Pathogenicity of Aeromonas veronii from Nile tilapia (Oreochromis niloticus) and efficacy of fish oral vaccine against motile aeromonad septicemia in tank trials

Download Supplementary MaterialMotile aeromonad septicemia (MAS), caused by the Aeromonas species, has been a serious problem in fish health management, particularly in Nile tilapia (Oreochromis niloticus). This study characterized an Aeromonas species isolated from farmed tilapia fingerlings in Binangonan, Rizal, Philippines, and tested for its pathogenicity in tank trials. The isolate, designated as Aeromonas veronii DFR01 (Diseased Fish Rizal), was identified based on 16S rRNA phylogenetic analysis, 16S rRNA homology, and MALDI-TOF mass spectrometry. Its biochemical profile was generated from API and Biolog Gen III systems. A median lethal dose of A. veronii DFR01 was determined to be 107 CFU/mL in tank trials and was utilized as a whole-cell inactivated antigen for oral vaccine development. The immunized tilapia fingerlings produced elevated levels of immunoglobulin M (IgM) in the blood as determined by an enzyme-linked immunosorbent assay (ELISA). There was a significant increase in IgM levels 14 days post-vaccination. A quantitative polymerase chain reaction (qPCR) showed increasing levels of IgM gene expression after vaccination until 38 days of culture. Vaccinated fish showed 25–35% cumulative mortality after the challenge, while non-vaccinated-challenged fish showed 75% mortality. The findings of this research suggest that the fish oral vaccine may prove beneficial for farmed tilapia populations. The vaccine elicited improved immune responses in the fish and resulted in higher survival rates.Financial support for this study came from a research grant to AMA from the Department of Science and Technology (DOST) Philippine Council for Aquatic and Marine Research and Development (PCAMRD), now the Philippine Council for Agriculture, Aquatic, and Natural Resources Research and Development (PCAARRD; Program Code: 2021-01-A1-CRADLE-3042; approved 3 November 2021). Many thanks to the Trinity University of Asia and Santeh Feeds Corporation for the support and counterpart funding

Achieving sustainable aquaculture in Southeast Asia: A case study on community-based giant freshwater prawn production in Laguna Lake, Philippines

The Aquaculture Department of the Southeast Asian Fisheries Development Center (SEAFDEC/AQD) implemented the project “Sustainable Aquaculture through Cost-effective Culture Systems, and Prompt and Effective Aquatic Animal Health Management” from 2020 to 2024 with support from the Japanese Trust Fund (JTF). The Project consists of three main activities: 1) cost-effective culture system, 2) prompt and effective aquatic animal health management, and 3) capacity enhancement for sustainable aquaculture. It complies with Resolution No. 16 Strengthen aquaculture governance and implement good aquaculture practices to sustain production for food safety and security, sustainable livelihoods, and rural development of the ASEAN-SEAFDEC Resolution and Plan of Action on Sustainable Fisheries for Food Security for the ASEAN Region Towards 2030 (RES&POA-2030). Recognizing the success and expertise of AQD in the development of aquaculture technologies, especially in broodstock management, spawning, larval rearing, nursery and grow-out culture of aquatic fish, crustaceans, mollusks, sandfish, and seaweeds, feed development, fish health management, development of vaccine treatment, protective measures against existing and emerging diseases, community-based resource management, and implementation of aquaculture related training courses, the Project was conducted to improve the stability and sustainability of aquatic food production and for technology dissemination in the Southeast Asian region. Under Activity 1 of this Project, this study aims to establish a community-based seedlings supply system. This article highlights the inherent challenges of hatchery production, particularly our growing vulnerability to climate variability, including temperature fluctuations and water quality issues. Effective data monitoring can guide adaptive management strategies through science-based strategies, such as investing in appropriate technologies, adjusting densities, and changing feeding practices to boost production yields

Morphological and genetic diversity assessment of freshwater prawns (Macrobrachium spp.) in the Cairawan river, Antique province, Panay island, Philippines

Freshwater prawns of the genus Macrobrachium are among the most valuable cultured aquatic species in the world. The systematic study of Macrobrachium species in the Philippines has often been based on morphological trait assessment. Here, we combined morphology and molecular approaches to study the presence and actual distribution of Macrobrachium species along the Cairawan River in Laua-an, Antique Province, Panay Island. Using morphological characteristics, we identified 11 Macrobrachium species, the highest number of species reported from a single river. Molecular results based on the cytochrome oxidase subunit I (COI) mitochondrial DNA (mtDNA) sequences confirmed the morphological identification. The analysis revealed eight major clades with 19 distinct haplotypes within the species. Our results provide information on the identification of Macrobrachium species inhabiting the Cairawan River. The baseline information can be helpful for future genetic studies involving freshwater prawns with potential use in aquaculture. It can provide scientific data to facilitate the formulation of selective breeding plans and direct governance policies in freshwater prawn resource conservation and management in the Philippines

