Now showing items 1-20 of 26

    • Book

      Breeding and seed production of the Asian catfish Clarias macrocephalus (Gunther) 

      JD Tan-Fermin, AC Fermin, RF Bombeo, MAD Evangelista, MR Catacutan & CB Santiago - 2008 - Aquaculture Department, Southeast Asian Fisheries Development Center
      Series: Aquaculture extension manual; No. 40
      Among the topics discussed in this 28-page manual are broodstock development and management, hatchery and nursery, health management and financial analyses of the breeding and seed production of the Asian catfish. This manual was published to disseminate science-based aquaculture technologies developed by AQD to assist catfish nursery and hatchery growers in producing high-quality fingerlings. Researchers in the field of fisheries, students and teachers could benefit from the information on the breeding and seed production of this important aquaculture commodity.
    • magazineArticle

      Catfish aquaculture 

      JD Tan-Fermin - SEAFDEC Asian Aquaculture, 2003 - Aquaculture Department, Southeast Asian Fisheries Development Center
      This article deals with the biology, broodstock management, seed production techniques and grow-out culture practices in C. macrocephalus.
    • Book chapter

      Changes in the gastrointestinal tract and associated organs during early development of the grouper (Epinephelus coioides) 

      GF Quinitio, AC Sa-an, JD Toledo & JD Tan-Fermin - In MA Rimmer, S McBride & KC Williams (Eds.), Advances in grouper aquaculture, 2004 - Australian Centre for International Agricultural Research
      Series: ACIAR Monograph 110
      The histomorphological changes in the gastrointestinal tract of Epinephelus coioides and associated organs during its early development were studied. Larvae of E. coioides were reared in 5-tonne tanks using the semi-intensive culture system. Larval samples were collected at days 0, 2, 4, 6, 8, 10, 12, 14, 16, 20, 25, 30, 35, 40, 45 and 60. The total length (TL) of about 10-20 larvae per sampling was measured. At least 3 samples were examined from each stage for longitudinal sections using light microscopy. The digestive tract of day 0 larvae was a straight, undifferentiated tube composed of simple cuboidal cells. At day 2, cellular differentiation was observed in the pharynx, oesophagus, primordial stomach and intestine. The primordial stomach broadened into a voluminous pouch at day 10. The gastric gland was observed in the stomach from day 20. Day 35 seemed to be the proper time to feed larvae with minced fish when using the semi-intensive rearing system. Insignificant histomorphological changes in the metamorphosing grouper larvae were observed from days 40-60.
    • Article

      Economic evaluation of grow-out diets for Asian catfish Clarias macrocephalus (Gunther) production 

      EB Coniza, JD Tan-Fermin, MR Catacutan, AT Triño & RF Agbayani - UPV Journal of Natural Sciences, 2000 - University of the Philippines in the Visayas
      The economic feasibility of four grow-out diets for the Asian catfish Clarias macrocephalus was evaluated on a 1000 m2/crop basis. Hatchery-bred catfish juveniles with mean body weight (MBW) of 3.6 g and mean total length (MTL) of 7.8 cm were stocked at 10 fish/m2. Laboratory-formulated diet with 20% crude protein (CP; Diet 1) resulted in net losses. Laboratory-formulated diet with 34% CP (Diet 2), commercial feed pellet with 29% CP (Diet 3), and a mixed diet of blanched chicken entrails (80%) and rice bran (20%) with 32% CP (Diet 4) gave acceptable return on investment (ROI) of 131-326% and return on operating capital of 52-71%. Culture of Asian catfish fed Diet 2, however, attained higher net profit before tax per 1000 m2/crop, ROI (326%), and has the lowest payback period on investment (0.3 yr) or operating capital (1.4 yr) compared with using Diets 3 and 4. Partial budget analysis showed that higher net benefit can be earned by using Diet 2 as feed for C. macrocephalus compared with using Diet 4. Sensitivity analysis done by increasing in feed cost by 20% and decreasing the selling price of fish by 20% showed that ROI were 107-262% and 46-159%, respectively and return on operating capital of 42-57% and 18-35%, respectively. Payback period on investment were 0.4-0.9 yr and 0.6-1.9 yr, respectively while payback period on operating capital were 1.7-2.2 yr and 2.7-4.7 yr, respectively. Results suggest that C. macrocephalus culture is economically feasible with Diets 2, 3 and 4 as feed but the use of Diet 2 is more profitable.
    • Article

