Now showing items 503-522 of 1070

    • Article

      Hormone-induced spawning and embryonic development of the rabbitfish, Siganus vermiculatus (Pisces: Siganidae) 

      EM Avila - The Philippine Scientist, 1984 - San Carlos Publications, University of San Carlos
      Induced spawning experiments were conducted on captive Siganus vermiculatus with the use of human chorionic gonadotropin (HCG APL Ayerst). The hormone was administered intramuscularly and the intraovarioan oocyte development and milt conditions of the fish were monitored by in vivo methods. Likewise, the spawning behavior and early life history of the species were observed and documented.

      Spontaneous spawnings and natural fertilization of the eggs occurred following ovulation in the fish injected with 500 IU HCG between 17 and 18 hrs after the last of a series of injections delivered at 24-hour intervals. Accelerated oocyte maturation was indicated by progressive changes in the gross morphological characters of the eggs and further thinning of milt. Dominant and aggressive behavior of the female characterized the spawning activities which commenced in the mornings.

      Newly-fertilized demersal eggs measured 0.52 ± 0.01 mm in diameter and each had a narrow perivitelline space, the yolk containing several centrally-located oil globules. Embyonic development was basically similar to that exhibited in most bony fishes. Atretic eggs retained in the body cavity averaged 0.57 ± 0.01 mm in diameter. Yolksac larvae, 1.75 ± 0.14 mm in standard length, hatched 23 to 24 hrs after fertilization in 25-25 ppt sea water at ambient temperature (25.9-28.1°C).
    • Article

      The hydraulic control structure: A threat to the fishpen industry in Laguna de Bay. 

      BH Nielsen, AE Santiago & F Petersen - Likas Yaman, Journal of the Natural Resources Management Forum, 1981 - Natural Resources Management Center
    • Article

      Hydrolyzed tuna meat by-product supplement for juvenile red sea bream, Pagrus major, and its effect on growth, enzyme activity, plasma parameters, and apparent nutrient digestibility 

      RE Mamauag, JA Ragaza, S Koshio, M Ishikawa & S Yokoyama - The Israeli Journal of Aquaculture-Bamidgeh, 2014 - Society of Israeli Aquaculture and Marine Biotechnology (SIAMB)
      A growth experiment was conducted on juvenile red sea bream, Pagrus major to investigate the effect of the inclusion in fish diets, of tuna meat by-product hydrolysate which was processed through enzymatic hydrolysis using a commercially available enzyme, derived from Bacillus subtilis. Six experimental diets were formulated in the experiment. Three diets contained 50, 150 and 250 g/kg of TPM-H (tuna meat by-product hydrolysate), and two diets with the unprocessed TPM (tuna meat by-product) at an inclusion level of 50 and 250 g/kg. A control diet was formulated without any addition of the test ingredients. Treatment diets were fed ad libitum to juvenile fish with an initial average body weight of 0.81 ±0.13 g for 56 days. Results of the feeding trial suggest that the inclusion of TPM-H at 250 g/kg in fish diets improved body weight gain rate (3271.58%), feed intake (24.55 g/fish/56 days) and feed conversion efficiency (1.12) of the fish. Apparent nutrient digestibility of hydrolyzed tuna meat by-product improved compared to the unhydrolyzed ingredient. These results suggest that TPM processed as hydrolysates can be efficiently utilized by fish.
    • Article

      Identification and characterization of vitellin in a hermaphrodite shrimp, Pandalus kessleri 

      ET Quinitio, A Hara, K Yamauchi, T Mizushima & T Fuji - Comparative Biochemistry and Physiology - B: Comparative Biochemistry, 1989 - Elsevier
      1. A female specific protein (FSP, vitellogenin) in hemolymph and its related ovarian protein (vitellin) of Pandalus kessleri were studied by means of electrophoretical and immunological procedures.

      2. The vitellin was purified from vitellogenic ovaries using hydroxylapatite, DEAE cellulose and Sepharose 6B columns, consecutively.

