Important Fish Research Articles

Current Status of Hilsa (Tenualosa ilisha) Fisheries in Bangladesh and Implications for Future Research and Development

ABSTRACTHilsa shad (Tenualosa ilisha) is an anadromous fish, making the single largest wild fishery in Bangladesh, supporting the livelihoods of about 2% of the population and contributing 1% to the national GDP. Several studies reported positive outcomes associated with its catch status, biology, ecology, nutritional profile, conservation and management and socio‐economic impacts. However, significant knowledge gaps exist in hilsa fisheries, particularly in the areas crucial for research and development. In this article, we conducted a systematic review of literature to identify and address the knowledge gaps, challenges and research priorities in hilsa fisheries to ensure their sustainable management and production. Recent data from the Department of Fisheries (DoF) indicate rising production of hilsa in Bangladesh, sparking debate about its accuracy. Reliable data are essential to avoid miscalculations that could lead to risk of overfishing or underfishing of this important fish. Hilsa matures at 6–12 months, lives 2–6 years, feeds primarily on phytoplankton and spawns mostly during full moon of September and October. The abundance of brood hilsa in the river systems before and after the peak breeding season suggests further research is needed to refine breeding period for sustainable production. Although recent molecular studies have mapped the complete genome of hilsa, there remains a lack of comprehensive knowledge on its biology, ecology, conservation and life cycle—the key areas for sustainable catches and domestication. Enhancing global demand for this species requires value addition, such as removing sharp pin bones in the flesh. DoF has implemented various policies and projects, including establishment of sanctuaries to protect and conserve hilsa fisheries for sustainable exploitation. However, these measures have sparked controversy due to their adverse impacts on income and livelihoods of fishermen. Addressing these challenges and knowledge gaps requires focused research and development initiatives to ensure sustainable hilsa fisheries in Bangladesh.

Chromosome-level genome assembly and annotation of the gynogenetic large-scale loach (Paramisgurnus dabryanus)

sThe large-scale loach (Paramisgurnus dabryanus; Cypriniformes: Cobitidae) is primarily distributed in East Asia. It is an important economic fish species characterized by fast growth, temperature-dependent sex determination and the ability to breathe air. Currently, molecular mechanism studies related to some aspects such as sex determination, toxicology, feed nutrition, growth and genetic evolution have been conducted. However, the lack of a high-quality reference genome has hindered further research. In this study, we performed PacBio HiFi and Hi-C sequencing on a female (ZW) specimen and assembled the first high-quality chromosome-level genome of the large-scale loach. The assembled genome comprises 24 chromosomes, with a total length of 1.04 Gb, a scaffold N50 of 41.7 Mb, and a BUSCO completeness of 95.8%, including 28,311 protein-coding genes. These findings not only provide new insights into the genome structure of the large-scale loach but also establish a crucial reference point for omics studies and serve as an essential genomic resource for breeding programs in this species.

Chromosome-level genome assembly of black carp Mylopharyngodon piceus using Nanopore and Hi-C technologies

Black carp (Mylopharyngodon piceus) is one of the “four famous domestic fishes” in China and an important economic fish in freshwater aquaculture. A high-quality genome is essential for advancing future biological research and breeding programs for this species. In this study, we aimed to generate a high-quality chromosome-level genome assembly of black carp using Nanopore and Hi-C technologies. The final genome assembly was 848.70 Mb in length, with a contig N50 of 3.37 Mb and a scaffold N50 of 34.13 Mb. The genome was anchored onto 24 chromosomes by Hi-C technology. The BUSCO (Benchmarking Universal Single-Copy Orthologs) completeness score of the genome assembly is 97.6% when compared to the Actinopterygii_odb10 database. In total, 203.54 Mb of repeat sequences and 37,418 protein-coding genes were predicted in the genome assembly. Taken together, our study provides a chromosome-level genome assembly, which can serve as a valuable genetic resource to support further biological studies and breeding efforts of black carp.