      Effect of season on oocyte development and serum steroid hormones in LHRHa and pimozide-injected catfish Clarias macrocephalus (Günther) 

      JD Tan-Fermin, CL Marte, H Ueda, S Adachi & K Yamauchi - Fisheries Science, 1999 - Japanese Society of Fisheries Science
      Oocyte and blood samples were taken from gravid female catfish Clarias macrocephalus at 4-h intervals to monitor the stage of oocyte development and serum steroid hormone profiles after injection of luteinizing hormone-releasing hormone analogue (LHRHa) and pimozide (PIM) during the off-season (February) and the peak of the natural breeding period (August). Results showed that the onset of final oocyte maturation (12h) and ovulation (16h), and levels of serum estradiol-17β (E2) did not vary with season in LHRHa+PIM-injected fish. In February, ovulated eggs were stripped from three and two hormone-treated fish at 16h and 20h post-injection, respectively. In August, ovulation was observed in all hormone-treated females (n=5) at 16h post-injection but stripping of the eggs was possible only 4h thereafter. Serum E2 levels were significantly different only with varying time post-injection; a marked increase occurred at 12h, but the elevation was higher in fish induced to ovulate during the peak (16.8ng/ml) than off-season (7.7ng/ml). Hormone-treated fish showed higher serum testosterone (T) levels during the peak season (17-23ng/ml) than those injected during the off-season (10-20ng/ml) at 4-12h post-injection. Serum 17α, 20β-dihydroxy-4-pregnene-3-one (DHP) levels of hormone-treated fish during the off-season were only about half the level (0.29 and 0.52 ng/ml) of those treated with the same hormones during the peak season (0.54 and 0.9ng/ml) at 8 and 12h postinjection, respectively. Development of oocytes and serum steroid hormone profiles after LHRHa+PIM-induced ovulation provide basic understanding of the processes that mediate final oocyte maturation and ovulation in captive C. macrocephalus.
    • Article

      Effects of unilateral eyestalk ablation on ovarian histology and oocyte size frequency of wild and pond-reared Penaeus monodon (Fabricius) broodstock 

      JD Tan-Fermin - Aquaculture, 1991 - Elsevier
      Effects of eyestalk ablation on ovarian maturation of wild and pond-reared Penaeus monodon were determined to compare their reproductive potential. This was done by counting the oocyte size frequency in four regions of the ovary and comparing the percentage of each cell type present at each stage of maturation per group. Sampling of ablated prawns was done during three maturation or spawning periods within the first molt cycle after ablation. It took 5 and 14 days for wild and pondreared prawns, respectively, to show signs of ovarian maturation after ablation. Percentage of proliferating cells, the smallest germinal cells in the prawn ovary, was higher in wild unablated (8.3%) than ablated (2.5–5.0%) groups. Significant differences were observed in all cell types at different stages of maturation. In both unablated and ablated prawns, there was a uniform development of the whole ovary and similar occurrence of atresia at all stages. The presence of bigger oocytes in the ovaries of ablated prawns sampled after spawning provided histological evidence for lower number of eggs per spawn and faster rematuration.
    • Book

      Grow-out culture of the Asian catfish Clarias macrocephalus (Gunther) 

