Proceedings of the Seminar-Workshop on Breeding and Seed Production of Cultured Finfishes in the Philippines. 4-5 May 1993, Tigbauan, Iloilo, Philippines. SEAFDEC/AQD, Tigbauan, Iloilo, Philippines.

The seminar-workshop was conducted at AQD's Tigbauan Main Station, 4-5 May 1993. About 130 scientists and technicians from Japan, Malaysia, Singapore, Canada, UK, USA, Australia, and the Philippines attended. The workshop promoted the exchange of information and views regarding breeding and seed production of various fishes. The scientists became aware of each other's past and ongoing research projects. Priority research areas were recommended and so was the closer cooperation among various institutions and private individuals who share the common goal of sustainable aquaculture. The workshop was sponsored by the Government of Japan.

Recent Submissions

  • Conference paper

    Effects of different fat sources on the egg quality of grouper, Epinephelus suillus 

    GF Quinitio, RM Coloso, A Duller & D Reyes - 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 - SEAFDEC Aquaculture Department
    The effect of different fat sources on the egg quality of grouper, Epinephelus suillus eggs was evaluated. Fish in three tanks, each containing 3 females and 1 male, were fed various types of feeds namely: trash fish (control), trash fish + cod liver oil (treatment 1) and trash fish + SELCO, a lipid emulsion containing high levels of highly unsaturated fatty acid (HUFA) (treatment 2).

    Approximately 77.9 million eggs spawned from January to October 1992 by the control group, 40.0 million by fish in treatment 1, and 36.4 million by the treatment 2 group. Egg production (0.45 million eggs/kg BW) among the control group was significantly higher than treatment 2. Egg production of treatment 1 (0.06-0.36 million eggs/kg BW) was not significantly different (P<0.01) from the control group nor treatment 2 (0.02-0.30 million eggs/kg BW). Fertilization and hatching rates showed significant differences among the three groups with control > treatment 1 > treatment 2. There were no differences detected in the egg and oil globule diameters among the treatments. Crude protein and lipid levels of floating (good) and sinking (bad) eggs collected in February to March 1992, and August to September 1992 were similar in all treatments. Unfed larvae from treatment 1 survived until the fifth day after hatching while those in the control and treatment 2 groups lasted only until the third day. These results suggest that supplementation of cod liver oil and SELCO in the trash fish diet of E. suillus broodstock does not influence egg production, fertilization and hatching rates, and egg quality.
  • Conference paper

    Feeding habits of hatchery-reared grouper, Epinephelus suillus larvae 

    MN Duray - 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 - SEAFDEC Aquaculture Department
    The feeding habits of hatchery-reared Epinephelus suillus larvae were determined by examining their gut contents. The larvae (2.6 mm TL) were initially fed rotifers on day 2 and newly-hatched Artemia nauplii on day 21 (9.1 mm TL). The amount of rotifers initially ingested averaged 1.3 individuals/larva. The ingestion rate increased as larvae grew. Larvae immediately showed strong preference for Artemia to rotifers on the first day of introduction. E. suillus larvae showed diurnal feeding pattern at day 7 (3.6 mm TL), day 14 (4.9 mm TL), day 21 (9.1 mm TL) and day 28 (11.1 mm TL). Feeding incidence decreased in the evening and was nil at 2100-2200 h. Active feeding started earlier in older larvae and satiation was between 0900-1000 h. The results of this study will be used as a basis in developing a good feeding scheme for E. suillus larvae.
  • Conference paper

    Growth and survival of milkfish (Chanos chanos) larvae reared on artificial diets 

    IG Borlongan, CL Marte & J Nocillado - 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 - SEAFDEC Aquaculture Department
    A preliminary feeding experiment was conducted to determine growth and survival of milkfish larvae reared on various feeding regimes involving the use of artificial diets. Two larval diets (Feed A and Feed B) containing 45% protein and 10% lipid were fed either alone or in combination with Brachionus from day 8 to day 21. The feed in the control treatment were Brachionus (10 ind/ml) from day 8 to day 14 and Artemia (2-3 ind/ml) from day 15 to day 21. Larvae in all treatments were fed Brachionus (10 ind/ml) from day 2 to day 7.

