Search Results (21)

We investigated the occurrence of Radiospongilla inesi in a tilapia aquaculture facility located at the Chavantes Reservoir, Paranapanema River, Brazil. Specimens were collected from both artificial (net cages) and natural substrates along the reservoir margins in October and November 2024. Morphological analyses of 8 sponge samples, including 20 structures per sample (gemmules, megascleres, microscleres and spicules), identified the species as Radiospongilla inesi (Spongillidae). This is the third documented record of R. inesi in Brazil, and the first within the Paraná River Basin and in aquaculture net cage systems. Morphological features were consistent between individuals from natural and artificial substrates, although gemmules were absent in specimens colonizing the cages. The proliferation of R. inesi poses biofouling challenges by obstructing cage mesh openings, reducing water flow and dissolved oxygen levels, and potentially compromising fish welfare and production efficiency. These impacts increase operational costs and highlight the need for sustainable management strategies in freshwater aquaculture. Additionally, this study raises questions regarding the species’ native status in the Paraná Basin versus potential invasive dispersal, emphasizing the need for further ecological and distributional investigations. Potential dispersal mechanisms and possible biofouling impacts are discussed, with recommendations for future quantitative and molecular studies. Full article

This study examined long-term trends (1991–2019) in landings and fish community structure in the four Egyptian Nile Delta lakes. Using fisheries data, we explored trends in the catch per unit effort (CPUE) and temporal dynamics of landings and fishing effort. Non-metric Multidimensional Scaling (nMDS) and Similarity Percentage Analysis (SIMPER) were employed to assess long-term changes in fish community structure. The results revealed variable productivity across the lakes. Lake Manzala often exhibited higher yields between 1991 and 2004, and notably in 2013 (e.g., 62,372 tons), while Lake Burullus peaked at 81,399 tons in 2019. A reciprocal trend was often observed in their total yields. Lake Burullus catches were dominated by Tilapia and Mullets, while Edku and Mariout showed lower productivity. CPUE patterns varied, with Lake Manzala showing a notable increase, peaking at approximately 52 tons per boat per year in 2013, and Lake Burullus experienced a sharp increase to about 29 tons per boat per year in 2019. A shift towards amateur fishing was observed predominantly in Lake Manzala, alongside a decline in traditional licensing. An increase in fishers operating without boats was also noted across all the Northern Lakes, with contributions from Lake Edko and Lake Manzala. nMDS and SIMPER analyses revealed distinct temporal groupings of years within each lake, indicating significant shifts in fish community structure, likely in response to invasive species, pollution, and habitat degradation. These findings underscore the need for lake-specific management and long-term monitoring to address unsustainable fishing and ecological changes, ensuring biodiversity conservation and fisheries sustainability in the region. Full article

A total of 32 fish species were detected in Xinglin Bay using a combination of environmental DNA metabarcoding (eDNA) and traditional morphological survey methods (TSM), covering eight orders, fifteen families, and twenty-six genera. The dominant order was Perciformes, accounting for 43.75% of the total species. Among the identified species, there were ten non-native fish species. Compared with the TSM, the eDNA detected 13 additional fish species, including two additional non-native fish species—Gambusia affinis (Baird and Girard, 1853) and Micropterus salmoides (Lacepède, 1802). In addition, the relative abundance of fish from both methods revealed that tilapia was overwhelmingly dominant, accounting for 80.75% and 75.68%, respectively. Furthermore, the AS-ISK assessment revealed that all non-native fish species were classified as medium or high-risk, with five identified as high-risk species, four of which belong to tilapia. These findings demonstrated that tilapia are the dominant and high-risk invasive species in Xinglin Bay and should be prioritized for management. Population reduction through targeted harvesting of tilapia is recommended as the primary control strategy. Additionally, the study highlights the effectiveness of eDNA in monitoring fish community structure in brackish ecosystems. Full article

