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    • Conference paper

      Constraints and prospects in aquaculture development. 

      F Lacanilao - In E Ohnishi, Y Nagahama & H Ishizaki (Eds.), Proceedings of the First Congress of the Asia and Oceania Society for Comparative Endocrinology (AOSCE), 4-7 November 198, Nagoya, Japan, 1987 - Nagoya University Corporation
      The development of aquaculture in developing countries of the Asia-Pacific region is constrained by inadequate seeds, diseases and other causes of mortality, lack of effective natural food and formulated feeds, problems associated with technology of culture systems, and lack of knowledge of the breeding biology of culture species. Other problems include inaadequate qualified technicians and skilled labor and high cost of fertilizers, pesticides, pumps, and blowers. All these are only those related with production part of aquaculture. Problems associated with post harvest are also numerous, not to mention financing, socio-economic condition, and local peace and order situation. The problems are aggravated when fish farmers go into semi-intensive and intensive methods of culture.

      Applications of endocrinology willhave their greatest impact in enhancing aquaculture development by improving the seed supply. These may be done through induced maturation and spawning, larval rearing, and nursery management. T. J. Lam reviewed the application of endocrinilgy to fish culture in 1982. Hormonal intervention of seed production can result in (1) year round supply of fry, (2) accelereted larval development and metamorphosis, which save on cost of hatchery operation, and (3) production of monosex individuals that are faster growing and which reduce rearing cost. The quantity and quality of seed supply will determine the extent of development, whether by expansion in area by intensification of culture. The present source of seeds in many areas is still largely from the wild which is inadequate, uncertain, and threatened by coastal pollution. M ilkfish farming, for instance, in the Philippines and Indinesia alone covers olny 400,000 hectares but the seeds come entirely from the wild. In 1983 the Asia-Pacific region produced 8.4 million metric tons from aquaculture, and contributed 82% of the total aquaculture production for that year. As the developing countries of the region go into industrialization and coastal pollution is increased, the natural supply of seed will have to depend largely on artificial breeding.
    • Article

      Milt production of sea bass Lates calcarifer Bloch administered an analogue of luteinizing hormone-releasing hormone and 17α-methyltestosterone 

      GV Hilomen-Garcia, RB Baldevarona & F Lacanilao - The Israeli Journal of Aquaculture-Bamidgeh, 2002 - Society of Israeli Aquaculture and Marine Biotechnology
      The milt production responses of sexually mature sea bass Lates calcarifer to (D-Ala6, Pro9-N- ethylamide) luteinizing hormone-releasing hormone (LHRHa) and 17α-methyltestosterone injections were examined.

      At 24 h after injection of a low dose of LHRHa (20 μg/kg BW), the sperm count decreased significantly compared to saline-treated fish, but it returned to pre-treatment levels 48 h after injection, suggesting a possible hydration of the milt. Other milt parameters (milt volume, spermatocrit, sperm production) in LHRHa-treated fish did not vary from their controls at 24 or 48 h after injection but the overall pattern suggested a reduction in milt viscosity. Total expressible milt and spermatozoa collected over the 48-h experiment was approximately three-fold higher in LHRHa-injected fish than in saline-injected fish, indicating a stimulation of spermatozoa production, not merely milt dilution due to hydration.

      In a second experiment, sperm count and spermatocrit were significantly lower than those of saline-injected fish at 17 and 48 h after a single injection of a high dose of LHRHa (80 μg/kg BW). A methyltestosterone injection combined with the LHRHa injection also resulted in a significantly lower sperm count, but the spermatocrit remained comparable to the control group, suggesting a suppression of the LHRHa-induced milt hydration response.

      Results demonstrate that LHRHa stimulates milt hydration and spermatozoa production in milting sea bass and that a simultaneous methyltestosterone injection partially suppresses this response.