Now showing items 1-20 of 3384

    • Article

      Point-of-no-return and delayed feeding mortalities in first-feeding larvae of the silver therapon Leiopotherapon plumbeus (Kner) (Teleostei: Terapontidae) 

      LMB Garcia, MJP Sayco & FA Aya - Aquaculture Reports, 2020 - Elsevier
      This study examined the incidence of mortalities among first-feeding post-yolk sac silver therapon Leiopotherapon plumbeus (Kner) larvae deprived of live food in the hatchery. Starting after their yolk was consumed at 40 h post-hatch (hph) and every 2 h thereafter until 54 hph, larvae were fed and exposed to live food for an hour only and their performance was observed after initial feeding at 25 °C. Feeding incidence progressively increased until 48 hph as larval mouth gape increased during exogenous feeding, but oil globule volume progressively declined until full exhaustion at 52 hph. All starved larvae fed at 48 hph but feeding incidence progressively declined until larvae ceased to feed at 54 hph to coincide with a significant reduction in survivorship, indicating that larvae have reached their point-of-no-return (PNR) at 50 hph despite the availability of food. Delayed initial feeding of un-fed post-yolk sac larvae starting at 46 hph until 54 hph resulted in significantly higher feeding incidence among 46−48 hph larvae than those fed after 50 hph, which did not survive longer than 10 h after initial feeding. These results demonstrate that silver therapon larvae have a very brief transitional or mixed-feeding period of 12 h after yolk exhaustion so that initial feeding beyond 50 hph when larvae have reached their PNR results in early onset of death.
    • Article

      Behavioural evidence for colour vision determined by conditioning in the purple mud crab Scylla tranquebarica 

      G Kawamura, TU Bagarinao, HS Cheah, H Saito, ASK Yong & LS Lim - Fisheries Science, 2020 - Springer Verlag
      Crabs and shrimps (order Decapoda) use colours in various tasks such as foraging and mate choice. Colour vision requires at least two types of photoreceptors with different spectral sensitivities. Previous physiological studies revealed that most crabs including Scylla mud crabs have a single visual receptor system, i.e. they are colour blind. We determined colour vision by means of a behavioural experiment on hatchery-produced and wild-captured purple mud crab Scylla tranquebarica in a roofed hatchery. Adult crabs (8-10 cm carapace width) were subjected to classical conditioning to associate a food reward with a blue or a green stimulus placed among seven shades of grey. The hatchery-produced crabs learnt this task after 14 days of reward training, and thereafter distinguished blue in 27 non-reward trials, and green in 39 non-reward trials. The wild-captured crabs did so after 25 days of reward training, and distinguished green in 49 non-reward trials. These results indicated colour vision in S. tranquebarica. However, the crabs were unable to distinguish blue or green in dim light of 4.4 cd/m2 (which is slightly brighter than full moon light). The high colour vision threshold was attributed to the small optic parameters of the apposition compound eyes of S. tranquebarica.
    • Article

      Morphological descriptions and morphometric discriminant function analysis reveal an additional four groups of Scylla spp 

      There are four species of mud crabs within the genus Scylla, and most of them live sympatrically in the equatorial region. Apart from a report in Japan about the finding of a natural Scylla hybrid more than a decade ago after the division of genus Scylla into four species by Keenan, Davie & Mann (1998), no subsequent sighting was found. Thus, this study investigates the possible natural occurrence of potential hybridization among Scylla species in the wild. A total of 76,211 individuals from mud crab landing sites around the Malacca Straits, South China Sea and Sulu Sea were screened. In addition to the four-purebred species, four groups (SH 1, n = 2, 627; SH 2, n = 136; SH 3, n = 1; SH 4, n = 2) with intermediate characteristics were found, mostly at Sulu Sea. Discriminant Function Analysis revealed that all Scylla species, including SH 1 - 4, are distinguishable via their morphometric ratios. The most powerful discriminant ratios for each character and the top five discriminant ratios of males and females were suggested. The carapace width of SH 1 males and females were significantly smaller than pure species. Based on the discriminant ratios and the description of morphological characters, we hypothesize that the additional four groups of Scylla with intermediate characteristics could be presumed hybrids. Future work at the molecular level is urgently needed to validate this postulate.
    • Newsletter

      AQD Matters 2019 November - December 

      JMV de la Cruz (Ed.) - 2020 - Aquaculture Department, Southeast Asian Fisheries Development Center
    • Article