Chinese yam polysaccharide induces the differentiation and natural antibody secretion of IgM+ B cells to prevent Aeromonas hydrophila infection in grass carp.

Chinese yam polysaccharide (CYP) is an effective immunostimulant, however, its efficacy in grass carp, an important commercial fish species in Asia, remains untested. Here, our study evaluated the immunostimulatory effects of CYP on IgM+ B cells in vitro and on humoral immunity and immune defense against Aeromonas hydrophila infection in vivo. In vitro stimulation experiments showed that CYP could induce the secretion of IgM antibodies, because it could stimulate the proliferation and differentiation of head kidney IgM+ B cells. Moreover, CYP could also enhance the phagocytic activity of IgM+ B cells. When grass carp were intragastrically administrated (i.g.) with CYP, the serum IgM level increased, as did the capacity of serum IgM to bind to peptidoglycan (PGN) and lipopolysaccharide (LPS), indicating that CYP induced natural IgM production in grass carp. Correspondingly, the serum bactericidal ability to A. hydrophila enhanced. Immune protection experiments showed that CYP could protect grass carp from A. hydrophila infection in vivo, because the mortality rate and gut Aeromonas load of grass carp significantly decreased after CYP administration. Taken together, our study reveals immunostimulatory effects of CYP in grass carp, laying important foundation for the usage of CYP to control diseases in grass carp aquaculture.

Uncovering the chromatin-mediated transcriptional regulatory network governing cold stress responses in fish immune cells.

Temperature fluctuations challenge ectothermic species, particularly tropical fish dependent on external temperatures for physiological regulation. However, the molecular mechanisms through which low-temperature stress impacts immune responses in these species, especially in relation to chromatin accessibility and epigenetic regulation, remain poorly understood. In this study, we investigate chromatin and transcriptional changes in the head kidney and thymus tissues of Nile tilapia (Oreochromis niloticus), a tropical fish of significant economic importance, under cold stress. By analyzing cis-regulatory elements in open chromatin regions and their associated transcription factors (TFs), we construct a comprehensive transcriptional regulatory network (TRN) governing immune responses, including DNA damage-induced apoptosis. Our analysis identifies 119 TFs within the TRN, with Stat1 emerging as a central hub exhibiting distinct binding dynamics under cold stress, as revealed by footprint analysis. Overexpression of Stat1 in immune cells leads to apoptosis and increases the expression of apoptosis-related genes, many of which contain Stat1 binding sites in their regulatory regions, emphasizing its critical role in immune cell survival during cold stress. These results provide insights into the transcriptional and epigenetic regulation of immune responses to cold stress in tilapia and highlight Stat1 as a promising target for enhancing cold tolerance in tropical fish species.

Multi-omics dataset of individual variations in growth performance of large yellow croaker

Large yellow croaker (Larimichthys crocea) is a highly economically important marine fish species in China. However, substantial individual variations in growth performance have emerged as a limiting factor for the sustainable development of the large yellow croaker industry. Gut microbiota plays a crucial role in fish growth and development by regulating metabolic processes. To explore these dynamics, we employed metagenomics, transcriptomics, and untargeted metabolomics to comprehensively analyze the structure of the intestinal microbiome and its relationship with intestinal metabolism and host gene expression. We constructed association models for “gut microbiota–differentially expressed genes”, “differentially expressed genes–metabolites,” and “gut microbiota–metabolites.” Sequencing data and LC–MS/MS raw data have been deposited in NCBI and MetaboLights databases for public access. Our findings offer critical insights into the molecular mechanisms underlying growth variations in L. crocea and provide valuable data for the selective breeding of improved strains.

