Fish and macrophyte diversity in a tropical river under threat from municipal waste

Fishes thrive in balanced ecosystems, where threats like invasive fish species and extensive anthropogenic activity can significantly reduce native fish populations. Macrophytes play a crucial role in providing shelter and breeding grounds for small native fish species. This study was conducted to assess the fish and macrophyte diversity, water quality parameters, and potential pollution sources in a tropical river (Virinjipuram (Palar) River, Tamil Nadu) in India between January and March 2025. It also highlights the anthropogenic impacts on fish population. Our results show that 20 species were identified including 18 native and 2 exotic species (Oreochromis niloticus and Oreochromis mossambicus). Cypriniformes was the most dominant order with 12 fish species, followed by Perciformes (3 species), Cichliformes (3 species) and Siluriformes (2 species). IUCN global status of native species revealed 16 species as Least Concern, Parambassis lala as Near Threatened and Devario fraseri as Vulnerable. Five macrophytes were observed, indicating potential interactions between fish populations and macrophytes in influencing habitat dynamics. The presence of invasive species and extensive municipal waste dumping along the riverbank is of major concern. Our present finding suggests that measures have to be taken to mitigate the anthropogenic activities to conserve the native fish fauna

Phylogeny, genetic diversity and divergence dating of Monodactylus argenteus (Linnaeus, 1758) (Actinopterygii: Monodactylidae) from marine waters of Odisha Coast, Bay of Bengal, India

Among the many different types of aquatic life found in marine ecosystems, fish are the most diverse and commercially important organisms. To support their conservation and management, accurate species identification, genetic, and phylogenetic association studies are crucial. Monodactylus argenteus, the silvery Moony fishes were collected from Gopalpur-on-sea, Odisha Coast of the Bay of Bengal, India and identified as using traditional morpho-taxonomy methods followed by DNA barcoding using cytochrome c oxidase subunit I (COI) gene. Following identification, the phylogeny, genetic diversity, and divergence time of M. argenteus were investigated. The current study looked at the number of variable sites, parsimony informative sites, nucleotide diversity, and haplotype diversity. The 16 sequenced individuals of M. argenteus produced a total of 13 haplotypes, with 11 unique haplotypes and two shared haplotypes. There were 67 polymorphic sites, including 56 parsimony informative sites and 11 singleton variable sites with 72 mutations. Phylogenetic tree was drawn and all the sequences clustered in agreement with their species level taxonomic classification were observed. The divergence time of the M. argenteus species was estimated to be in the late oligocene sub-epoch, about 25.98 mya, using the RelTime maximum likelihood method. The findings of this study serve as noteworthy confirmation of the utility of DNA barcode sequences for tracking diversity of species and also contribute information on the phylogeny, genetic diversity, and divergence dating of M. argenteus

Factors affecting export competitiveness of fisheries industry in Malaysia

Fisheries constitute the most highly traded food commodity internationally owing to its fundamental contribution to global food security and nutrition. Malaysia has been amongst the world’s leading fish producers; however, it has faced a serious fish trade deficit, implicating an absence of export competitiveness in the industry. This study aims to measure the export competitiveness (i.e. Comparative Export Performance index, CEP) of the industry and examine factors affecting CEP by adopting the Autoregressive Distributed Lag (ARDL) approach on the time series data for 2001 – 2022. The major findings revealed that Malaysia recorded an absence of export competitiveness (i.e. CEP < 0) in the international fisheries market, and this issue was significantly affected by fish consumption, followed by foreign income and fisheries production. Fisheries production and foreign income positively affected the CEP in the short-run while fish consumption negatively affected it. In the long-run, fish consumption and foreign income exerted a negative effect on the CEP. The findings of this study are significant for understanding the short- and long-run effects on export competitiveness in Malaysia and can be used for fisheries development strategies

Comparative efficacy of different doses of inducing agent on breeding performance of a near threatened catfish pabda (Ompok bimaculatus Bloch, 1794) in West Bengal, India