      3. The vitellin had a molecular weight of approximately 560 kD and was composed of two subunits, 81 and 110 kD, respectively.

      4. The vitellogenin concentrations in the hemolymph increased as vitellogenesis in the ovarian oocytes advanced and dropped markedly after the release of mature eggs.
    • Article

      Identification of postlarvae of the genus Penaeus appearing in shore waters 

      H Motoh & P Buri - Researches on Crustacea, 1981 - Carcinological Society of Japan
      Diagnostic features for the identification of postlarval Penaeus found in the shore waters of the Philippines are described and categorized based on specimens caught from the wild and those hatched and reared in the laboratory.

      Differentiating features for postlarval Penaeus are given which include the relative length of the antennular flagellum, the shape of the rostrum and number of rostral teeth, the antennal spine, the spinules on the dorsal caina of the sixth abdominal segment, and chromatophore patterns.

      Postlarval Penaeus were classified into two species and two groups as follows: (1) P. monodon, larger in size with dense chromatophores, and the long inner antennular flagellum being more than 2.0 times the outer antennular flagellum; (2) P. semisulcatus, the inner flagellum being 1.6 to 2.0 times the outer antennular flagellum, the the absence of chromatophore on the middle portion of the telson and uropods; (3) P. merguiensis group, less pigmented, the inner flagellum being less than 1.6 times the outer flagellum and (4) P. japonicus group, a short rostum, presence of spinules on the dorsal carina of the sixth abdominal segment, and dense chromatophores. The determinations were confirmed by rearing experiments.
    • Article

      Identification of Pseudomonas sp. strain S3 based on small subunit ribosomal RNA gene sequences. 

      AAA Hamid, S Hamdan, RV Pakingking Jr. & F Huyop - Biotechnology, 2010 - Asian Network for Scientific Information
      Pseudomonas sp. strain S3 was isolated from Paddy (rice) field agricultural area. This organism, which can utilize a halogenated compound of D,L-2-Chloropropionic acid as sole carbon and energy source, catalyses the hydrolytic dehalogenation of both D- and L- isomers of 2-Chloropropionic acid. Identification of Pseudomonas sp. S3 is still ambiguous due to the lack of basic studies, especially their molecular genetic information. In this study, the amplified 16S rRNA gene sequence of Pseudomonas sp. S3 (Accession No. FJ968758) was compared to other nine selected gene sequences from the same group of Pseudomonas sp. and/or dehalogenase producing bacteria using in silico method. Their phylogenetic relationships were then determined. The results were analysed using MEGA4 software to ascertain its evolutionary distance by reconstructing a phylogenetic tree of these organisms. The evolutionary history and bootstrap consensus tree were inferred using the Neighbour-Joining method from 500 replicates. The tree is drawn to scale, with branch lengths (next to the branches) in the same units as those of the evolutionary distances used to infer the phylogenetic tree. The evolutionary distances were computed using the p-distance method and were in the units of the number of base substitutions per site. Based on this analysis, Pseudomonas sp. S3 16S rRNA gene was closely related to the Pseudomonas chlororaphis with genetic distance 0.170 base substitutions per site. S3 gene was also compared among known dehalogenase producing bacteria 16S rRNA genes. Results suggested that S3 was closely related to the Pseudomonas sp. R1 with a genetic distance 0.040 base substitutions per site. From present study, evolutionary relationships of 16S rRNA gene of Pseudomonas sp. S3 were elegantly illustrated by phylograms, comparable to a pedigree showing which microorganisms are most closely related.
    • Article

      Identification of stressors that affect white spot syndrome virus (WSSV) infection and outbreak in pond cultured Penaeus monodon. 