      EB Coniza, MR Catacutan & JD Tan-Fermin - 2008 - Aquaculture Department, Southeast Asian Fisheries Development Center
      Series: Aquaculture extension manual; No. 41
      Asian catfish Clarias macrocephalus is an esteemed food fish especially in Southeast Asia due to its tender and delicious meat. This commodity constitutes a valuable fishery for small-scale fishers in the region and has a great potential for aquaculture. The important considerations in the grow-out culture of catfish are reliable water supply, soil with good compaction properties for dike construction, supply of fingerlings, feeds, labor, pond supplies and technology assistance. The farm must also be accessible by road, near to market facilities and has a peaceful environment. Rearing catfish in ponds is the most popular and commonly practiced. The pen culture is a system fully enclosed by nets on all sides but utilizes the dug-out pond, dam or lake bed as bottom enclosure. Tanks in abandoned old hatcheries with freshwater source can be used for catfish culture. In the cage culture system the stock is fully enclosed by nylon nets on all sides and bottom similar to an inverted mosquito net installed in suitable areas like reservoirs, dams, lakes and dug-out ponds. The rice-fish (catfish) culture is also practiced where the rice pond canals are utilized to retain water at 1-2 m depth to provide shelter to the fish while the rice plot maintains 10-20 cm water depth. For the stock, select fingerlings that are active, healthy and uniform in size. Handling of fish stock is important to avoid mortality due to stress during harvest, sorting, counting and transport. Furthermore, stocking of fish is recommended during the cooler part of the day. Catfish fingerlings stocking density is about 5 to 20 pcs/m2 depending on the water supply and support facilities of the farm. The catfish, C. macrocephalus, requires a substantial amount of dietary protein for growth. For this species a formulated diet with crude protein (CP) of 34%, moist diet (trash fish or blanched chicken entrails plus rice bran or cooked broken rice), and a combination of pellet feeds (50%) and moist diet (50%) have been tested and acceptable for the grow-out culture. Economic evaluation based on a grow-out culture in pond with an area of 1,000 m2 showed that feeds and fingerlings are the major variable costs. The net income, return on investments and payback period, respectively range from PhP22,972-PhP35,741, 80-122% and 0.8-1.2 years when using pellet, moist feed or a combination of these feeds. Feeding using formulated diet has an advantage of convenience, quality and quantity over moist diet which has issues such as inconsistent supply, storage requirement and fouling the rearing water.
    • magazineArticle

      Growth and yield of Asian catfish Clarias macrocephalus (Gunther) fed different grow-out diets 

      EB Coniza, MR Catacutan & JD Tan-Fermin - SEAFDEC Asian Aquaculture, 2003 - Aquaculture Department, Southeast Asian Fisheries Development Center
    • Article

      Growth and yield of Asian catfish Clarias macrocephalus (Gunther) fed different grow-out diets 

      EB Coniza, MR Catacutan & JD Tan-Fermin - The Israeli Journal of Aquaculture-Bamidgeh, 2003 - The Society of Israeli Aquaculture and Marine Biotechnology (SIAMB)
      Juveniles of the Asian catfish Clarias macrocephalus (3.6±0.17 g; 78.0±0.09 mm) were fed one of four diets: a laboratory-formulated diet of 18.9% (Diet 1) or 34.2% (Diet 2) protein, a com- mercial feed pellet of 28.9% protein (Diet 3) or a diet of 80% blanched chicken entrails and 20% rice bran (31.7% protein; Diet 4). After 120 days of culture, catfish fed Diet 2 grew significantly better (p<0.05) than the other groups, reaching 108.9 g and 232.8 mm (daily weight gain 0.88 g; specific growth rate 2.9%), with a condition factor of 0.86 and production of 18.2 kg per 25 m2 pen. Feed conversion with Diets 2 and 3 (2.5 and 2.3, respectively) was better than with Diets 1 and 4 (3.4 and 5.0). Survival (68-81%) did not differ significantly among treatments (p>0.05). Catfish fed Diet 2 had the highest apparent lipid retention (131.7%). The protein efficiency ratio was lowest (1.3) in Diet 2, but did not differ significantly from Diets 1 and 3. Catfish fed Diet 4 were fatty and had a lower crude protein content. Results suggest that C. macrocephalus fed 34.2% crude protein have a significantly higher weight and total yield. Further, a taste test showed that odor, flavor and appearance did not differ amongst the diets.
    • Article