In India, diversification in shrimp culture area is required due to climate changes, fluctuation in resources, and its marginal profit. Near Threatened pabda (Ompok bimaculatus) may be an alternative aquaculture species which can fulfil all the demands for the shrimp farmers. In this study, healthy, disease-free, 12-month reared brood fishes were collected and stocked in eight tanks (8×4×2 feet) sex wise (130 pairs) with shower facilities. Synthetic hormone was used to induce both male and female fishes at 0.3 and 0.6 ml (T1); 0.5 and 0.7 ml (T2) and 0.7 and 0.8 ml (T3) kg-1 body weight (bw) respectively, having 3 replicates for each treatment. Ovulation period (7 to 11 hours), relative fecundity (105.20±39.93 eggs g–1 bw of female), fertilization rates (67.37±20.73 to 75.88±24.84%), hatching rates (62.57±18.46 to 79.67±26.68%) and survival rates (55.01±14.93 to 65.62±19.91%) were observed. Among treatments, T2 exhibited better breeding performance but no significant differences with other treatments were observed. Important water quality parameters like temperature (28.27±1.68°C), pH (7.10±0.44), dissolved oxygen (4.25±0.37 mg L–1), hardness (210.96±9.31 mg L–1) and alkalinity (202.78±8.00 mg L–1) were also recorded during this experiment. After 48 hours of hatching, hatchlings were reared in aerated tanks for another four days with close observation and fries were harvested 24 days of rearing. From the present experiment, T2 exhibited best effective dose for successful induced breeding of pabda

Impact of environmental factors on the dietary preferences of Salmophasia bacaila in the Dhepa River, Bangladesh

This study investigates the environmental variability and gut contents of an indigenous fish chela (Salmophasia bacaila) in the Dhepa River, Bangladesh. We conducted fish sampling and measured water quality across three sites from September 2017 to February 2018. The results revealed significant fluctuations in water temperature, dissolved oxygen, and pH (PERMANOVA: p = 0.001). There was spatio-temporal variation in water transparency (PERMANOVA: p = 0.001). The prey analysis identified 13 prey groups in the diet of fish, predominantly consisting of phytoplankton (92.9%), while zooplankton contributed only 7.1%. Twenty phytoplankton and seven zooplankton genera were recorded in the guts, with significant temporal variations in prey diversity (PERMANOVA: p = 0.010). These findings highlight that S. bacaila are primarily plankton feeders, with shifts in prey diversity driven by environmental factors in the Dhepa River. This research enhances our understanding of ecological dynamics and the relationship between S. bacaila and their prey in riverine ecosystems

The effect of different dietary protein levels on the water quality and reproductive performance of Nile tilapia (Oreochromis niloticus) broodstock in biofloc system

This study investigated the effect of protein levels on the water quality and reproductive performance of Nile tilapia (Oreochromis niloticus) in the biofloc system. Three isocaloric diets with different protein levels (32%, 38%, and 44%) were formulated. A total of nine one-tone tanks with a water holding capacity of 0.9 tons were prepared and equipped with the necessary materials to form biofloc. Seventy-two female and thirty-six male fish were tagged, numbered, and randomly released into the tanks at a female: male ratio of 2:1. The results showed that the lowest amount of TAN (0.21 mgL–1), NO2, and NO3 were observed in the treatment of 32% protein. Mean final weight in the 32% and 38% treatments was 350 and 356 g, respectively, with no significant difference. The highest absolute fecundity (654) was observed in the 32% group, but no significant difference was found between the absolute fecundity of the 38% and 44% groups. The longest interval (17.8 days) was observed in the 44% protein group. The percentage of fertilization and hatching did not significantly differ between the groups. The highest percentage of fertilization (93%) and hatching (89%) were observed in the 32% protein group. The total number of eggs per female fish did not differ between the 32% (12840) and 38% (12670) groups, while the 44% group had the lowest number of eggs (12040). The present study showed that a dietary protein level of 32% is optimal for water quality and reproductive performance of Nile tilapia in the biofloc system

Application of machine learning to growth model in fisheries

Traditional growth models, such as length-weight relationships (LWRs) and the von Bertalanffy (VB) growth function, have been widely used in fishery science. Their limitations in capturing nonlinear patterns necessitate alternative approaches. Machine learning (ML) techniques have recently gained attention as a powerful tool for enhancing predictive accuracy in biological studies. In this study, the growth parameter of Eastern mosquitofish, Gambusia holbrooki (135 females: 21–58.78 mm and 0.152–3.424 g; 59 males: 19.25–43.20 mm; 0.108–1.075 g), was determined with traditional LWRs, VB, and machine learning algorithms. The LWRs growth equations of female and male individuals were W=0.00002102 L2.8849 and W=0.00003064 L2.8212, respectively. The VB equations were determined Lt=80.990 [1–e–0.990(t+0.208)] for female and Lt=64.172 [1-e–0.610(t+0.271)] for male. In general, the performance of both methods (VB model and ML algorithms) in predicting lengths, as measured by Mean Absolute Percentage Error (MAPE), was satisfactory, with the VB model demonstrating slightly superior performance (2.734). In addition, the ML algorithm gives better results in length data prediction with multilayer perceptron and in weight data prediction with Sequential Minimum Optimization (SMO) algorithm when ML algorithms are examined. The diverse ML algorithms positively impacted the investigations addressing growth-related issues in fisheries

