Now showing items 1-14 of 14

    • Article

      Broodstock management and egg production of milkfish, Chanos chanos Forsskal 

      AC Emata & CL Marte - Aquaculture Research, 1993 - Blackwell Publishing
      The milkfish, Chanos chanos Forsskal, industry in the Philippines suffers from a limited supply of wild fry. The demand for milkfish fry has spurred research in artificial propagation to supplement the natural seed supply. Spontaneous maturation and spawning of milkfish beginning at 5 years of rearing in floating net cages or concrete tanks coupled with improved egg collection technique have increased daily egg collection to a maximum of 3 million eggs and provided adequate volumes of eggs for mass fry production. Annual egg collection and number of spawnings were markedly higher in cage-reared stocks older than 9 years old than stocks less than 9 years old. Egg collection of tank-reared stocks were comparable to those collected in cages. As feed constitutes a major portion of the operating expenses for establishing and maintaining milkfish broodstock, further studies must be geared towards defining optimum dietary requirements and ration size for gonadal maturation and spawning. Also environmental manipulation studies must be conducted for year-round spawning. Developments in these areas should ensure the production of maximum numbers of high quality eggs and fry year-round.
    • Article

      Dietary vitamin C and E supplementation and reproduction of milkfish Chanos chanos Forsskal 

      AC Emata, IG Borlongan & JP Damaso - Aquaculture Research, 2000 - Blackwell Science Ltd
      Milkfish Chanos chanos Forsskal broodstock (11 years old, average body weight 5.23–5.73 kg) reared in 10-m-diameter by 3-m-deep floating net cages (31–36 fish per cage) at SEAFDEC AQD's Igang Marine Substation in Guimaras Island, central Philippines, were fed daily at 3% of total body weight formulated diets (36% protein, 7–8% lipid) supplemented with 0.1% vitamin C, 0.05% vitamin E, both vitamin C and E or no vitamin supplementation (control) for 3 years. Reproductive performance was assessed in an attempt to determine the optimum nutrition for successful spawning of milkfish. The total egg production, mean number of eggs per spawning, number of spawns and mean egg diameter were not affected by dietary vitamin C and E supplementation. However, broodstock given dietary supplementation of vitamin C alone or in combination with vitamin E had a higher percentage of spawns with higher (> 90%) percentage egg viability, hatching and cumulative survival rate than those of the control. Broodstock given dietary vitamin E supplementation alone had few spawns, which made the results difficult to analyse. The results confirm the essentiality of vitamin C supplementation in producing more spawns with good egg and larval quality. The production of an adequate volume of good quality eggs and larvae to support hatchery operation is necessary to offset the huge investment in broodstock development, as it takes at least 5 years for milkfish to attain sexual maturation and spawning.
    • Article

      Economic assessment of commercial hatchery production of milkfish (Chanos chanos Forsskal) fry 

      LMB Garcia, RF Agbayani, MN Duray, GV Hilomen-Garcia, AC Emata & CL Marte - Journal of Applied Ichthyology, 1999 - John Wiley and Sons
      The economic viabilities of two types of commercial hatchery milkfish (Chanos chanos) fry operations were assessed and compared. Based on the actual cost of input, the physical facilities, and the potential production yields, four commercial hatcheries previously used for shrimp (Penaeus monodon fry production were classified as either largeor smallscale operations. Cost-return analysis revealed high profits for both types of operation. The return on investment (54-61 %) and the payback period ( approximately 1.5 years) were comparable between the two types, although a large-scale operation (476 %) had double the working capital return of a small-scale hatchery (221 %). Benefit-cost analysis over a 5-year period also revealed positive and above-baseline discounted economic indicators [net current value = 0.2-2.2 million Philippine Pesos (1 US Dollar = 25 Philippine Pesos); internal rate of return = 88-107 %]. The net benefit-cost ratio of a large-scale operation (2.0) was higher than that of a small-scale hatchery (1.4), suggesting a slight edge in the investment viability of a large-scale hatchery. Compared with a large-scale operation, a small-scale hatchery was more sensitive to changes in the acquisition price of eggs or newly-hatched larvae and in the price of selling hatchery fry. Both types of operation are viable nonetheless when the acquisition cost is P6000 per million eggs or larvae and hatchery fry are sold at P0.50 each. Together, profit and investment in milkfish hatchery fry production appear viable, making milkfish an alternative commodity for production in many abandoned shrimp hatcheries. The limited availability of spawned eggs and larvae for rearing and the quality of hatchery fry are issues requiring urgent attention.
    • Conference paper