      Induced spawning by LHRHa and pimozide in the Asian catfish Clarias macrocephalus (Gunther) 

      JD Tan-Fermin & AC Emata - Journal of Applied Ichthyology, 1993 - Blackwell Publishing
      Experiments were conducted to determine the optimum dose of luteinizing hormone-releasing hormone analogue (LHRHa) and pimozide (PIM) injected simultaneously to yield a high ovulation rate and produce sufficient eggs in the Asian catfish Clarias macrocephalus. In June 1990, injection of 0.05 or 0.10 μg LHRHa/g body weight (BW) + 1 μg PIM/g resulted in 100% ovulation, while only 80% of gravid catfish injected 0.025 μg LHRHa + 1 μg PIM/g ovulated. Most of the eggs stripped from 6 out of 8 control fish were not mature. Fertilization and hatching rates of LHRHa + PIM-induced fish (75–90% and 39–51%, respectively) were higher than those of control fish (36–39% and 0–1% respectively). In August and September 1990, at gravid catfish ovulated after injection of 0.05–0.10 μg LHRHa + 1 μg PIM/g BW. However, only 20% of the fish given 0.025 μg LHRHa/g + 1 μg PIM/g BW in August ovulated. No eggs could be striped from any of the control fish in August and September 1990. Techniques developed in this study, showed a simple and effective way of spawning captive catfish, C. macrocephalus. A simultaneous intramuscular injection of 0.05 μg LHRHa + 1 μg PIM/g and stripping of eggs at 16–20 h post-injection have been tested to yield high ovulation, fertilization and hatching rates.
    • Article

      Induction of oocyte maturation and ovulation in the freshwater Asian catfish, Clarias macrocephalus by LHRHa and pimozide 

      JD Tan-Fermin - Journal of Applied Ichthyology, 1992 - Blackwell Publishing
      Three experiments were conducted to determine the effects of a simultaneous injection of varying doses of luteinizing hormone-releasing hormone analogue (LHRHa; 0.005–0.10 μg)/body weight (BW) in combination with a fixed dose of pimozide (PIM; 1 μg)/g BW on oocyte maturation and ovulation in the catfish Clarias macrocephalus (body weight: 39 to 167 g). This was done by monitoring the development and size of the oocytes after hormone injection at various sampling intervals for 48 hours. In Experiment I (March 1989), only the fish injected with 0.10 μg LHRHa + 1μg PIM/g BW underwent final maturation and ovulation. However, oocyte maturation and ovulation were observed in all treated fish in Experiment II (April 1989). Oocyte maturation and ovulation were also induced except in fish injected with the lower dose combination (0.005 μg LHRHa + 1 μg PIM/g BW) or PIM alone (1 μg/g BW) in Experiment III (September 1989). No maturation was observed in all vehicle-injected control fish in the three experiments. Mean egg diameter of fish that were induced to mature increased during ovulation but remained similar in size in fish which did not undergo final maturation. This study showed that captive C. macrocephalus can be induced to undergo oocyte maturation and ovulation at 15 to 16 h after a simultaneous injection of 0.01 to 0.10 μg LHRHa + 1 μg PIM/g BW.
    • Article

      Induction of sex inversion in juvenile grouper, Epinephelus suillus, (Valenciennes) by injections of 17α-Methyltestosterone 

