Serum steroid hormones, reproductive and larval performance of the Asian catfish Clarias macrocephalus (Gunther) during the off- and peak reproductive seasons
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Serum samples were taken from gravid female catfish 0 to 24 h after injection of luteinizing hormone releasing hormone analogue (LHRHa) and pimozide (PIM) to monitor the serum steroid hormone levels during the off seasons (February) and the peak of the natural breeding period (August). A parallel study was also conducted to compare egg production, fertilization, hachuring and larval rates upon yolk resorption from spawn’s of hormone-treated fish. Serum E2 levels were significantly different only with varying times after injection (PI); a marked increase occurred at 13 h, but the elevation was higher in fish induced to ovulate during the peak (16.8 ng/ml) than off season(7.7ng/ml). Hormone-treated fish showed higher serum testosterone (T) levels during the peak season (17-23 ng/ml) than those injected during the off season (10-20 ng/ml) at 4-12 h PI. Serum 17¤, 20ß-dihydroxy-4-pregnene-3-one (DHP) levels og hormone-treated fish during the off season were only about half the level (0.29 and 0.52ng/ml) of those treated with the same hormones during the peak season (0.54 and 0.9 ng/ml) at 8 and 12 h PI, respectively. Initial eggs size was larger in fish induced to spawn in August (1.54 mm) than in fish induced in February (1.49 mm). All fish ovulated when induced to spawn during the peak of the natural breeding period, but ovulation rate was only 60% when were injected during the off season. Egg production, fertilization, hatchery and survival rates were similarly much higher when gravid females were induced to spawn in August (88 eggs/g body weight, 97%, 73%, and 95%, respectively) than those spawned in February (20 eggs/g BW,36%, 20%, and 47%, respectively). Results indicate that more eggs and of better quality, higher levels of T and DHP were produced during the peak season.
Tan-Fermin, J. D., Marte, C. L., Adachi, S., & Yamauchi, K. (2001). Serum steroid hormones, reproductive and larval performance of the Asian catfish Clarias macrocephalus (Gunther) during the off- and peak reproductive seasons. In J. Y.-L. Yu (Ed.), Recent Advances in Comparative Endocrinology. Proceedings of the Fourth Congress of the Asia and Oceana Society for Comparative Endocrinology, May 14-18, 2000, Academia Sinica, Taipei, Taiwan, R.O.C. (pp. 288–297). Taipei, Taiwan, R.O.C.: Institute of Zoology, Academia Sinica.
PublisherInstitute of Zoology, Academia Sinica, Taipei, Taiwan, R.O.C.
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Conference paperAD Munro & TJ Lam - In CL Marte, GF Quinitio & AC 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, 1996 - SEAFDEC Aquaculture DepartmentDespite their great variety of reproductive strategies, a general characteristic of most teleosts is that (where known) natural reproduction shows a long-term periodicity, even in tropical habitats (e.g. see contributions in Munro et al. 1990a). Typically, gonad development from puberty leads to fully-grown gonads by the advent of the spawning season; if conditions are appropriate, then final gonad maturation leads to the production of viable gametes during one or more breeding bouts. Subsequently, in those larger species which spawn over more than one season, the gonads regress and the individual returns to a phase where any growth is somatic. However, there is wide interspecific variability in the pattern of gonad development (Wallace and Selman 1981, de Vlaming 1983, Billard 1986, Selman and Wallace 1989).
