Neolissochilus Hexagonolepis Research Articles

Crassocephalum crepidioides as a sustainable protein supplement in Chocolatemahseer (Neolissochilus hexagonolepis) diets: Implications for growth,health, and economic viability in sustainable aquaculture

This study investigated the potential of Crassocephalum crepidioides, an abundant weed as a protein supplement in chocolate mahseer (Neolissochilus hexagonolepis) diets. The plant replaced a combination of fish meal and mustard oil cake at 0%, 25%, 50%, 75%, and 100% in experimental diets. A 12-week feeding trial was conducted to assess growth performance, survival, biomass yield, digestive enzyme activity, blood parameters, and economic viability. Results indicated that C. crepidioides can effectively replace up to 61.3% of the combined fish meal and mustard oil cake protein without negatively impacting fish health or growth, while reducing feed costs. Fish fed diets with 25% replacement showed improved weight gain (15.5±0.7 g) and biomass yield (6.05±0.25 kg/m³) compared to the control (14.6±0.8 g and 5.75±0.28 kg/m³, respectively). Survival rates were high across all treatments (94.0- 97.3%). Digestive enzyme activities and blood parameters remained within normal ranges for inclusion levels up to 75%. Economic analysis revealed potential cost savings of up to 15.5% when incorporating C. crepidioides into mahseer diets. This finding presents an opportunity to develop low-cost fish feed for resource-poor farmers in Meghalaya, effectively converting a local weed into a valuable aquaculture input, with broader implications for sustainable aquaculture practices globally.

Analysis of Phylogenetics and Structural Relationships of the Cytochrome b Gene Protein in Mahseer Fish (Tor sp.)

Abstract The Cytochrome b gene from mitochondrial DNA encodes a protein that can be used as a genetic marker to identify species. This study aims to determine the bioinformatic characteristics of the gene encoding Cyt b isolated from various Mahseer species, Tor tambroides, Tor douronensis, Tor khudree, and Tor putitora. Mahseer Cyt b sequences can be used for detailed computational investigation of the properties of 3D protein models and phylogenetics. The data analysis technique uses nucleotides with a sequence length of 330 bp obtained from NCBI. The MEGA X program was used for phylogenetic analysis. 3D protein structure predictions were obtained through the Swiss model and protein homology program using PYMOL software. The results of phylogenetics show close kinship relationships with the closest genetic distance of 0.000, while the farthest distance is 0.068. The nucleotide composition contains Thymine (30.23%), Cytosine (25.81%), Arginine (28.05%), and Guanine (15.92%). 3D modeling of the Cyt b protein Mahseer referring to the species Neolissochilus hexagonolepis (McClelland, 1839). The 3D protein structure prediction was assessed via a Ramachandran plot of 99.07%. This study can be used as a reference to support sustainable conservation efforts by observing the populations and habitat conditions.

Insights on the distribution, catch and release and public sentiment towards recreational angling of mahseers—A study of YouTube videos from India

Abstract Masheers are a group of large‐bodied freshwater fishes popularly known as the ‘Tiger of Rivers’. Their size and fighting power make them one of the most popular game fishes and a dream catch of many recreational anglers in the Indiansubcontinent. The present study explored the recreational angling (RA) videos of five mahseer species (Tor khudree [Deccan mahseer], Tor putitora [golden mahseer], Tor remadevii [humpback mahseer], Tor mosal [mosal mahseer] and Neolissochilus hexagonolepis [chocolate mahseer]) recorded from India and uploaded on the social media platform YouTube from January 2010 to October 2022. We did not come across any RA videos of T. mosal and T. remadevii; hence, further analyses were carried out on the remaining three focal species. No seasonality was observed in the frequency of RA videos uploaded on YouTube, and T. khudree attracted the highest number of views per video. Catch and release, an ethical RA practice, was noticeably low in the case of N. hexagonolepis. The length of catch was found to be positively associated with the social engagement received by the RA videos of all three mahseer species. Angler‐ and angling‐related remarks and words associated with positive emotions (trust, joy and anticipation) dominated the comments received by the angling videos. The results are discussed in light of the trending discourses on developing social media data as a complementary tool for monitoring and managing RA and conserving fish.