      Egg and larval quality of cage-reared milkfish broodstock. 

      AC Emata - In J Muir & F Sevila (Eds.), Measures for Success. Abstracts of contributions presented at the International Conference Bordeaux Aquaculture '94, 23-25 March 1994, Bordeaux, France, 1996 - European Aquaculture Society. EAS Special Publication No. 21
    • Article

      Growth, maturity and induced spawning of mangrove red snapper, Lutjanus argentimaculatus, broodstock reared in concrete tanks 

      AC Emata, JP Damaso & BE Eullaran - The Israeli Journal of Aquaculture-Bamidgeh, 1999 - Society of Israeli Aquaculture and Marine Biotechnology
      Mangrove red snapper, Lutjanus argentimaculatus, fry (n=30) were collected in 1993 and reared in concrete tanks. They were fed trash fish every other day initially at 10% to 5%, until they reached three years. They reached 4.18 plus or minus 0.14 kg (mean body weight) after five years in captivity. Males matured in four years (mean body weight 2.55 kg, mean total length 49.6 cm) and females in five years (3.92 kg, 57.0 cm). As with other lutjanids, L. argentimaculatus exhibited separate sexes and no sexual dimorphism. Mangrove red snapper broodstock were sexually mature from April to October coinciding with the appearance of fry in the wild and the breeding season of wild-caught adults. Reproductive performance (egg production and quality) of first-time spawning mangrove red snapper broodstock was poorer than that of wild-caught adults. However, the results demonstrate the feasibility of developing mangrove red snapper broodstock in concrete tanks to ensure the sustainability of snapper aquaculture.
    • Article

      Induced spawning and early life description of the mangrove red snapper, Lutjanus argentimaculatus 

      AC Emata, B Eullaran & TU Bagarinao - Aquaculture, 1994 - Elsevier
      Wild-caught mangrove red snapper, Lutjanus argentimaculatus, reared in a concrete tank for 1 year, spontaneously matured in June 1992. On 19 August 1992, a sexually mature female and male (4.6 and 3.2 kg body weight, respectively) were administered a single intramuscular injection of HCG 1500 IU·kg−1 body weight. Spawning occurred 27 h after injection. Hatching occurred 16 h after spawning at 28°C and 32 ppt. Yolk resorption was completed 72 h after hatching. Growth was slow in the first week but rapid in the second and third weeks. Egg and larval development is similar to that of other lutjanids. Larval rearing revealed two critical periods: days 3–5 and days 18–20. Future studies must be geared to avoid mass mortality of the larvae during the critical stages for mass seed production.
    • Conference paper

      The influence of broodstock nutrition on the reproductive performance and egg and larval biochemical composition of the mangrove red snapper, Lutjanus argentimaculatus, for its sustainable aquaculture production 

      AC Emata - In M Maeda, Y Maeno & M Yokoyama (Eds.), Studies on Sustainable Production Systems of Aquatic Animals in Brackish Mangrove Areas, 2002 - Japan International Research Center for Agricultural Sciences
    • Conference paper

      Management of fish health in broodstock and larvae of milkfish, sea bass and grouper 

