Now showing items 1-7 of 7

    • magazineArticle

      Breeding and seed production of the mangrove red snapper 

      AC Emata - Aquaculture Asia, 2002 - Network of Aquaculture Centers
    • Conference paper

      Changes in lipid and fatty acid content during early larval development of milkfish (Chanos chanos): influence of broodstock diet 

      CL Marte, IG Borlongan & AC Emata - In CL Marte, GF Quinitio & AC Emata (Eds.), Proceedings of the Seminar-Workshop on Breeding and Seed Production of Cultured Finfishes in the Philippines, Tigbauan, Iloilo, Philippines, 4-5 May 1993, 1996 - Aquaculture Department, Southeast Asian Fisheries Development Center
      The influence of amount and type of lipid given to milkfish broodstock by developing larvae was investigated by feeding broodstock commercial diets that differed in lipid content and composition. The two commercial feeds used had the following proximate composition: RFP - 28.16% crude protein, 2.40% crude fat, 7.58% crude fiber, 53.94% N-free extract; RCP - 43.28% crude protein, 4.58% crude fat, 6.18% crude fiber, 37.0% N-free extract.

      The lipid content and fatty acid composition of spawned milkfish eggs reflected that of the broodstock feed. Percent lipid in egg from broodstock fed RFP and RCP dropped by 22.5% and 26.9% in newly-hatched larvae and by 53.0% and 65.0% in day 2 larvae (>90% yolk resorbed), respectively. Decreases in total PUFA and increase in monoenoic fatty acids during yolk resorption indicate that milkfish as in other marine fishes utilize PUFA during early larval development. While differences in rate of utilization of individual n-3 and n-6 FA in two groups of larvae seem to be influenced by levels of the fatty acids in eggs, the influence of other nutrients on fatty acid utilization need to be investigated.
    • Article

      Daily variations in plasma hormone concentrations during the semilunar spawning cycle of the gulf killifish, Fundulus grandis 

      AC Emata, AH Meier & SM Hsiao - Journal of Experimental Zoology, 1991 - Wiley-Liss
      Male and female gulf killifish, Fundulus grandis, were kept in large cages submerged in their natural habitat in the Gulf of Mexico. Gonadosomatic indices (GSI: 100 × gonad weight/body weight) and blood samples were obtained from male and female fish every 4 hours (beginning at 1600) throughout a day on 3 separate days of the semilunar cycle: at the GSI and spawning peak (July 27–28), at midcycle (August 2–3), and on a day prior to the probable spawning peak (August 9–10). Blood samples of females were assayed for cortisol, estradiol-17β (E2), progesterone, testosterone, thyroxine (T4), and triiodothyronine (T3). The daily rhythms of hormones at each of the three days during the cycle differed markedly from one another. At the spawning peak, E2 and T3 peaks occurred at 1200, testosterone and progesterone peaks were found at 2400 and the GSI and cortisol peaks were at 0400. The GSI decreased sharply at 0800 indicating a period of probable spawning. At midcycle, most hormone levels were low throughout the day and the amplitudes of the hormone rhythms were suppressed. One day prior to the spawning peak, testosterone and progesterone variations (peaks at 2400) were similiar to those found on the day of the first semilunar GSI and spawning peaks. Daily variations of other hormones, especially E2, were prominent on the day prior to peak spawning but different from those found on the day of peak GSI/spawning. In males, plasma concentrations of cortisol, testosterone, T3 and T4 also underwent daily variations that differed from one another on the 3 days of the cycle. The results clearly demonstrate that there are dramatic changes in the daily variations of plasma hormone concentrations during the semilunar spawning cycle.
    • Article

      Fatty acid composition of five candidate aquaculture species in Central Philippines 