Insights into the toxic impact of long-term exposure to diethyl phthalate on commercially important species Catla (Labeo catla)

BackgroundDiethyl phthalate (DEP), used as a plasticizer, is more prevalent in the aquatic environment due to its widespread usage in plastics, cosmetics, and numerous pharmaceutical industries. It is a potential endocrine disruptor, but the underlying mechanism in fish needs to be investigated. The present study evaluated the toxic impacts of DEP exposure for 30 days on commercially important fish Labeo catla (Catla). Alterations at multiple level endpoints of the hypothalamic–pituitary–gonadal axis (HPG axis) were assessed. DEP-induced changes in oxidative stress, histopathological changes (liver, kidney and brain) and bioaccumulation in fish muscle were also evaluated.ResultsDEP exposure to 1/10th (1.62 mg/L) and 1/50th (0.32 mg/L) LC50 dose for 30 days to Catla revealed that it stimulated the expression of kisspeptin (Kiss 1 and Kiss 2) genes in the hypothalamus, leading to an increased GnRH concentration (36.75%) in the higher dose. The brain FSH levels increased by 11.24 and 55.42% times than control in both the doses. This led to an increase in circulating sex steroids E2 (41.62%) and 11 KT (24.59%) and eventually triggered hepatic Vtg production (23.90%) in a dose-dependent manner. DEP exposure lowered the concentration of antioxidants superoxide dismutase (SOD) and catalase (CAT), the effect being more pronounced in the higher dose. The histopathological alterations, such as hepatocyte vacuolization, sinusoidal congestion, loss of brush border, degeneration of lumen, infiltration of eosinophilic cells in liver, kidney and brain, respectively, were noted.ConclusionsThis pioneering study could provide detailed insight into the endocrine disruptive potential of DEP in fish, as evidenced by its impact at multiple endpoints, even at low doses after 30 days of exposure. The output of this investigation thus emphasized the need for regular monitoring of DEP for ecological risk assessment.

Temporal dynamics and distributions of sardine and anchovy in the southern California Current Ecosystem

Anchovies and sardines are some of the most economically and ecologically important and well-studied fishes on earth but there is still uncertainty regarding how distributions and abundances change through time and space. We bring together larval abundance data for northern anchovy (Engraulis mordax) and Pacific sardine (Sardinops sagax) collected by United States and Mexican scientists over 50 years (1963-2015) to test the Basin and Asynchrony hypotheses. The Basin Hypothesis states that a species’ geographic range and spawning area (R) increases with overall abundance (A) according to a power law, R=aAb, where the exponent (b) is less than ~ 0.5 when the rate of increasing area occupied saturates as population size increases. The Asynchrony Hypothesis postulates that anchovy and sardine abundances are negatively correlated through time. We found that the Basin Hypothesis was supported for both species but the Asynchrony Hypothesis was not during this 53-year period. Due to collaboration between U.S. and Mexican scientists we were able to better understand how two important fishes utilize their environment.

Establishment and Molecular Characterization of a Liver-derived Cell line from Schizothorax esocinus (Chirruh) for Cold Water Fish Research

Schizothorax esocinus, commonly known as Chirruh, is an important indigenous coldwater fish of the Kashmir. The new cell line was developed from the liver tissue of Schizothorax esocinus, and was characterized by molecular technique. The developed cell line was maintained and passaged 14 times in Leibovitz’s L-15 medium. The cell line was standardized using L-15 media by testing at various FBS (fetal bovine serum) concentrations and temperature ranges. Cell numbers increased more rapidly in 20% FBS, compared to other concentrations ranging from 5% to 25%. The tissue got fully adhered after 72hrs when seeded at 24°C as compared to other temperatures ranging from 8 to 28°C. The tissue preparation approach was more reliable than the enzymatic dissociation approach. Cell colonies of various sizes were formed after 1 week and 60-70% confluent cell monolayer were achieved after 20 days. The cell morphology was found to be of epithelial-like cells. The origin of the cell line was confirmed at passage 12 by the amplification of 629 bp of cytochrome oxidase subunit I (COI) similar to the original liver issue. The current cell line developed from liver tissue of S. esocinus has tremendous potential to enhance the generation of cold-water fish cell lines could and potentially be used as a important approach for conservation genetics and biotechnological applications.

