Tilapia culture: The basics

This new aquaculture extension manual revisits the basics of tilapia culture with updated information on the grow-out technology in cages and ponds. Updated cost and returns analyses were also included to guide farmers regarding the profitability of farming tilapia. A fresh chapter on tilapia health management is also included to promote the prevention of tilapia diseases

Efficacy of the inactivated nervous necrosis virus vaccine against viral nervous necrosis in pond-reared orange-spotted grouper Epinephelus coioides

The field efficacy of the formalin-inactivated nervous necrosis virus (NNV) against viral nervous necrosis (VNN) in orange-spotted grouper (Epinephelus coioides) reared in floating net cages in earthen pond was investigated. Seroneutralization assay conducted on the sera of vaccinated fish exhibited the occurrence of neutralizing antibody titers from Day 30 (mean titer 1:1792±701) to Day 150 (1:704±351) with the highest titer observed at Day 60 (1:6656±3435) post-vaccination. Because mortality attributed to VNN was not encountered during the pond experiment, intramuscular challenges of vaccinated and unvaccinated (L-15 injected) fish with NNV (106.5 TCID50/fish) were conducted in indoor tanks at Day 30 (Mean body weight [MBW]: vaccinated [21±3.4 g]; unvaccinated [20.6±1 g) and Day 120 (MBW: vaccinated [178±27 g]; unvaccinated [176±19 g) postvaccination, respectively, to demonstrate the in vivo efficacy of the inactivated vaccine. Nil and 25 % mortality rate were obtained in vaccinated and control fish, respectively, challenged with NNV at Day 30 post-vaccination. On the contrary, nil mortality were obtained in both groups challenged with NNV at Day 120 post-vaccination. Although nil mortality was obtained in NNV-challenged unvaccinated fish, 30 % of the fish manifested dark coloration of the skin and abnormal swimming behavior that commenced and disappeared at Day 3 and Day 7 post-NNV challenge, respectively, suggesting an age/ weight-dependent resistance to the disease. Our current data illustrate that single vaccination with inactivated vaccine could mount the production of protective antibodies and concomitant conferment of protection against VNN in groupers especially during the early phase of grow-out culture in earthen ponds where they are highly susceptible to the disease.This study was funded by Government of Japan Trust Fund VI through the Regional Fish Disease Project (study code: FH01- F2015-T) and in part by SEAFDEC/ AQD. We express our heartfelt gratitude to Dr. Takuro Shibuno and Dr. Chihaya Nakayasu, former GOJ-TF managers, Dr. Koh Ichiro Mori, current GOJ-TF manager, and the Marine Fish Hatchery staff especially Mr. A. Gamuza

Edwardsiellosis

Edwardsiellosis is an acute to chronic systemic disease in fish characterized by exophthalmia, ascites, hernia, and severe lesions of the internal organs. It is caused by Edwardsiella tarda, a Gram-negative intracellular pathogen implicated in enormous economic losses of cultured seawater and freshwater fish species. E. tarda has a broad host range and geographic distribution, and possesses important virulence factors that enhance its survival and pathogenesis in hosts. This chapter discusses some of the recent research on edwardsiellosis in fish including the etiologic agent's identification, pathology, diagnosis, and virulence factors, and as well as novel strategies aimed at preventing and controlling the disease

Viral encephalopathy and retinopathy

Viral nervous necrosis (VNN), also referred to as viral encephalopathy and retinopathy (VER), has been reported in at least 120 cultured or wild marine and freshwater fish species and has caused serious economic losses among farmed marine fish species in the past decades. Since the first description of this disease at the end of the 1980s, substantial amounts of researches have been instrumental in understanding the mechanisms involved in fish infection, development of reliable diagnostic methods, and disease prevention and control. This chapter presents some important aspects of the disease with particular emphasis on etiologic agent, clinical signs and gross pathology of the disease, histopathology, disease risk factors, virus propagation and identification, molecular diagnostics, and concomitant prevention and control methods

Aeromonas load and species composition in tilapia (Oreochromis niloticus) cultured in earthen ponds in the Philippines

Aeromonas load and species composition in the rearing water, sediment, gills and intestines of healthy tilapia Oreochromis niloticus collected every 2 weeks from Days 30 to 120 after stocking in six earthen ponds in the Philippines were determined. Presumptive Aeromonas counts (PACs) in the water and sediment ranged from 101–103 c.f.u./ml and 101–103 c.f.u./g while in the gills and intestines, PACs ranged from 104–107 c.f.u./g and 102–105 c.f.u./g, respectively. Presumptive Aeromonas counts in the water, sediment, and gills of tilapia varied among days of culture while in the intestines of tilapia, PACs markedly dropped by approximately 2 logs at Day 75 and either remained in the same level or decreased by another 1 log at Day 120 of grow‐out culture. Aeromonas hydrophila predominantly constituted 94% of all presumptive Aeromonas spp. examined (n = 343), followed by A. sobria (4%) and A. salmonicida (2%). Taken together, current data provide some putative threshold levels of tilapia reared in earthen ponds to Aeromonas spp. The dominance of A. hydrophila together with negligible population of A. salmonicida and A. sobria indicate that Aeromonas are common commensal bacteria in tilapia and their environment which under conditions of stress could instigate disease epizootics.This study was funded by the Department of Science and Technology-National Research Council of the Philippines (DOST-NRCP; NRCP project no. E-225) and partly by SEAFDEC AQD (study code: FH02-F2013-T). We would like to thank Dr. Evelyn Grace de Jesus-Ayson for the critical review of the manuscript, and Mr. Eric Ledesma and the laboratory staff of NPPMCI for the invaluable assistance during our sampling

