Milkfish hatchery operations

The manual is intended primarily for practicing prawn hatchery operators who would like to diversify their operations to include larval rearing of milkfish (Chanos chanos). Only those procedures important in the daily operations of a milkfish hatchery are described in detail, under the following headings: Essential facilities - tanks and equipment; Production of natural food - Chlorella culture and Brachionus culture; Production of milkfish fry - preparation of hatching and larval rearing tanks, hatching of milkfish eggs, stocking of larvae, larval rearing, and harvesting

LHRHa and pimozide-induced breeding in the catfish, Clarias macrocephalus (Gunther)

Abstract only.Clarias macrocephalus is endemic yet dwindling freshwater foodfish in the Philippines. Induced breeding protocol was developed by monitoring the size and maturation of eggs at 0-48 h after a simultaneous injection of luteinizing hormone-releasing hormone analogue (LHRHa; 0.0005 - 0.10 µg/g BW) and pimozide (PIM; 1 µg/g BW). Based on its similar osmotic pressure with catfish plasma, eggs were fixed in 1% phosphate-buffered formalin. Mean egg diameter of fish that were induced to mature increased during ovulation. Oocyte maturation, indicated by oocytes with germinal vesicle breakdown (GVBD), was observed at least 12 h post-injection in fish given 0.01 - 0.10 µg LHRHa + 1 µg PIM/g BW, followed by ovulation 4 h thereafter. Results showed that a simultaneous injection of C. macrocephalus with 0.05 µg LHRHa + 1 µg PIM/g BW at 1800-1900 h followed by stripping at 16-20 h post-injection resulted in high ovulation, fertilization and hatching rates

Oral administrations of chemotherapeutics via the bioencapsulation technique: A tool for therapeutic treatment in larviculture

The application of the bioencapsulation technique as a tool for curative treatment in fish larvae was investigated. Antibacterials, trimethoprim (TMP) and sulphamethoxazole (SMX), incorporated in an oil emulsion (SELCO, Artemia Systems N.V., Ghent, Belgium) were bioencapsulated at different concentrations (20% and 40%) in Artemia (Instar II) nauplii. Chemotherapeutics-loaded nauplii were fed to European sea bass (Dicentrarchus labrax) larvae only once at 5 individuals/ml. Larvae were sampled after feeding at time intervals 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 12, 16, 20, 24, 36, 48, 60, 72 h. Drug concentrations in the larval tissue were analyzed by high-performance liquid chromatography (HPLC). Results indicated that larvae fed 40% "medicated"-Artemia assimilated significantly higher levels of chemotherapeutics in the tissue as compared with those fed 20% "medicated"-Artemia. Chemotherapeutics given at higher concentration (40%) reached peak levels (19.3 µg TMP/g DW, 23.32 µg SMX/g DW) in the larval tissues within 2 h while at lower concentration (20%) peak levels (8.74 µg TMP/g DW, 6.73 µg SMX/g DW) were observed within 5 h. Moreover, TMP persisted longer (>72 h) in the tissues than SMX (12-16 h) suggesting a more efficient uptake and retention of TMP and/or faster metabolism and elimination of SMX

An inexpensive tag for short-term studies in milkfish (Chanos chanos Forsskal) and in seabass (Lates calcarifer Bloch)

An opercular tag for marking adult milkfish (Chanos chanos Forsskal) and seabass (Lates calcarifer Bloch) is described. High tag retention and relatively low mortality rates were observed in adult fish handled two to ten times during 14-to 60-day tests. The features and advantages of the tag for marking large-sized fish in short-term studies are discussed

Response of the tropical abalone, Haliotis asinina, larvae on combinations of attachment cues

The effects of different diatom species and types of substrates in combination with 0.45 μM GABA on the metamorphosis of Haliotis asinina larvae were tested. Diatom slurry elicited the best metamorphic response followed by Amphora sp., Amphora + Nitzschia and Nitzschia cf. frustulum in that order. With regards to substrate types, roughened plexiglass seemed to be the most preferred while fibrocement the least preferred surface. Overall, diatom slurry grown on plexiglass surface promoted the greatest number of metamorphosed H. asinina postlarvae. For economic considerations and practical reasons, chemical inducers like gamma-aminobutyric acid (GABA), should be used singly or separately from other settlement-inducing cues, such as the “substrate-diatom” complex.We thank R. Sañares for the statistical advice, N. Bayona, B. Boja, and F. Sumalinog for the technical assistance and the anonymous reviewers for their constructive comments on the manuscript. The financial support of SEAFDEC/AQD under Study Code Nr-01-M98T is gratefully acknowledged

Postlarvae density and photoperiod effects on the settlement and metamorphosis of the donkey's ear abalone, Haliotis asinina Linne, 1758