Effects of Feed Supplementation With Fulvic Acid on the Systemic and Mucosal Protective Mechanisms of Juvenile Rainbow Trout (Oncorhynchus mykiss).

Rainbow trout (Oncorhynchus mykiss) is an important fish species raised in aquaculture, but it is susceptible to stress, infections diseases. The present study aimed to determine the effects of fulvic acid feed addition on the systemic and mucosal protective mechanisms of juvenile rainbow trout and to elucidate the underlying molecular mechanisms of changes in the gut. Rainbow trout (4.30 ± 0.6 g) diet was supplemented with different levels of fulvic acid: 0% (Control), 0.5%, 1% and 2%. At the end of 8-week feeding trial, growth parameters such as final weight gained weight (%), SGR (F1%) increased, and FCR (all levels) decreased significantly compared to the control group. We found that the activity of lysozyme, glutathione peroxidase, and catalase in the serum were significantly improved, especially after the addition of 0.5% and 1% of fulvic acid. At the same time, the immunoglobulin concentration in the skin mucus was increased with 0.5% supplementation. However, the expression of tnf-α, il-6 and gpx in the intestine was strongly upregulated after supplementation with 2%, indicating oxidative stress and inflammation with this level of fulvic acid inclusion. Furthermore, the mucus lysozyme activity was reduced at this concentration, which can increase the susceptibility to pathogen invasion. The results suggest that adding 0.5%-1% of fulvic acid to the feed of juvenile rainbow trout can help to improve their immune and antioxidative defenses and thereby support the wellbeing of fish.

Antitumor activity of edible fishes (Channa striata and Anabas testudineus) and gastropods (Helix aspersa and Pila virens) rudimentary mucus against HT-29 cell line and its biochemical properties

BackgroundThe mucus from fish and gastropods contains a wide range of bioactive molecules with biomedical properties. The fish and gastropods were collected from Oragadam lake, Kanchipuram district, Tamil Nadu, India. In this study, we wanted to examine the anticancer potential of fish and gastropods mucus. The biochemical components of the crude mucus were screened.ResultsThe biochemical analysis showed that the mucus of Anabas testudineus and Pila virens contained a high level of carbohydrates (2.8 and 1.5 mg/ml), the mucus of Channa striata contained a high level of lipids (0.9 mg/ml), and the mucus of Helix aspersa contained a high level of protein (1.3 mg/ml). The results showed morphological variations in the HT-29 cells upon treatment with crude mucus. Upon 24 h of gestation, the frozen cells began to shrink and seem round in shape. Using the MTT assay, the mucus crude extract was evaluated for its anticancer properties against the human colon cancer cell line (HT 29). The inhibitory concentration (IC50) was determined at 100 µg/ml after 24 h. Using specific staining techniques; fluorescent microscopy was utilized to examine the cell morphology and early and late apoptotic stages. Propidium iodide staining showed nuclear damage followed by DNA damage. This showed that the rudimentary mucus could prompt cell death and increased the number of fragments and mucus concentration, respectively.ConclusionThis study showed that the edible or commercially important fish and gastropod mucus have potential anticancer activity against HT-29 cancer cells.

The Observation of Meiotic Union Behavior of Gametophytes Provides a New Basis for Ploidy of Carassius auratus gibelio.

As an important aquaculture fish, the genus Carassius exhibits different ploidy, including tetraploids and hexaploids [...].

