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Nano-sized Zn particles are recognized for its ability to elevate fish health and well-being, enhancing antimicrobial and antioxidant capacities and reinforcing the immune system. In the present study we explored the effects of Zn-NPs supplementation on augmenting the growth performance and nutritional indicators and physiological aspects of the catfish, Clarias batrachus. Zn-NPs were prepared by heating the mixture of [Zn(CH3COO)2.2H2O], ethylene glycol and polymer surfactant (PVP) at 70°C for 45  min using an oil bath heater. The resultant solution was centrifuged at 6000  rpm on a heated plate at 70°C until the precipitation of Zn-NPs was achieved. Crystal structure, growth mechanisms and shapes of Zn-NPs were characterized by the atomic force microscopy. Produced Zn-NPs was characterized by spectrophotometer and the zeta potential and mean size was recorded as −32.5  ±  1.0  mV and 14.7  ±  2.5  nm, respectively. The experiment comprised six distinct test diets, categorized by the incorporation of Zn-NPs at levels of 0, 10, 20, 30, 40, and 50  mg/kg into the feed where the initial diet was employed as a control group, devoid of any Zn-NPs supplementation. Three glass aquariums were employed for each diet. In each aquarium, 12 fish with an initial mean weight of 5.23  ±  0.06  g were stocked. The fish underwent experimental feeding for 60  days, with the feed amount set at 3% of their body weight. After the experimental period, growth performance (weight gain, length gain, average daily gain, specific growth rate, thermal growth co-efficient, condition factor and survival rate), nutritional indices (feed conversion ratio, protein efficiency ratio, annual net protein utilization), proximate composition of muscle (protein, lipid, carbohydrate, ash and moisture), hematological parameters (RBC, WBC, hemoglobin, hematocrit, MCV, MCH, MCHC, total protein, albumin and globulin), serum lipid and enzymatic parameters (total cholesterol, HDL, LDL, triglycerides, ALP, AST, ALT, amylase, lipase and protease), and bioaccumulation of Zn in different organs of fish were estimated following standard methods. Growth analysis revealed that C. batrachus fed with Zn-NPs at 40  mg/kg of feed had significantly (p  <  0.05) improved growth performance (WG  =  18.87  ±  0.91  g, SGR  =  2.52  ±  0.06% g/day, TGC  =  1.09  ±  0.05 and CF  =  1.47  ±  0.12), nutritional indices (FCR  =  1.35  ±  0.06, PER  =  2.24  ±  0.10 and ANPU  =  41.46  ±  2.56%), hematological parameters, and enzymatic activity compared to control and other groups. The optimal dietary supplementation of Zn-NPs for final weight, weight gain and specific growth rate of C. batrachus was estimated to be ranged between 30.4 and 30.5  mg/kg per diet, respectively. [ABSTRACT FROM AUTHOR]

Reliance on fish meal can be reduced by incorporating plant-based ingredients, making aquaculture more economical, sustainable and environmental friendly. In this study, the efficacy of plant protein ingredients (PPI) such as mustard oil cake (MOC), soybean meal (SBM) and rice bran (RB) as Partial substitute of fishmeal (FM) was investigated for a commercially important fish, Labeo rohita in cages for 90 days. Three experimental diets, labeled as Diet 1, Diet 2, and Diet 3, were formulated to be isonitrogenous (with protein content ranging from 32.20 to 32.29%) and iso-caloric (with gross energy ranging from 4.12 to 4.17 kcal/g). These diets contained different proportions of PPI (45, 68, and 79%) and FM (46, 23, and 11%, respectively). Square-shaped cages with a volume of 1m3 (1 m × 1 m × 1 m) were stocked with 40 fish/m3 each with an average initial weight of 52.97 g in triplicates. Fish were hand-fed to apparent satiation twice daily for 7 days a week at a feeding rate of 5% in the initial month and 3% for the rest of the culture period. 50% of the caged fish was sampled monthly to monitor growth performance and at the termination of the experiment, all the fish was harvested to measure production economics performance. The results indicated improved growth performance and higher feed utilization at Diet 2, yielding significantly (p < 0.05) higher fish production compared to Diet 3, while these parameters were insignificant with Diet 1. By replacing FM with PPI, the total feed cost compared to Diet 1 was reduced to 20.62 and 32.76% for Diet 2 and Diet 3, respectively. The replacement of 50% FM in Diet 2 also yielded a 15.61% higher total economic net return than the Diet 1 group. However, a higher inclusion rate of PPI in Diet 3 potentially reduced fish growth, with a consequent decline of 41.61% total economic net return compared to the Diet 1 group. In conclusion, the replacement of 50% FM in Diet 2 compared to Diet 1 returned a higher benefit-cost ratio (1.72) among the feeding groups. Therefore, this FM replacement experiment suggested a 50% FM replaced diet as an unconventional, cost-effective, and readily available novel protein source without compromising the inherent nutritional quality of fish and feed in the cage culture of L. rohita. The results could be widely applicable to the fastgrowing approach of cage culture technology across Asia and beyond. [ABSTRACT FROM AUTHOR]

The current knowledge regarding the presence of microplastics (MPs) in the digestive tracts of fish, particularly the non-edible parts, provides limited assistance in assessing the risk to human health and establishing guideline values for policy-making purposes. Therefore, we conducted the first investigation into MPs within the commercially significant catfish species S. silondia, form a major tropical estuary assessing their accumulation, characteristics, and associated risks in various tissues, particularly the consumable muscle. A sum of 132 MPs were identified, and the mean abundance of MPs were 7.40 ± 4.12 item/DT, 3.20 ± 1.69 item/gill and 2.60 ± 1.65 item/muscle found in digestive tract (DT), gill and muscle of the fish, respectively. The strong relationships of MPs among three different tissues (y = 0.6069x - 22.69, R2 = 0.7589) indicated the pathways and how MPs were influenced by the physiology of organisms. The prevalence of MPs in fish muscle demonstrated their trophic transmission to humans. Moreover, fishes with higher weight had higher MPs in their gill, and DT. The dominant type, color and size of MPs were fibrous (89.67%), violet (41%) and < 0.5 mm sized (94%), respectively. The high percentage of fibers suggests that they might have come from ropes, fishing nets or sewage. FTIR chemical composition analyses of microplastics (MPs) identified three primary polymer types: PET (44.5%), PE (33.3%), and PP (22.2%) in fish. These polymers are commonly associated with packaging materials, household wastes and plastic pipes. Contamination level assessment by CF (CF = 2.76) and PLI (PLI > 1) indicated moderately to highly contaminated fish with MPs ingestion. While the complete understanding of the direct negative effects of microplastics (MPs) on human health remains elusive, their presence in estuarine fish raises concerns for both human and ecosystem health. The findings will be useful for assessing the hazards to human health from exposure to MPs and for creating effective risk management plans to reduce those risks. [ABSTRACT FROM AUTHOR]

This editorial discusses the impact of climate change on aquatic organisms, focusing on their ecology, diversity, and migration patterns. The Intergovernmental Panel on Climate Change (IPCC) reports that climate change is a significant threat to global biodiversity, and aquatic species are expected to shift their habitats in response to climate changes. The rise in temperature negatively affects marine species' performance and survival, and climate change also has unpredictable impacts on freshwater resources. The editorial highlights the importance of understanding these impacts and provides insights into specific topics such as siphonophores, odour-producing microorganisms, and the vulnerability of coral reefs. The authors emphasize the need for further research and conservation efforts to mitigate the effects of climate change on aquatic ecosystems. [Extracted from the article]