Tilapia Cage Culture Research Articles

Effect of the Booming Tilapia Cage Culture on The Water Quality in Selected Bays of The Bukavu Basin, Lake Kivu, Democratic Republic of The Congo

Effect of the Booming Tilapia Cage Culture on The Water Quality in Selected Bays of The Bukavu Basin, Lake Kivu, Democratic Republic of The Congo

Optimizing feed restriction strategies for profitable Oreochromis niloticus culture in floating cages in riverine ecosystems

High feed cost is a major obstacle for promoting the growth of nutrient-rich fish species like Nile tilapia (Oreochromis niloticus) in cage aquaculture. To address this issue, cage farming of O. niloticus was studied for a 75-day period in the Gurukchi River of Bangladesh. Three different feeding strategies (FS) were tested in floating cages: FS5- weekly restriction on feed supply for two days, FS6- weekly restriction on feed supply for one day, and FS7- no weekly restriction on feed supply, with three replications for each treatment. Water quality parameters were monitored weekly and found within suitable levels for fish cultivation. The analysis of length–weight relationship and the condition factor of O. niloticus showed positive allometric growth regardless of the diverse feeding tactics employed that consistently exhibit stability across all treatments. Both FS6 and FS7 had significantly higher (p < 0.05) final individual length, final individual weight, net yield, total yield, and specific growth rate than FS5. FS6 yielded significantly higher fish production with significantly lower feed conversion ratio than FS7. Economic analysis revealed the highest benefit–cost ratio and net revenue in FS6, recommending its use to minimize the need for supplemental feed and reduce production costs in tilapia cage culture.

Molecular epidemiology and current management of Infectious Spleen and Kidney Necrosis Virus (ISKNV) infection in Ghanaian cultured tilapia

Infectious Spleen and Kidney Necrosis Virus (ISKNV) is globally gaining more attention, due to its highly significant economic impact on the aquaculture industry. In late 2018, unusually high levels of mortality (60–90%) was reported in some intensive tilapia cage culture systems on the Eastern bank of Lake Volta in Ghana. This resulted in the fold-up of several small and medium scale farms. Preliminary investigations confirmed the involvement of ISKNV, a viral pathogen noted for fatal systemic infections in many fish species. As a follow-up on the outbreak situation, and post-mass vaccination of affected fish farms, the need to investigate further the molecular epidemiology and phylogeography of the virus across Lake Volta became paramount. A multiplexed PCR assay to detect the virus and MinION™ nanopore sequencing of the Major Capsid Protein (MCP) were performed to investigate the presence and genotype of ISKNV in tilapia collected from 30 randomly selected farms at various geographical locations. ISKNV was found to be widely distributed across the lake and detected in 80% of farms with a reported average daily mortality of 40%. Fry and juvenile fish were the most affected, and approximately 50% of fish that tested positive were asymptomatic. These apparently healthy fish are likely contributors of virus transmission across farms. Phylogenetic analysis of the MCP revealed that all 35 isolates from 14 different farms distributed across the lake clustered with ISKNV clade I with 100% homology to isolates from the 2019 outbreak strain. Vaccination and heat-shock treatment; the two main specific interventions currently employed to control the viral pathogen have not achieved much success, and ISKNV remains a threat to the growth of the aquaculture industry in Ghana. The outcome of this study can be useful in improving fish health management and biosecurity policies in the aquaculture industry.