      Biosecurity policy and legislation for the global seaweed aquaculture industry 

      I Campbell, CSB Kambey, JP Mateo, SB Rusekwa, AQ Hurtado, FE Msuya, GD Stentiford & EJ Cottier-Cook - Journal of Applied Phycology, 2019 - Springer Verlag
      Each year a significant proportion of global food production is lost to pests and diseases, with concerted efforts by government and industry focussed on application of effective biosecurity policies which attempt to minimise their emergence and spread. In aquaculture the volume of seaweeds produced is second only to farmed fish and red algal carrageenophytes currently represent approximately 42% of global production of all seaweeds. Despite this importance, expansion of the seaweed sector is increasingly limited by the high prevalence of recalcitrant diseases and epiphytic pests with potential to emerge and with the demonstrated propensity to spread, particularly in the absence of effective national and international biosecurity policies. Developing biosecurity policy and legislation to manage biosecurity risk in seaweed aquaculture is urgently required to limit these impacts. To understand current international biosecurity frameworks and their efficacy, existing legislative frameworks were analysed quantitatively for the content of biosecurity measures, applicability to the seaweed industry, and inclusion of risks posed by diseases, pests and non-native species. Deficiencies in existing frameworks included the following: inconsistent terminology for inclusion of cultivated seaweeds, unclear designation of implementation responsibility, insufficient evidence-based information and limited alignment of biosecurity hazards and risks. Given the global importance of the cultivation of various seaweeds in alleviating poverty in low and middle income countries, it is crucial that the relatively low-unit value of the industry (i.e. as compared with other aquatic animal sectors) should not conflate with a perceived low risk of disease or pest transfer, nor the subsequent economic and environmental impact that disease transfer may impact on receiving nations (well beyond their seaweed operations). Developing a clear basis for development of robust international biosecurity policies related to the trade in seaweeds arising from the global aquaculture industry, by first addressing the gaps highlighted in this study, will be crucial in limiting impacts of pests and diseases on this valuable industry and on natural capital in locations where seaweeds are farmed.
    • Article

      Dietary lipid requirement of whiteleg shrimp Litopenaeus vannamei juveniles cultured in biofloc system 

      A Hamidoghli, S Won, FA Aya, H Yun, J Bae, IK Jang & SC Bai - Aquaculture Nutrition, 2019 - Wiley
      An eight-week feeding trial was conducted to evaluate the contribution of biofloc on dietary lipid requirement in whiteleg shrimp Litopenaeus vannamei. Five diets with graded levels of dietary lipid (45, 60, 90, 120 and 150 g/kg) were fed to juvenile shrimp. Final weight, weight gain and specific growth rate of shrimp fed diets with 60, 90 and 120 g/kg lipid levels were significantly higher than those of shrimp fed diets with lipid levels 45 and 150 g/kg (p < .05). Feed efficiency and protein efficiency ratio of shrimp fed 60, 90 and 120 g/kg were higher than those fed 150 g/kg diet. Plasma total cholesterol and triglyceride levels were lower in shrimp fed 45 g/kg compared with those fed the 90 g/kg (p < .05). Also, lysozyme activity for 90 g/kg group was higher than the 15 g/kg group. Hepatopancreas lipase and amylase activities of shrimp fed 90 and 120 g/kg diets were significantly higher than those of shrimp fed 45 and 150 g/kg diets. Broken-line regression analysis for weight gain indicated that the dietary lipid requirement of whiteleg shrimp juveniles reared in a biofloc system was estimated to be higher than 56 g/kg but <60 g/kg.
    • Article

      Draft genome sequence of multidrug-resistant Vibrio parahaemolyticus strain PH698, infecting penaeid shrimp in the Philippines 

      CP Saloma, SMU Penir, JMR Azanza, LD dela Pena, RC Usero, NAR Cabillon, ADP Bilbao & EC Amar - Microbiology Resource Announcements, 2019 - American Society for Microbiology
      The emergence of multidrug-resistant bacterial strains in diverse settings has been reported globally. In the Philippine shrimp aquaculture industry, antibiotics are used for the treatment of bacterial diseases during the production cycle. We report the draft genome of Vibrio parahaemolyticus PH698, a multidrug-resistant strain isolated from a Philippine shrimp farm.
    • Article

      Enriched Ulva pertusa as partial replacement of the combined fish and soybean meals in juvenile abalone Haliotis asinina (Linnaeus) diet 

