Now showing items 874-893 of 1070

    • Article

      Salinity effect on the embryonic development, larval growth and survival at metamorphosis of Placuna placenta Linnaeus (1758) 

      JA Madrones-Ladja - Aquaculture, 2002 - Elsevier
      The effects of salinity on the embryonic development, growth, and survival of D-larvae to plantigrade as well as settling in Placuna placenta were studied. Embryos were developed to D-larvae of shell length (SL) 86±12 μm (SL±S.D.) after 20 h at salinities of 22–34 ppt, but not at lower salinity levels. Percentage production of straight-hinged larvae from fertilized eggs at these salinities ranged from 51% to 63% (P≥0.05). P. placenta larvae survived and settled in salinities of 16–34 ppt. Settlement occurred first (14 days) in salinities of 22–34 ppt and later (19 days) in 16 ppt when SL≥200 μm. Larval size at metamorphosis was not significantly different among these salinities (P≥0.05). Percentage survival of plantigrades at 34 ppt (13%) was significantly higher (P≤0.05) than at 16 ppt (4.5±3%), but not greater than at 22 (6.3±3%) or 28 ppt (7±4%) salinity. The best salinity levels for embryonic development and larval survival at metamorphosis ranged from 22 to 34 ppt and larval growth from 16 to 34 ppt. The tolerance of P. placenta to lower and higher salinities progressively increased as larvae develop from embryo to the plantigrade stage.
    • Article

      Salinity tolerance of fertilized eggs and yolk-sac larvae of the rabbitfish Siganus guttatus (Bloch) 

      PS Young & CE Dueñas - Aquaculture, 1993 - Elsevier
      Among naturally spawned and hormonally induced eggs of Siganus guttatus, salinity levels, at which at least 90% of the eggs hatched, ranged from 7 to 67 ppt for naturally spawned eggs and from 9 to 67 ppt for hormonally induced eggs. Salinity levels at which naturally spawned eggs yielded at least 50% normal larvae ranged from 7 to 62 ppt; salinity levels providing at least 90% normal larvae ranged from 10 to 51 ppt. Salinity levels at which 50% larvae survived for 12 h after hatching ranged from 10 to 45 ppt, and for 24 h after hatching, from 14 to 37 ppt. From the results, it is recommended that the incubation salinity of S. guttatus be within the range 10–51 ppt, and for yolk-sac larval maintenance, within the range 14–37 ppt.
    • Article

      Salinity tolerance of larvae of the mangrove red snapper (Lutjanus argentimaculatus) during ontogeny 

      CB Estudillo, MN Duray, ET Marasigan & AC Emata - Aquaculture, 2000 - Elsevier
      Salinity tolerance and the effects of salinity on growth, condition factor and chloride cell (CC) densities were evaluated for Lutjanus argentimaculatus larvae during ontogeny. Tolerance of L. argentimaculatus larvae to abrupt changes of salinity from 32 ppt varied with age. Periods to 50% mortality (LT50) were significantly (P<0.05) longer for 0-day-old larvae than for 7-, 14- and 21-day-old larvae. Tolerance of abrupt salinity change increased remarkably, starting on day 28. Although abrupt transfer to test salinities caused substantial mortalities, L. argentimaculatus larvae, regardless of age (0-, 7-, 14-day-old), showed significantly longer LT50 when abruptly transferred to 8 and 16 ppt than for transfers to 24 and 40 ppt (P<0.05). Growth of L. argentimaculatus larvae at 16, 24, 32 (control) and 40 ppt was not significantly different either at the end of the first rearing phase (days 0–21) or second phase of rearing (days 22–50). Survival was significantly lowest at 40 ppt (4.3%) at the end of first phase of rearing (P<0.05). There were no significant differences in survival rates at the end of the second phase of rearing; however, the condition factor (K) of larvae reared at lower salinities was significantly higher than that of fish at 40 ppt (P<0.05). Gill epithelia of 42- and 50-day-old larvae showed increasing density of CC with increasing salinity.
    • Article

