Showing items related by title, author, creator and subject.

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  Broodstock management and seed production of milkfish 

  Marte, Clarissa L. (Aquaculture Department, Southeast Asian Fisheries Development Center, 1988)

  Milkfish (Chanos chanos Forsskal) remains one of the cheapest sources of protein for developing countries in Southeast Asia, particularly in the Philippines. The unpredictable supply of wild fry, the only source of seed for the milkfish farmer, contributed largely to the slow growth of the milkfish industry. Research on the artificial propagation of this fish was, therefore, given emphasis. Major research achievements in milkfish breeding of the SEAFDEC Aquaculture Department in the last decade include: (1) successful induced spawning of wild and captive breeders using gonadotropin preparations and gonadotropin-releasing hormone analogues (GnRHa); (2) spontaneous maturation and spawning of captive breeders; (3) completion of the life cycle of milkfish in captivity; (4) development of a simple egg-collecting method; and (5) development of techniques for mass production of milkfish fry. Information on fry ecology and behavior, larval morphology and physiology were also gathered. These published data constitute the bulk of current knowledge on milkfish biology and natural history. Milkfish breeding technology is currently being pilot-tested in several breeding sites of the Bureau of Fisheries and Aquatic Resources (BFAR). Spontaneous maturation and spawning of milkfish have been verified in four sites which differ in environmental characteristics. The economic feasibility of producing milkfish fry and the socio-economic impact of artificial propagation of milkfish are now being assessed.
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  Review of SEAFDEC/AQD finfish seed production research 

  Quinitio, G. F.; Duray, M. N. (Aquaculture Department, Southeast Asian Fisheries Development Center, 1996)

  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.
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  Research on marine and freshwater fishes 

  Emata, Arnil C. (Aquaculture Department, Southeast Asian Fisheries Development Center, 1995)

  Most of the fish research at SEAFDEC AQD in 1992-1994 was on milkfish. Studies were conducted on year-round spawning through hormonal or environmental manipulation; optimum lipid and protein levels and ration size for captive broodstock; and the influence of spawner age on reproductive performance. The economics of hatchery operations, alone or integrated with broodstock as a commercial enterprise, was assessed. Mass production of larvae was refined with the use of commercial or SEAFDEC-formulated larval diets. Alternative rearing schemes in large tanks and ponds were tried. Hatcheryproduced and wild-caught larvae were compared in terms of growth and production in experimental nursery and grow-out ponds. Supplemental diets for brackishwater grow-out culture were formulated. Studies on broodstock management of grouper Epinephelus spp. included lipid enrichment of the diet and hormonal induction of sex inversion. Seed production techniques were developed but survival rates were low. Grouper culture was found economically feasible in experimental ponds with 'trash' fish as feed. The mangrove red snapper Lutjanus argentimaculatus was successfully induced to spawn with injection of human chorionic gonadotropin. Initial larval rearing trials were successful but survival rates must be improved. Hormonal manipulation of spawning of the Asian sea bass Lates calcarifer allows seed production during most of the year. Photoperiod manipulation leads to maturation of females, but not males, beyond the natural breeding season (April-November). Nursery rearing of 9 mm juveniles is feasible in floating net cages with night lights that attract food zooplankton. The requirements of sea bass for lipid, protein, carbohydrates, and essential amino acids were determined. In the rabbitfish Siganus guttatus, weekly injections of luteinizing hormone releasing hormone analogue (LHRHa) sustains milt production for three weeks. Thyroid hormones injected into broodstocks improved the growth of larvae to day 7. Induced spawning techniques for the Asian catfish Clarias macrocephalus were refined by determining the seasonal responsiveness to LHRHa and pimozide injections and testing for pheromonal induction of spontaneous spawning. The optimum insemination rate was determined and egg hatchability was enhanced by removal of the adhesive coat before incubation. Several practical diets for catfish during grow-out culture were tested against 'trash' fish. The broodstock management for bighead carp Aristichthys nobilis was studied. Cage-reared juveniles from cage-reared broodstock showed the best growth. To improve the reproductive performance, the broodstock diets were supplemented with vitamins A, C, and E. Research on tilapias focused on genetics and strain selection. Several strain testing procedures for Nile tilapia were evaluated in their efficiency to detect economically important strain differences. Reference lines were developed from two existing red tilapia strains to measure and reduce the effects of uncontrolled nongenetic variables in strain evaluation experiments with Nile tilapia. The tolerance of two Nile tilapia strains to heavy metals was similar when gauged by the 24-hour and 96-hour lethal concentration and by fish growth, survival, and reproductive performance. In a separate study, four strains of red tilapia showed generally higher seed production when reared in tanks than in cages. Improvements in the feed and feeding management for Nile tilapia were also studied. Intensive tilapia farming and feeding have led to oxygen depletion and fish kills in Sampaloc Lake. To rehabilitate the lake, it is imperative to reduce the farming area from 30 to 6 hectares; stop the use of commercial feeds; and remove the water hyacinths and other debris. Fish kills in Laguna de Bay have also become serious in recent years, and a review of the occurrences, losses, and possible causes is currently being conducted. Studies on the epizootic ulcerative syndrome of snakeheads in Laguna de Bay have yet to pinpoint the pathogen. Skin lesions in tilapias in several ponds and lakes in the country were found to be due to bacteria.