      R Santizo-Taan, M Bautista-Teruel & JRH Maquirang - Journal of Applied Phycology, 2019 - Springer Verlag
      The potential of enriched Ulva pertusa meal as feed ingredient in abalone juveniles, Haliotis asinina was evaluated. Four isonitrogenous and isolipidic diets were formulated which contain 27% protein and 5% lipid. Enriched U. pertusa meal replaced 0% (control), 10%, 20%, and 30% of protein from fish and soybean meals in the formulated diets. Thirty randomly selected abalone juveniles with average weight and shell length of 0.45 g ± 0.01 and 12.71 mm ± 0.01, respectively, were placed in each of the twelve 60-L oval fiberglass tanks equipped with a flow-through seawater system. Abalone were given diets at 3–5% body weight daily for 120 days in three replicate samples. Results showed no significant differences (p > 0.05) in percent weight gain, shell length, specific growth rate, feed conversion ratio, and protein efficiency ratio even up to 30% replacement level. Apparent dry matter digestibility of U. pertusa meal in abalone diet was 92%. Crude protein content of the abalone fed diets 1 (10% enriched U. pertusa meal) and 3 (30% enriched U. pertusa meal) was significantly (p < 0.05) higher than those fed on basal diet. Enriched U. pertusa meal can partially replace fish and soybean meals as protein source in formulated diets for abalone, Haliotis asinina juveniles.
    • Article

      Draft genome sequence of Vibrio parahaemolyticus strain PH1339, which causes acute hepatopancreatic necrosis disease in shrimp in the Philippines 

      SMU Penir, LD dela Pena, NAR Cabillon, ADP Bilbao, EC Amar & CP Saloma - Microbiology Resource Announcements, 2019 - American Society for Microbiology
      We report the first draft genome sequence of an acute hepatopancreatic necrosis disease (AHPND)-causing Vibrio parahaemolyticus strain isolated from a Penaeus vannamei sample from the Philippines. The strain carries the genes encoding the Pir-like toxin pair PirAvp and PirBvp.
    • Article

      Effects of replacing dietary fish oil with beef tallow on growth performance, serological parameters, and fatty acid composition in juvenile olive flounder, Paralichthys olivaceus 

      S Lee, FA Aya, S Won, A Hamidoghli & SC Bai - Journal of the World Aquaculture Society, 2019 - Wiley
      This study evaluated the effects of replacing fish oil (FO) with beef tallow (BT) in juvenile olive flounder, Paralichthys olivaceus (3.93 ± 0.07 g), over 8 weeks. Seven diets, consisting of 0, 25, 50, 75, and 100% replacement of FO with BT and 63 and 75.9% replacement supplemented with docosahexaenoic acid (DHA) at 0.9 and 1.1% of 100 g diet, respectively, were distributed into 21 tanks in a semi‐recirculation system with 15 fish per tank. The replacement of FO with BT at the given levels showed no significant changes (p > .05) in growth performance and whole‐body proximate composition. Fish fed the diet of 75.9% replacement with 1.1% DHA supplementation showed the best performance in these measurements among the treatments. Plasma glutamic pyruvic transaminase, cholesterol, high‐ and low‐density lipoproteins, and total protein were not significantly influenced by the replacement of FO with BT. The FO replacement generally resulted in a reduction of eicosapentaenoic acid, DHA, and n‐3/n‐6 polyunsaturated fatty acid ratio in the whole body, whereas the DHA supplementation recovered the level of DHA and the n‐3/n‐6 ratio to those observed in the group fed the 0% replacement diet. Taken together, BT along with DHA supplementation can potentially be a cost‐effective alternative for FO in olive flounder culture.
    • Patent

      Hatchery protocol for silver therapon (Leiopotherapon plumbeus, Kner 1864) 

      FA Aya - 2019 - Intellectual Property Office of the Philippines
      The hatchery protocol for silver therapon (Leiopotherapon plumbeus, Kner 1864) in outdoor tanks is disclosed. The process includes timed provision of preferred natural food commensurate with the age of larvae, pre-conditioning of rearing water, utilizing ambient lake water and the addition of fresh tropical almond leaves Terminalia catappa to enhance natural food supply in tanks. A stocking density of 0.1 to 1 larvae /L was used to enhance survival and growth. Survival of larvae increased to 35.41 ± 15.32 per cent using the invention.
    • Article