      JD Tan-Fermin, LMB Garcia & AR Castillo Jr. - Bulletin of Environmental Contamination and Toxicology, 1994 - The Ichthyological Society of Japan
      Four groups of two-year old juvenile groupers (Epinephelus suillus), each with 8-9 individuals of mean body weight (BW) 1.2 kg, were treated with 17α-methyltestosterone (MT). MT was injected intramuscularly within the range of 0.5-5.0 mg kg-1 BW every 15 days. Gonadal biopsy and stripping of the abdomen was done every 15 days, the fish being sacrificed after six or twelve injections. Initial controls had immature ovaries containing primary oocytes in lamellae that extended into the central lumen. After six injections, proliferation of stromal and gonial cells were observed in all fish sampled. Regardless of treatment, gonad sections of fish with a minimum BW of 1.2 kg showed degeneration of primary oocytes and the presence of spermatogenic cells. Milt was also present in larger-sized fish (BW: 1.5 kg) given 0, 0.5 and 1.0mg MTkg-1 BW, after such fish had received an accumulated dose of 5 or 12mg MTkg-1 BW. However, gonad sections of smaller-sized fish following these treatments contained only primary oocytes and gonial cells after six (BW: 0.7-1.0kg) or twelve (BW: 0.6-1.3 kg) injections. In contrast, all fish treated with 5 mg MT kg-1 BW had testes in active spermatogenesis after six (BW: 1.2-1.6 kg) or twelve (BW: 0.8 kg) injections. Gonad weight and gonadosomatic index values decreased during consecutive sampling. Induction of female-to-male sex inversion in juvenile E. suillus by MT was probably synergistic with age and size.
    • Article

      LHRHa and pimozide-induced spawning of Asian catfish Clarias macrocephalus (Gunther) at different times during an annual reproductive cycle 

      JD Tan-Fermin, RR Pagador & RC Chavez - Aquaculture, 1997 - Elsevier
      Captive Clarias macrocephalus were induced to spawn during the off-season (February), before (May), during (August) and end (November) of the natural breeding period to test their seasonal responsiveness to hormone treatment, and assess the resulting egg and larval quality. Intramuscular injections were given to five fish in each treatment consisting of 0.05 μg LHRHa + 1 μg PIM g−1 body weight (BW), 0.05 μg LHRHa, 1 μg PIM, or LHRHa vehicle (0.9% NaCl) and PIM vehicle (1 dimethylsulfoxide: 9 propylene glycol, v/v). At any phase of the annual cycle, only fish injected with a combination of LHRHa and PIM spawned, although initial egg size was similar among fish within a season. However, initial egg size was largest in fish induced to spawn in May (1.59 mm), followed by fish induced in August and November (1.54 mm), and smallest in fish induced in February (1.49 mm). All fish ovulated when induced to spawn in May and August, but ovulation rates decreased to 80% and 60% when fish were injected in November and February, respectively. Catfish induced to spawn in May, August and November had higher egg production, fertilization and larval survival rates than the fish induced in February. Hatching rates were higher in fish induced in May and August than in February, while hatching rate of fish induced in November was similar to those spawned at other times of the year. These results provide useful information regarding the broodstock management and hatchery production of C. macrocephalus.
    • Book chapter

      Localisation of enzymes in the digestive system during early development of the grouper (Epinephelus coioides) 

      GF Quinitio, AC Sa-an, JD Toledo & JD Tan-Fermin - In MA Rimmer, S McBride & KC Williams (Eds.), Advances in grouper aquaculture, 2004 - Australian Centre for International Agricultural Research
      Series: ACIAR Monograph 110
      This study was undertaken to investigate the occurrence of some digestive enzymes in the gastrointestinal tract during early development in the grouper. This work was conducted to provide information on formulating an appropriate feeding scheme and an artificial diet for the early development of the grouper, Epinephelus coioides. Larvae of E. coioides were reared in 5 tonne rectangular concrete tanks. The digestive enzymes localized were acid phosphatase (ACP), alkaline phosphatase (ALP), nonspecific esterase (NSE), aminopeptidase (AMP), trypsin (TRP), maltase (MAL) and lipase (LIP). Weak enzyme activity occurred during the yolk sac stage. High AMP activity started at day 14 prior to Artemia feeding at day 16. Fluctuations in TRP activity might be related to stomach formation. Occurrence of MAL during early development demonstrated a capacity to digest carbohydrates. An increase in LIP activity coincided with the occurrence of gastric glands. Insignificant changes in digestive enzymes were observed in the metamorphosing grouper larvae from day 40 to 60.
    • Article

      Marine leech (Zeylanicobdella arugamensis) infestation in cultured orange-spotted grouper, Epinephelus coioides 