Breeding, seed production, and culture of African catfish Clarias gariepinus

This manual summarizes the existing techniques on the induced breeding, seed production, and culture of the African catfish based on surveys done in Iloilo, Philippines. SEAFDEC Aquaculture Department will present a standardized way of breeding and culturing the African catfish under captive conditions, but will not encourage growing them in natural freshwater habitats. Previous data have shown that their presence in lakes adversely affects the population of other indigenous species and may lead to a loss of biodiversity

AQD Matters 2024 March - April

In this issue: 1) SEAFDEC builds up stock of tuna breeders to enhance research efforts; 2) SEAFDEC/AQD attends 33rd NACA meeting; 3) SEAFDEC officials pay courtesy visit to DA-BFAR; 4) SEAFDEC fish health management training attended by 5 member countries; 5) Progress of Japan-funded SEAFDEC/AQD programs reviewed; 6) SEAFDEC/AQD, BFAR, LGUs unite: Marine fish hatchery operations training organized for BFAR, LGU staff; 7) Sea cucumber hatchery technicians upskilled to solve a production bottleneck; 8) SEAFDEC/AQD info staff serve as resouce persons in inter-departmental workshop; 9) Experts from SEAFDEC/AQD share insights on marine aquaculture; 10) University of Massachusetts Lowell professors tour SEAFDEC/AQD; 11) Igang Marine Station harvest ields pompano, milkfish; 12) Rescued sea turtle back into the wild after eight months; 13) The benefit of intermittent fasting – for eels; 14) Davao rep donates P1 million to FishWorld Museu

Complex patterns of genetic structure in the sea cucumber Holothuria (Metriatyla) scabra from the Philippines: implications for aquaculture and fishery management

The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fmars.2024.1396016/full#supplementary-materialThe sandfish Holothuria (Metriatyla) scabra, is a high-value tropical sea cucumber harvested from wild stocks for over four centuries in multi-species fisheries across its Indo-Pacific distribution, for the global bêche-de-mer (BDM) trade. Within Southeast Asia, the Philippines is an important centre of the BDM trade, however overharvesting and largely open fishery management have resulted in declining catch volumes. Sandfish mariculture has been developed to supplement BDM supply and assist restocking efforts; however, it is heavily reliant on wild populations for broodstock supply. Consequently, to inform fishery, mariculture, germplasm and translocation management policies for both wild and captive resources, a high-resolution genomic audit of 16 wild sandfish populations was conducted, employing a proven genotyping-by-sequencing approach for this species (DArTseq). Genomic data (8,266 selectively-neutral and 117 putatively-adaptive SNPs) were used to assess fine-scale genetic structure, diversity, relatedness, population connectivity and local adaptation at both broad (biogeographic region) and local (within-biogeographic region) scales. An independent hydrodynamic particle dispersal model was also used to assess population connectivity. The overall pattern of population differentiation at the country level for H. scabra in the Philippines is complex, with nine genetic stocks and respective management units delineated across 5 biogeographic regions: (1) Celebes Sea, (2) North and (3) South Philippine Seas, (4) South China and Internal Seas and (5) Sulu Sea. Genetic connectivity is highest within proximate marine biogeographic regions (mean Fst=0.016), with greater separation evident between geographically distant sites (Fst range=0.041–0.045). Signatures of local adaptation were detected among six biogeographic regions, with genetic bottlenecks at 5 sites, particularly within historically heavily-exploited locations in the western and central Philippines. Genetic structure is influenced by geographic distance, larval dispersal capacity, species-specific larval development and settlement attributes, variable ocean current-mediated gene flow, source and sink location geography and habitat heterogeneity across the archipelago. Data reported here will inform accurate and sustainable fishery regulation, conservation of genetic diversity, direct broodstock sourcing for mariculture and guide restocking interventions across the Philippines.The author(s) declare financial support was received for the research, authorship, and/or publication of this article. Australian Centre for International Agriculture Research (ACIAR) project FIS/2016/122: “Increasing technical skills supporting community-based sea cucumber production in Vietnam and the Philippines”. Philippine Council for Agriculture, Aquatic and Natural Resources Research and Development of the Department of Science and Technology (DOST-PCAARRD: Project Numbers QSR-MR-CUC.02.01 and QSR-MR-CUC.02.02)

Supplementation of commercial probiotic Lactobacillus casei in rearing early-stage silver therapon (Leiopotherapon plumbeus) larvae: Effects on growth, body composition and stress tolerance