      A review of reported seaweed diseases and pests in aquaculture in Asia 

      GM Ward, JP Faisan, EJ Cottier‐Cook, C Gachon, AQ Hurtado, PE Lim, I Matoju, FE Msuya, D Bass & J Brodie - Journal of the World Aquaculture Society, 2019 - Wiley
      Seaweeds have been used as a food for centuries in Asia and are increasingly exploited as a source for dietary supplements, animal feed, chemicals, and biofuels. In recent years, there has been an increase in the prevalence of diseases and pests in these aquaculture crops, with a subsequent reduction in their quantity and commercial value. In this article, we review diseases that have been reported in the scientific literature for species of red and brown seaweeds. We have focused on the major seaweed crops grown in Asia, where much of this production is centered. We also provide information on disease management and biosecurity and some observations on future directions.
    • Article

      Evaluation of the bioremediation potential of mud polychaete Marphysa sp. in aquaculture pond sediments 

      MAE Mandario, VR Alava & NC Añasco - Environmental Science and Pollution Research, 2019 - Springer
      Organic enrichment from aquaculture could alter the chemical composition of the fishpond bottom by increasing the levels of organic matter (OM), sulfur (S), iron (Fe), and lower pH of the sediment. Polychaetes can contribute to the nutrient cycling and remediation of polluted sediment. A laboratory experiment was conducted to test the remediation potential of small and large mud polychaete Marphysa sp. introduced to two types of fishpond sediment. Initially, Sediment A had lower OM, S, Fe, and higher pH than Sediment B. After 30 days, in Sediment B, large polychaetes significantly decreased the OM level (27%) while both small and large polychaetes promoted significant decreases of S (71%) and Fe (70–73%) in both sediment types. The increase of sediment pH was promoted by the presence of polychaetes (0.53–0.69) although pH level in small polychaete was not significantly different with the no polychaete treatment. Regardless of polychaete treatment, the pH level of Sediment B (1.04 ± 0.10) was significantly improved than that of Sediment A (0.17 ± 0.02). In both sediments, large polychaetes (95%) had better survival rates than small polychaetes (73%). These findings reveal that large Marphysa sp. can significantly improve sediment quality by decreasing the levels of OM, S, and Fe and improve pH level to a more basic form without compromising its survival. Large polychaetes are recommended to be used as bioremediators of organically enriched aquaculture pond sediment.
    • Article

      A new species of the sanguinea-group Quatrefages, 1866 (Annelida: Eunicidae: Marphysa) from the Philippines 

      CJ Glasby, MAE Mandario, I Burghardt, E Kupriyanova, LM Gunton & PA Hutchings - Zootaxa, 2019 - Magnolia Press
      A new species of the Marphysa sanguinea group, M. iloiloensis n. sp. (Annelida: Eunicida: Eunicidae), is described from the Marine Annelids Hatchery of the Southeast Asian Fisheries Development Center, Aquaculture Department (SEAFDEC- AQD), Iloilo Province, Philippines. It represents the first record of this group in the Philippines. The new species is most similar morphologically to M. hongkongensa Wang, Zhang & Qiu, 2018, but can be distinguished from it by having fewer branchial filaments, a pair of faint eyes (absent in M. hongkongensa), and in slight differences in jaw morphology and chaetation. The embryos of the new species develop inside a jelly cocoon attached to the entrance of the adult burrow; this is the first time that egg-containing cocoons have been found in any species of the sanguinea-group. Phylogenetic analysis based on the mitochondrial gene cytochrome c oxidase subunit I (COI) revealed that Marphysa iloiloensis n. sp. is genetically distinct from all other analysed Marphysa species and forms a sister group to M. hongkongensa. A revised identification key to members of the sanguinea-group in Southeast Asia is provided.
    • Article

      Fire + water + bombs: Disaster management among academic libraries in Marawi City, Lanao del Sur, Philippines 