The effects of photoperiod and density of postlarvae on settlement and metamorphosis of the native abalone, Haliotis asinina were determined in two separate experiments. Abalone larvae were hatched from spontaneously spawned eggs of tank-held broodstock. Experiments were conducted in static water conditions within a 10 day-period. Post-larvae held under at 24 h light regime showed higher settlement rates (mean: 12 %) than did larvae held at different light-and-dark periods (range: 3-9 %). Larvae kept in the dark had the lowest survival (3 %). Postlarvae stocked at lower stocking densities of 100 and 150 l -1 had higher settlement rates (12-12.5 %) than postlarvae stocked between 200 and 600 postlarvae l -1 (1-5 %)

Induction of larval settlement and metamorphosis in the donkey-ear abalone, Haliotis asinina Linnaeus, by chemical cues

The effects of the chemical inducers, gamma-aminobutyric acid (GABA) and potassium chloride (KCl), on the larval settlement and metamorphosis of the donkey-ear abalone, Haliotis asinina, was investigated. H. asinina larvae (5–6 h post-hatch) were exposed to a range of GABA (0.125–2.00 μM) and KCl (1.00–12.00 mM) concentrations for 72 h. Results of the dose response experiments showed that settlement and metamorphosis vary according to the dose levels of the inducer compounds. Under controlled laboratory conditions, 0.45–0.50 μM and 6.0 mM seemed to be the optima for GABA and KCl, respectively, as these concentrations elicited the greatest number of postlarvae that metamorphosed, settled or survived. However, GABA generally promoted better attachment and metamorphic response as well as survival than KCl in H. asinina postlarvae.The authors thank N. Bayona for the technical assistance, Dr M. Catacutan for the helpful comments on the earlier draft and the two anonymous referees for critically reviewing the final version of the manuscript. This research work was financially supported by SEAFDEC/AQD under Study Code Nr-01-M98T

Vaccination of European sea bass fry through bioencapsulation of Artemia nauplii

European sea bass (Dicentrarchus labrax) fry vaccinated orally via bioencapsulation in Artemia nauplii or by bath method exhibited better performance than control fish in terms of growth, food conversion and resistance to stress. The comparable survival between vaccinated and non-vaccinated animals suggests that vaccination methods are not stressful. The present study shows that oral vaccination can be used to enhance growth in fish fry

Field efficacy evaluation of a formalin-inactivated white spot syndrome virus (WSSV) vaccine for the preventive management of WSSV infection in shrimp grow-out ponds

A shrimp grow-out trial was conducted in four 700 m2 earthen ponds in Dumangas Brackishwater Station of SEAFDEC Aquaculture Department, in Iloilo, Philippines to evaluate the efficacy of a combination of immersion- and orally-administered formalin inactivated vaccine (FIV) as an antiviral strategy against WSSV. Purified virus prepared by sucrose gradient ultracentrifugation was inactivated by overnight incubation in 0.5% buffered formalin. PCR-screened Penaeus monodon postlarvae (PL14) obtained from a commercial hatchery were divided into two groups: 1) immersed in FIV solution for 2 h before stocking in ponds (VAC); and 2) unexposed control (CON). Both groups were stocked at a density of 15 m−2 and grown for 115 d following recommended good practices. Pond water was aerated using two 20-HP electric blowers. Shrimp were given commercial feed following the manufacturer's protocol. They were booster-vaccinated by administering FIV-coated feed every 15 d until the termination of the trial. Shrimp samples were regularly collected to obtain estimates of growth, survival, and feed conversion ratio. In addition, shrimp and extraneous crustacean species were analyzed for the presence of WSSV and IHHNV by PCR. Water quality and bacterial load were monitored regularly. After 115 d of culture (DOC), shrimps grew to 12.93 ± 1.26 g in VAC and 8.54 ± 0.78 g in CON. Likewise, survival and yield was higher in VAC (71.2 ± 3.13% and 1311 ± 70.4 kg ha−1, respectively) compared to CON (52.7 ± 5.05% and 640 ± 3.0 kg ha−1, respectively). PCR analysis showed both shrimp and extraneous crustaceans to be lightly infected with WSSV and IHHNV. A few dead shrimp were noted during routine pond inspection as shrimp biomass increased towards the end of the trial. However, no mass mortalities occurred and shrimp were successfully harvested on 115 DOC. VAC and CON shrimp were also collected on day 70, 90, and 105 and experimentally infected with WSSV in tanks. Significant differences in survival rates (p < 0.05) between the groups were obtained 15 d post-challenge. Further studies in tanks and in ponds on prophylactic oral delivery of antiviral treatments with the use of protein vaccines and vectors/carriers are recommended.This work was fully supported by project funds from SEAFDEC/AQD and the Government of Japan Trust Fund under Study Code 8400-T-RD-FH0210. We wish to thank the management of the Dumangas Brackishwater Station (DBS) for use of the facilities during the field trial. The generous assistance of DBS and Fish Health Section staff are gratefully acknowledged