    No significant differences were observed in survival rates, total length, wet weight and dry weight among fish fed combination of Brachionus and Feed B and the control feed (Brachionus and Artemia). These promising results indicate the possibility of using Feed B as partial replacement or supplement to live food. However, lowest survival rates, total length, and weight were obtained in fish fed either Feed A or Feed B alone, indicating that the test artificial diets given solely to milkfish larvae starting from day 8 can not support good growth and survival. Further studies on the development of improved artificial diets for larval milkfish need to be done.
  • Conference paper

    Review of SEAFDEC/AQD finfish seed production research 

    GF Quinitio & MN Duray - 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 - SEAFDEC Aquaculture Department
    Research on seed production of several foodfishes has been a continuing activity of SEAFDEC/AQD since 1976. Fry and juvenile production methods of these fish commodities are in various stages of advancement. For instance, advances in the development of hatchery rearing, particularly feeding and water management schemes, have made mass production of milkfish (Chanos chanos) seed a reality, resulting further in the application of the technology in commercial hatcheries. Recent studies now focus on assessing the quality of hatchery seed stocks of milkfish vis-a-vis wild seed during nursery and grow-out culture. Likewise, sea bass (Lates calcarifer) seed production has undergone significant improvements since the technology was introduced in the Philippines in 1982. Fatty acid-enrichment of a zooplankton diet can enhance growth and survival of sea bass fry, although other cheaper alternatives and early weaning to formulated diet preparations are currently being tested. Hatchery fry production of grouper (Epinephelus salmoides and E. suillus syn. E. coioides) and snapper is in its infancy, but trials complemented by research on their larval feeding habits and requirements are underway to establish reliable methods of rearing larvae of these species. Although fairly well-established, seed production of rabbitfish (Siganus guttatus) requires further improvement in determining an appropriate zooplankton diet to ensure adequate growth and survival of larvae. Hatchery fry production of tilapia (Oreochromis sp.), carps (Aristichthys nobilis, Hypothalmichthys molitrix) and, to a certain extent, catfish (Clarias macrocephalus) can already be categorized as a flourishing industry in some parts of the Philippines. Nonetheless, SEAFDEC/AQD continues to conduct research on these freshwater species, with particular emphasis on nutrition and feed development during the nursery production phase. Together, results of past and on-going research studies ensure that seed supply of these important foodfishes become adequate and sustainable for the grow-out.
  • Conference paper

    Larviculture of milkfish (Chanos chanos) in outdoor tanks 

    MN Duray - 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 - SEAFDEC Aquaculture Department
    In the past, larviculture of milkfish depended entirely on the use of rotifers and brine shrimp nauplii and rearing trials were done under roofed facilities. Since the dietary value of live food varies according to culture and feeding conditions, rotifers were enriched with SELCO, a lipid emulsion containing high levels of highly unsaturated fatty acids (HUFA) prior to feeding the larvae. Alternatively, a microbound larval feed (Nosan R-1) was given as a supplement to rotifers during the first two weeks of culture. Larval growth was enhanced and survival was significantly improved when rotifers were enriched or supplemented with these diets. All rearing trials were conducted in 5-10 tons concrete circular/rectangular outdoor tanks.

    Verification runs on the use of HUFA-enriched rotifers to milkfish larvae were tried in two nearby private hatcheries. Results from mis collaborative work are presented.
  • Conference paper

    A review of grouper (Epinephelus suillus) fry production research in Malaysia 

    HM Ali - 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 - SEAFDEC Aquaculture Department
    Research on grouper (Epinephelus suillus) fry production in captivity has been carried out in Malaysia since 1986 at Tanjung Demong Marine Finfish Production and Research Centre (TDMFPRC) but the breakthrough was only achieved four years later in 1990. Eggs were obtained through natural and induced spawning in tanks. Natural spawning of grouper in captivity seldom occurred and was unpredictable. However induced spawnings were successfully carried out by injecting human chorionic gonadotropin (hCG) intramuscularly at a dose of 500-1000 IU/kg fish.