      Sargassum studies in Currimao, Ilocos Norte, Northern Philippines I. Seasonal variations in the biomass of Sargassum carpophyllum J. Agardh, Sargassum ilicifolium (Turner) C. Agardh and Sargassum siliquosum J. Agardh (Phaeophyta, Sargassaceae) 

      AQ Hurtado & AR Ragaza - Botanica Marina, 1999 - Walter de Gruyter
      Three species of Sargassum (S. carpophyllum, S. ilicifolium and S. siliquosum were collected each month for a period of one year from the inter- and subtidal zones of Pangil, Currimao, Ilocos Norte, The Philippines. Average monthly biomass was species-specific and significantly influenced by the effect of fertility states of the seaweed, collecting zone, and collecting months. A higher biomass of reproductive plants was accounted for in all species in both zones. Among the three species, S. siliquosum had the highest reproductive and vegetative biomass in both zones, followed by S. carpophyllum and S. ilicifolium. Maximum fertility was observed in October for S. carpophyllum and in November for S. ilicifolium and S. siliquosum. Minimum and maximum reproductive biomass was recorded in May and December, respectively in all species. Biomass of vegetative or non-fertile plants was highest in September in all species except for S. carpophyllum, while minimum biomass was recorded in March for S. carpophyllum and May for S. ilicifolium and S. siliquosum. Reproductive plants had more biomass than vegetative plants.

      The average monthly wet biomass (g m−2) of other Sargassum species was higher in the subtidal than in the intertidal zone. The biomass of seaweeds associated with Sargassum did not follow a definite pattern. Although water temperature, pH and salinity values were relatively constant, slight variations of temperature were positively correlated (P = 0.05) with subtidal biomass.
    • Article

      Sargassum Studies in Currimao, Ilocos Norte, Northern Philippines II. Seasonal Variations in Alginate Yield and Viscosity of Sargassum carpophyllum J. Agardh, Sargassum ilicifolium (Turner) C. Agardh and Sargassum siliquosum J. Agardh (Phaeophyta, Sargassaceae) 

      AR Ragaza & AQ Hurtado - Botanica Marina, 1999 - Walter de Gruyter
      The yield (%) and viscosity (cps) of alginate from Sargassum carpophyllum, S. ilicifolium and S. siliquosum collected along the inter- and subtidal zones of Currimao, Ilocos Norte were determined monthly for a period of one year. Results show that each species demonstrated an individual pattern of alginate characteristics which is significantly influenced by the collecting zone, fertility state, and collecting month (P < 0.05). Positive correlations were observed in alginate yield and viscosity with species and fertility states. Among the three species, S. ilicifolium is the best species for alginate production for the food industry based on viscosity characteristics, followed by S. siliquosum and S. carpophyllum.
    • Article

      Screening of vibriosis in Asian seabass, Lates calcarifer using loop-mediated isothermal amplification (LAMP) assay 

      CMA Caipang, RV Pakingking Jr. & MJS Apines-Amar - Human & Veterinary Medicine, 2012 - Bioflux Society
      The aim of this study was to standardize a loop-mediated isothermal amplification (LAMP) assay for the detection of Vibrio harveyi , the causative agent of vibriosis in Asian seabass, Lates calcarifer. The dnaJ gene of the bacterial pathogen was used as the target gene for the LAMP assay. It was optimized at an incubation time of 1 h at 63°C. The assay was highly specific for V. harveyi and did not cross-react with other bacterial pathogens offish. However, the assay was able to detect V. harveyi that was isolated from infected shrimps. The limit of detection of the LAMP assay was 40 pg of DNA mL-1 or 40 fg of the genomic DNA per LAMP reaction and was 10 times more sensitive than conventional PCR in detecting the bacterial pathogen from infected samples. The LAMP products can be quantified spectrophotometrically using hydroxynaphthol blue (HNB) dye and showed positive correlation with the amount of the pathogen. These results demonstrated that LAMP is a simple and sensitive detection technique that has potential application for routine diagnosis of vibrosis caused by V. harveyi in Asian seabass and other aquatic species.
    • Article

