Now showing items 21-28 of 28

    • Article

      Milt-egg ratio in artificial fertilization of the Asian freshwater catfish, Clarias macrocephalus, injected salmon gonadotropin-releasing hormone analogue and domperidone 

      MVP Tambasen-Cheong, JD Tan-Fermin, LMB Garcia & RB Baldevarona - Aquatic Living Resources, 1995 - Cambridge University Press
      The author deals with the catfish Clarias macrocephalus which are artificially fertilized by inducing females to spawn using various hormones. This paper investigates the effect of Ovaprim on milt production and fertilizing ability of Clarias macrocephalus and determines the optimal milt-egg ratio required for artificial fertilization. Materials and methods used are: fish collection and handling, hormone administration, preparation of testicular homogenate, measurement of sperm density, dry fertilization, statistical analysis.
    • Conference paper

      Preliminary trials on the effects of weaning and larval diets on survival and growth of silver therapon (Leiopotherapon plumbeus) larvae 

      FA Aya, VSN Nillasca & LMB Garcia - 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 Center
      Success in larval rearing of silver therapon can be achieved through early weaning of fish larvae from live food to artificial diet. Two experiments were carried out to investigate the effects of (a) weaning age (abrupt and gradual) and (b) larval diets (artificial and live foods) on survival and growth of silver therapon (Leiopotherapon plumbeus). In the first experiment, larvae were randomly stocked in round 4-l plastic basins at 15 larvae per basin to provide triplicates of four weaning age treatments (8, 14, 20 and 26 days after hatching or DAH, respectively). Larvae were fed thrice daily for 21 days with commercial feed (CF) and with copepods (COP) which served as the control. Larvae weaned at 26 DAH had the highest survival, body weight and total length among the treatment groups, which were comparable with that of the control. In the co-feeding protocol, larvae were fed Artemia nauplii (ART) as the control group and co-fed with either zooplankton i.e. 50% COP + 50% CF or 50% ART + 50% CF for 8 (8-15 DAH), 6 (14-19 DAH) and 4 (20-23 DAH) days, and suddenly weaned to FM until 21 days. Survival ranged from 22.2 ± 16.8 to 40.0 ± 24.0% between treatments, but was still lower than the control (88.9 ± 3.8%). Body weight and total length were significantly higher in larvae with co-feeding for 4 days (70.1 ± 2.8 mg; 18.1 ± 0.8 mm), but were still lower than that of the control (142.8 ± 7.6 mg; 22.3 ± 0.3 mm).

      In the second experiment, 26-day old larvae were stocked in 20-l glass aquaria at 4 larvae l-1. Larval diets ((I) commercial prawn feed (38% crude protein); (II) Artemia nauplii; (III) copepods; and (IV) free-living nematode Panagrellus redivivus) were given twice daily for 28 days. Survival was highest in larvae fed Artemia nauplii and poor in copepod fed larvae. Final total length (TL) of larvae fed prawn diet was higher than those fed copepod or nematodes. However, best growth was noted in larvae fed Artemia nauplii (TL= 24.30 ± 0.81 mm; BW = 156 ± 8 mg; specific growth rate or SGR = 5.33 ± 0.19%/d).
    • Conference paper

      A review of SEAFDEC/AQD finfish breeding research 

      LMB Garcia - 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 - Aquaculture Department, Southeast Asian Fisheries Development Center
      Recent progress undertaken by SEAFDEC/AQD in the development of broodstock of a variety of cultured fish in the Philippines is reviewed. Spontaneous maturation and spawning has been achieved among captive breeders of grouper, milkfish, sea bass, rabbitfish, and tilapia. Hormonal intervention methods have been developed mainly to accelerated final gonadal maturation to synchronize release of mature gametes, and to control sex inversion among hermaphroditic fish such as grouper. These methods entailed the development of gonadal biopsy procedures and hormone administration protocols such as mode on introducing a variety of exogenous hormones to fish, administration intervals, and lately response times.Enhancement of reproduction by improving the diet fed to Nile tilapia, rabbitfish, and milkfish breeders has also been achieved in recent years. Protein or lipid enrichment of the diet may enhance growth of broodstock to subsequently increase reproductive performance and fry survival.Limited success has been achieved with photoperiod manipulation to effect year-round sexual maturation and spawning of milkfish and sea bass broodstock.
    • Conference paper