This study examined the behavioral responses of Nile Tilapia (Oreochromis niloticus), a key aquaculture species, to ammonia stress using non-invasive image processing techniques. The experiment was conducted under controlled laboratory conditions and involved four groups exposed to ammonium chloride concentrations (0, 100, 200, and 400 mg·lt⁻¹). Movement trajectories of individual fish were recorded over 10 h using high-resolution cameras positioned above and beside glass tanks. Images were processed with the Optical Flow Farneback algorithm in Python, implemented in Visual Studio Code with OpenCV and NumPy libraries, achieving a 91.40% accuracy rate in tracking fish positions. The results revealed that increasing ammonia levels restricted movement areas while elevating movement irregularity and activity. The 0 mg·lt⁻¹ group utilized the glass tank homogeneously, covering 477 m. In contrast, the 100 mg·lt⁻¹ group showed clustering in specific areas (796 m). At 200 mg·lt⁻¹, clustering intensified, particularly along the glass tank’s left edge (744 m), and at 400 mg·lt⁻¹, fish exhibited severe restriction near the water surface with markedly increased activity (928 m). Statistical analyses using Kruskal–Wallis and Dunn tests confirmed significant differences between the 400 mg·lt⁻¹ group and others. No difference was observed between the 0 mg·lt⁻¹ and 100 mg·lt⁻¹ group, indicating tolerance to lower concentrations. The study highlights the importance of ammonia levels in water quality management and reveals the potential of image processing techniques for automation and stress monitoring in aquaculture. Full article

In aquaculture practices, fish are mostly protected from lethal actions of predators. However, sub-lethal effects can be challenging to prevent, as they may be associated with chemical cues signaling predation risk that easily dissolve and spread in water, serving as potential stressors. These cues originate from predators, stressed or injured prey releasing blood, a conspecific alarm substance (CAS), and/or other bodily fluids. In this study, we simulated a small-scale net cage system and assessed the feeding and growth of Nile tilapia exposed chronically to a CAS. Nile tilapia, an invasive species in many aquatic systems, frequently coexist freely alongside those cultivated in cages. Consequently, caged tilapia may regularly be exposed to a CAS, potentially leading to chronic stress and impacting growth and development. Fish were exposed daily to either a CAS or a control vehicle (distilled water) for 45 days (one fish per cage). Fish in both conditions exhibited similar increases in body mass, weight gain, and length over time and displayed an allometric negative growth profile, indicating that the CAS did not affect the length–weight relationship as well. Specific and relative growth rates, condition factor, body axes, food intake, and feeding conversion efficiency were also unaffected by the CAS over time. This body of evidence suggests that the CAS did not act as a chronic stressor for caged Nile tilapia and a possible explanation is habituation. Full article

Non-native fish species introduced into new areas, especially when they develop into large populations, pose a threat to native fauna. Understanding the current status of the fish community and invasion risks of non-native fish are essential for invasive species control and diversity conservation. The community structure of fish and a risk assessment on 10 non-native fish species were systematically assessed in the Jiulong River Basin, China, in January, April, and July of 2024. The species richness, with 105 species, showed a notable decrease compared to the 124 species recorded in 1975, while the number of non-native species has increased from zero to ten. Furthermore, the non-native fish species, Coptodon zillii and Sarotherodon galilaeus, have become dominant species, with IRI values of 4038.43 and 1180.30, respectively. The AS-ISK established risk thresholds for BRA and BRA + CCA as 29.5 and 35.5, respectively, identifying 70% of the non-native fish species as high-risk species, including C. zillii, S. galilaeus, Oreochromis niloticus, Clarias batrachus, Hypostomus plecostomus, and Oreochromis aureus. This study indicates that the fish species richness in the Jiulong River Basin has declined, with C. zillii and S. galilaeus becoming dominant and posing high ecological risks to the native fish community. In addition, targeted fishing during the breeding season should be used to control the population of tilapia and restore fish diversity. Full article