      The sea cucumber fishery in Palawan, Philippines 

      JBS Jontila, HM Monteclaro, GF Quinitio, SM Santander-de Leon & JP Altamirano - Kuroshio Science, 2018 - 高知大学大学院黒潮圏海洋科学研究科
      This paper presents the nature of sea cucumber fishery in Palawan, Philippines with information on gathering practices, commonly traded species and secondary accounts on wild populations. Current issues on sea cucumber fishery are also presented here along with recommended doable management measures.
    • Article

      Sea lice (Copepoda, Caligidae) parasitic on marine cultured and wild fishes of the Philippines 

      Js Ho, IH Kim, ER Cruz-Lacierda & K Nagasawa - Journal of the Fisheries Society of Taiwan, 2004 - The Fisheries Society of Taiwan
      Four species of sea lice were found parasitic on ten species of marine fishes either cultured in the coastal ponds or occurring in the sea water supply canals in the Philippines. They are: Caligus epidemicus Hewitt, 1971 on Acanthurus mata Cuvier), Epinephelus coioides (Hamilton), Glossogobius celebius (Valenciennes), Liza parmata (Cantor), Lutjanus argentimaculatus (Forsskael), Monodactylus argenteus (Linnaeus), Oreochromis urolepis hornorum (Trewavas), Oreochromis mossambicus (Peters), Rachycentron canadum (Linnaeus), and Siganus guttatus (Bloch); Caligus quadratus Shiino, 1954 on L. argentimaculatus and S. guttatus; Lepeophtheirus sigani n. sp. on S. guttatus; and Pseudocaligus uniartus n. sp. on S. guttatus and L. argentimaculatus. These ten species of fishes are new host to C. epidemicus, except for O. mossambicu which has been reported to carry C. epidemicus from Taiwan. Caligus quadratus is new to the Philippines and the two species of fish harboring it are the new host. While L. sigani was found only on S. guttatus, P. uniartus was recovered mostly from S. guttatus, and C. quadratus, largely from L. argentimaculatus. Caligus epidemicus exhibits extremely low host specificity and was found on all species of fishes examined.
    • Article

      Sea lice, Lepeophtheirus salmonis and Caligus orientalis (Copepoda: Caligidae), of wild and farmed fish in sea and brackish waters of Japan and adjacent regions: A review 

      K Nagasawa - Zoological Studies, 2004 - Institute of Zoology, Academia Sinica
      This paper reviews various aspects of the biology and effects of 2 caligid copepods, Lepeophtheirus salmonis and Caligus orientalis, on wild and farmed fish in sea and brackish waters of Japan and adjacent regions. Lepeophtheirus salmonis is a common parasite of wild adult chum (Oncorhynchus keta) and pink (O. gorbuscha) salmon migrating in northern Japanese waters. Masu salmon (O. masou) have the lowest level of infection. Juvenile chum salmon are sometimes infected. This parasite is also found on salmonids in Korean and Russian waters. The species occurs on coho salmon (O. kisutch) and rainbow trout (O. mykiss) farmed in coastal waters of northern Japan, but its infection is not a serious problem, because only young fish are reared and harvested in less than a year of culture and thus no fish are cultured during summer. This situation is very different from that in Scotland, Ireland, Norway, and Canada where L. salmonis causes serious damage to farms of Atlantic salmon (Salmo salar). Caligus orientalis is a parasite of coastal marine and brackish-water fish in Japan and neighboring countries (Taiwan, China, Korea, and Russia). This parasite has a wide host range and has been reported from over 20 fish species from different orders and families. It infects farmed and experimentally reared fish, such as rainbow trout in Japan, grey mullet (Mugil cephalus) and black porgy (Acanthopagrus schlegeli) in Taiwan, and Mozambique tilapia (Oreochromis mossambicus) in China. Heavy infection results in appetite reduction and death of fish. The parasite is one of the most important pathogens at brackish-water fish farms in Far East Asia.
    • Article