Economic valuation of ecosystem services trade-offs of tilapia cage culture farm and native capture fisheries in Lake Maninjau, Indonesia

Research on the effects of cage aquaculture on native fish populations has revealed its negative and positive impacts. However, a separate analysis of its ecological and economic effects creates incomplete information for the decision-makers. Moreover, the inadequacy of time series data has caused challenges to knowledge-based decision-making in establishing new cage aquaculture sites, especially in low-middle income countries. We use the ecosystem services (ES) framework to analyse the synergy and trade-off of cage aquaculture to a native fish species, Gobiopterus sp. in Lake Maninjau, Indonesia, as an effort to provide comprehensive information to support local decision-makers and to fill the information gap. We engaged some modelling techniques such as the Maximum Entropy Model (MaxEnt) validated with field survey data, Bayesian Networks (BN), and Monte Carlo Simulation (MCS) in this research. The results show that cage aquaculture provides habitat services for the species and temporary forgone fish production due to the accelerated sulfur upwelling. The economic value of habitat provision reached 74,500 IDR per year per cage or 1,128 million IDR per year in 2017. Further, the average value of the forgone benefit of fish production in the current cage aquaculture business extends from more than 550 million IDR per year in the dry season to almost 600 million IDR per year in the rainy season. The results indicate that the negative impacts of cage aquaculture on the native fish population outweigh its benefit. The recommendation for management actions includes applying alternative aquaculture techniques and other technological interventions.

Economic and financial risks of commercial tilapia cage culture in a neotropical reservoir

The aim of this study was to analyze the financial and economic risks of tilapia cage culture across different production water volumes (m³). The production water volumes evaluated were 10 to 50 thousand m³ (Small Volume, SV), 51 to 150 thousand m³ (Medium Volume, MV), 151 to 300 thousand m³ (Large Volume, LV), and >301 thousand m³ (Extra-Large Volume, ELV). Productivity and economic data were obtained from a commercial Nile tilapia cage farm with 232 net cages installed in a neotropical reservoir, in Brazil, from 2017 to 2019. Cost and profitability analyses, economic feasibility, and risk and sensitivity analyses were performed using a Monte Carlo simulation. The implementation of commercial tilapia cage farming relies mainly on feed prices. The initial investment demand is proportional to the size of the farms. On the other hand, MV, LV, and ELV tilapia farms showed the lowest financial risks despite the higher investments. These farms presented a medium-low risk at ≈39% probability, whereas the SV farm presented a medium to medium-high risk at 51.17% probability. Thus, fish farms with a production volume above 51 thousand m³ tend to be more profitable and have a ≈36% probability of low financial and economic risk with a Payback period of fewer than 10 years, mainly due to the lower feed costs per mass of fish produced. This study assists investors in choosing a better path toward a more viable and profitable activity.

A Multiplexed, Tiled PCR Method for Rapid Whole-Genome Sequencing of Infectious Spleen and Kidney Necrosis Virus (ISKNV) in Tilapia.

Tilapia farming is one of the most important sectors in aquaculture worldwide and of major importance to global food security. Infectious spleen and kidney necrosis virus (ISKNV) has been identified as an agent of high morbidity and mortality, threatening tilapia aquaculture. ISKNV was detected in Lake Volta, Ghana, in September 2018 and spread rapidly, with mortality rates between 60 and 90% and losses of more than 10 tonnes of fish per day. Understanding the spread and evolution of viral pathogens is important for control strategies. Here, we developed a tiled-PCR sequencing approach for the whole-genome sequencing of ISKNV, using long read sequencing to enable field-based, real-time genomic surveillance. This work represents the first use of tiled-PCR for whole genome recovery of viruses in aquaculture, with the longest genome target (>110 kb dsDNA) to date. Our protocol was applied to field samples collected from the ISKNV outbreaks from four intensive tilapia cage culture systems across Lake Volta, between October 2018 and May 2022. Despite the low mutation rate of dsDNA viruses, 20 single nucleotide polymorphisms accumulated during the sampling period. Droplet digital PCR identified a minimum requirement of template in a sample to recover 50% of an ISKNV genome at 275 femtograms (2410 viral templates per 5 µL sequencing reaction). Overall, tiled-PCR sequencing of ISKNV provides an informative tool to assist in disease control in aquaculture.

Emergence of colistin resistance and characterization of antimicrobial resistance and virulence factors of Aeromonas hydrophila, Salmonella spp., and Vibrio cholerae isolated from hybrid red tilapia cage culture.