    The results from several trials on larval rearing conducted since 1989 until recently showed that larvae obtained from natural spawnings survived longer with some reaching the juvenile stage. The highest recorded survival rate of 43 days posthatch (32.5 mm total length) was 12.1% at 28-32 °C water temperature. On the other hand, 100% mortality usually occurred in larvae obtained from induced spawning 7 days after hatching.

    The major constraints of grouper fry production in Malaysia are lack of male spawners, inconsistent and unpredictable natural spawning, small quantity of eggs released every spawning day, poor fertilization and hatching rate, weak hatchlings, and high mortality rate at the early stages of larval development. The latter is probably due mainly to problems on initial feeding.
  • Conference paper

    Endocrine changes associated with overripening of ovulated eggs in goldfish, Carassius auratus L. 

    MJ Formacion & TJ Lam - 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 - SEAFDEC Aquaculture Department
    Changes in steroid hormone levels in the serum and ovarian fluid were studied during overripening in goldfish. Ovulated eggs retained in the ovarian cavity become overripe at around 12 h after ovulation and completely overripe 24 h after. Blood and ovarian fluid were taken at 0, 3, 6, 12, 18, and 24 h after ovulation. Estradiol-17ß (E 2) , testosterone (T), progesterone (P) and 17α,20ß-dihydroxy-4-pregnen-3-one (17α,20ß-P) in the serum were extracted directly with a solvent while those in the ovarian fluid were separated by HPLC before radioimmunoassay. Both serum and ovarian fluid P showed a highly significant decline at 18 h with a further decline at 24 h; P levels were higher in the ovarian fluid. Serum 17α,20ß-P showed a progressive and more rapid decline, decreasing significantly at 12 h with further decreases at 18 h and 24 h; the level was five-fold lower at 24 h compared to the 0 h level. Serum T increased significantly at 3 h which was maintained until 18 h, when it declined to 0 h level. No significant changes in E2 were observed in the serum, except for a significant difference between 6 and 24 h. There were no significant changes in E2, T and 17α,20ß-P in the ovarian fluid. Of the four steroids measured, only 17α,20ß-P and P showed changes which bear some correlation with the time course of overripening. The declines in the mean ratios of 17α,20ß-P/E2 in the serum and P/E2 in the ovarian fluid also appeared to have a good correlation with the time course of overripening. The postovulatory follicles (POFs) showed degenerative features which likewise correspond to the decline in P and 17α,20ß-P.
  • Conference paper

    Maturation of Oreochromis niloticus gonads 

    AA Casauay & VS Carino - 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 - SEAFDEC Aquaculture Department
    At hatching when fry were 5 to 6 mm, primordial germ cells (PGCs) were found to concentrate along the dorsomedian region of the peritoneal wall at the root of the developing mesentery and in places far from the appearance of testocoel and ovocoel. At 56 days posthatching, oogenic cells in the ovary had enlarged approximately 2 to 3 times their former size. The testis remained quiescent although the stromal tissues with developing efferent ducts increased distinctly in amount. Spermatogenesis occurred at three months posthatching.
  • Conference paper

    Successful use of cryopreserved oyster trocophores as a live first feed larval marine fish and invertebrates 

    BJ Harvey - 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 - SEAFDEC Aquaculture Department
    Trochophore-stage larvae of the Pacific oyster Crassostrea gigas were cryopreserved in bulk and stored in liquid nitrogen for periods up to two years before thawing and feeding to a variety of warmwater and coldwater larval marine fish, as well as to marine shrimps and other invertebrates. The commercial product ("TrochoFeed"), marketed in both pre-thawed and cryopreserved versions, has been used successfully in the early rearing of cultured species including red drum, snook, grouper, and black cod, as well as for numerous warmwater and coldwater aquarium display fish.

