities (8, 16, 24, 32 and 40 ppt). Hemolymph samples were then taken 1, 2, 3, 5, 7 and 10 days after transfer. Results showed that in general, osmolality, total protein and chloride concentrations in the hemolymph did not vary with time within the same salinity.Both sizes exhibited hyperosmotic and hyperionic regulation in lower salinities and hypoosmotic and hypoionic regulation in higher salinities. The isosmotic values obtained were approximately 676 to 720 mOsm (24 to 28.8 ppt) for the 10 g, and 724 to 792 mOsm (26 to 28.5 ppt) for the 30 g size group. For chloride, the isoionic values ranged from 324 to 339 mM in 10 g prawns. Slopes of the regression lines of hemolymph osmolality versus salinity in 10 g prawns were not significantly different from slopes of similar regression lines in 30 g prawns. These results suggest that the ability to regulate osmotic and total protein concentration in the hemolymph is similar in the two size groups.
    • Conference paper

      Overview of penaeid culture in the Americas. 

      GJ Escobar - 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 paper discusses the reasons behind the farming success of Ecuador, as well as the limitations associated with farming throughout the rest of the Americas. Emphasis is given to specific farming practices, management techniques, and physical design characteristics. Through improved techniques the farmer is approaching the point where he can reliably manage his crop size and harvest time as dictated by market trends and postlarval supply.

      Until recently, pond production has been characterized by relatively small-scale operations often experimental in origin. Due to the farming success in one country, production output has risen from 4,800 tons in 1978 to 23,390 tons in 1983. As evidenced by this dramatic rise in production, Ecuador is in a period of expansion and increasing technical awareness, the combined results of which have led it to become the production leader in pond-grown shrimp.

      The economic pull towards Ecuador is now slowly giving way to shrimp development in other parts of the Americas. Owing to the technical gains brought about by government programs, universities and private industries, shrimp farming has become a potential activity in many areas previously thought inadequate. Production methods have progressed from the traditional extensive method to sophisticated closed system raceways. All but the latter method are exemplified by the techniques used throughout Ecuador.

      Presently, Ecuador has in production 50,000 ha of ponds. Of these, 30,000 ha are farmed using the extensive method characterized by low cost and low output. The successful approach referred to as the semi-extensive method occupies approximately 15,000 ha. This style of farming, while requiring increased cost, leads to a proportionately higher production output. The third approach is the semi-intensive method under which an estimated 5,000 ha are in production. Increasingly higher production rates are being achieved through improvements in physical pond design, pond maintenance and preparation, feeding and fertilization regimes, technical management, and control.
    • Conference paper

      Overview of penaeid culture research: Impact on commercial culture activity. 

      Aquacop - 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 paper gives a comprehensive review of the state of penaeid culture research, its impact on commercial activity, and the major research efforts required to solve remaining problems. After providing a brief historical perspective and describing the dominant penaeid species under culture, the paper discusses the major components or phases of a production system: constitution of broodstock and maturation, larval and postlarval rearing, pregrowing in nursery systems, and grow-out. The extensive, semi-intensive and intensive grow-out systems are described including applied research on fertilization, water management, feeding, etc. needed to support these systems.

      Artificial diets (pellets, microcapsules) in relation to basic nutritional requirements and diseases (nutritional, environmental or caused by pathogens) in the larval rearing, grow-out and other production phases, and their respective research priorities are discussed. Lastly, the need for fundamental research in shrimp physiology, digestion, ecdysis, maturation, hormones, pheromones and genetics to complement applied research is highlighted.