      EA Tendencia & JAJ Verreth - The Israeli Journal of Aquaculture-Bamidgeh, 2011 - The Society of Israeli Aquaculture and Marine Biotechnology
      White spot syndrome virus (WSSV) has been a big problem to the worldwide shrimp industry. Exposure to stressors related to physicochemical water parameters affect WSSV infection but not all WSSV infections result in outbreaks. This paper describes a detailed monitoring of important physicochemical water parameters on a farm with 11 ponds that had WSSV infection. The virus was detected in shrimp exposed to two or more simultaneous stress factors (temperature, pH, water level) or multiple stressors for a number of days. Exposure to more than three stressors resulted in an outbreak of the disease within 3-6 days. Outbreaks were experienced in ponds with a temperature of 26-27°C, a pH lower than 8.0, pH fluctuation of 1.0, and a water depth of less than 1 m. Shrimp stocked in eight of the ponds were successfully harvested after 128-173 days of culture.
    • Article

      Identifying mangrove areas for fisheries enhancement; population assessment in a patchy habitat 

      MJH Lebata, ME Walton, JB Biñas, JH Primavera & L Le Vay - Aquatic Conservation: Marine and Freshwater Ecosystems, 2012 - Wiley
      1. Small-scale fisheries are an important element of the ecosystem goods and services that mangrove habitats provide, especially to poorer coastal communities that rely most on natural resources, and have similar values to payments for ecosystem services (PES) under carbon-trading schemes.
      2. In advance of fishery-enhancement trials for the mud crab Scylla olivacea, a mark–recapture study was conducted to estimate population size and turnover in 50 ha of isolated mangrove on Panay Island, Philippines. A total of 811 crabs were released in six sessions with an overall recapture rate of 41.5 ± 3.6%. Population size ranged from 607–1637 individuals.
      3. There was a high degree of site-fidelity, with 45.5% of recaptures in the same sampling areas as releases. Total mortality was 0.79 month-1, with fishing mortality accounting for 95% of overall mortality.
      4. Von Bertalanffy and Gompertz growth models yielded estimates for L (carapace width) of 117.3 ± 14.7 and 110.6 ± 2.1 mm and for k of 2.16 ± 0.74 and 3.25 ± 0.81, respectively. Crab densities of 12–33 individuals ha-1 in the study area were lower than in other mangrove systems owing to intermittent recruitment, while growth rates indicated no limitation in terms of food supply.
      5. The study demonstrates that in specific mangrove habitats that are below carrying capacity, there is potential for fisheries enhancement to sustain or increase direct economic benefits from mangrove ecosystems and hence promote community engagement in broader conservation and PES initiatives.
    • Article

      The identity of Limnoncaea diuncata Kokubo, 1914 (Copepoda: Poecilostomatoida) from Hokkaido, Japan, with the relegation of Diergasilus Do, 1981 to a junior synonym of Thersitina Norman, 1905 

      S Ohtsuka, Js Ho, K Nagasawa, J Morozinska-Gogol & W Piasecki - Systematic Parasitology, 2004 - Springer Verlag
      Both sexes of an ergasilid copepod, Limnoncaea diuncata Kokubo, 1914, are redescribed based on planktonic specimens collected from the type-locality in Hokkaido, Japan. Comparison of this species with Thersitina gasterostei (Pagenstecher, 1861) revealed that they are conspecific. Another ergasilid genus with two claws on the antenna, DiergasilusDo, 1981, is relegated to synonymy with Thersitina Norman, 1905. The diagnosis of Thersitina is amended.
    • Article

      Illuminating the need for ecological knowledge in economic valuation of mangroves under different management regimes - a critique 

      P Rönnbäck & JH Primavera - Ecological Economics, 2000 - Elsevier
      This is a commentary on a paper by Gilbert and Janssen (Gilbert, A.J., Janssen, R., 1998. Ecol. Econ. 25, 323–346) that deals with valuation of management alternatives for the Pagbilao mangroves, Philippines. Our main critique focuses on the undervaluation of fisheries as well as the inability to quantify the value of ecological services and internalize aquaculture's environmental costs. In addition, the sustainability criteria set up for the aquaculture management alternatives is open to debate. These weaknesses affect the result of Gilbert and Janssen's analysis so that the value of the unexploited mangrove forest is underestimated, and the value and sustainability of converting the forest into aquaculture ponds are overestimated. If applied to decision-making, the erroneous results from this partial cost–benefit analysis may have dire consequences for the mangroves and coastal communities of Pagbilao.
    • Article