The invasion of blackchin tilapia in Thailand is a critical ecological threat affecting native biodiversity and destabilizing ecosystems. It is also resulting in significant ecological and socio-economic impacts. Originally from West Africa and introduced globally for aquaculture, blackchin tilapia thrive in Thailand’s brackish and freshwater ecosystems because of their high reproductive rates, environmental adaptability, and trophic plasticity. This review evaluates potential solutions for the invasion of blackchin tilapia in Thailand from a scientific perspective. The successful invasion of blackchin tilapia in Thailand can be attributed to several key factors, including late detection of the species, the delayed government response, the absence of effective management strategies, and the species’ high invasive potential. Given its wide distribution, large population size, and high reproductive rate, the eradication of the entire blackchin tilapia population is unlikely. Management efforts should focus on containment and impact reduction. Early detection and monitoring at the invasion front remain crucial to limit the species’ spread. Developing an online platform for tracking invasive species would aid these efforts. Public education and outreach are essential for promoting responsible behaviors for preventing further spread. Encouraging the utilization of blackchin tilapia as a food source and for commercial purposes could help suppress its population while supporting local economies. Biological control and other potentially harmful strategies should be avoided unless supported by strong scientific evidence to ensure minimal risks to ecosystems. Scientific research into controlling blackchin tilapia should be encouraged to develop suitable strategies, including using sterile triploid tilapia. The “polluter pays” policy should be implemented to cover the costs associated with invasive species. Coordinated efforts between researchers, policymakers, and the public are crucial for formulating effective management strategies to promote a balance between economic benefits and long-term environmental sustainability. Full article

Flavobacterium davisii is one of the causative agents of columnaris disease, significantly impacting Nile tilapia aquaculture. This study examines the invasion and immune evasion mechanisms of a highly virulent F. davisii strain through transcriptomic profiling of tilapia gills following acute immersion. We identified 8192 differentially expressed genes (DEGs) at 2 h, 6 h, and 12 h post-infection. They are enriched in pathways related to oxidative stress, immune suppression, tissue necrosis, and bacterial infection. Notably, early overexpression of rhamnose-binding lectin and mucin genes facilitated bacterial adhesion. Key immune genes, including those encoding major histocompatibility complex (MHC), immunoglobulins (Ig), Toll-like receptors (TLRs), and chemokines, were downregulated, indicating immune suppression. Conversely, immune evasion genes such as Fc receptor-like (FcRL) and programmed death-ligand 1 (PDL1) were upregulated, along with genes associated with reactive oxygen species (ROS) production, leading to increased tissue damage. Additionally, the upregulation of fibroblast growth factor and collagen genes suggested active tissue repair. In conclusion, F. davisii rapidly invades its host by enhancing adhesion to gill tissues, suppressing immune function, and inducing tissue damage. These findings enhance our understanding of F. davisii infection mechanisms and support the future breeding of disease-resistant tilapia and the development of sustainable control strategies. Full article

Aquaculture requires precise non-invasive methods for biomass estimation. This research validates a novel computer vision methodology that uses a signature function-based feature extraction algorithm combining statistical morphological analysis of the size and shape of fish and machine learning to improve the accuracy of biomass estimation in fishponds and is specifically applied to tilapia (Oreochromis niloticus). These features that are automatically extracted from images are put to the test against previously manually extracted features by comparing the results when applied to three common machine learning methods under two different lighting conditions. The dataset for this analysis encompasses 129 tilapia samples. The results give promising outcomes since the multilayer perceptron model shows robust performance, consistently demonstrating superior accuracy across different features and lighting conditions. The interpretable nature of the model, rooted in the statistical features of the signature function, could provide insights into the morphological and allometric changes at different developmental stages. A comparative analysis against existing literature underscores the competitiveness of the proposed methodology, pointing to advancements in precision, interpretability, and species versatility. This research contributes significantly to the field, accelerating the quest for non-invasive fish biometrics that can be generalized across various aquaculture species in different stages of development. In combination with detection, tracking, and posture recognition, deep learning methodologies such as the one provided in the latest studies could generate a powerful method for real-time fish morphology development, biomass estimation, and welfare monitoring, which are crucial for the effective management of fish farms. Full article