      DL Superio, EM Abaday, MGH Oliveros, AS Delgado, VEV Palcullo & JF Geromiano - International Journal of Disaster Risk Reduction, 2019 - Elsevier
      The academic libraries in Marawi City, Lanao del Sur, Philippines are vulnerable to disasters. In the last ten years, the majority of the 13 respondent libraries have sustained at least one disaster that may have been caused by civil unrest, war or terrorism, flood, earthquake, or fire. The majority were unprepared to face such disasters, may it be small-scale or catastrophic, and only one library has a disaster management plan. The lack of significant holdings of rare books, shortage of financial resources, no perceived risk, and the unavailability of staff to write a disaster management plan, are the reasons why most libraries do not have a plan. Moreover, the majority lacked staff that has undergone training in disaster preparedness and management. On the other hand, all of the libraries have disaster management practices that although not enough, will still enable them to lessen the effects of the disaster and save their library and parts of their collection when necessary. The respondents identified management support as an essential factor in their success in disaster management. The results of the study provide valuable information on the current state of the libraries in the Philippines with regards to disaster preparedness and management. Therefore, it is an essential addition to the literature on disaster management in the Philippines, which is very scarce as of the moment.
    • Article

      Induction of gonadal development in protogynous grouper with orally delivered FSH DNA 

      P Palma, J Nocillado, J Superio, EG de Jesus-Ayson, F Ayson, A Takemura, MW Lu & A Elizur - Marine Biotechnology, 2019 - Springer
      The availability of sexually mature fish often dictates the success of its captive breeding. In this study, we induced reproductive development in juvenile protogynous tiger grouper through oral administration of a plasmid (p) containing an engineered follicle-stimulating hormone (FSH). An expression construct (pcDNA3.1) was designed to express a single-chain FSH consisting of giant grouper FSH β-subunit and glycoprotein subunit-α (CGα), linked by the carboxy-terminal peptide (CTP) sequence from the human chorionic gonadotropin (hCG). Single oral delivery of pFSH encapsulated in liposome and chitosan to tiger grouper yielded a significant increase in plasma FSH protein level after 4 days. Weekly pFSH feeding of juvenile tiger groupers for 8 weeks stimulated ovarian development as indicated by a significant increase in oocyte diameter and progression of oocytes to cortical alveolar stage. As the pFSH treatment progressed from 20 to 38 weeks, female to male sex change was initiated, characterized by oocyte regression, proliferation of spermatogonial cells, and occurrence of spermatogenic cysts. It was also associated with significantly lower mRNA expression of steroidogenic genes (cyp11b, cyp19a1a, and foxl2) and basal plasma levels of sex steroid hormones 17β-estradiol (E2), testosterone (T), and 11-ketotestosterone (11KT). Results suggest that pFSH stimulates ovarian development up to cortical alveolar stage and then initiates sex change in tiger grouper. These findings significantly contribute to our knowledge on the role of FSH in the development of protogynous hermaphroditic fish. This study is the first to demonstrate induction of reproductive development in fish through oral delivery of plasmid gonadotropin.
    • Article

      Solar irradiation as an alternative bleaching process for agar extracted from Gracilariopsis heteroclada in Iloilo, Philippines 

      LF Endoma, LM Nacional & MRJ Luhan - Botanica Marina, 2019 - De Gruyter
      The current industrial practice of using chemical bleach to achieve the pure white colour of agar is deleterious to both human and environmental health. This study evaluates the potential of solar irradiation as an alternative bleaching process for agar extracted from Gracilariopsis heteroclada in Iloilo, Philippines. The physico-chemical properties of agar obtained from alkaline-treated seaweed after exposure to different bleaching conditions (e.g. solar irradiation, hypochlorite solution, and ultraviolet and fluorescent lights) were examined and compared with commercial bacteriological agar. Photobleaching through solar irradiation produced agar with superior gel strength (1038.61 g cm−2), high 3,6-anhydrogalactose content (41.44%) and low total inorganic sulphate content (1.87%) without compromising agar yield (19.37%). Solar irradiation offers very promising results as a simple, low-cost, environmentally friendly alternative to the chlorine bleaching process for agar extraction.
    • Article

      Fish performance, nutrient digestibilities, and hepatic and intestinal morphologies in grouper Epinephelus fuscoguttatus fed fermented copra meal 