      Immune responses of Asian sea bass, Lates calcarifer Bloch, against an inactivated betanodavirus vaccine 

      RV Pakingking Jr., R Seron, LD de la Peña, K Mori, H Yamashita & T Nakai - Journal of Fish Diseases, 2009 - Blackwell Publishing
      Asian sea bass, Lates calcarifer (Bloch), exhibited strong immune responses against a single injection of the formalin-inactivated red-spotted grouper nervous necrosis virus (RGNNV), a betanodavirus originally isolated in Japan. Fish produced neutralizing antibodies at high titre levels from days 10 (mean titre 1:480) to 116 (1:1280), with the highest titre at day 60 post-vaccination (1:4480). When fish were challenged with the homologous RGNNV at day 54 post-vaccination, there were no mortalities in both the vaccinated and unvaccinated control fish. However, a rapid clearance of the virus was observed in the brains and kidneys of vaccinated fish, followed by a significant increase in neutralizing-antibody titres. Furthermore, the vaccine-induced antibodies potently neutralized Philippine betanodavirus isolates (RGNNV) in a cross-neutralization assay. The present results indicate the potential of the formalin-inactivated RGNNV vaccine against viral nervous necrosis (VNN) of Asian seabass.
    • Article

      Immunization regimen in Asian sea bass (Lates calcarifer) broodfish: A practical strategy to control vertical transmission of nervous necrosis virus during seed production 

      R Pakingking Jr., EG de Jesus-Ayson, O Reyes & NB Bautista - Vaccine, 2018 - Elsevier
      Outbreaks of viral nervous necrosis (VNN) in Asian sea bass (Lates calcarifer) at the larval stages via vertical transmission of nervous necrosis virus (NNV) from asymptomatic broodfish remain as a major deterrent during seed production. A five-year study was conducted to produce NNV-specific-free sea bass broodfish reared in land-based tanks through an annual immunization regimen with the formalin-inactivated NNV. We primarily immunized (intraperitoneal injection) sea bass juveniles (5 g) and monitored the neutralizing antibody (Nab) titers in the sera of these fish at scheduled intervals post-immunization. Nab titers in the sera of immunized fish peaked at Month 2 (titer: 1:4480 ± 1185) but thereafter gradually declined and significantly dropped (1:260 ± 83) at Month 12 post-primary immunization. Booster immunization of these fish at Month 12 post-immunization led to abrupt increases in Nab titers in booster immunized (B-Im) fish at Month 1 (1:12800 ± 6704) but thereafter declined and dropped at Month 12 (1:480 ± 165) post-booster immunization. The annual booster injections with the inactivated vaccine or L-15 (Unimmunized [U-Im]) were consecutively conducted for 4 years until the fish became sexually mature. Mature fish from both groups were successively induced to spawn twice (1-month interval) via intramuscular injection with luteinizing hormone-releasing hormone analogue (LHRH-a; 100 µg/kg BW). NNV was not detected by RT-PCR in oocytes and milts, and spawned eggs of B-Im fish. In contrast, oocytes and milts, and spawned eggs of U-Im fish were NNV positive. Spawned eggs of B-Im broodfish exhibited Nab titers ranging from 1:192 ± 34 to 1:240 while such was not detected (<1:40) in eggs of U-Im fish. Taken together, current data clearly demonstrate that annual immunization regimen with inactivated NNV vaccine is a pragmatic approach for sustaining immunocompetent sea bass broodfish reared in land-based tanks and circumvent the risk of vertical transmission of NNV from asymptomatic broodfish to their offspring under stress of repetitive spawning.
    • Article