Morphometric and Molecular Assessment of Tor putitora and Neolissochilus hexagonolepis Population in Jia Bhoroli river Ecotone Zone, Assam

Background: Ecotones are areas of overlap between different ecosystems, referred to as ‘junction zones or tension belts’, that harbor a distinct collection of organisms. Tor putitora and Neolissochilus hexagonolepis are two threatened Mahseer species which requires urgent conservation attention. Bhalukpung area in the River Jia Bhoroli is an ideal example of an ecotone, as its ecosystem transforms from resembling a foothill river ecosystem to a river floodplain ecosystem. However, studies on threatened fish populations in ecotone zones, which could be used as conservation sites, are lacking. Therefore, the present study aims to generate firsthand information on the relationship between the populations of these threatened fish and their foothill-floodplain river interface ecotone in the Jia Bhoroli River. Methods: The data on water quality, topography was collected for a period of one year from January to December, 2021 along with fish samples. The mahseer species were identified and catch per unit effort (CPUE) was also calculated. Result: Identification of the collected mahseer fish as T. putitora and N. hexagonolepis were confirmed using both morphometric as well as molecular tools. CPUE was found to be 4.3-12.6 for N. hexagonolepis and 4.1-10.3 for T. putitora. The ecotone zone was found to have a thriving mahseer population and ecotones are believed to play a crucial role as a diverse food source for the fish. Conserving Bhalukpong as a designated ecotone site in the Jia Bhoroli River as a fish sanctuary can help to protect their populations. Further research that encompasses all aspects of ecology is recommended for the future.

Bionomics, length-weight relationship and condition factor of Chocolate mahseer, Neolissochilus hexagonolepis from Dikhu River, Nagaland

Aim: Chocolate mahseer (Neolissochilus hexagonolepis) is widely distributed in the North-eastern region of India. The study aimed to evaluate the bionomic aspects of chocolate mahseer of Nagaland to validate its status. Methodology: Fish Neolissochilus hexagonolepis were collected from March 2019 to February 2020 from Dikhu River, Nagaland. Regression analysis for morphometric study was conducted using the least square method. Logarithmically transformed total length and weight data were utilized to determine the correlation coefficient 'r', coefficient of determination 'r²', and condition factor for male, female, and pooled groups. Results: The highest correlation was seen in standard length ('r' = 0.9968), and the least correlation was observed in eye diameter ('r' = 0.7769). The length-weight relationship exhibited two growth patterns, namely negative allometric growth, which were represented by females (b = 2.807) and pooled (b = 2.868) population, whereas the population of males displayed positive allometric growth (b = 3.015). The correlation coefficient and coefficient of determination of males, females and the pooled sexes showed a positive correlation with relation to its length and weight ranging from 'r' = 0.970 - 0.981 and 'r²' = 0.941 - 0.961, respectively. The condition factor for all the groups ranged from 1.10 - 1.14. Interpretation: Morphometric traits like standard length, snout length, head length etc. (dependent variable) were analyzed on total length (independent variable), signifying a positive correlation among variables. Length-weight relationship displayed high significance between length and weight parameters. The condition factor for all the groups indicated general well-being of fish condition in their environment. Key words: Chocolate mahseer, Condition factor, Length-weight relationship, Morphometric studies

Environmental DNA (eDNA) based fish biodiversity assessment of two Himalayan rivers of Nepal reveals diversity differences and highlights new species distribution records

Although over 180 freshwater fish species have been reported from Nepal, little is known of their ecology and distribution. This information is needed because their diversity may be threatened by developments like hydropower constructions. We conducted Nepal’s first environmental DNA (eDNA) based fish biodiversity assessment in two major river systems- Karnali River (KR), which is still pristine and Trishuli River (TR) with numerous hydropower plants. The eDNA was concentrated by filtering (0.45 μm pore size) two liters of water collected at different sampling points in each study site. A total of 224 eDNA samples (KR = 162 and TR = 62) were collected, from which fish species were identified by 12S rRNA metabarcording approach utilizing Illumina sequencing platform. Alpha and beta diversity of species between two river basins were compared. Also, in KR site, fish (N = 795) were caught, and identified using COI gene based DNA barcoding method- building Nepal’s first fish DNA reference database. Field sampling identified 21 species through morphology and DNA barcoding, where Barilius spp. and Schizothorax spp. were the most abundant. From 244 eDNA samples, 24 Operational Taxonomic Units (OTUs) were identified in TR and 46 in KR with 19 being common to both sites, 27 being unique in KR, and five in TR only. Most fishes were of Cypriniformes and Siluriformes orders, with Barilius spp. and Schizothorax spp. being the most abundant. Long distance migratory fish (Tor spp, Neolissochilus hexagonolepis) and non-native fishes were identified in eDNA samples as well. Alpha diversity in TR was significantly lower than in KR. High beta diversity between the two sites indicated low similarity in fish diversity between the TR and KR. This study demonstrated the utility of eDNA as a non-invasive technique for biodiversity assessment which is particularly useful in areas like Nepal with scarce data on fish species distribution.