Tilapia is a primary aquaculture fish in Thailand, but little is known about the occurrence of antimicrobial resistance (AMR) in Aeromonas hydrophila, Salmonella spp., and Vibrio cholerae colonizing healthy tilapia intended for human consumption and the co-occurrence of these AMR bacteria in the cultivation water. This study determined the phenotype and genotype of AMR, extended-spectrum β-lactamase (ESBL) production, and virulence factors of A. hydrophila, Salmonella spp., and V. cholerae isolated from hybrid red tilapia and cultivation water in Thailand. Standard culture methods such as USFDA's BAM or ISO procedures were used for the original isolation, with all isolates confirmed by biochemical tests, serotyping, and species-specific gene detection based on PCR. A total of 278 isolates consisting of 15 A. hydrophila, 188 Salmonella spp., and 75 V. cholerae isolates were retrieved from a previous study. All isolates of A. hydrophila and Salmonella isolates were resistance to at least one antimicrobial, with 26.7% and 72.3% of the isolates being multidrug resistant (MDR), respectively. All A. hydrophila isolates were resistant to ampicillin (100%), followed by oxytetracycline (26.7%), tetracycline (26.7%), trimethoprim (26.7%), and oxolinic acid (20.0%). The predominant resistance genes in A. hydrophila were mcr-3 (20.0%), followed by 13.3% of isolates having floR, qnrS, sul1, sul2, and dfrA1. Salmonella isolates also exhibited a high prevalence of resistance to ampicillin (79.3%), oxolinic acid (75.5%), oxytetracycline (71.8%), chloramphenicol (62.8%), and florfenicol (55.3%). The most common resistance genes in these Salmonella isolates were qnrS (65.4%), tetA (64.9%), bla TEM (63.8%), and floR (55.9%). All V. cholerae isolates were susceptible to all antimicrobials tested, while the most common resistance gene was sul1 (12.0%). One isolate of A. hydrophila was positive for int1, while all isolates of Salmonella and V. cholerae isolates were negative for integrons and int SXT. None of the bacterial isolates in this study were producing ESBL. The occurrence of mcr-3 (20.0%) in these isolates from tilapia aquaculture may signify a serious occupational and consumer health risk given that colistin is a last resort antimicrobial for treatment of Gram-negative bacteria infections. Findings from this study on AMR bacteria in hybrid red tilapia suggest that aquaculture as practiced in Thailand can select for ubiquitous AMR pathogens, mobile genetic elements, and an emerging reservoir of mcr and colistin-resistant bacteria. Resistant and pathogenic bacteria, such as resistance to ampicillin and tetracycline, or MDR Salmonella circulating in aquaculture, together highlight the public health concerns and foodborne risks of zoonotic pathogens in humans from cultured freshwater fish.

Impacts of Nile tilapia cage culture on water and bottom sediment quality: The ability of an eutrophic lake to absorb and dilute perturbations