Myxozoa is a unique group of obligate endoparasites in the phylum Cnidaria that can cause emerging diseases in wild and cultured fish populations. Recently, we identified a new myxozoan species, Myxobolus bejeranoi, which infects the gills of cultured tilapia while suppressing host immunity. To uncover the molecular mechanisms underlying this successful parasitic strategy, we conducted transcriptomics analysis of M. bejeranoi throughout the infection. Our results show that histones, which are essential for accelerated cell division, are highly expressed even one day after invasion. As the infection progressed, conserved parasitic genes that are known to modulate the host immune reaction in different parasitic taxa were upregulated. These genes included energy-related glycolytic enzymes, as well as calreticulin, proteases, and miRNA biogenesis proteins. Interestingly, myxozoan calreticulin formed a distinct phylogenetic clade apart from other cnidarians, suggesting a possible function in parasite pathogenesis. Sporogenesis was in its final stages 20 days post-exposure, as spore-specific markers were highly expressed. Lastly, we provide the first catalog of transcription factors in a Myxozoa species, which is minimized compared to free-living cnidarians and is dominated by homeodomain types. Overall, these molecular insights into myxozoan infection support the concept that parasitic strategies are a result of convergent evolution. Full article

The gut microbiome is thought to play vital roles in host fitness and local adaptation to new environments, thereby facilitating the invasion of the host species. The Nile tilapia (Oreochromis niloticus) (NT) is an aggressive and omnivorous species that competes with native fishes for food resources, and it has successfully invaded much of the Pearl River basin in China. Here, we investigated the gut microbiomes of invasive Nile tilapia and indigenous black Amur bream (BA) in the same river section using high-throughput 16S rRNA gene sequencing. The results indicated that the gut microbiome of NT had several special characteristics, e.g., higher alpha diversity and greater niche breadth, compared with the bream. The gut microbiota of the small size of Nile tilapia (NTS) and small size of black Amur bream (BAS) groups were dominated by Proteobacteria, while those of the NTS and large size of Nile tilapia (NTL) and BAS and large size of black Amur bream (BAL). BAL and NTL were characterized by Firmicutes and Fusobacteriota, respectively. We found that Pseudomonas, Cetobacterium, Ralstonia, and Romboutsia were biomarkers of the NTS, NTL, BAS, and BAL groups, respectively. Moreover, the results collectively suggested that the clustering coefficients of BAL and NTL networks were greater than those of BAS and NTS networks, and BAS had the smallest network among the four groups. Positive interactions between two ASVs dominated the BAS, NTS, and NTL networks, while the proportion of negative interactions between two ASVs in the BAL network was remarkably increased. Low levels of interspecies competition in the NT gut microbiome would contribute to high diversity in the dietary niches and would also benefit the survival and local adaptation of the host. Our results identified specific biomarkers of gut microbial species in invasive Nile tilapia and provided useful information concerning how to monitor and manage invasive Nile tilapia populations. Full article

Tilapia is an invasive species that has become widely distributed around the world. In Korea, introduced tilapia into its aquatic ecosystem for the first time with a species from Thailand in 1955, and later additionally introduced two more species from Japan and Taiwan, thus securing a total of three species of tilapia (O. niloticus, O. mossambicus and O. aureus) as food resources. Since then, O. niloticus has been reported to inhabit certain streams with thermal effluent outlets. Morphological species identification is very difficult for tilapia and a combined analysis of morphological and molecular-based species identification is therefore necessary. This study investigated a tilapia population that inhabits a thermal effluent stream (Dalseo Stream) in Daegu Metropolitan City, Korea, in order to conduct a morphological and genetic species identification of this population. In total, 37 tilapia individuals were sampled. The results of the morphological and genetic species identification analyses found that two species, O. aureus and O. niloticus, inhabit the Dalseo Stream. In Korea, the habitat of the O. niloticus natural population has been reported, but the O. aureus natural population has not been reported. Thus, we observed for the first time that a new invasive species, O. aureus, inhabits a stream in Korea. They are known to cause disturbances to aquatic organisms (e.g., fish, aquatic insects, plankton, aquatic plants) and the habitat environment (e.g., water quality, bottom structure). Accordingly, it is important to study the ecological effects of O. aureus and O. niloticus on the corresponding freshwater ecosystem closely and to prepare a management plan to prevent the spread of these species, as they are notoriously invasive. Full article

