Influence of LHRHa and methyltestosterone on milt production of sea bass Lates calcarifer (Bloch)
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Abstract
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.
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Suggested Citation
Hilomen-Garcia, G. V., Baldevarona, R. B., & Lacanilao, F. J. (1996). Influence of LHRHa and methyltestosterone on milt production of sea bass Lates calcarifer (Bloch). In C. L. Marte, G. F. Quinitio, & A. C. 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 (p. 108). Tigbauan, Iloilo, Philippines: Aquaculture Department, Southeast Asian Fisheries Development Center.
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Conference paperISBN
9718511326Related items
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Seed production of marine fish in Malaysia
(Aquaculture Department, Southeast Asian Fisheries Development Center, 1993)Aquaculture especially brackishwater fish culture in Malaysia has a very high potential for development. It is also a very important source of protein. The three major species cultured in cages are sea bass, grouper, and snapper. They are very popular, especially sea bass which is a highly esteemed delicacy. Sea bass culture started in the mid-1970. The fry was obtained from the wild or imported from Thailand or Singapore. This industry developed slowly because of inadequate supply of seed. During this period also, the culturist had very little experience in managing the cages. As an answer to the problems of the industry, the Fisheries Research Institute (FRI) of the Department of Fisheries, Ministry of Agriculture, Glugor, Penang, established a unit responsible for research on hatchery propagation, larval feed development, and cage culture of sea bass. The Brackishwater Unit of FRI situated in Gelang Patah, Johor is responsible for research and development of sea bass grow-out in coastal ponds. The Marine Finfish Production and Research Centre (MFPRC) situated in Tanjung Demong, Terengganu was set up in 1982 for marine fish fry mass production. The Extension Branch of the Department of Fisheries in Kuala Lumpur is responsible for all extension services, including promotion of sea bass aquaculture as well as other species. The Extension Branch also operates the MFPRC and organizes training on coastal aquaculture at the Brackishwater Aquaculture Centre in Johor. The Fisheries Development Authority of Malaysia (LKIM), a government statutory body formed in 1971 with the objectives of upgrading the socioeconomic status of fishermen and developing the fisheries industry, is also involved in marine fish culture, especially in setting up commercial culture projects involving local fishermen. In addition to government bodies, some universities in Malaysia also carry out activities related to marine fish culture, especially disease studies. -
Research on marine and freshwater fishes
(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. -
Aquaculture development in Malaysia
(Aquaculture Department, Southeast Asian Fisheries Development Center, 1988)Malaysia is a fish-consuming country with fish representing 60% of a total animal protein intake. At an annual per capita consumption of 32 kg some 560 000 mt of fish is required for the projected of 17.5 million people in year 2000. Coastal marine capture fisheries, the mainstay of Malaysia's fishsupply, has not shown any increase in landings over the last few years. In fact in 1985 there was a decline of 3.7% compared to 1984 fish landings. This declining contribution of marine fisheries is compensated by an increase in aquaculture production. In 1985, aquaculture contributed 51 709 mt to the total fish supply. This represents 10% of the total fish landings of 514 570 mt or 13% of total table (edible) fish landings. Malaysia does not have a long standing aquaculture tradition unlike its neighbours in the Indo-Pacific. Even then, the industry has seen rapid growth in the last few years. Today there are 19 species of finfishes, crustaceans and shellfish cultured in the country. The main freshwater fish species bred and cultured are bighead carp (Aristichthys nobilis), grass carp (Ctenopharyngodon idella), common carp (Cyprinus carpio), Indonesian carp (Punctius gonionotus), catfish (Clarias macrocephalus and Pangasius spp), snakefish gourami (Trichogaster pectoralis) and tilapia (mainly Oreochromis niloticus). Marine finfishes bred and cultured are sea bass (Lates calcarifer), grouper (Epinephelus sp.) and snapper (Lutjanus johni). Penaeus monodon is the dominant marine prawn species bred and cultured but culture of P. merguiensis is receiving considerable interest. Macrobrachium rosenbergii is the only freshwater prawn cultured commercially. Molluscs cultured are the blood clam (Anadara granosa) and the green mussel (Perna viridis). In 1985, blood clam and mussel culture accounted for 87% of all aquaculture production of Malaysia, freshwater fish 12%, floating cage culture of marine fish 0.7% and brackishwater pond culture 0.3%. In terms of value blood clam and mussels represented 30% (M$15M) of total value (M$49.5M), freshwater fish 57% (M$28M),cage culture of marine fin fishes 7% (M$3.4M),and brackishwater pond production 6% (M$2.1M). Aquaculture in Malaysia has considerable growth potential. It is projected that 22 000 ha of mangrove will be opened by the year 2000 for shrimp culture. Some 330 000 m2 of protected coastal waters have been identified for cage culture. Some 6500 rafts can considerably expand the present capacity. In freshwater culture about 8000 ha of land and 17 500 ha of mining pools can be developed while 200 000 ha of artificial lakes and impoundments for freshwater fish cage culture are available. Yet such development is not without constraints. Freshwater finfish culture is hampered by lack of good quality broodstock. There is also a limited market for freshwater finfishes. Marine finfish culture is limited by lack of fingerlings and good quality compounded diet to replace trash fish which is deteriorating in quality and quantity. Marine prawn culture is heavily dependent on wild spawners, the supply unpredictable and inadequate. Acid sulfate soil continues to cause the deterioration of brackishwater ponds. Cockles and mussels can be sold to export markets only if they meet specific quality standards.