AbstractEnvironmentally sustainable aquaculture depends on accurate understanding of the impacts of aquaculture‐derived organic matter (AOM) and the ability of aquaculture systems to absorb and dilute perturbations. To this end, the present study assessed the impacts of AOM from cage culture of Nile tilapia on the ecology of Lake Victoria, Kenya, using fish cages near Anyanga Beach in Siaya County from December 2018 to October 2019. Four locations were surveyed for organic loadings from cage cultures, located 0, 50, 150 and 500 m (as a control site) away from the cages. The cage aquaculture produced increased P and N concentrations near the cages and a decreased N:P molar ratio. These changes stimulated algal growth which, in turn, affected the water quality. The organic material accumulated on the bottom under the cages, increasing the benthic BOD (BOD, &gt;10 mg/g), a sensitive indicator of the ecological footprint of the cage aquaculture. Further, the negative ORP observed in the benthic layer suggested anoxic bacterial metabolism, possibly causing build‐up of sulphides and methane. These changes altered the abundance and composition of both limnetic and benthic communities. At the beginning of the study, 22 zoobenthic taxa existed around the cages and 18 at the reference sites. Only 3 saprophilous taxa, chiefly gastropods (Physellaspp.), bivalves (Sphaeriumspp.) and oligochaetes (Tubifexspp.) were present at the cage site and 17 at the reference site at the end of the culture period. The Shannon diversity index exhibited a declining tendency with the length of culture period at the cage site, signifying a negative impact of aquaculture on biodiversity. The water quality recovery after cage disturbance is rapid (&lt;4 months), noting there was no significant difference in the water quality recorded at the cage site and the other sampling sites after a fallow period of 4 months. However, the recovery of the sediment and meiofauna was far from complete at the end of this period. Moving the cages slightly (50–100 m) away from the former location may allow the benthic communities to recover and alleviate the problem. Further, the fallowing period, particularly for the Anyanga Beach site, should be extended from four to at least 5 months to allow for the environment to recover. With the rapid increase of cage fish farming in the African Great Lakes Region and with the potential for its occurrence in other lakes, there is a need to develop regulations to guide the industry, as well as the need for continuous monitoring of the environment, in order to provide information to guide investments and ensure sustainable cage farming.

Effect of Different Stocking Density on Growth and Survival of Monosex Tilapia Cage Culture in Perumpallam Reservoir, Tamil Nadu

Effect of Different Stocking Density on Growth and Survival of Monosex Tilapia Cage Culture in Perumpallam Reservoir, Tamil Nadu

A technical and economic evaluation of supplemental feeding strategies for Nile tilapia (Oreochromis niloticus L.) reared in lake-based cages

Tilapia cage farming in eutrophic lakes uses low stocking densities since tilapias can thrive mainly on natural food or minimal supplementary feeding. For semi-intensive Nile tilapia cage culture, feeding strategies to improve productivity are adopted based on technical viability and cost efficiency, as assessed in the present study. Tilapia fingerlings stocked in triplicate cages per treatment were reared in Laguna de Bay, Philippines for five months, one run each during the dry and wet seasons. The treatments were: I – UNFED or no feeding; II - FED, fish fed for the entire 155 days; III - D45, fish fed from day 45 to harvest; and IV - D75, or fish fed from day 75 to harvest. Average weight gain or AWG (153.18 g and 225.85g, for dry and wet seasons, respectively) were highest in FED. Growth parameters in all fed treatments were significantly higher (p&lt;0.05) than in UNFED for both seasons. Survival rates were higher during the wet season (66-70%) compared to the dry season (35-37%). Moreover, in the wet season, when the lake’s primary productivity is low, full feeding can be done without compromising lake water quality. Results showed that it favored high AWG, survival, reasonable market price, and profit.

Geospatial Assessment of Site Suitability for Tilapia Cage Culture in Cross River State, Nigeria

Geospatial Assessment of Site Suitability for Tilapia Cage Culture in Cross River State, Nigeria

Bioeconomic and Financial Risks of Commercial Tilapia Cage Culture in Neotropical Reservoir for Aquaculture Investors

Bioeconomic and Financial Risks of Commercial Tilapia Cage Culture in Neotropical Reservoir for Aquaculture Investors

Risk of Climate Variability on Tilapia Cage Culture in Songkhram River in Northeastern Thailand

