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

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  The broodstock floating cages of AQD 

  Surtida, Marilyn B. (Aquaculture Department, Southeast Asian Fisheries Development Center, 1998)
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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.
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  Marine fish hatchery: developments and future trends 

  Marte, Clarissa L.; Toledo, Joebert D. (Aquaculture Department, Southeast Asian Fisheries Development Center, 2015)

  The basic procedures for producing marine fish fry in hatcheries developed for milkfish fry production nearly 3 decades ago are the basis of fry production systems for all other marine fish species that are now reared in hatcheries in the Philippines and other Southeast Asian countries. These include large-scale microalgae production in outdoor tanks, feeding of appropriate sized rotifer grown on microalgae such as Nannochlorum during the first feeding phase, and shifting to larger prey such as Artemia towards the latter stages of production. In recent years, the increasing demand for high-value species such as groupers, sea bass, red snapper, and pompano in both local and export markets has encouraged a number of hatcheries to produce fry to supply the requirements of fish cage farmers. Techniques are modified using information from research institutions and multi-national firms active in developing products and equipment to improve commercial production of these species. Larval feeds of appropriate sizes, forms and presentation for various larval stages incorporating essential nutrients, micronutrients, and feed stimulants are now available in the market. Diseases in marine fish hatcheries have become common occurrences such that various chemotherapeutants, vaccines, and immunostimulants are now available and increasingly being applied in fish hatcheries. Technological developments in hatchery systems, such as the use of recirculating systems, water pretreatment protocols (ozonation, mircrofiltration, UV light treatment) are also increasingly being adopted by commercial establishments. A critical link between fry production and production of marketable fish is fingerling/ juvenile production in nurseries. Fry are commonly grown in brackishwater fishponds to appropriate size for stocking in fish cages. Methods to improve growth through proper feeding and nutrition, eliminate or reduce disease occurrence and parasite infestation, reduce cannibalism in cannibalistic species such as sea bass, grouper and snappers are active areas of research. Nursery production is integrated with fry production in large commercial facilities but is also done by small-scale fish farmers who have access to fry either from the wild or hatcheries. Commercial hatcheries adopt fingerling production from well-studied species in developed countries. Smallscale farmers however still rely on zooplanktons collected from the wild such as copepods, Moina, mysids, and trash fish as feed. Production is dependent on availability of feed sources and susceptibility to pathogens and parasites that come with the feed. It can also be erratic since smallscale farms are vulnerable to changes in climate and weather conditions. Further technological advancement in marine fish hatcheries will increasingly be led by commercial establishments and industries developing equipment like photobioreactor for microalgae to produce algal paste, or methods to develop intensive systems for rotifer culture. Research institutions will however need to support the needs of the small-scale farmers and hatchery operators who may not be able to apply costly products from these companies by developing innovative simple techniques that can improve culture systems such as producing fry and fingerlings in mesocosm pond system, appropriate use of probiotics as water stabilizer, and production of zooplankton in ponds.