GILLNET SELECTIVITY PARAMETERS FOR COMMERCIALLY IMPORTANT SPECIES, <i>LABEO ROHITA</i> IN A TROPICAL RESERVOIR, KERALA, INDIA

The selectivity of fishing gear characterizes its capacity and efficiency in capturing fish. This knowledge helps in selecting the appropriate mesh size to suit the available fish population. The present study aims to estimate the gillnet selectivity parameters of a commercially important fish species, Labeo rohita, from a tropical reservoir in Meenkara, Kerala, India. The study was conducted from September 2019 to February 2020 through experimental fishing using gillnets of different mesh sizes (120, 130, 140, and 150mm) of identical design and dimensions. Selectivity parameters were estimated using Holt’s indirect method. The estimated optimum selection length of L. rohita for three different mesh sizes (120, 130, and 140mm) was 46.56, 50.44, and 54.32cm, and the common selection factor (SF) was 3.88. The estimated optimum mesh size of 127 mm was found to be ideal for the commercial exploitation of L. rohita in the Meenkara reservoir. The gillnet selectivity estimates obtained in the present study will be beneficial to increase the likelihood of capturing targeted size classes as well as better management of the L. rohita fishery in Meenkara reservoir.

Fatty Acids of European Sardine (Sardina pilchardus) White Muscle Can Discriminate Geographic Origin Along the Iberian Atlantic Coast.

The European sardine (Sardina pilchardus) ranks among the most valuable species of Iberian fisheries, and the accurate tracing of its geographic origin, once landed, is paramount to securing sustainable management of fishing stocks and discouraging fraudulent practices of illegal, unreported, and unregulated (IUU) fishing. The present study investigated the potential use of S. pilchardus white muscle fatty acids (FAs) to successfully discriminate the geographic origin of samples obtained in seven commercially important fishing harbors along the Iberian Atlantic Coast. While 35 FAs were identified using gas chromatography-mass spectrometry in the white muscle of S. pilchardus, the following, as determined by the Boruta algorithm, were key for sample discrimination: 14:0, 22:6n-3, 22:5n-3, 18:0, 20:5n-3, 16:1n-7, 16:0, and 18:1n-7 (in increasing order of relevance). An average 83% correct allocation of landed specimens was achieved, with some landing locations presenting 100% correct allocation (e.g., Ría de Pontevedra in northern Spain and Peniche in central Portugal). Linear discriminant analysis revealed a separation of samples from northern Spain and Peniche, and a partial overlap of all other locations. The present results highlight the potential of using FAs of S. pilchardus white muscle to reliably discriminate the geographic origin of landed individuals along the Iberian Atlantic coast.

Caracterização do pescado comercializado em Monte Alegre, Baixo Amazonas, estado do Pará

The Amazon has fish of financial and food importance, and its main form of commercial distribution is through street markets, including in Monte Alegre, Pará. However, there are few studies on the variety of species offered in the municipality and how their trade behaves. Thus, this research diagnosed the fish found in municipal markets and aspects of local trade. The data were obtained through monthly interviews with fishmongers, over a period of one year. The price variation of the five most frequent species, considering the months and the seasonal period, was analyzed using ANOVA (one-way) and Kruskal-Wallis, considering α=0.05 and subsequent post-hoc tests. Thirty-one species were recorded, the main ones being tambaqui (Colossoma macropomum), pirarucu (Arapaima gigas), curimatã (Prochilodus nigricans), pirapitinga (Piaractus bachypomus), tucunaré (Cichla sp.) and surubim (Pseudoplatystoma sp.), which were the fish most frequently mentioned in the fishmongers' responses. The price of some of the most important species in the market in Monte Alegre was related to the seasonal period, with the highest market value during the flood period, as observed for pirarucu and curimatã. Tambaqui had the highest price in April, the month with the highest rainfall during the period studied. This research highlights the diversity of fish sold in Monte Alegre, confirming the importance of natural fishing resources for feeding local populations. In addition, the study demonstrates the correlation between the dry and rainy seasons and the price of fish, in which the commercial value of relevant species becomes higher during the rainy season.

Effects of Algal-Derived β-Glucan on the Growth Performance, Intestinal Health, and Aeromonas veronii Resistance of Ricefield Eel (Monopterus albus).