Environmental and other non-infectious diseases

The chapter presents some of the environmental non-infectious diseases of aquatic animals. Non-infectious diseases are caused by adverse environmental conditions, nutritional disorders, or genetic defects. While they can result a sudden mass mortality or death, they are not contagious. Environmental diseases are the most important in aquaculture. This includes low dissolved oxygen, high ammonia, high nitrite, or natural or man-made toxins in the aquatic environment

Quantitative and qualitative analyses of the bacterial microbiota of tilapia (Oreochromis niloticus) cultured in earthen ponds in the Philippines

The quantity and composition of the bacterial microbiota in the rearing water, sediment, gills and intestines of tilapia Oreochromis niloticus collected every 2 weeks from Day 30 to Day 120 after stocking for grow-out culture in 6 earthen brackish water ponds in the Philippines were examined. The total heterotrophic aerobic bacterial counts obtained in the water, sediment, gills and intestines of tilapia ranged from 103 to 104 c.f.u. ml−1, 103–105, 105–107 and 104–107 c.f.u. g−1, respectively. In terms of composition, a total of 20 bacterial genera and 31 species were identified with the preponderance of gram-negative bacteria constituting 84% of all bacterial isolates examined. Aeromonas hydrophila, Bacillus spp., Plesiomonas shigelloides, Shewanella putrefaciens, Pseudomonas fluorescens, Staphylococcus spp. and Vibrio cholerae were the dominant bacteria identified in the gills and intestine of tilapia. These bacteria also dominated in the pond sediment and rearing water, except for the nil isolation of S. putrefaciens and V. cholerae in the water samples examined, indicating that resident bacteria in the pond water and sediment congruently typify the composition of bacterial microbiota in the gills and intestine of tilapia which under stressful conditions may propel the ascendance of disease epizootics

Studies on the efficacy of Sarafin® (sarafloxacin hydrochloride) on vibrios associated with vibriosis in black tiger shrimp (Penaeus monodon)

In vitro activity of Sarafin® (sarafloxacin hydrochloride) was determined against 7 luminous Vibrio harveyi isolates and 3 non-luminous Vibrio species (V. parahaemolyticus, V. alginolyticus and Vibrio species) isolated from diseased shrimp (Penaeus monodon) and rearing water, a strain of V. anguillarum from diseased marine fish, 1 strain each of V. alginolyticus, V. vulnificus, and V. mimicus from diseased grouper (Epinephelus coioides), and V. alginolyticus from diseased seabass (Lates calcarifer). Bacterial susceptibility was expressed as minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The MIC and MBC values obtained for all V. harveyi isolates ranged from 50 µg/ml Sarafin®. These results indicate that Sarafin® is a potential candidate as a chemotherapeutic agent against luminous vibriosis in P. monodon

Supporting ASEAN good aquaculture practices: Preventing the spread of trans-boundary aquatic animal diseases

The FAO Fishery Statistics had indicated that Asia is the top producer of fish and fishery products from both capture fisheries and aquaculture. Specifically, Southeast Asia had contributed 9-31% of the total aquaculture production in Asia from 1950 to 2014 with Indonesia and the Philippines accounting for the most at 23-63% and 10-45% of the total, respectively. Aquaculture has been viewed as a solution to the growing concern on food security issues as well as for the socio-economic stability of many countries in Southeast Asia. For such reason, aquaculture operations are being intensified to compensate for the declining production from capture fisheries and in order to nail the gap between supply and demand for fish and fishery products in the world. With intensification, aquaculture production has already overtaken the contribution of capture fisheries to the world’s total fisheries production. However, concerns on the safety and quality of aquaculture products have been raised as result of intensified fish farming operations. Added to such concern is the irresponsible introduction of aquatic species for aquaculture that serve as carriers of pathogens. As a result, a large number of infectious aquatic diseases have emerged threatening the sustainability of aquaculture in the Southeast Asian region. In an effort to address the emergence of transboundary diseases in the region, the Aquaculture Department of SEAFDEC (SEAFDEC/AQD) launched a program on Healthy and Wholesome Aquaculture which includes as one of its main objectives, the need to continue improving aquaculture production through innovations in fish health management