      Sea bass (Lates calcarifer Bloch) reproduction in captivity: a research update 

      LMB Garcia - In LM Chou, AD Munro, TJ Lam, TW Chen, LKK Cheong, JK, Ding, KK Hooi, HW Khoo, VPE Phang, KF Shim, KF Shim & CH Tan (Eds.), The Third Asian Fisheries Forum. Proceedings of the Third Asian Fisheries Forum, 26-30 October 1992, Singapore, 1994 - Asian Fisheries Society
      Recent advaces in the spontaneous and hormoneinduced breeding of caged sea bass (Lates calcarifer bloch, Family Centropomidae) are reviewed. Spontaneous spawnings follow a semilunar rhythm, with most spawings accurring in the evening of quarter moon. Independent of the Lunar-associatd rhythm, mature sea bass which have attained the critical oocyte size of 0.40 mm spawns after an injecton or implantation of luteinizing hormone-releasing hormone analogue (LHRHa) Pelleted LHRHa along together with methyltestosterone can advance sexual maturation and spawning in April-May, ahead of peak breeding in July-August. Depending on the pelleted or injected LHRHa dose, mature female sea bass spawns singly or consecutively over 4 evenings. LLHRHa-induced egg release peaks during the first day of a multiple spawning bout. Daytime injection of LHRHa stimulates spawning in the evening until dawn, while fish injected LHRHa at night induces spawning at daytime and releases fewer eggs compared to nighttime spawning. these results optimize the use of LHRHa to stimulate gonad maturation and spawning so that sea bass seed are made available for hatchery rearing and grow-out.
    • Article

      Spawning response latency and egg production capacity of LHRHa-injected mature female sea bass, Lates calcarifer Bloch 

      LMB Garcia - Journal of Applied Ichthyology, 1990 - Blackwell Publishing
      Mature female sea bass (Lates calcarifer Bloch) were injected once intramuscularly with 20 μg luteinizing hormone-releasing hormone analogue (D-Ala6, Pro9-LHRH-ethylamide) per kg body weight (BW) at different times of the day. Following hormone injection, the incidence of initial spawning and the number of eggs spawned by each fish were recorded. Saline-injected fish did not spawn. Fish spawned at dawn or 33.7–40 h after an LHRHa injection at either 11.00 h or 17.00 h. When LHRHa was administered at 23.00 h or 05.00 h, sea bass spawned during the day or at 38–47.3 h post-injection. Mean egg production levels of 26.8–34.4 × 104 per kg BW were higher for fish which spawned at dawn. Low mean egg production levels (6.2–19.9 × 104 eggs per kg BW) were observed when LHRHa-injected fish spawned during the day. These results demonstrate that the time of initial occurrence of spawning varied with the time of day that LHRHa was administered and that the number of eggs shed was influenced by the time of day that hormone-induced sea bass spawned.
    • Article

      Spawning response of mature female sea bass, Lates calcarifer (Bloch), to a single injection of luteinizing hormone-releasing hormone analogue: effect of dose and initial oocyte size 

      LMB Garcia - Journal of Applied Ichthyology, 1989 - Blackwell Publishing
      The effect of various doses of luteinizing hormone-releasing hormone analogue (LHRHa) ranging from 1 to 100 μg/kg body weight on the spawning response of mature female sea bass, Lates calcarifer (Bloch) was tested. A single intramuscular injection of LHRHa resulted in a dose-related increase in the spawning rate (number of spawnings of each fish over four consecutive days) of mature fish. An LHRHa dose of 5 μg/kg and less induced low spawning rates of 16.7% to 37.5% or at least one spawning every four days. However, mature sea bass spawned more than once (43.8–58.3%) in four days at dose levels of 10 μg/kg and above. Hormone treatment within the dose range tested did not influence the number, fertilization and hatching rates of spawned eggs.