      The sea turtles captured by coastal fisheries in the northeastern Sulu Sea, Philippines: Documentation, care, and release 

      TU Bagarinao - Herpetological Conservation and Biology, 2011 - Herpetological Conservation and Biology
      This paper presents the first substantive data on sea turtles in the northeastern Sulu Sea. Working with fishers and government, the Southeast Asian Fisheries Development Center (SEAFDEC FishWorld) documented 109 juvenile and adult sea turtles captured or stranded around Panay and Guimaras Islands, Philippines from 2001 to mid- 2011. These included 65 Green Turtles (Chelonia mydas), 15 Hawksbill Turtles (Eretmochelys imbricata), 24 Olive Ridley Turtles (Lepidochelys olivacea), three Leatherback Turtles (Dermochelys coriacea), and two Loggerhead Turtles (Caretta caretta). From the four fishing villages within 1 km of FishWorld came 29 Green Turtles, eight Olive Ridleys, and one specimen each of the three other species. Approximately 77% of the Green Turtles were caught in nearshore fish corrals, mostly between October and May; whereas, 75% of the Olive Ridley Turtles were caught in offshore gill nets and long lines between April and October. Seventy-nine captured turtles were released, 73 of them with inconel flipper tags. Several turtles died from entanglement, serious injuries, slaughter for market, or diseases. An Olive Ridley Turtle and three Green Turtles were seen nesting at three beaches in southern and western Panay. Nesting of Hawksbill Turtles has been recorded at secluded beaches in Lawi, Guimaras about every three years; several batches of hatchlings have been raised by local residents before being released. Size-specific growth rates of Green Turtles and Hawksbill Turtles were highest among post-hatchlings and decreased sharply with size among juveniles and adults.
    • Article

      Seabream GnRH: partial cDNA cloning, localization and stage-dependent expression in the ovary of snake head murrel, Channa striatus 

      I Swapna, G Sreenivasulu, MK Rasheeda, K Thangaraj, R Kirubagaran, K Okuzawa, H Kagawa & B Senthilkumaran - Fish Physiology and Biochemistry, 2005 - Springer Verlag
      Vertebrate reproduction is under the neuroendocrine control of the hypothalamic decapeptide GnRH which synchronizes various reproductive events and influences other reproduction related aspects like spawning behavior and pheromonal action in fish. Multiple forms of GnRH peptides have been reported across diverse vertebrate and invertebrate classes. Here we report the partial seabream GnRH (sbGnRH) cDNA sequence cloned from the brain of Channa striatus (snake head murrel) a fresh water perciform with immense economic and medicinal value across Asiatic countries. sbGnRH mRNA was found in brain, gill and ovary of mature murrel with possible implications to the effect of GnRH on pheromonal phenomena and on reinitiation of oocyte meiosis. In keeping with the earlier reported role of GnRH in initiation of oocyte meiosis we here present evidence from RT-PCR, ICC demonstrating an increase in the level of sbGnRH mRNA in ovary from pre-vitellogenic to post-vitellogenic follicles.
    • Article

      Seasonal abundance, distribution and recruitment of mud crabs (Scylla spp.) in replanted mangroves 

      ME Walton, L Le Vay, JH Lebata, J Binas & JH Primavera - Estuarine, Coastal and Shelf Science, 2006 - Elsevier
      The abundance and distribution of mud crabs were studied in a replanted mangrove forest in Buswang, Aklan, Philippines. Two fishing gears, lift nets and bamboo traps, were used to monitor relative abundance of Scylla spp. populations from March 2002 to December 2003 inside the mangrove forest. A third gear, a stakenet set across a creek, was used to monitor crabs migrating out of the mangroves during the ebb tide. Scylla olivacea formed 99.3% and 70.3% of the catch in the mangrove and the stakenet, respectively. The percentage of Scylla tranquebarica increased from <1% in the mangrove catches to 29% in the stakenet. Scylla serrata was present at very low levels in both catches. The lack of modal progression in the size–frequency plots and the year-round catch rate of gravid females suggested that recruitment was constant throughout the year. Even though relative abundance decreased over the study period indicating that the stock is being over-exploited, mud crab production is more than equivalent to that of most natural mangroves.
    • Article

