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The objective of this study was to reveal the growth, colouration and gonado-physiological changes due to the exogenous aromatase inhibitor (AIs) in an ornamental fish. 17α-methyltestosterone (MT) and letrozole (LET) were used as potential AIs. The AI were supplemented with a gel-based feed (LET: 50, 100, 150 and MT: 12.5, 25, 37.5 mg/kg feed) in Rosy barb, Pethia conchonius fry. The fishes were reared in a 45-L glass tank using AI treated gel-based feed for 3 months. Growth in AI-based diets was reduced but the reduction was minimal compared to the control. At 25 mg/kg feed of 17 MT, the highest male proportion (84.72% 6.05%) was recorded, which was significantly higher (P≤0.05) than other groups. L*, a*, and b* values showed that 17α-MT-fed groups had brighter coloration (P≤0.05). Histological sections showed that LET-17α-MT suppressed ovarian development, causing atretic oocytes. Testicular development was unaffected. 25 mg/kg-treated feed increased SOD, CAT, GST, and GPX. The AI (MT) at 25 mg/kg gel-based feed could therefore be utilised for musculinization without impacting growth, colour, and antioxidant activity of rosy barb, which serves the entire male population in the ornamental fish sector.

The ornamental fish industry has the potential to enhance profitability through the development of high-value, high-demand species, where value and demand are influenced by factors such as size, coloration, and sex. The aim of this research is to evaluate the combination of 17α-methyltestosterone (MT) and letrozole (LET), an aromatase inhibitor (AI), in inducing masculinization in the rosy barb, Pethia conchonius . The fry of the rosy barb was acclimated to the gel-based diet for 5 days prior to beginning a 90-day experiment in a closed environment. The experimental design included a control (without AI) group and three treatment groups: T1 (M 12.5 +L 150 ), T2 (M 25  + L 100 ), and T3 (M 37.5 +L 50 ) mg/kg feed. The highest percentage of males (86.90 ± 0.59%) was recorded in the M 37.5 +L 50 mg/kg group after 90 days, which was significantly different from the other groups. The histological sections showed suppressed ovarian development with atretic oocytes, while testicular development remained unaffected. Additionally, the concentration of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), and glutathione peroxidase (GPX), were significantly increased in the control group compared to treated groups ( P  < 0.05). Instrumental color analysis on the basis of L*, a*, and b* values showed fed gel-based feed with M 37.5 +L 50 mg/kg had significantly more vibrant color than those in the control groups ( p  < 0.05). Digestive enzyme activity, such as protein (70 ± 0.52), protease (0.054 ± 0.001), lipase (11.16 ± 0.28), and amylase (8.80 ± 0.78), varied among treatment and control groups. These findings suggest that incorporating AI at a concentration of 37.5 mg/kg + L50 mg/kg within a gel-based feed is a promising approach for masculinizing rosy barbs without significantly impacting their growth, color, or antioxidant activity. This approach holds significant potential for the ornamental fish industry by enabling the production of all-male populations.

Fish, being highly sensitive to changes in the physico-chemical parameters of water, are good indicators of contamination. Teesta, a prominent northern West Bengal River system, is increasingly contaminated due to anthropogenic activities. This study aims to determine agricultural pesticide contamination and its genotoxic impact on the resident fish, Pethia conchonius , as an experimental organism. Sample water analysis from three riverine sites I, II & III, showed the presence of the insecticides imidacloprid (IMI), chlorpyrifos (CPF), bifenethrin (BF), cypermethrin (CP), difenthiuron, acetamiprid (AC) in the sites II and III only with adjoining agricultural lands. Comet assay revealed a significantly lower % Head DNA (~ 1.2 times), higher %Tail DNA (~ 16 times), and %Tail length (~ 3.1 times) in the gills of Pethia conchonius from sites II and III. About 4 and 10 times increase of micronuclei and other nuclear abnormalities were also noted in the erythrocytes of the fish from sites II and III than I, which was not contaminated. The antioxidant enzymes SOD, CAT, and GST activity and MDA levels were significantly higher ( p <  0.05) in the liver samples from sites II and III, while AChE activity was significantly decreased ( p <  0.001) in the brain tissues. Moreover, the sod , cat , and gpx expression in the hepatic cells were significantly upregulated compared to the β actin mRNA indicating increased oxidative stress. Increased genomic damage, antioxidant enzyme activity, higher MDA levels, decreased AChE activity in the brain, and the upregulation of hepatic genes strongly suggested the genotoxic effects of the detected insecticides in combination with other contaminants.