      CR Lavilla-Pitogo, AC Emata, MN Duray & JD Toledo - In K Main & C Rosenfeld (Eds.), Aquaculture health management strategies for marine fishes : proceedings of a workshop in Honolulu, Hawaii, October 9- 13, 1995, 1996 - The Oceanic Institute
      Historically, reports on the occurrence of disease problems in milkfish, seabass and grouper were mainly on the isolation and identification of etiological agents. Studies on the tolereance of fish to chemotherapeutants were also conducted. Various species of vibrios and gill-infesting parasites have been associated with diseases in all life stages of these fish. Presently, mortalities due to diseases of unknown etiology, environmental failure and nutritional or husbandry shortfalls affect successful fry production in the hatchery. Morphological deformities in hatchery-produced milkfish fry is a major problem to be solved. In seabass fry production, swim-bladder stress syndrome occasionally occurs and results in mass mortalities. In larval grouper culture, the problem of low survival is being addressed through improved husbandry and nutrition. For cage-held broodstock that naturally spawn in captivity, such as milkfish and grouper, the main problem is fouling of net enclosures in the cages. However, for fish that need hormonal manipulation to spawn, such as seabass and snapper, stressful handling procedures during sampling and hormone injection may lead to injuries and scale loss. The damaged areas become focal points for secondary bacterial infection. Future fish health management strategies in these fish should incorporate a holistic approach to include environmental monitoring, nutritional manipulation, immunostimulants and vaccine use, and biological control in addition to pathogen exclusion in the rearing system and the fish.
    • Conference paper

      Maturation and induced spawning of the mangrove red snapper (Lutjanus argentimaculatus) reared in a floating net cage in the Philippines 

      AC Emata - In F Arreguín-Sánchez, JL Munro, MC Balgos & D Pauly (Eds.), Biology, Fisheries and Culture of Tropical Groupers and Snappers. Proceedings of an EPOMEX/ICLARM International … Workshop on Tropical Snappers and Groupers held at the University of Campeche, Campeche, Mexico, 26-29 October 1993, 1996 - International Center for Living Aquatic Resources Management (ICLARM)
      Wild-caught mangrove red snapper (Lutjanus argentimaculatus) were reared in a floating net cage at SEAFDEC/AQD's Igang Marine Substation at Guimaras Island, Central Philippines. In 1993, monthly samplings and induced spawning trials were conducted as part of a project on seed production. Gonadal development began in February for males and April for females, reached a peak in September and declined in December. Males and females had ripe gonads for up to 5-6 consecutive months. Spawning occurred in the evening (2000 to 2300 hours), 32-36 hours after a single intramuscular injection of 1,500 IU human chorionic gonadotropin kg-1 body weight (BW). About 0.53-2.14 million eggs were collected per female (2.5-4.4 kg BW) with fertilization rates of 21-97% and hatching rates of 42-80% resulting in 30-85% normal larvae (straight and without deformities). The results strongly suggest the feasibility of breeding mangrove red snapper in floating net cages.
    • Article

      Natural spawning, egg and fry production of milkfish, Chanos chanos (Forsskal), broodstock reared in concrete tanks 

      AC Emata & CL Marte - Journal of Applied Ichthyology, 1994 - Blackwell Publishing
      Gonadal maturation, rematuration, and spawning of nine- (1982 stock) and ten-year-old (1981 stock) milkfish reared in 150 and 200 m3 concrete tanks were observed in 1990 and 1991. From 23 September to 9 November 1990, the 1981 stock spawned 15 times with an average daily collection of 61,000 ± 21,000 eggs. From 4 larval rearing trials, the mean overall survival rate (from eggs to 21 -day-old fry) was 9.68 ± 4.3%. From 25 Aril to 31 October 1991, the stock spawned a totaf of 108 times. Mean daily egg collection increasef to 305,000 ± 32,000. Successful rearing trials conducted during the latter part of the spawning season had a mean overall survival rate of 17 ± 3% (n = 17) indicating that mass fry production techniques can be improved. Spawning of milkfish broodstock in concrete tanks provides an alternative to other existing methods of seed production.
    • Conference paper