      Seasonal availability of calanoid copepods (genus Acartia) in eastern Thailand using a light trap, as food organisms for marine fish larval rearing 

      A Ohno, T Singhagraiwan & M Doi - Asian Fisheries Science, 1996 - Asian Fisheries Society
      Zooplankton collected by the torch lighting method were investigated in a tropical coastal seawater pond in eastern Thailand. Copepods of the genus Acartia, such as A. sinjiensis, A. erythaea and A. pacifica, were predominant among the zooplankton collected. A. sinjiensis occurred almost throughout the year with a prolonged peak season from August to April. The highest abundance of adult A. sinjiensis aggregated under the light reached 35,700 individuals•l-1. The occurrence of A. erythaea and A. pacifica was intermittent with a short-term peak from March to April, during which their abundance was higher than A. sinjeinsis. The combination of water temperature and salinity was suggested to affect or regulate the biomass of these Acartia species. Among the Acartia species, A. sinjiensis seems to be the most important as a food organism available for marine fish larval rearing in eastern Thailand.
    • Article

      Seasonal changes and coliform load of Jalaur river, province of Iloilo, Panay island, Philippines 

      I Lantin-Olaguer, SA Pedrajas-Mendoza, R Pakingking & A Yamamoto - Silliman Journal, 2010 - Silliman University
      Determination of the presence/absence of coliforms as the pollution indicator bacteria, total coliform count (TCC) and fecal coliform counts specifically Echerichia coli were carried out on specific sampling points in Jalaur River namely: Banban Pequeño (upstream), Calinog, Moroboro, Dingle, Passi near Sugar Central Mill and National Power Corporation (NPC) (midstream), and Nabitasan, Leganes (downstream) during the wet and dry months. Samples were analyzed using a defined technology, the Colilert® method, and its accuracy was verified with the conventional method (APHA Standard Methods).

      Results showed that coliforms were present in all sampling sites. In Calinog, total coliform count (TCC) was high (900 x101 MPN/100 ml) in July. Increased coliform abundance was associated with high rainfall due to animal wastes that were carried by runoffs. In September, Passi, near NPC, TCC and E. coli counts were 640 x101 and 630 x 101 MPN/100 ml, respectively. Reduction in counts in January, February and March was observed. Sediments in Passi near Sugar Central Mill during milling time in February showed a high TCC of 116 x 104 MPN/100 ml which was attributed to reduced current and disturbance, and silty loam sediments texture that favored bacterial adsorption to sediments. Dingle site exhibited a domination of other coliforms over E. coli in January and March. In Leganes, highest TCC of 551 x 101 MPN/100 ml was obtained in September. Coliform loads varied by season which was influenced by the availability of the nutrients and tolerance range to physical and chemical factors in the environment. Variability of the resultant interaction can also be attributed to climate changes such as extreme weather events—El niño phenomenon and increased nutrient loadings during heavy rains hence, increased coliform concentration in the river. The presence of coliforms in Jalaur River is indicative of contamination that can be aggravated by climate changes and implies that a potential health risk associated with pathogens causing water-borne diseases is present.
    • Article

      Seasonal gonad cycle of the climbing perch Anabas testudineus (Teleostei: Anabantidae) in a tropical wetland 