The cage culture of Nile Tilapia in the river is one of the most important methods for Nile Tilapia (Oreochromis niloticus) farming in Thailand. Songkhram river is a significant river in north-eastern Thailand where Nile Tilapia river-based cage culture has been applied widely. However, river-based cage culture is an open culturing system where farmers do not fully control weather and water quality. This study investigates the risks of climate variability on Nile Tilapia in riv-er-based cage culture. This study recommends strategies to reduce fish yield losses. The samples of this study are the Nile Tilapia river-based cage culture farmers along the Songkhram river in 5 districts in Sakon Nakhon and Nakhon Phanom, including Thauthen, Khamtakla, Akatamnuai, Sisongkhram and Nathom. This study applies a simple random sampling method. We used structured questionnaires to collect the data from 148 fish farmers between April and December 2017. Hot weather during March and April was perceived to be the most important factor causing fish diseases and led to losses (68.2 %). The other significant factors that led to fish death were drought (52.7 %) and flood (40.5 %). Flood typically takes place between June and August. Cold weather was perceived not to affect the fish losses (32.4 %). However, it did affect the growth rate. Cold weather typically takes place between December and February. Re-garding the hot weather, fish farmers applied preventive measures such as mon-itoring and surveillance, stopping or delaying stocking schedules. For drought, the fish farmers relocated the cages towards the deeper water areas and used aerators to control water quality. Most farmers tie their cages securely during flooding season and relocate them closer to the bank. The fish farmers moni-tored their cages more closely than usual for the cold weather and postponed the stocking date. The study of risks and loss mitigation from climate variabilities in this research will be helpful for strategic aquaculture planning to cope with cli-mate variabilities in the future.

Challenges for the development of environmentally sustainable cage culture farming in Lake Maninjau, Indonesia: an institutional perspective

ABSTRACT The environmental condition of Lake Maninjau, a complex tropical system in Indonesia, has been suffering from the proliferation of tilapia cage culture practices. The area around the lake is inhabited by the Minangese ethnic group, which has strong customary laws and clan system. Applying the Institutional Analysis and Development (IAD) framework and based on face-to-face semi-structured interviews, this paper aims to understand the challenges for the development of environmentally sustainable cage culture farming. Our institutional analysis reveals that the main challenges are low levels of trust between communities and officials, and conflicting formal and informal institutions which have prevented the emergence of strong rules-in-use. This is a particularly interesting theoretical contribution to the literature on the management of common pool resources (CPR), as our case study is an example of private property farming in a common pool resource (the lake), a dynamic which remains understudied in the CPR literature. We provide suggestions for local stakeholders as well as regional and national government related to the importance of seeking local legitimacy of the working rules to govern cage culture. The lessons learned from this case study might be useful for the governance of aquaculture in other lakes in Indonesia and countries of the Global South.

Climate change-related risk adaptation in striped catfish, tilapia and shrimp farming systems in the Mekong Delta, Vietnam

This study aims to determine climate change-related risk (CCR) impacts, responses of farmers, and assistant activities in tilapia cage culture (TC), striped catfish nursery (SCN), striped catfish grow-out (SCG), improved extensive shrimp (IES) and intensive shrimp (IS) systems. A survey of 601 farmers in the Mekong Delta, Vietnam, was conducted using clustered sampling. Intense rainfall events and rapid changes in temperature affected all five surveyed farm systems. Extreme high temperatures impacted the TC, IES and IS systems, while extreme low temperatures impacted the striped catfish groups (SCN and SCG). Striped catfish farming systems were more sensitive to low temperatures in comparison to shrimp and tilapia. For risk management purposes, increasing pond dike height was applied in the SCN and SCG farming systems. While increased pond depth was observed in the SCN, SCG and IS systems, the IS and SCN systems had higher counts of additional pond construction. Water quality was monitored and feed supplements/medicines were used by farmers in all five farm systems; however, these activities were higher for the SCN, SCG and IS systems than for the TC and IES groups. Reduced stocking density was observed in TC, SCN, SCG and IS, but not in IES. In addition, the use of aerators or mixers was the most-employed solution in the IS system. Amongst information sources of climate-related risks, television was found to be the most important, followed by neighbouring farmers and the Department of Fisheries (DOF)...