      Reproductive performance of wild-caught mangrove red snapper, Lutjanus argentimaculatus 

      AC Emata - In P Lavens, E Jaspers & I Roelants (Eds.), Larvi '95 - Fish & Shellfish Larviculture Symposium, 3-7 September 1995, Gent, Belgium, 1995 - European Aquaculture Society
      Series: Special Publication; No. 24
      Interest in the culture of snappers, belonging to the family Lutjanidae, is increasing in Southeast Asia due to their relatively high market price. However, the fry needed for culture still comes exclusively from the wild. The anticipated demand for snapper fry has stimulated studies to develop methods of supplementing the natural fry supply. This paper evaluates the reproductive performance of wild-caught mangrove red snapper broodstock induced to spawn as part of a project to establish seed production techniques at SEAFDEC Aquaculture Department.
    • Article

      Survival of captive milkfish Chanos chanos Forsskal broodstock subjected to handling and transport 

      LMB Garcia, GV Hilomen-Garcia & AC Emata - Aquaculture Research, 2000 - Wiley-Blackwell
      The survival of milkfish broodstock (body weight range 1–11 kg) was determined until 30 days after handling and transport in open tanks or in sealed oxygenated bags containing chilled sea water (20–25 °C). Maintenance of cool sea water was achieved by the gradual addition of ice chunks or frozen gel packs. A survival rate of 50% after transporting fish at a loading density of 45 kg m−3 for 4 h in open tanks was not significantly different from those that were handled but not transported (86%). Similarly, survival rates (67–83%) among broodstock confined for 8 h in chilled sea water at 40 and 60 kg m−3 were not significantly different from each other or from a group not subjected to confinement. Nevertheless, low dissolved oxygen (DO) and accumulation of total ammonia–nitrogen beginning 1 h after transport and confinement may be responsible for low survival rates of milkfish in open tanks. In contrast, all milkfish survived 10 h of overland transport in sealed bags with chilled and diluted (28 g L−1) sea water. Likewise, all milkfish survived after being bagged and immediately transferred to a communal rearing tank, or bagged and placed in a styrofoam box for 10 h. Except for total ammonia–nitrogen levels, which increased slightly (0.7–0.8 mg L−1) above background, seawater temperature (20–24 °C), salinity (28 g L−1) and DO (6 to > 20 mg mL−1) titres in transport bags were maintained during the 10-h test. The effectiveness of handling and transporting milkfish broodstock in sealed bags containing chilled sea water was verified in actual field trials. Spawning of sexually mature milkfish subjected to these stressors was not impaired. These results demonstrate that mortalities of large milkfish broodstock can be minimized when fish are handled and transported in sealed oxygenated bags containing chilled sea water.
    • magazineArticle

      Updates in the Philippines: Where are the captive milkfish breeders? 

      AC Emata - SEAFDEC Asian Aquaculture, 2001 - Aquaculture Department, Southeast Asian Fisheries Development Center
      A map is provided showing the location of milkfish rearing facilities in the Philippines. Most of the 17,443 milkfish broodstocks are located in central Philippines. A table shows details as to the rearing facility (cage, pen, pond, tank), number of broodstocks, and age. There are 13,420 broodstocks in ponds; 2,081 in cages; 842 in tanks, and 1,100 in pens. The youngest is 3 years, the oldest 23 years old.
    • Article

      The use of a Visual Implant tag to monitor the reproductive performance of individual milkfish Chanos chanos Forsskal 

      AC Emata & CL Marte - Journal of Applied Ichthyology, 1992 - Blackwell Publishing
      Nine-year old milkfish (3.8 kg., average body weight) were individually marked with Visible Implant (VI) tags to monitor their reproductive performance following hormonal induction. All tags were retained after one year; only 5 out of 64 tags were not readable due to improper implantation. The advantages of using VI tags include: less tagging time (less than one minute), high retention rate, longer retention, infection-free, and easily readable.