      RAD Bernal, FA Aya, EGT de Jesus-Ayson & LMB Garcia - Ichthyological Research, 2015 - Springer Verlag
      Seasonal reproduction of the climbing perch Anabas testudineus in the Candaba wetland, Philippines, is described. Monthly specimens were collected, gonads and viscera excised, and the gonads histologically examined. Low mean female gonadosomatic index [GSI (%)] from September to February (0.3–2.1 %) increased in March (8.7 %), peaked in May (10.9 %), and declined in June (3.3 %), but increased again in July and August (8.3–5.5 %). Male GSIs (at least 1 %) were low from September until May, increased in June (2.5 %), and then declined thereafter. All the six oocyte and four spermatogenic cell development stages were observed in the gonads throughout the annual cycle. The ovary was dominated by primary growth oocytes (chromatin nucleolus, perinucleolus) from August to February (77–90 %), but yolky oocytes (previtellogenic, vitellogenic) comprised 15 % to 28 % of the ovary from March to July. Mature oocytes were present for most of the year, comprising 40 % of the total oocytes in March-April, peaking in May (50 %), but declining to 30 % in June–July. Spermatozoa consistently dominated the testis throughout the annual cycle, particularly in November and March (58 %). Food intake in both sexes was generally low during the dry season (December–April) when gonad activity was also low, but started to increase at the onset of the wet season (May–November) when gonad activity began to peak. These results demonstrate that the climbing perch gonads exhibit asynchronous development, allowing a protracted breeding season with intense gonad activity timed at the onset of the wet season, concurrent with increasing food intake through the rest of the season.
    • Article

      Seasonal variation in food and feeding of Penaeus monodon Fabricius (Decapoda, Natantia) 

      CL Marte - Crustaceana, 1982 - E.J. Brill
      A preliminary study on feeding habits of P. monodon F. (cf. Marte, 1980) indicated seasonal variations in feeding in this species. Similar observations have been reported for P. aztecus Ives and P. duorarum Burkenroad. The present paper confirms this preliminary observation and provides indications of a relationship between feeding activity and spawner occurrence.
    • Article

      The seasonality and economic feasibility of cultivating Kappaphycus alvarezii in Panagatan Cays, Caluya, Antique, Philippines 

      AQ Hurtado, RF Agbayani, R Sanares & MTR de Castro-Mallare - Aquaculture, 2001 - Elsevier
      Vegetative thalli of brown and green Kappaphycus alvarezii were cultivated in Panagatan Cays, Caluya, Antique, Philippines, over 60- and 90-day periods using hanging-long line (HL), fixed off-bottom (FB), and hanging long line–fixed off-bottom (HL–FB) methods to determine the daily growth rate and yield. A completely randomized design experiment with six replicates of 5-m line cultivation rope was used in the study. An economic analysis was prepared to determine the viability of the culture systems used. To determine the effect of strain, culture technique, culture days and culture month on the daily growth rate and yield, a combination of these different factors was treated as a single treatment. Results show that at 60-day culture period, daily growth rate and yield in all techniques were lowest in July–August and highest in January–February. Higher growth rate (2.3–4.2% day−1) and yield (3.6–15.8 fresh weight kg m−1 line−1) were obtained from September to February. Significant differences (P<0.05) in growth rate and yield were determined between culture months. At 90-day culture period, there were no significant differences in growth rate and yield between culture months; however, a significant difference was found between culture techniques. The average production (dry weight kg crop−1) of K. alvarezii when grown at 60-day culture period during lean and peak months using HL, FB and HL–FB techniques ranged from 421 to 3310 kg with HL–FB the highest and FB the lowest. Net income, return on investment (ROI) and payback period were all positive during peak months, but negative values were obtained during lean months. Only seaweed grown on HL technique during the peak months at 90-day culture period showed positive income, ROI and payback period. The seasonality of cultivating K. alvarezii is shown in this present study. This paper further shows the best culture technique to be adopted at certain months of the year to produce the highest yield and income.
    • Article

      Seed production of Charybdis feriatus (Linnaeus) 