    This paper describes the nutritional profile of the cryopreserved trochopores and presents a summary of the available growth and mortality data.
  • Conference paper

    Tilapia breeding and seed production for brackishwater culture in the Philippines 

    RD Guerrero III, LA Guerrero & RG Cornejo - 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 - SEAFDEC Aquaculture Department
    Tilapias are important foodfishes in the Philippines second only to milkfish. While farming of tilapias in freshwater ponds and cages is already established, there is a need for wider application of the available technologies for brackishwater culture. This paper presents the tilapia species used for brackishwater farming and the commercial methods applied for their hatchery/nursery rearing.
  • Conference paper

    Mass larval rearing technology of marine finfish in Japan 

    K Fukusho - 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 - SEAFDEC Aquaculture Department
    With economic development and increased demand for high price fish, industrial scale marine finfish culture in Japan was started in 1960-1965 for yellowtail Seriola quinqueradiata. Sustainable supply of wild juvenile and development of floating cage with synthetic fiber net have spurred the culture of nearly 30 species and total production in 1991 is 265 x 103 metric tons (nearly 25% of total aquaculture production). Although salmon ranching had been started in 1888, a national project of ocean ranching was only initiated in 1963 with the present target of 26 species of marine finfish. Ocean ranching aims to increase fisheries resources in coastal sea by stocking hatchery-reared juveniles and preservation of environmental capacity and habitat. Therefore, mass production of marine finfish juveniles is being done for the intensive culture in net cage and for stocking coastal sea in Japan.

    Nearly 200 million juveniles are produced by ocean ranching centers (14 national, 49 prefectural, 21 city and town, 53 fishermen's association). The number of target fish is about 60 species (excluding salmon and trout). The main species produced are red sea bream, Pagrus major, flounder, Paralichthys olivaceus, puffer, Takifugu rubrapes, rockfish, Sebastes shlegeli, and mud dab, Limanda yokohamae. More than one million juveniles of these species are produced at one hatchery or ocean ranching center per one fry production season. About 70% of total production of juveniles consist of red sea bream and flounder. Red sea bream could be used to introduce mass larval rearing technology in Japan since its mass production is well developed. The focus of the present paper is the present status and short history of the development in larval rearing technology for red sea bream.
  • Conference paper

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

    JD Tan-Fermin, RSJ Gapasin, AM Tan, MA Garcia & 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 - SEAFDEC Aquaculture Department
    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.
  • Conference paper

    Natural spawning of four Epinephelus species in the laboratory 

    MNR Alava, MLL Dolar & JA Luchavez - 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 - SEAFDEC Aquaculture Department
    Natural spawnings of four Epinephelus species reared in the laboratory were observed from 1987 to 1992. These species are: E. summana, E. caeruleopunctatus, E. macrospilus and E. fuscoguttatus. Spawning was serial, usually occurring at night, on or 1-6 days after the new moon. Egg characteristics of these four species were compared. Fertilized egg and early larval development of E. summana and E. fuscoguttatus are discussed.
  • Conference paper

    Correlations of oocyte diameter with some morphometric characters in the nile tilapia, Oreochromis niloticus L. 

    MAR Garcia-Abiado, HJS Paras & GC Mair - 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 - SEAFDEC Aquaculture Department
    A study was conducted to determine the correlation of oocyte diameter with some morphometric characters in a Philippine strain of Oreochromis niloticus L. One hundred and thirty-five 7- to 9-month old sexually mature female broodstock (body weight: 71±35 g; standard length: 13.1±2.1 cm) were randomly sampled from a pool of broodstock maintained in 4 m2 net enclosures suspended in an earthen pond. The following morphometric characters were determined for each fish: body weight, standard length, genital pore dimension, and genital papilla dimension. Intra-ovarian oocyte samples were obtained by inserting a soft silicon rubber tubing into the ovipore of the fish and aspirating the oocytes by mouth. There were no significant correlations between the average oocyte diameter and any of the morphological characters studied. Results justify the adoption of an ovarian biopsy technique for assessing the stage of gonadal maturity in sexually mature tilapia.
  • Conference paper