Aim: The effects of Difenoconazole fungicide were assessed on Pethia conchonius (Hamilton, 1882) by examining their behavioural, histopathological and brain acetylcholinesterase activity. Methodology: Acute toxicity test was carried out following the OECD Guideline (2019) to estimate the 96 hr-LC50 of Difenoconazole (1.886 mg l-1). Three concentrations of Difenoconazole, (0.037, 0.188 and 0.377 mg l-1) designated as SLC I, II and III were used to expose the fish for 96 hr. Behaviour was monitored regularly. Brain tissue was collected at 24 hr intervals for histopathological study and biochemical assay of acetylcholinesterase. Temperature, pH, total alkalinity, total hardness, and dissolved oxygen of test water, were also analyzed following the standard method. Results: Exposed fish exhibited significantly reduced acetylcholinesterase activity and mild to severe behavioural changes including sluggish movement, loss of equilibrium, bottom-crowding and excessive mucus secretion in a dose and time-dependent response. Necrosis, vacuolation and layer detachment were also noted in the optic tectum of brain. Interpretation: Inhibition of acetylcholinesterase activity, severe neural damage and behavioural modulations strongly highlighted Difenoconazole's neurotoxic potential. Key words: Biomarker, Difenoconazole, Neurotoxicity, Pethia conchonius, Triazole

For aquaculture assessments, the length-weight relationship and condition factor are considered as standard methods for determining fish growth, its health and the potential yield. A year-long study was conducted to calculate length-weight relationships (LWRs) and condition factor (K) for seven fish species, Schizothorax niger (Alghad or snowtrout), S. curvifrons (Sattar snowtrout), Cyprinus carpio (Common carp), Carassius carassius (Crucian carp), Pethia conchonius (Rosy barb), Crossocheilus diplochilus (Kashmir latia) and Gambusia holbrooki (Mosquito fish) in Manasbal Lake. The results revealed that four captured fish species (S. niger, S. curvifrons, C. diplochilus and G. holbrooki) exhibited negative allometric growth, while other fish species (C. carpio, C. carassius, P. conchonius) exhibited positive allometric growth. LWR was significant at P < 0.01 in all seven fish species, with a coefficient of determination (R2) ranging between 0.73 to 0.96. The K was higher in C. carpio than C. carassius, P. conchonius, G. holbrooki, C. diplochilus, S. niger and S. curvifrons. The current study providing the LWRs and condition factor of seven fish species from Manasbal Lake, Kashmir will be helpful for the management of fish species as well as for assessing the ecological condition of the Lake.

The ornamental fish trade provides a pathway for the global translocation of aquatic parasites. We examined a total of 1020 fish imported from Singapore, Malaysia, Thailand, or Sri Lanka to Australia (including freshwater and marine fish species) for monogenean ectoparasites. Fish were received following veterinary certification that they showed no clinical signs of pests and diseases from the exporting country and visual inspection at Australian border control. Australian import conditions require mandatory treatment for goldfish with parasiticides (e.g. trichlorfon, formaldehyde, sodium chloride) for the presence of gill flukes (Dactylogyrus vastator Nybelin, 1924 and Dactylogyrus extensus Mueller and Van Cleave, 1932) prior to export. Over 950 individual parasites were detected in five imported fish species, representing 14 monogenean species. Seven Dactylogyrus spp. including D. vastator and three Gyrodactylus spp. infected goldfish, Carassius auratus Linnaeus, 1758, from Malaysia, Singapore, and Thailand. Dactylogyrus ostraviensis Řehulka, 1988, infected rosy barb, Pethia conchonius Hamilton, 1822, from Singapore, Sri Lanka, and Thailand while two Trianchoratus spp. infected three spot gourami, Trichopodus trichopterus Pallas, 1970 and pearl gourami Trichopodus leerii Bleeker, 1852, from Sri Lanka. Urocleidoides reticulatus Mizelle & Price, 1964, infected guppy, Poecilia reticulata Peters, 1859, from Sri Lanka. The discovery of D. vastator in goldfish, as well as 13 other monogenean species, shows that pre-export health requirements, which include chemical treatment of goldfish, and inspection of all ornamental fish species did not prevent infection by monogeneans. Inspection prior to exportation and at border control must account for the highly cryptic nature of monogenean parasites and consider alternatives to current pre-export conditions and visual inspection at border control.