Supplementation of probiotics in live feeds and rearing water may improve the growth, survival, and resistance of fish larvae. This study examined the beneficial effect of a commercial probiotic bacteria Lactobacillus casei on the growth, body composition, and stress resistance in early-stage silver therapon (Leiopotherapon plumbeus) larvae. Larvae at 12 d post-hatch (DPH) (9.76 ± 1.32 mm total length [TL] and 13.48 ± 4.80 mg body weight [BW]) were reared in triplicate groups of 15 larvae per tank from 12 – 40 DPH (Phase 1) and 41 – 96 DPH (Phase 2). From 12 – 40 DPH, larvae were fed (I) unenriched Artemia nauplii (no-PB or control group); (II) probiotic-enriched Artemia nauplii (PB); and on (III) probiotic-enriched Artemia nauplii and rearing water (PB + W). The same feeding regime was used from 41 – 96 DPH except that the larvae were co-fed Artemia nauplii and microparticulate diet (MPD). Mean survival rates at 40 (97.78% – 100%) and 96 DPH (86.67% – 91.11%) did not show significant differences among treatments. However, except for body depth (BD) and Fulton’s condition factor (K), mean TL, BW, length increment (LI), and length- (SGRL) and weight-specific growth rates (SGRW) of PB + W-fed larvae were significantly higher than PB-fed and no-PB-fed larvae at 40 DPH. While these parameters were similar among treatment groups at 96 DPH, slightly higher values for BW and SGRW were noted for the PB + W group, as supported by the higher proportion of L. casei to total microbiota in the intestines of early-stage larvae. Whole body protein and lipid contents were highest in the PB + W and PB groups, respectively, but did not differ from the no-PB group. Survival rates (93.33% – 100%) after 18 h exposure to 30 ppt did not show significant differences. However, recovery rates after 15 min of air exposure of early juveniles in the PB and PB + W groups (93.33%) were significantly higher than those fed unenriched Artemia (66.67%). These results indicate that supplementation of probiotic bacteria L. casei in live feed and rearing water may support growth of early-stage larvae of silver therapon and its resistance to stress conditions during culture.Funding for this study was provided by the SEAFDEC Aquaculture Department (Br-02-F2015B). The authors thank R. Celebre and R. Lazartigue for the laboratory assistance

Promoting sustainable aquaculture of freshwater species: The continuous quest for alternative feeds and adoption of feeding strategies

Among farm inputs, feeds are the highest recurring cost in aquaculture. Indeed, feeds have become even more expensive after the COVID-19 pandemic, undeniably affecting the aquaculture economics. The pressing need to alleviate feed costs has to be prioritized, considering its implications for sustained aquaculture production to support the ever-increasing global population. Substantially, the rising costs of manufactured feeds have driven the continuous quest for new alternative feed ingredients in aquafeeds and the adoption of feed management strategies to improve the profitability of aquaculture operations. These two strategies addressed in this study are imperative in promoting freshwater aquaculture among the ASEAN Member States. This article highlights the exploration of feeding trials using alternative protein sources and feeding strategies. Because of their economic relevance to the freshwater aquaculture industry in the Philippines, Nile tilapia, giant freshwater prawn, and tropical anguillid eel, particularly the Pacific shortfin eel, were chosen in this study

Sandfish (Holothuria scabra) as potential reservoir of white spot syndrome virus (WSSV) when co-cultured with black tiger prawn (Penaeus monodon)

Since the first occurrence of White Spot Disease (WSD) in 1992, it is still listed as one of the crustacean diseases by the World Organisation for Animal Health in 2022. Horizontal transmission in co-culture systems is one of the usual modes in the spread of the disease. WSD outbreak was recorded during the experimental run of the co-culture of black tiger prawn (Penaeus monodon) and sandfish (Holothuria scabra) in the grow-out phase. In this study, artificial infection through two cohabitation experiments were conducted to determine if H. scabra is a potential non-crustacean vector or reservoir of WSSV. Samples were checked using one-step and nested PCR for increased readout sensitivity of virus infection to investigate the horizontal transmission between prawn and sandfish. During the first cohabitation (5 days) where WSSV (+) prawn were cohabited with WSSV (-) sandfish, 100% of the prawn were one-step PCR positive for WSSV while 100% of the sandfish were nested PCR positive. Subsequently, WSSV (+) sandfish from the first cohabitation were transferred to another tank to be cohabited with WSSV (-) prawn. Sampling of both prawn and sandfish was done every 6 days post-infection (dpi). At 6 to 18 dpi, prawn and sandfish were nested PCR positive. At 25 dpi, there were no prawns left due to mortality and 1 of the 3 remaining sandfish was nested PCR positive. Based on the results, it elucidates the ability of sandfish to bioaccumulate the viral particles when cohabited with WSSV (+) prawn. Results suggest that WSSV is viable in the sandfish confirming its potential as a vector or reservoir due to the consistent nested PCR positive results of the prawn during the second cohabitation. Hence, it can be inferred that sandfish can be a potential non-crustacean vector or reservoir of WSSV for a limited period of time.Special thanks to SEAFDEC/AQD and JIRCAS for the funding support (6195-T-RD-WATANA), the shrimp farm and sandfish hatchery for providing experimental animals, and the staff of the Fish Health Section for the assistance during the conduct of this study