    Role of growth hormone in the adaptation to sea water of juveline brown trout, (Salmo trutta) 

    JME Almendras & P Punet - 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 - SEAFDEC Aquaculture Department
    The first part of the study investigates the ability of ovine growth hormone (oGH) to enhance the hypo-osmoregulatory and growth performance of juvenile brown trout after exposure to sea water (SW). Three groups of fish were either intraperitoneally implanted with cholesterol pellet (sham) or with a cholesterol pellet containing 250 µg oGH (treated) or not implanted (control). While still in fresh water (FW), gill Na+/K+ATPase activity of the oGH-treated group was four times higher than that of sham and control groups. Exposure to SW resulted to dramatic increases in plasma electrolyte levels of the sham and control groups, whereas the oGH-treated group showed only minor perturbations in plasma electrolyte concentrations. Further increases in gill Na+/K+ ATPase activity were observed in the oGH-treated group after SW exposure, while in the sham and control, a lag time of seven days was needed before gill ATPase activity started to increase. Additionally, by the end of the experiment, oGH-treated fish were significantly larger than non-treated ones.

    The second part of the study examines the time course of changes in plasma GH levels and GH free binding sites and affinity of the organs involved in osmoregulation in juvenile brown trout kept in FW or exposed to SW. Plasma GH levels increased significantly one day after SW exposure, reaching a peak on the 14th day. Concomitantly, GH free binding sites in the gills and liver decreased significantly in trout exposed to SW but remained unchanged in trout kept in FW. Reduction in GH free binding sites in SW-exposed trout indicates occupation of the gill and liver GH receptor by GH during the course of SW adaptation which may point to a direct role of GH on gill and liver physiology during hypo-osmoregulation.

    The second part of the study examines the time course of changes in plasma GH levels and GH free binding sites and affinity of the organs involved in osmoregulation in juvenile brown trout kept in FW or exposed to SW. Plasma GH levels increased significantly one day after SW exposure, reaching a peak on the 14th day. Concomitantly, GH free binding sites in the gills and liver decreased significantly in trout exposed to SW but remained unchanged in trout kept in FW. Reduction in GH free binding sites in SW-exposed trout indicates occupation of the gill and liver GH receptor by GH during the course of SW adaptation which may point to a direct role of GH on gill and liver physiology during hypo-osmoregulation.
  • Conference paper

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

    RSJ Gapasin, HJ Nelis & P Sorgeloos - 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 - SEAFDEC Aquaculture Department
    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.
  • Conference paper

    Influence of LHRHa and methyltestosterone on milt production of sea bass Lates calcarifer (Bloch) 

    GV Hilomen-Garcia, RB Baldevarona & FJ Lacanilao - 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 - SEAFDEC Aquaculture Department
    Milt volume, sperm density, and number of spermatozoa were determined to quantify milt production of mature sea bass after a single injection of LHRHa [(D-Ala6,Pro9-N-ethylamiide)LHRH] in saline solution and 17α-methyltestosterone in corn oil (MT). Two measures of sperm density, sperm count and spermatocrit, were highly correlated (r=0.85). Compared with control, milt volume and the number of spermatozoa collected increased but sperm count decreased (24% at 24 h) after a LHRHa (20 µg/kg body weight treatment, suggesting a stimulation of spermatozoa production and not merely milt dilution. Further milt dilution (44%) was induced by 80 µg/kg LHRHa (LHRHa80) at 12 h post-treatment but not by 200 µg/kg MT (MT200) alone. A milt dilution of only 27% at 12 h after simultaneous injections of LHRHa80 and MT200 may indicate some inhibitory effect of MT on the efficiency of LHRHa. These results demonstrate that the stimulation of milt production by LHRHa involves testicular hydration resulting in milt dilution.
  • Conference paper