      ER Cruz-Lacierda, JD Toledo, JD Tan-Fermin & EM Burreson - Aquaculture, 2000 - Elsevier
      Heavy infestation of a marine leech occurred among tank-reared juvenile and adult orange-spotted grouper, Epinephelus coioides Hamilton, at SEAFDEC AQD, Philippines with a prevalence of 83% and 17%, respectively. The leeches were attached in large numbers on the fins, lower jaw, under the operculum, eyes, and inside the mouth of the fish. The attachment and feeding sites exhibited frayed fins, hemorrhages and swelling of the host's skin. External and internal features indicate that the leech is Zeylanicobdella arugamensis De Silva (Hirudinea, Piscicolidae). The parasite can be effectively controlled using 50 ppm formalin bath treatment for 1 h.
    • 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.
    • Article

      Nursery rearing of the Asian catfish, Clarias macrocephalus (Günther), at different stocking densities in cages suspended in tanks and ponds 

      RF Bombeo, AC Fermin & JD Tan-Fermin - Aquaculture Research, 2002 - Blackwell Publishing
      Growth and survival of hatchery-bred Asian catfish, Clarias macrocephalus (Günther), fry reared at different stocking densities in net cages suspended in tanks and ponds were measured. The stocking densities used were 285, 571 and 1143 fry m−3 in tanks and 114, 228 and 457 fry m−3 in ponds. Fish were fed a formulated diet throughout the 28-day rearing period. Generally, fish reared in cages in ponds grew faster, with a specific growth rate (SGR) range of 10.3–14.6% day−1, than those in cages suspended in tanks (SGR range 9–11.3% day−1). This could be attributed to the presence of natural zooplankton (copepods and cladocerans) in the pond throughout the culture period, which served as additional food sources for catfish juveniles. In both scenarios, the fish reared at lower densities had significantly higher SGR than fish reared at higher densities. In the pond, the SGR of fish held at 228 and 457 m−3 were similar to each other but were significantly lower than those of fish held at 114 m−3. The zooplankton in ponds consisted mostly of copepods and cladocerans, in contrast to tanks, in which rotifers were more predominant. Per cent survival ranged from 85% to 89% in tanks and from 78% to 87% in ponds and did not differ significantly among stocking densities and between rearing systems. In conclusion, catfish nursery in cages suspended in tanks and ponds is density dependent. Catfish fry reared at 285 m−3 in tanks and at 114 m−3 in ponds had significantly faster growth rates than fish reared at higher densities. However, the desired fingerling size of 3–4 cm total length for stocking in grow-out culture can still be attained at stocking densities of 457 m−3 in nursery pond and 571 m−3 in tanks.
    • Article

      Ovarian development and serum steroid hormone profiles in hatchery-bred female catfish Clarias macrocephalus (Gunther) during an annual reproductive cycle 

      JD Tan-Fermin, S Ijiri, H Ueda, S Adachi & K Yamauchi - Fisheries Science, 1997 - Japanese Society of Fisheries Science
      Ovarian development e.g. gonadosomatic index, oocyte diameter, fecundity, histology, and related steroid hormones e.g. testosterone (T), estradiol-17 β (E2), 17α, 20 β-dihydroxy-4-pregnen-3-one (DHP), were examined in captive female catfish Clarias macrocephalus during an annual cycle to establish the optimum season for its artificial propagation. Results showed that captive C. macrocephalus had a group-synchronous pattern of ovarian development, as indicated by the presence of oocytes at all stages of development throughout the annual cycle. Mean gonadosomatic index (GSI; 11-13%), oocyte diameter (1.54-1.56 mm), fecundity (80-110 eggs/g body weight), and serum T levels (36-37 ng/mL) were lowest in January-April, suggesting that it is not the optimum season to induce C. macrocephalus to spawn during these months. Serum E2 levels were lowest in January (7 ng/mL), and highest in December (20 ng /mL). Serum DHP levels were below detectable limits (<0.02 ng/mL) throughout the year, supporting the observation that final maturation and ovulation do not occur in this species under captive conditions. Changes in various reproductive parameters and steroid hormone levels indicate that January-March, April-June, July-September and October-December correspond to the refractory, preparatory, spawning and post-spawning periods, respectively, of the annual cycle. The results of the present investigation can be used as a guide for the controlled breeding and commercial aquaculture of C. mucrocephalus in the Philippines.
    • Article