      Immuno-response in tilapia Sarotherodon niloticus vaccinated with Edwardsiella tarda by hyperosmotic infiltration method 

      G Lio-Po & H Wakabayashi - Veterinary Immunology and Immunopathology, 1986 - Elsevier
      Sarotherodon niloticus with average weight of 28.42 ± 1.87g were immunized with formalin-killed Edwardsiella tarda using the hyperosmotic infiltration method. Test fish maintained in 30 l aquaria were grouped into four treatments. Group 1 and 2 were exposed to a single hyperosmotic treatment on day 0. Group 1 was bled on day 14 and group 2 was bled on day 28. Group 3 was given hyperosmotic treatments twice: on day 0 and day 14 and bled on day 28. Group 4 was an untreated control bled on day 28. All sera were analyzed for agglutinating antibody titer against E. tarda flagellar and somatic antigens. Results showed that flagellar and somatic agglutinin titers in all treatments were not statistically significant. Likewise, infection experiments where test fish were challenged with intraperitoneal injection of the test bacterium showed that the vaccination experiment did not effectively protect the test fish from infection by Edwardsiella tarda.
    • Article

      Immunolocalisation of nervous necrosis virus indicates vertical transmission in hatchery produced Asian sea bass (Lates calcarifer Bloch)—A case study 

      IS Azad, KP Jithendran, MS Shekhar, AR Thirunavukkarasu & LD de la Pena - Aquaculture, 2006 - Elsevier
      A probable vertical mode of piscine nodavirus transmission is reported in the present investigation based on a case of nodavirus associated larval mortalities in hatchery produced Asian sea bass. Polyclonal rabbit anti-SJNNV antibodies (SGWak97) detected the viral antigens in the tissue sections from the eggs and the larvae at different time intervals from − 1 to 42 days post hatch (dph). Immunopositive ovarian connective tissue associated with the oocytes along with the progressive localization of the viral antigens in the brain, spinal cord, liver, stomach and dermal musculature during the larval development indicates a probable vertical transmission of nodavirus in the Asian sea bass. The surviving larger larvae, from the batch suffering mass mortalities, produced very intense immunofluorescent positivity in the liver, stomach and dermal musculature. Results of this investigation demonstrating a possibility of vertical transmission of the nodavirus emphasize the need for screening of eggs and larvae for evolving suitable preventive and prophylactic health management strategies.
    • Article

      Impact of AMPEP on the growth and occurrence of epiphytic Neosiphonia infestation on two varieties of commercially cultivated Kappaphycus alvarezii grown at different depths in the Philippines 

      IAG Borlongan, KR Tibubos, DAT Yunque, AQ Hurtado & AT Critchley - Journal of Applied Phycology, 2011 - Springer
      Two varieties of the carrageenophyte Kappaphycus alvarezii (Tungawan, TUNG; and Giant tambalang, GTAM) from Zamboanga Sibugay, Philippines were used to test the efficacy of Acadian Marine Plant Extract Powder (AMPEP) as source of nutrients for growth, and to determine if applications had any effect on the percent occurrence of an epiphytic infestation of the red alga Neosiphonia sp. at four different depths in the sea. Results showed that the use of AMPEP significantly (P < 0.05) increased the growth rate of both Kappaphycus varieties tested but decreased the percent occurrence of Neosiphonia sp. The percent occurrence of Neosiphonia sp. infection (6–50% at all depths) of both Kappaphycus varieties with AMPEP treatment was significantly lower than the controls (i.e., 10–75% at all depths). Both the growth rate of the cultivated seaweed and the percent occurrence of the epiphytes decreased as the cultivation depth increased. Plants dipped in AMPEP and suspended at the surface had the highest growth rates (i.e., 4.1%, TUNG; 3.1%, GTAM) after 45 days; those without AMPEP dipping had the highest percent occurrence of Neosiphonia infection (viz. 70–75%). The occurrence of Neosiphonia infestation was found to be correlated with changes in irradiance and salinity at the depths observed. The results suggested that both varieties of K. alvarezii used in this study have the fastest growth rate when grown immediately at the water surface. However, in order to minimize damage caused by the occurrence of epiphytic Neosiphonia, K. alvarezii should be grown within a depth range of 50–100 cm. These observations are important for the improved management of Kappaphycus for commercial farming. Furthermore, the use of AMPEP treatments for enhancement of growth and reduction deleterious Neosiphonia sp. infections is encouraging.
    • Article