      HY Ogata, AC Emata, ES Garibay & H Furuita - Aquaculture, 2004 - Elsevier
      Fatty acid composition was determined in five candidate aquaculture species, mangrove red snapper (Lutjanus argentimaculatus), two rabbitfish (Siganus guttatus and S. canaliculatus), coral trout (Plectropomus leopardus) and striped jack (Caranx fulvoguttatus) sampled in the Central Philippines. Special attention was paid to arachidonic acid (ARA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Total lipids of hatchery-produced eggs and newly hatched larvae of mangrove red snapper unexpectedly had equal levels of ARA and EPA. Ovarian polar lipids were subsequently found to have intermediate or high ARA (5.5–10.7%) and DHA (14.4–20.4%) levels but relatively low EPA levels (1.5–1.9%), consequently showing high ARA/EPA (4.4–6.0) and DHA/EPA (7.4–14.9) ratios in wild mangrove red snapper and rabbitfish (S. guttatus and S. canaliculatus). Similar trends were observed even in hatchery-reared mangrove red snapper, rabbitfish (S. guttatus) and coral trout. Not only ovary but also liver and muscle contained relatively higher ARA compared with EPA in mangrove red snapper, regardless of the sample source. ARA, EPA and DHA levels in the polar lipids of wild fry (whole body) ranged respectively from 3.2% to 4.0%, from 2.7% to 4.7% and from 23.5% to 27.6% with intermediate or high ARA/EPA (0.8–1.5) and DHA/EPA (5.9–8.8) ratios in mangrove red snapper, rabbitfish (S. canaliculatus) and striped jack. As overall traits, the five species in the Central Philippines appear to have intermediate or high ARA and DHA levels with low EPA level, consequently having high ARA/EPA and DHA/EPA ratios compared to species in high and temperate northern hemisphere. Thus, the present results indicate that ARA is not a minor component in the tropical species, suggesting that ARA may be nutritionally much more important for egg development and larvae growth in the tropical species than in cold water species. The information of the present study can be used as a guideline for development of appropriate broodstock and/or larval diets in the Philippines.
    • Conference paper

      Hormonal, environmental, and dietary manipulation of milkfish broodstock to enhance egg production 

      AC Emata - In Towards More Effective Utilization of Resources for Sustained Development. Proceedings of the First IFS-NRCP Seminar-Workshop, 26-29 April 1993, Makati, Metro Manila, Philippines, 1993 - International Foundation for Science
      The insufficient supply of milkfis fry severely limits the expanion of milkfish aquaculture. While natural spamning and hatchery production of milkfish fry have been attained recently, there is sitll a need to incease egg production from available broodstock. A number of studies geared towards this concern are currently conducted at SEAFDEC Aquaculture Department with moderate success. Chronic administration of estradiol-17B and 17A-hydroxy-progesterone to femaleand male milkfish broodstock increased maturation and rematuration rates. Milkfish kept under constant long phtoperiod (16L:8D) appeared to have prolonged gonadal development than thoes of milkfish reared under long to normal to short photoperiod. Ffrmulated diet containing 6% liquid that is feed to milkfish broodstock at a daily ration 4% of total body weight appeared sufficient for maintaning sexual maturation andspawning. Refinements in these areas canensure a better management technique that can provide maximum number of good quality eggs required by hatcheries.
    • Article

      Induced spawning by LHRHa and pimozide in the Asian catfish Clarias macrocephalus (Gunther) 

      JD Tan-Fermin & AC Emata - Journal of Applied Ichthyology, 1993 - Blackwell Publishing
      Experiments were conducted to determine the optimum dose of luteinizing hormone-releasing hormone analogue (LHRHa) and pimozide (PIM) injected simultaneously to yield a high ovulation rate and produce sufficient eggs in the Asian catfish Clarias macrocephalus. In June 1990, injection of 0.05 or 0.10 μg LHRHa/g body weight (BW) + 1 μg PIM/g resulted in 100% ovulation, while only 80% of gravid catfish injected 0.025 μg LHRHa + 1 μg PIM/g ovulated. Most of the eggs stripped from 6 out of 8 control fish were not mature. Fertilization and hatching rates of LHRHa + PIM-induced fish (75–90% and 39–51%, respectively) were higher than those of control fish (36–39% and 0–1% respectively). In August and September 1990, at gravid catfish ovulated after injection of 0.05–0.10 μg LHRHa + 1 μg PIM/g BW. However, only 20% of the fish given 0.025 μg LHRHa/g + 1 μg PIM/g BW in August ovulated. No eggs could be striped from any of the control fish in August and September 1990. Techniques developed in this study, showed a simple and effective way of spawning captive catfish, C. macrocephalus. A simultaneous intramuscular injection of 0.05 μg LHRHa + 1 μg PIM/g and stripping of eggs at 16–20 h post-injection have been tested to yield high ovulation, fertilization and hatching rates.
    • Article | Short communication

      Live transport of pond-reared milkfish Chanos chanos broodstock 

      AC Emata - Journal of the World Aquaculture Society, 2000 - World Aquaculture Society