Group B Streptococcus (GBS) is a major pathogen of humans and aquatic species. Fish have recently been recognized as the source of severe invasive foodborne GBS disease, caused by sequence type (ST) 283, in otherwise healthy adults in Southeast Asia. Thailand and Vietnam are among the major aquaculture producers in Southeast Asia, with GBS disease reported in fish as well as frogs in both countries. Still, the distribution of potentially human-pathogenic GBS in aquaculture species is poorly known. Using 35 GBS isolates from aquatic species in Thailand collected from 2007 to 2019 and 43 isolates from tilapia collected in Vietnam in 2018 and 2019, we have demonstrated that the temporal, geographical, and host-species distribution of GBS ST283 is broader than previously known, whereas the distribution of ST7 and the poikilothermic lineage of GBS are geographically restricted. The gene encoding the human GBS virulence factor C5a peptidase, scpB, was detected in aquatic ST283 from Thailand but not in ST283 from Vietnam or in ST7 from either country, mirroring current reports of GBS strains associated with human sepsis. The observed distribution of strains and virulence genes is likely to reflect a combination of spill-over, host adaptation through the gain and loss of mobile genetic elements, and current biosecurity practices. The plastic nature of the GBS genome and its importance as a human, aquatic, and potentially foodborne pathogen suggests that active surveillance of GBS presence and its evolution in aquaculture systems may be justified. Full article

Widespread introductions of non-native species, including aquaculture and ornamental species, threaten biodiversity and ecosystem functioning by modifying the trophic structure of communities. In this study, we quantified the multiple facets of trophic disruption in freshwater communities invaded by Nile tilapia, by comparing uninvaded and invaded rivers downstream of the Pearl River, China. Nile tilapia invasion reduced the trophic status of native fish species by forcing native herbivores and planktivores to seek new food sources. The food chain was also shortened by decreasing the trophic levels of native invertivores, omnivores, and piscivores, while the total isotopic niche area (TA) of native invertivores, omnivores, piscivores, and planktivores species also decreased. Simultaneously, Nile tilapia invasion affected the isotopic diversity of the fish community. Decreasing isotopic richness (IRic), isotopic evenness (IEve), and increasing isotopic uniqueness (IUni) indicated that Nile tilapia had a high trophic niche overlap with native species and competed with native species for food resources, and even caused the compression of the trophic niche of native species. Understanding the process described in this study is essential to conserve the stability of freshwater ecosystems, and improve the control strategy of alien aquatic organisms in south China. Full article

Waterbirds may be a good indicator of harmful metal levels in aquatic environments. Waterbirds’ organs and tissues were tested for the presence of pollutants, such as metals. However, very few reports describe the use of bird feathers and their prey in metal analysis. In the present research, seven metals were measured in the tissue, kidney, liver, and feathers of the Indian pond heron, the black-crowned night heron, and their prey species, including crabs, prawns, molluscs, and fishes from a freshwater lake. Metals were examined using an ECIL-4141-double beam atomic absorption spectrophotometer (DB-AAS). Metal concentrations differed considerably in the tissue, kidney, liver, and feathers of the Indian pond heron and black-crowned night heron (p < 0.001). Indeed, this research discovered a good correlation between the metals of prey species and the tissues, kidneys, liver, and feathers of waterbirds that were tested. The regression model explained that the Cyprinus carpio influence the accumulation of metals about 98.2% in tissues, Macrobrachium rosenbergii and Cyprinus carpio around 86.3% in the kidney, the Labeo rohita almost 47.2% in the liver and Labeo rohita nearly 93.2% on the feathers of the Indian pond heron. On the other hand, the Mystus vittatus, Cyprinus carpio, Labeo rohita influence about 98.8% in tissue, the Claris batrachus and Tilapia mossambica around 93.3% in kidney, the Mystus vittatus, Cyprinus carpio, about 93.2% in liver and the freshwater crab (Travancoriana schirnerae), freshwater prawn (Macrobrachium rosenbergii) and a fish (Cyprinus carpio) nearly 93.2% in feathers in the black-crowned night heron. This research evaluated metals in the dead carcasses of waterbirds, a non-invasive biomonitoring technique for pollution. Overall, the investigation revealed that the lake is severely contaminated with metals. Therefore, the management and protection of aquatic habitats, particularly freshwater lakes, should be enhanced to rescue wild species that rely on aquatic ecosystems and to ensure that people have access to clean drinking water. Full article