      Impacts of aquaculture on fish biodiversity in the freshwater lake Laguna de Bay, Philippines 

      MLA Cuvin-Aralar - Lakes and Reservoirs: Research & Management, 2016 - Wiley
      Laguna de Bay is the largest inland water body in the Philippines, being used predominantly for aquaculture and open water fisheries. Aquaculture in the lake began decades ago, with many changes in the lake ecosystem having occurred since that time. Most dominant species for fish culture are introduced species. Other invasive species were also introduced to the lake as escapees from land-based aquaculture facilities. This study was conducted to monitor fish diversity in two adjacent, but distinctly different, sites in the lake, namely an open fishery area (OFS), with no adjacent aquaculture structures, and an aquaculture site (AQS), with cages for the culture of various commodities. Fish traps were installed at both sites, with the traps being sampled at least every 2 weeks from April 2013 to February 2015. The results of pairwise t-tests indicated significantly higher Shannon–Wiener diversity index (H′), evenness (J′), Simpson's similarity index (D) and species richness (s) in OFS than in AQS. In terms of total catch per day, significantly greater fish biomass were obtained from AQS than from OFS. Introduced aquaculture species had a mean dominance of 83% and 47% in AQS and OFS, respectively. However, invasive species introduced from the ornamental fish trade exhibited a mean relative dominance of 10.3% in AQS and 13.5% in OFS. The relative dominance of native species was also significantly higher in OFS (41%) than in AQS (6.5%). The results of this study demonstrated the adverse impacts of aquaculture in regard to the species diversity of fish in localized areas in Laguna de Bay. The dependency of aquaculture on introduced fish species adversely impacted the natural fish population in the lake. Focusing on the culture of commercially important local species for aquaculture, rather than introduced species, will improve fish production of inland waters without accompanying adverse impacts on biodiversity.
    • Article

      Improved growth performance of Gracilariopsis heteroclada via short-term nitrogen enrichment 

      SS Santander-Avanceña, MRJ Luhan & J Felera-Panizales - Botanica Marina, 2015 - De Gruyter
      This study examined the effect of short-term nitrogen (N) enrichment on Gracilariopsis heteroclada growth and agar quality. Planting materials were soaked in different concentrations of ammonium chloride (NH4Cl) for 6 h. Total thallus N content was highest in Gp. heteroclada enriched in 300 mg l-1 NH4Cl. Growth experiments showed that this enrichment treatment (300 mg l-1 NH4Cl for 6 h) increased the growth of Gp. heteroclada (4.22±0.09% day-1) compared with the control (3.68±0.12% day-1). Pond culture using enriched Gp. heteroclada resulted in high growth rates (6.14±0.50% day-1). No epiphyte growth was observed during either the growth experiment or the pond culture. There were no significant differences between the agar yields of the enriched (3.65±0.36%) or control (3.78±0.18%) Gp. heteroclada. Additionally, no significant differences were detected when the gel strength of the enriched (611±22 g cm-2) and control (587±11 g cm-2) Gp. heteroclada were compared. The results suggest that the short-term N enrichment method could be an alternative culture strategy to increase Gp. heteroclada production and lower farming costs.
    • Article

      Improved hatchery rearing of mangrove red snapper, Lutjanus argentimaculatus, in large tanks with small rotifer (Brachionus plicatilis) and Artemia 