Exploring shellfish diversity, utilisation and conservation threats in the Chalan Beel, Bangladesh

Shellfish are important components of aquatic ecosystems, including freshwater wetlands. In this study, we examined shellfish species diversity and their utilisation by humans in the largest wetland of Bangladesh, the Chalan Beel. Through systematic, standardised field surveys, we recorded 19 shellfish species, including 14 molluscs and five arthropods. The global conservation status of the recorded species was retrieved from the IUCN Red List database, and all were classified as Least Concern. Among the 19 recorded species, the majority—11 species—are used for human consumption, followed by use as animal feed (e.g. for fish, shrimp and poultry) (eight species), as fish bait (eight species), in traditional medicine (eight species), as ornamental species in aquariums (two species) and in freshwater pearl culture (one species). Six threats to shellfish populations have been identified: (i) harvesting for commercial trade, (ii) use of illegal fishing gear, (iii) construction of irrigation canals, (iv) destructive ‘katha’ fishing methods, (v) changes in land use and (vi) duck farming in the wetland. The findings of this study will serve as baseline data for future research. To ensure a sustainable supply of shellfish for human consumption and animal feed, we recommend focusing on shellfish aquaculture rather than harvesting from the wild. This approach may be particularly beneficial for mollusc populations. We also advocate for the formulation of conservation regulations for shellfishes in the country

Effects of Streptococcus agalactiae infection and oral florfenicol administration on the hemato-biochemistry, erythrocyte morphology and histopathology of Oreochromis niloticus

Streptococcosis is considered one of the most important diseases affecting farmed tilapia, causing severe economic losses. Antimicrobial therapy is the principal control measure applied during outbreaks. This research assessed the efficacy of florfenicol (FFC) when fed at 15 mg kg biomass–1 day–1 for 10 days against Streptococcus agalactiae infection in Oreochromis niloticus in terms of survival, changes in hemato-biochemistry, erythro-morphology, and histoarchitecture of the vital organs. Streptococcus agalactiae was moderately virulent to O. niloticus with a lethal dose (LD50) of 1.26×108 cells fish–1 and sensitive to FFC with a minimal inhibitory concentration of 0.78 μg mL–1. It caused systemic infection in tilapia. FFC therapy reduced bacterium-induced mortality and physiological stress. The histopathological findings indicated significant improvement in the kidney and liver tissues of fish. The erythrocyte morphological alterations noted in the challenged fish were irregularly shaped, elongated, crenated, and teardrop cells, hypochromic erythrocytes, ragged cytoplasmic membranes, hypertrophied nuclei, eccentric nuclei, and vacuolation, all of which were mitigated with FFC therapy. Eventually, FFC therapy improved wound healing, normalized plasma biochemistry, and aided recovery from bacterial infection. This study revealed that the therapeutic dose of FFC was effective against S. agalactiae infection in O. niloticus and lessened the physiological stress

Stock assessment of Crossocheilus diplochilus (Heckel, 1838) in Dal Lake of Kashmir Himalayas

The intricate dynamics governing population parameters stand as pivotal pillars in the realm of fish management and conservation. Accordingly, the various parameters of population dynamics of Crossocheilus diplochilus (Heckel, 1838) from the Dal Lake of Kashmir valley were investigated. The study reported that the fish exhibits a length range of 5.4 to 14.8 cm and a weight range of 1.24 to 17.19 g. The b value was reported to be 2.9 depicting negative allometric growth. The Fulton and relative condition factors were reported to be 0.86 and 0.99 respectively. The growth constant, asymptotic length, age at zero length and growth performance index were reported to be 0.33 year–1, 17.40 cm, –0.62 years and 2.0 respectively. Fishing mortality was found to be higher than the natural mortality. The exploitation ratio was reported to be 0.52 which was found to be lower than the exploitation rate producing maximum yield (0.81). This is suggestive of an underexploited state of fishery of C. diplochilus from this lake