Effect of juvenile hormone and serotonin (5-HT) on mixis induction of the rotifer Brachionus plicatilis Muller WG Gallardo, A Hagiwara & TW Snell -
Journal of Experimental Marine Biology and Ecology, 2000 - ElsevierJuvenile hormone (JH) and serotonin (5-HT) were previously shown to enhance mictic (sexual) female production of the rotifer Brachionus plicatilis in batch cultures. To explore the basis of these effects, experiments were conducted on isolated individuals. JH treatment of maternal rotifers with 5 and 50 µg ml-1 (18.8 and 187.7 µM) resulted in significantly higher (P < 0.05) mictic female production in the second (F2) and third (F3) generations. JH treatment was effective even at a lower food concentration of 7 × 105 cells ml , but it was not effective when free ammonia was added at 2.4 and 3.1 µg ml-1. Mictic female production was not increased with exposure to 5-HT up to 50 µg ml-1 (129.1 µM) concentrations. When food level was reduced to 7 × 105 cells ml-1, however, 5-HT-treated rotifers produced significantly (P < 0.05) more mictic females than the control, particularly in F3 generation. Mictic female production of 5-HT-treated rotifers did not differ from that of the control with or without free ammonia, but the intrinsic rate of natural increase (r) of 5-HT-treated rotifers at 3.1 µg ml-1 free ammonia was significantly higher than the control. These results show that juvenile hormone increases mictic female production under optimum and sub-optimum food levels, whereas 5-HT increases both mictic female production at low food level and population growth rate at high free ammonia concentrations. These compounds could be used to manage rotifer cultures and probe the mechanisms controlling the rotifer life cycle as it switches to mictic reproduction.
Assessment of humphead wrasse (Cheilinus undulatus), spawning aggregations and declaration of marine protected area as strategy for enhancement of wild stocks FG Romero & AS Injaki - In MRR Romana-Eguia, FD Parado-Estepa, ND Salayo & MJH Lebata-Ramos (Eds.), Resource Enhancement and Sustainable Aquaculture Practices in Southeast Asia: Challenges in Responsible Production … International Workshop on Resource Enhancement and Sustainable Aquaculture Practices in Southeast Asia 2014 (RESA), 2015 - Aquaculture Department, Southeast Asian Fisheries Development CenterHumphead wrasse, known as the Napoleon fish (Cheilinus undulatus), is the largest living member of the family Labridae. It is slow growing but can grow to a maximum size exceeding 2 m and 190 kg. This species was the first commercially important coral reef food fish to be listed in the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) Appendix II in 2004 because of its vulnerable status and the ongoing threat to its conservation from international trade. Like many coral reef fishes, the humphead wrasse, Cheilinus undulatus, aggregate in reef areas when they spawn and this spawning behaviour makes them highly vulnerable to overfishing. Assessment of the spawning aggregations of this species was conducted in the municipalities of Sibutu and Sitangkai in the province of Tawi-Tawi, Philippines. Key informant interviews (KII) with fishermen, mariculturists, and other stakeholders and focus group discussions (FGD) with local government leaders, Fisheries and Aquatic Resources Management (FARMC) members, mariculturists, and exporters were conducted. Guided by the results of these KII and FGDs, underwater visual census of mameng (local common name for Napoleon wrasse) populations (juvenile and mature) were conducted to document spawning aggregation sites. Since there was no photo-documentation of actual spawning aggregations of mameng in the reef areas, indirect measures were used. Result of the KII and FGD indicated that the Baligtang Reef in Sipangkot and Tando Owak are major sources of spawners. Anecdotal accounts of Bajau fishermen showed that Dungun Dungon, Baligtang reef, Tando Owak and Tugalan are traditional fishing grounds for mameng spawning aggregations. From the length-frequency analysis of mameng caught by hook and line and fish pot in the Baligtang Reef in Sipangkot, the estimated length at maturity of this species was found to be 25-35 cm. There were 134 individuals caught within this size range so they are considered potential spawners. Another indirect proof used was the underwater documentation of juvenile humphead wrasse which were regularly observed and photographed in association with seagrass beds and branching coral reefs in Baligtang Reef in Sipangkot, Sitangkai. Gonadal study also indicated that the mameng caught in this area had mature and ripe gonads but the number of mature fish depends on the season. These were the basis of declaring Spawning Aggregation Sites in Tando Owak and Dungun Dungun in Sibutu and Baligtang Reef, Sipangkot and Tugalan in Sitangkai. These were declared as marine protected areas by ordinance of the municipal Sangguniang Bayan of the two municipalities. Management and enforcement plans have been developed and Bantay Dagat have been trained to protect the spawning aggregations and this strategy aims to protect the wild stocks of humphead wrasse. Protecting the spawners would ensure that there would be enough recruits, prevent recruitment overfishing and enhance the wild stocks.