      FD Parado-Estepa, ET Quinitio & E Rodriguez - Aquaculture Research, 2007 - Blackwell Publishing
      Some aspects of the reproductive biology of Charybdis feriatus (Linnaeus) were investigated to identify suitable techniques for broodstock management and seed production. Likewise, factors such as ablation, water depth and light requirements affecting survival or reproductive performance were tested. Production of megalops in tanks and juveniles in net cages installed in earthen ponds was conducted. Wild-caught berried females produced a significantly higher number of zoeae per gram body weight (BW) of the female (3300±600) than captive spawners (867±58). Ablated and unablated crabs spawned after a month and ovaries of both had oocytes in all developmental stages after spawning, indicating that ablation was not necessary. Broodstock survived higher when stocked in 1 m-deep water and kept in dark conditions compared with shallow (0.5 m depth) water or ambient lighting. There were six zoea and one megalopa stage. Megalops were produced (survival of 2–22% in 1 tonne or 23–55% in 3 L tanks) when methods for the mud crab Scylla serrata (Forsskål) were used, but feeding with Artemia started only at the Z4 stage. Survival of megalops after 1 month was higher when stocked in net cages installed in an earthen pond (32–82%) than when reared continuously in land-based tanks (5–11%).
    • Article

      Seed production of mud crab Scylla serrata juveniles 

      ET Quinitio, FD Parado-Estepa, OM Millamena, E Rodriguez & E Borlongan - Asian Fisheries Science, 2001 - Asian Fisheries Society
      A protocol for the large-scale rearing of the mud crab Scylla serrata juveniles was developed based on the results of small-scale experiments on feeding and water management. This paper also reports the success in producing the second generation (F2) crabs.

      Pond-reared adult S. serrata held in 10 m3 concrete tanks with sand substrates were given fish, mussel, annelids and formulated diet. The zoeae produced were stocked in 1.5 or 10 m3 tanks at 30 to 50 ind-l-1 and fed 10 to 15 Brachionus rotundiformis ml-1, 1 to 5 Artemia sauna nauplii ml-1 and 1.5 to 2.0 g shrimp larval commercial diet-m-3 day. Water was replaced daily at 30 to 50% of the total volume starting day 3. Megalops were nursed until crab stage either in tanks or in net cages installed in ponds. Crabs were fed mussel or small shrimps (Acetes sp).

      Hatching occurred 6 to 12 days after spawning at 26.5 to 30.5°C. A female produced 0.42 to 5.23 x 106 zoeae at a time. Mean survival rate from zoea 1 to 3- to 5-day old megalopa was 2.6 ± 0.8% and 32.8 ± 4.8% from megalopa to crab stage. The development from zoea 1 to megalopa required 16 to 18 days. Cannibalism and luminescent bacteria were identified as the major causes of mortality. Highest mortality was observed during the metamorphosis from zoea 5 to megalopa and megalopa to crab 1. First crab stage was obtained 23 to 25 days after hatching. Sorting the crabs during the nursery period minimized cannibalism.

      Completion of the cycle in captivity was attained in 1997 and 1999 when spawns from pond-reared crabs grew to become the second-generation broodstock. The results point to a minimum age of 7.5 to 9 months at which S. serrata hatched their eggs after rearing from zoea 1.
    • Article

      Selective diversification of aquaculture stocks: A proposal for economically sustainable genetic conservation 

      RW Doyle, NL Shackel, Z Basiao, S Uraiwan, T Matricia & AJ Talbot - Canadian Journal of Fisheries and Aquatic Sciences, 1991 - NRC Research Press
      The genetic diversity of aquaculture stocks can be maintained, and their genetic impact on wild stocks minimized, by breeding programmes that deliberately generate genetic diversity. Current animal breeding practices are likely to reduce the diversity of domestic stocks if they are extended to aquaculture. It is proposed that national breeding programmes for aquaculture should, instead, try to develop numerous breeds specially adapted to local environments and aquaculture systems. An economic model is presented of decision-making by individual farmers who, in choosing which breed to produce, determine the "fitness" of the breeds in a meta-population that includes all breeds. As long as strong genotype-environment interaction for production traits is maintained by artificial selection, the economic self-interest of farmers should ensure the stability of genetic polymorphisms among breeds. Genetic variation would be conserved (in the among-breed component of genetic diversity) but not the primordial distribution of gene and genotype frequencies. Economic benefits to farmers, plus a high return on investment at the national or supra-national level, makes breed diversification an attractive conservation strategy even though it is admittedly a compromise from a purely genetic viewpoint.