    Nickel-induced pathohistologic alterations in Oreochromis mossambicus 

    G Gicaro & A Herrera - 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 - SEAFDEC Aquaculture Department
    A pathohistologic study was conducted to determine the effects of nickel on the testes of maturing Mozambique tilapia, Oreochromis mossambicus. The fish were treated with 0.5 mg/L and 1.0 mg/L sublethal dose of nickel sulphate for four weeks. A week reduction in spermatogenic activity together with the disintegration of seminiferous tubules and spermatocytes are commonly observed in the 0.5 mg/L-treated fish. This results in the scattering of germ cells and the occurrence of spaces within the spermatocysts. Pyknotic nuclei are also seen in some specimens. Connective tissues and blood cells invade the damaged regions of the organ. Enlargement of Sertoli cells and interstitial cells are also observed. These effects are more pronounced in the 1.0 mg/L-treated testes.

    Relatively low levels of nickel in aquatic ecosystems impose a great danger to the reproduction and survival of Mozambique tilapia.
  • Conference paper

    Resistance of two Nile tilapia, Oreochromis niloticus (L.) strains exposed to a mixture of zinc, cadmium and inorganic mercury 

    MLA Cuvin-Aralar - 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 - SEAFDEC Aquaculture Department
    Two strains of one month-old Oreochromis niloticus namely CLSU (obtained from Central Luzon State University, Philippines) and NIFI (from National Inland Fisheries Institute, Thailand) were exposed to a sublethal mixture of 1.0 mg L-1 Zn, 0.1 mg L-1 Cd, and 0.01 mg L-1 Hg for two months in aquaria. Another set served as control with only BFS tapwater in the aquaria. At the end of the exposure period the fish were grown for another 2 months in net cages in Laguna de Bay. During the exposure (aquarium) and grow-out (lake) phases, the uptake and elimination of the metals were determined by AAS. Accumulation of the metals peaked at 13.9 µg g-1 Hg, 78.5 µg g-1 Cd, and 1447.0 µg g-1 Zn for NIFI and 14.2 µg g-1 Hg, 82.4 µg g-1 Cd, and 1591.3 µg g-1 Zn for CLSU lost 94.9% Hg, 98.76% Cd, and 89.99% Zn after two months in the lake. After the grow-out period, 2 females and 1 male of each strain were stocked in replicate polyethylene tanks. Time to first spawning, spawning frequency, fry production, and fry survival (after 30 days) were monitored. Results showed no significant effect of treatment and strain with respect to time to first spawning, spawning frequency, and mean fry survival. There was also no significant difference between the treatment and strain in mean fry production when dam weight was used as a covariate in the analysis. The results suggest that both strains of O. niloticus are resistant to long-term exposure to the metals. In addition, the elimination of the metals during the grow-out phase may have also diminished their effect on the breeders of the two strains.
  • Conference paper

    A brief account of the experience of Sabah Fisheries Department in fish larval rearing 

    CF Komilus & FD Parado-Estepa - 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 - SEAFDEC Aquaculture Department
    Venturing into the aquaculture sector especially in pond and cage culture is a step that has been taken up by entrepreneurs and traditional fishermen of Sabah. However, shortage in the supply of fish fry is a stumbling block to the progress of the industry.

    The Sabah Fisheries Department has taken steps to overcome this problem by setting up a hatchery with the objectives to transfer know-how on hatchery technologies to the private sector besides producing fry for distribution.

    The Tanjong Badak multi-species hatchery is a newly established hatchery, completed in mid-1990. The species reared for production purposes are tiger shrimp and finfish which include red snapper, grouper, sea bass and polkadot grouper. The Department has not close to producing sea bass fry. Shrimp fry at juvenile stages (PL 40) are distributed as subsidies to local fish farmers while some are reared at the Department's various cage and pond culture projects. Limited success in producing grouper and red snapper fry have been achieved to date. The incidence of very low fertilization rates of eggs coupled with low survival rates are major problems facing the hatchery.

    In conclusion, the Sabah Fisheries Department's experience in fish larval rearing is still limited. Greater scientific research and studies need to be carried out to improve further the performance of the hatchery to achieve the target of fry sufficiency for the aquaculture industry.

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