      The influence of initial oocyte size on the LHRHa-induced spawning response of mature sea bass was also examined. Sea bass with an initial oocyte diameter of 0.30–0.39 mm did not respond to the single injection of 100 μg LHRHa/kg. In contrast, LHRHa induced spawning among sea bass with an initial egg size of 0.40–0.49 mm, although two of four sea bass of the same stage of ovarian maturity spawned spontaneously. Fish having an initial oocyte size of 0.50–0.55 mm spawned with and without LHRHa treatment. Spontaneous spawning among saline-injected sea bass occurred at a later time (24–58 h post-injection) compared to fish induced to spawn by a single injection of LHRHa (8–36 h post-injection). The initial spawning response time interval for fish with an initial egg size of 0.50 mm or greater was further reduced to 8–9 h by LHRHa. These results indicate that LHRHa can successfully induce spawning in mature female sea bass which have attained a critical oocyte diameter and that the spawning response interval is reduced with a further increase in egg size beyond the critical oocyte diameter limit.
    • Article

      Spermiation response of mature rabbitfish, Siganus guttatus Bloch, to luteinizing hormone-releasing hormone analogue (LHRHa) injection 

      LMB Garcia - Aquaculture, 1991 - Elsevier
      A method to quantify the spermiation response of mature rabbitfish to hormonal therapy is described. Spermatocrit or packed sperm volume was measured after milt loaded in non-heparinized microhematocrit capillary tubes was centrifuged for 45 min at 15 000 × g. Sperm density was estimated by a standard hemacytometer method. However, sperm density can be predicted from spermatocrit since their relationship is highly and positively correlated (Y = 29.5 + 2.95 Xr = 0.83; P < 0.01). Milt production by mature rabbitfish was highest (4.9 ml per kg body weight) at 24 h after injection of 20 μg of luteinizing hormone-releasing hormone analogue (D-Ala6, Pro9-LHRH-ethylamide) per kg body weight and coincided with low spermatocrit (68%) and sperm density (14.1 × 106 spermatozoa per μl milt) levels. These results demonstrate that spermiation in mature rabbitfish can be reliably assessed by a spermatocrit method and that LHRHa can effectively stimulate spermiation in this species.
    • Article

      Sustained production of milt in rabbitfish, Siganus guttatus Bloch, by weekly injection of luteinizing hormone-releasing hormone analogue (LHRHa) 

      LMB Garcia - Aquaculture, 1993 - Elsevier
      Mature male rabbitfish (Siganus guttatus Bloch) received weekly injections of 200 μg of luteinizing hormone-releasing hormone analogue (D-Ala6, Pro9-LHRH-ethylamide) per kg body weight for 5 consecutive weeks. Mean spermatocrit, or packed sperm volume (27–51%), and mean sperm density (3.2–9.6×106 spermatozoa per kg body weight) decreased significantly 24 h after each injection. The amount of expressible milt (mean: 5.8–11.7 ml per kg) in response to weekly injections of LHRHa increased significantly relative to saline-injected fish (1.0–2.9 ml per kg), but only during the initial 4 weeks of regular hormone treatment. Three weekly injections of LHRHa likewise augmented mean sperm production (29.2–112.5×109 spermatozoa per kg) in rabbitfish. However, no significant enhancement in sperm production by LHRHa-injected fish was observed over the last 2 weeks of hormone injection. These results demonstrate that weekly injection of LHRHa can sustain milt production in mature rabbitfish, although their capacity to produce spermatozoa is limited to only 3 consecutive weeks of regular hormone treatment.