Ricefield eel is an important economic fish in China. However, large-scale intensive breeding has increased the incidence of diseases in eels. In this study, we conducted an 8-week feeding trial to investigate the effects of β-glucan on the growth performance, intestinal health, and Aeromonas veronii resistance of Monopterus albus (M. albus). Three hundred healthy fish (initial body weight: 12.38 ± 0.50 g) were randomly divided into five groups: A1 (basal diet) was considered the control group, whereas A2, A3, A4, and A5 were the experimental groups. The fish in the experimental groups were fed a basal diet supplemented with 250, 500, 1000, and 2000 mg/kg β-glucan, respectively. The addition of 0.025%-0.2% β-glucan resulted in a notable enhancement of eel growth performance, with the most significant improvement observed in eels supplemented with 0.1% β-glucan (p < 0.05). Furthermore, 0.025%-0.2% β-glucan could significantly enhance the antioxidant properties of the eel intestinal tract (p < 0.05), and the addition of 0.1% β-glucan significantly improved trypsin (TPS), amylase (AMS), and lipase (LPS) activities in the intestine (p < 0.05). In terms of intestinal histology, the A3, A4, and A5 groups exhibited significantly greater villus height compared to the control group (p < 0.05). Concentrations of β-glucan at 0.1% and 0.2% enhanced the composition of the intestinal flora; specifically, the relative abundance of Proteobacteria increased, while the relative abundance of Firmicutes decreased. Moreover, the addition of 0.05%-0.2% β-glucan significantly improved the relative survival rate (SR) of A. veronii-infected eels and significantly decreased the bacterial load of the liver, spleen, and kidney (p < 0.05). In comparison to eels that did not receive β-glucan supplementation, eels supplemented with 0.2% β-glucan exhibited decreased intestinal structural damage. In summary, the addition of 0.1%-0.2% β-glucan can promote eel growth, improve intestinal digestion and antioxidant capacity, regulate intestinal flora, and enhance intestinal physical function and anti-infection ability.

Morphological and molecular characterization of Henneguya chirodactyli n. sp. (Cnidaria: Myxosporea), a parasite of the Peruvian morwong Chirodactylus variegatus (Valenciennes, 1833) (Centrarchiformes: Latridae).

A new species of Henneguya Thélohan, 1892 (Myxosporea: Bivalvulida: Myxobolidae) infecting the internal region of the stomach of the Peruvian morwong Chirodactylus variegatus (Valenciennes, 1833) (Centrarchiformes: Latridae), an economically important fish in Peruvian artisanal fishery, is described. Morphologically, Henneguya chirodactyli n. sp. differs from all its congeners due to the combination of myxospore dimensions, polar filament coil count, and an external envelope in the spore body. Phylogenetic analysis based on 18S rRNA gene sequences places this new species as sister to H. lagunensis de Azevedo, Negrelli, de Oliveira, Abdallah, Camara, Matos and Vieira, 2021. Furthermore, this species is located in a clade composed of 12 species of Henneguya and one of Myxobolus Bütschli, 1882, all of which infect marine fish. We emphasize that this is the first study performed with an integrative approach, including morphological (external), scanning electron microscopy (SEM) and molecular descriptions, of a Henneguya species from a Peruvian marine environment.

Environmental concentrations of antibiotics induced polymyxin B tolerance in Aeromonas hydrophila.