      REP Mamauag, JA Ragaza & T Nacionales - Aquaculture Reports, 2019 - Elsevier
      Protein enhanced copra meal (PECM®) is an alternative, cheap, and sustainable source of plant protein for the aquafeed industry, albeit its use on carnivorous fish species has been very limited. A 70-day feeding trial using grouper Epinephelus fuscoguttatus (initial mean body weight of 1.86 ± 0.19 g) tested fermented copra meal as feed ingredient. Six isonitrogenous (crude protein of 45%) and iso-lipidic (crude fat of 11%) diets consisted of PECM®: a control diet at 0% soybean meal replacement (C); four diets replacing soybean meal at 25% (FC25), 50% (FC50), 75% (FC75), 100% (FC100) – all with methionine and lysine supplementation; and 100% soybean replacement without methionine and lysine supplementation (FCW100). Growth and feed performance were not significantly (P > 0.05) affected by PECM® replacement of soybean meal up to 100%, even without methionine and lysine supplementation. Chemical body composition was likewise not significantly (P > 0.05) altered. PECM® when used as a grouper feed ingredient has protein, lipid, carbohydrate and dry matter digestibilities of 89.28%, 78.63%, 82.57%, and 48%, respectively. Hepatic and intestinal morphologies displayed no apparent pathological changes. PECM® can be efficiently utilized by grouper and can replace soybean meal up to 100% (16% in diet) for normal fish performance and digestive organ functions.
    • Article

      Reproductive development of the threatened giant grouper Epinephelus lanceolatus 

      The giant grouper is presumed to follow the reproductive pattern of most Epinephelus species, characterized by protogynous hermaphroditism wherein male maturation is attained through sex reversal of a functional female. This hypothesis, however, has not been verified due to lack of biological data. The present study addresses this gap by investigating the reproductive development of giant groupers from juvenile stage through sexual maturity. Gonad histological analysis of hatchery-bred juvenile giant grouper from Queensland, Australia (0.8–5.2 kg, n = 43) have shown earliest occurrence of primary oocytes (i.e. ovarian differentiation) in 47.8 cm and 2.5 kg fish. Monitoring of sexual maturity by gonadal biopsy was performed in a stock of wild-caught giant groupers (2–52 kg) held in sea cages in the Philippines and Vietnam from 2015 to 2017. Onset of female sexual maturity was at 96.9 ± 1.6 cm and 23.5 ± 1.5 kg in the Philippines, and 103.0 ± 4.1 cm and 33.5 ± 2.5 kg in Vietnam. In both locations, development of primary males was observed wherein fish produced milt (or spermiated) without passing through a functional female phase. The ratio of primary males to females in both locations was about 1:2. Size at maturity of primary males is 86.5 ± 4.8 cm and 17.1 ± 2.1 kg in the Philippines, and 97.3 ± 1.3 cm and 34.3 ± 0.9 kg in Vietnam. To aid in the monitoring of female maturation, we developed a non-invasive method based on immunoassay of vitellogenin in skin mucus and this was shown to be effective in detecting female maturation 9 ± 2 months prior to first observation of oocytes through gonadal biopsy. Our findings suggest that giant grouper is a diandric protogynous hermaphrodite. This study provides novel information on the reproductive biology of giant grouper, an economically important and vulnerable species.
    • Article

      Gonadal response of juvenile protogynous grouper (Epinephelus fuscoguttatus) to long term recombinant follicle-stimulating hormone administration 

      P Palma, J Nocillado, J Superio, EGdJ Ayson, F Ayson, I Bar & A Elizur - Biology of Reproduction, 2019 - Oxford University Press
      The role of follicle stimulating hormone (FSH) in the gonadal development of protogynous hermaphroditic grouper (E. fuscoguttatus) was investigated. Recombinant giant grouper (E. lanceolatus) FSH (rggFSH) was produced in yeast. Its receptor binding capacity and steroidogenic potency were confirmed in vitro. Weekly injections of rggFSH to juvenile tiger grouper for 8 weeks (100 μg/kg body weight, BW) resulted in significantly larger and more advanced oocytes (cortical alveolar stage vs. primary growth stage in control). Sustained treatment with rggFSH (20 to 38 weeks at 200 μg/kg BW) resulted in significant reduction in gonad size, degeneration of oocytes and proliferation of spermatogonial cells, indicative of female to male sex change. Gene expression analysis showed that, while initiating female to male sex change, the rggFSH significantly suppressed the steroidogenic genes cyp11b, cyp19a1a and foxl2 which restrained the endogenous production of sex steroid hormones thus prevented the differentiation of spermatogonial cells. Expression profile of sex markers dmrt1, amh, figla and bmp15 suggests that the observed sex change was restricted at the initiation stage. Based on these results, we propose that the process of female to male sex change in the protogynous grouper is initiated by FSH, rather than sex steroids and likely involves steroid-independent pathway. The cortical alveolar stage in oocyte development is the critical point after which FSH-induced sex change is possible in grouper.