The present study describes the length‐weight relationships (LWRs) for nine fish species from the Tetulia River, southern Bangladesh, namely Anabas testudineus, Coilia dussumieri, Otolithoides biauritus, Otolithoides pama, Pethia conchonius, Polynemus paradiseus, Puntius lateristriga, Setipinna taty and Sillaginopsis panijus. A total of 1380 specimens were caught using traditional fishing gear from March 2012 to February 2013. Individual total length (TL) and body weight (BW) were measured by digital slide calipers and digital balance, respectively. The LWR was calculated as W= a Lᵇ, where the W is the BW in g and L the TL in cm, a and b are regression parameters. This study presents the very first references on LWRs for seven of the species. The results are valuable for the application of sustainable management and conservation of these fishes in the Tetulia River and surrounding ecosystems.

Diversity, abundance and distribution pattern of the fish fauna are important aspects that need to be considered in order to frame the conservation and management strategies in any water body. To assess the composition, diversity and relative abundance of the fish fauna in the Manasbal Lake of Kashmir, the present study was carried out for two years (March 2018 - February 2020). A total of 22522 fish specimens were netted out during the sampling period, and the relative abundance and various diversity indices were used to assess the overall diversity of the inhabiting fish fauna. A total of 7 species belonging to two families, Cyprinidae and Poeciliidae, were reported, of which the family Cyprinidae was dominant in the catch. The relative abundance and diversity of the fish fauna showed spatio-temporal variation wherein Pethia conchonius was most abundant during spring and winter, while Gambusia holbrooki was most abundant during summer and autumn. Cyprinus carpio was found to be abundant during all the seasons at Site II and Site III as compared to native cyprinids, Schizothorax niger and S. curvifrons. The current study also indicated a good fish diversity in the lake which varies on spatio-temporal scales, showing maximum diversity during winter (Hʹ =1.498) and minimum diversity during summer (Hʹ = 1.247), while Site II showed maximum diversity (Hʹ =1.369) and Site I showed minimum diversity (Hʹ =1.085). Overall lake possesses good fish diversity that could be a great source of income for the local populace provided the fish assemblages are sustainably managed.

Tetracotyle wayanadensis n. sp. (Digenea, Strigeidae) infecting different organs of six species of freshwater fishes, Haludaria fasciata (eye, buccal cavity), Amblypharyngodon melettinus (eye, buccal cavity), Aplochelus lineatus (operculum, heart, mesenteries), Pethia conchonius (brain), Parambassis thomassi (muscles, mesenteries) and Lepidocephalus thermali (mesenteries) collected from water bodies in the Wayanad region of the Western Ghats is described and illustrated. Tetracotyle wayanadensis n. sp. is new to the genus and is separated from its congeners on the basis of differences in morphology and morphometry. The present paper also describes the prevalence, intensity, mean abundance and sites of infection of the parasite in each host. The prevalence of infection of T. wayanadensis n. sp. in Haludaria fasciata is 7.5%, intensity of infection is 2.66 and mean abundance is 0.2; in Amblypharyngodon melettinus 10%, 6 and 0.6; in Aplochelus lineatus 12.2%, 6.2 and 0.76; in Pethia conchonius 7.14%, 5 and 0.36; in Parambassis thomassi 100%, 2 and 2; in Lepidocephalus thermali 10%, 2 and 0.2 respectively.