      Ovarian maturation stages of the wild giant tiger prawn, Penaeus monodon Fabricius 

      JD Tan-Fermin & RA Pudadera - Aquaculture, 1989 - Elsevier
      A qualitative and quantitative study of the ovarian maturation stages of wild-caught Penaeus monodon was conducted to refine the existing method of staging. For industrial purpose, measuring the ovarian width at the first abdominal region can minimize arbitrariness in staging. A width of 20 mm indicates readiness for spawning while reproductive performance is improved when ovarian width is 30 mm or more. Based on histology, the usual 6 to 8 stages of development can be reduced to four stages: previtellogenic, vitellogenic, cortical rod, and spent. The previtellogenic stage (P) is characterized by the predominance of oogonia and primary oocytes in the chromatin nucleolus and/or perinucleolus stage. The vitellogenic stage (V) is marked by the presence of yolky oocytes. The cortical rod stage (C) is distinguished by the appearance of yolky oocytes with spherical or rod-like bodies at the peripheral cytoplasm. The spent stage (S) can be distinguished by the presence of few oocytes with yolky substance and/or cortical rods, thicker layers of follicle cells, and few darkly-stained, irregularly shaped primary oocytes. Individuals classified as stages II+ and III+ showed similarity in size and shape of all lobes in the posterior thoracic region, and histologically, corresponded to the revised stages V and C, respectively. Histochemical staining shows that glycoproteins and lipids are absent in the primary oocytes and present in yolky oocytes. Glycoproteins but not lipids occur in the cortical rods. Analysis of variance showed significant differences in mean gonad weight and gonadosomatic index values but not in the mean body length and body weight values in stages P to C. Uniformity in the number, stage and composition of oocytes in the four regions of the ovary at each stage showed that stage of ovarian maturity in wildprawns can be represented by any region of the ovary. Differences in the oocyte size frequency and mean values of average and maximum oocyte diameter in the four stages showed that these are good indicators of stage of maturation in wild P. monodon.
    • Article

      Possible application of mibolerone for induced sex inversion of grouper Epinephelus coioides 

      GF Quinitio, JD Tan-Fermin & A Nagai - Fisheries Science, 2001 - Japanese Society of Fisheries Science
      Thirty immature juvenile grouper Epinephelus coioides (19-168 g bodyweight, BW) were randomly stocked in four units 6 t tanks to determine if mibolerone can be used to induce sex inversion in groupers. After acclimatization and weaning to artificial feed, the feed given daily (4% BW/day) was supplemented with 0, 50, 100, and 200 μg mibolerone/kg feed for about 18 weeks. Thereafter, the hormone treatment was withdrawn and the experiment was terminated at Week 24. Ten fish were killed for gonad histology at stocking to serve as an initial control while about three to five fish were killed every 8 weeks. In general, ovaries of initial controls showed the presence of moderate stromal cells and gonia and few primary oocytes. At Weeks 8 and 16, ovaries of the control fish (0 μg/kg) were similar to that of the initial control except that primary oocytes increased at Week 24. Gonads of fish fed diets containing 100 and 200 μg/kg had none to moderate spermatocytes and few spermatids at Week 8 and 16, although spermatozoa were not observed, indicating that the fish were undergoing spermatogenesis. Spermatogenesis at 50 μg/kg was not as advanced since only few spermatocytes occurred at Weeks 8 followed by moderate gonia and no spermatocytes and spermatids at Week 16. However, the presence of few primary oocytes was observed when mibolerone was withdrawn suggesting that sex-inversed fish reverted back to a female condition. These results show that sex inversion in juvenile grouper can be induced by oral administration of mibolerone and may have possible application on mature females to produce functional males.