Polymyxin B is one of the last lines of defense in infections caused by multidrug-resistant Gram-negative bacteria. Aeromonas hydrophila are important fish pathogens and the occurrence of polymyxin B-resistant A. hydrophila isolates is increasing. While investigating 14 environmental chemical pollutants that may affect bacterial polymyxin B sensitivity in aquatic bacteria, we discovered that tolerance of A. hydrophila to polymyxin B is increased by short-term (90min) concurrent exposure to tetracyclines, tigecycline or gentamicin at environmentally relevant concentrations (0.0625μg/mL) and persists as long as the inducer is present. The exposure increased the growth of A. hydrophila at an inhibitory concentration of polymyxin B. The increased polymyxin B tolerance was attributed to changes in gene expression, without alterations in genotype and independent of cell surface charge variations. Such changes are relate to six KEGG pathways, including ribosome, nucleotide metabolism, pyrimidine metabolism, glyoxylate and dicarboxylate metabolism, purine metabolism, starch and sucrose metabolism. The dysregulated genes were involved in broad physiological changes, such as cell motility, flagella biosynthesis, quorum sensing, biofilm formation, and chemotaxis. Furthermore, the up-regulation of genes encoding Mg2+ transport, biotin synthesis, lipoprotein, glycerol phospholipid metabolism, phospholipid transport, and the down-regulation of genes, such as ompK, yidD and ompA related to enhanced cell membrane barrier, may contribute to the increased polymyxin B tolerance in A. hydrophila. In summary, the study results revealed the impact of environmental antibiotics in promoting microbial polymyxin B tolerance. Our findings underscore the role of environmental antibiotics in promoting polymyxin B tolerance and provide insights into the mechanisms of polymyxin B tolerance evolution in A. hydrophila.

Fish biodiversity in the Kampar watershed: an overview of the potential, threats, and management strategies

Abstract Kampar Watershed is one of the major rivers in Indonesia, which is divided into Riau and West Sumatra Provinces. Kampar watershed has a high diversity of fish species and has long been utilized to meet the needs of clean water, aquaculture, agriculture, plantations, as well as hydropower generation. This article presents data related to fish biodiversity, its status, utilization, potential and threats in the Kampar watershed summarized from various scientific literatures. Fish biodiversity was recorded as many as 125 species from 36 families. A total of 92.8% of the species are native, while 7.2% are introduced. 36% of fish species were utilized as consumed and 22% as ornamental fish. There are 11.2% that can be classified as economically important fish, two of which are C. lopis and S. formosus. A total of 8% species are threatened. Threats to the Kampar watershed include water resource issues such as the increasingly widespread conversion of land to agriculture, the narrowing of natural forest areas, the expansion of floating net cages, illegal logging, and waste pollution. The data and information presented are expected to be one of the scientific references in developing strategies for managing and utilizing fish biodiversity in the Kampar watershed.

Analysis of Microplastic Contamination and Associated Human Health Risks in Clarias gariepinus and Oreochromis niloticus from Kubanni Reservoir, Zaria Nigeria

Environmental safety has become a major concern in recent years due to the global increase in microplastic pollution. These ubiquitous, tiny, and potentially toxic plastic particles enter aquatic environments through weathering of larger plastics and the release of microbeads. Although numerous studies have focused on microplastic pollution in developed regions, information from developing countries remains limited. This study assessed the presence of MPs and associated oxidative stress responses in two commercial fish species, Clarias gariepinus (Catfish) and Oreochromis niloticus (Nile Tilapia), from Kubanni reservoir, Zaria, Nigeria, over six months spanning both the dry and rainy seasons. Fibers were identified as the most abundant MP particles, followed by fragments, films, and beads, in the order of fibers > fragments > films > beads. The highest fiber concentrations were recorded in the gills, with Clarias garipinus showing 11.5 MP items/individual and Oreochromis niloticus showing 22.5 MP items/individual. Black microplastics were predominant, and the most common ingested MP ranged from 1.0 to 2.0 mm. The primary polymers identified were polypropylene and polyethylene terephthalate. Evidence of oxidative stress and cellular damage was observed in the gills, liver, and dorsal muscles of both fish species, which correlated with MPs ingestion. According to recommendations from the European Food Safety Authority regarding fish consumption by children and adults, individuals consuming Clarias gariepinus and Oreochromis niloticus from the Kubanni reservoir may be exposed to between 70 and 700 MP items/organ. The risk associated with consuming MPs found in fish gills and guts was notably higher, posing significant concerns for human health. This study provides insights into microplastic contamination in commercially important fish from the Kubanni Reservoir and highlights the environmental and public health risks associated with consuming contaminated fish from this ecosystem.