A GIS‐based approach for delineating suitable areas for cage fish culture in a lake

AbstractWe present a GIS‐based approach to the delineation of areas that have different levels of suitability for use as tilapia cage culture sites the Kenyan part of Lake Victoria, Africa. The study area was 4,100 km2. The method uses high‐resolution bathymetric data, newly collected water quality data from all major fishing grounds and cage culture sites, and existing spatial information from previous studies. The parameters considered are water depth, water temperature, levels of dissolved oxygen, chlorophyll‐aconcentrations, distances to the lake shoreline and proximity to other constraints on cage culture development. The results indicated that the area most suitable for fish cages comprised about 362 km2, or approximately 9% of the total area; the remaining 91% (i.e., 3,737 km2) was found to be unsuitable for tilapia cage culture. We conclude that the successful implementation of this approach would need stakeholder involvement in the validation and approval of potential sites, and in the incorporation of lake zoning into spatial planning policy and the regulations that support sustainable use while minimising resource use conflicts. The results of this study have broader applicability to the whole of Lake Victoria, other African Great Lakes, and any lakes in the world where tilapia cage culture already occurs or may occur in the future.

Economic analysis of tilapia cage culture in Lake Victoria using different cage volumes

ABSTRACT The economic viability of tilapia cage culture in Lake Victoria was assessed using a profitability analysis model as the main decision support tool. One and five cages of 8 m3 (A), 62.5 m3 (B), and 471 m3 (C) were assessed. The break-even price (US$4.6 kg−1) for one cage of A appeared higher than the tilapia farm gate price in Kenya (US$3.5 kg−1), suggesting unprofitability of the venture. The decreased break-even price relative to increase in cage numbers showed economies of scale throughout the cage volume ranges. The longest payback period (PBP) for A (8 years) implied a risky venture. This was reaffirmed by an internal rate of return (IRR) of < 50% and negative Net present value (NPV) in the first two years of operations. The study affirmed the economic viability of operating large cage volumes (B or C) for Nile tilapia and for broader applicability to other Great Lakes.

First detection of infectious spleen and kidney necrosis virus (ISKNV) associated with massive mortalities in farmed tilapia in Africa.

In late 2018, unusual patterns of very high mortality (>50% production) were reported in intensive tilapia cage culture systems across Lake Volta in Ghana. Samples of fish and fry were collected and analysed from two affected farms between October 2018 and February 2019. Affected fish showed darkening, erratic swimming and abdominal distension with associated ascites. Histopathological observations of tissues taken from moribund fish at different farms revealed lesions indicative of viral infection. These included haematopoietic cell nuclear and cytoplasmic pleomorphism with marginalization of chromatin and fine granulation. Transmission electron microscopy showed cells containing conspicuous virions with typical iridovirus morphology, that is enveloped, with icosahedral and/or polyhedral geometries and with a diameter c.160 nm. PCR confirmation and DNA sequencing identified the virions as infectious spleen and kidney necrosis virus (ISKNV). Samples of fry and older animals were all strongly positive for the presence of the virus by qPCR. All samples tested negative for TiLV and nodavirus by qPCR. All samples collected from farms prior to the mortality event were negative for ISKNV. Follow‐up testing of fish and fry sampled from 5 additional sites in July 2019 showed all farms had fish that were PCR‐positive for ISKNV, whether there was active disease on the farm or not, demonstrating the disease was endemic to farms all over Lake Volta by that point. The results suggest that ISKNV was the cause of disease on the investigated farms and likely had a primary role in the mortality events. A common observation of coinfections with Streptococcus agalactiae and other tilapia bacterial pathogens further suggests that these may interact to cause severe pathology, particularly in larger fish. Results demonstrate that there are a range of potential threats to the sustainability of tilapia aquaculture that need to be guarded against.

Evaluation of oxygen budget and mechanical aeration requirements of red tilapia cage-culture in earthen ponds

Evaluation of oxygen budget and mechanical aeration requirements of red tilapia cage-culture in earthen ponds

Evaluation of oxygen budget and mechanical aeration requirements of red tilapia cage-culture in earthen ponds

Evaluation of oxygen budget and mechanical aeration requirements of red tilapia cage-culture in earthen ponds