      MN Duray, LG Alpasan & CB Estudillo - The Israeli Journal of Aquaculture-Bamidgeh, 1996 - Society of Israeli Aquaculture and Marine Biotechnology
      A hatchery rearing scheme for the red snapper, Lutjanus argentimaculatus, is described. The feeding regime consisted of Chlorella, Brachionus, Artemia and minced fish. The average survival rate at day 24 was 27% in 3-ton tanks but only 3% in 0.5-ton tanks. From an initial length of 2.15 mm at stocking, larvae grew to 8.2 mm on day 24 and 30.6 mm on day 55. Growth and survival were best when larvae were fed screened Brachionus (<90 μm) during the first 14 days. Larvae fed Artemia at 1, 2 and 3 per ml per day weighed similarly on day 35 but were longer at the higher feeding levels and survived better at the lower levels. Larvae fed Artemia at 2 per ml had a higher survival when the ration was given four times a day rather than 1-2 times a day.
    • Article

      Improved larval survival at metamorphosis of Asian seabass (Lates calcarifer) using ω3-HUFA-enriched live food 

      P Dhert, P Lavens, M Duray & P Sorgeloos - Aquaculture, 1990 - Elsevier
      Asian seabass (Lates calcarifer) larvae were fed Brachionus cultured on Chlorella and, as soon as ingestin was possible, different types of Artemia, i.e., nauplii of the San Francisco Bay (SFB) strain, Great Salt Lake (GSL) strain or GSL nauplii that had been bioencapsulated with an emulsion containing high levels of the ω3-HUFAs (highly unsaturated fatty acids) 20:5 and 22:6. San Francisco Bay Artemia with a good natural fatty acid profile and small body size could be offered earlier than the larger but HUFA-poor Great Salt Lake strain. The poor nutritional quality of the latter, however, could be corrected by enriching the nauplii with an ω3-HUFA emulsion for 24 h, after which time high levels of the ω3-HUFAs 20:5 and 22:6 were obtained. When the Artemia diet offered before metamorphosis included natural or supplemented essential fatty acids, no significant differences in dry weight, length or survival of the fish were noticed, as compared to fish fed the naturally deficient GSL Artemia. Onset of metamorphosis and physiological condition after metamorphosis, however, were influenced by the HUFA content of the ingested prey. Seabass larvae fed SFB or enriched GSL Artemia started metamorphosis on day 19, while those in the non-enriched series never achieved metamorphosis and died of a nutritional deficiency syndrome by day 27. An indication of the physiological condition of the larvae and the early detection of the syndrome was possible by subjecting 21- and 25-day-old larvae to a stress test: abrupt exposure of the larvae to 65-ppt saline water resulted in abundant and early mortality in HUFA-deficient fish larvae. Fry receiving ω3-HUFA-fortified Artemia had a superior physiological condition which was reflected by significantly lower mortality figures in the stress test.
    • Article

      An improved method for collecting naturally spawned milkfish eggs from floating cages 

      CL Marte - Aquaculture, 1988 - Elsevier
      Natural spawnings of captive milkfish (Chanos chanos Forsskal) held in floating cages were observed in 1980, 1981, 1983 and 1985. Frequency of spawnings increased from two in 1980 to 41 in 1985. Various collectors and collection methods were tried with only slight improvements in number of eggs collected. Although the number of eggs collected per spawning increased from 900 in 1980 to a maximum of 769 000 in 1985, the numbers were not sufficient for mass-scale fry production. The most urgent problem was egg predators inside the floating cages during the spawning season. This paper presents an improved method of egg collection using fine-mesh net cages ("hapa" nets, 1 mm mesh) which effectively prevented entry of egg predators. Before "hapa" nets were installed the number of eggs collected ranged from 3300 to 668 000. From 330 000 to 2 942 000 eggs were collected by using "hapa" net cages. With the new method mass-scale production of milkfish fry can be achieved.