Temperature alters the oxidative and metabolic biomarkers and expression of environmental stress-related genes in chocolate mahseer (Neolissochilus hexagonolepis).

Long-term acclimation temperature effects on biomarkers of oxidative stress, metabolic stress, expression of heat shock proteins (Hsps), and warm-temperature acclimation related 65-kDa protein (Wap65) were evaluated in the threatened chocolate mahseer (Neolissochilus hexagonolepis). Fifteen-day-old larvae were acclimated to different water temperatures (15, 19, 23-control group, 27, and 31°C) for 60days prior to the sampling for quantification of mRNA, enzyme, nitric oxide, and malondialdehyde (MDA) content. Acclimation to 31°C increased the basal mRNA level of glutathione S-transferase alpha 1 (GSTa1), and activities of catalase (CAT), glutathione reductase (GR), and GST enzymes and but downregulated the expression of superoxide dismutase 1 (SOD1) in the whole-body homogenate. Other antioxidant genes, i.e., CAT and GPx1a, were unaffected at 31°C, and nitric oxide (NO) concentration was significantly lower. In contrast, fish acclimated to 15°C showed an upregulated transcript level of all the antioxidant genes and no significant difference in the CAT, GR, and GST enzymes. Activities of the metabolic enzymes, aspartate transaminase (AST) and alanine transaminase (ALT), were significantly lower at 15°C. The expression of Hsp47 was upregulated at both 15 and 31°C groups, whereas Hsp70 was elevated at 27 and 31°C groups. Wap65-1 transcription did not show significant variation in treatment groups compared to control. Fish in the high (31°C) and low-temperature (15°C) acclimation groups were capable of maintaining oxidative stress by modulating their antioxidant transcripts, enzymes, and Hsps.

Ichthyofaunal diversity in the lower Narayani River, Chitwan, Nepal

Narayani River in Nepal is an excellent habitat for diverse groups of aquatic organisms. A stretch of 70 km of lower Narayani River was studied for fish diversity and composition. A total species richness of 40 representing 14 families and 7 orders was reported. Order cypriniformes had high taxa dominance of 67% whereas least taxa richness of only 2 % with single species were recorded from orders Beloniformes, Clupeiforms, Gobiiformes and Osteoglossiformes. Simpson diversity index ranged from 0.1 to 0.8 whereas Shannon diversity and Pielou’s evenness ranged from 0.2 to 2.1 and 0.3 to 0.8, respectively. Minimum taxa richness and abundance were recorded in river stretches with industrial effluents situated along the bank of the river. High conservation species such as Wallago attu, Chitala chitala, Tor tor and Neolissochilus hexagonolepis were documented in the most downstream section, i.e., Tribeni of the river. Non-metric multidimensional scaling (NMDS) analysis distinguished three clusters of sites for the river where fish community composition was found to be significantly different (p <0.05). The outcomes of the study help identifying critical river stretches that need high conservation efforts for conserving fish diversity in the lower Narayani River.

Assessment of ichthyofaunal diversity and identification of habitat specialist fishes along altitudinal gradient in river Murti, West Bengal

Despite of being rich in fish biodiversity, the freshwater resources of India are currently experiencing an alarming decline due to several factors. River conservation and management activities in most countries, including India, suffer from inadequate knowledge of the constituent biota. This emphasizes an immediate need for initiating global research to develop alternative conservation planning schemes to protect the biodiversity of these freshwater aquatic systems. So, the present study was aimed at monitoring ichthyofaunal diversity, richness and abundance of river Murti in relation to different habitat types. Fishes were collected from four different sites along altitudinal gradient in river Murti, West Bengal. Key parameters responsible for structuring such habitat types and fish assemblage pattern were also assessed to identify habitat specialist fish fauna. A total of 40 species representing 27 genera, 16 families and 5 orders were collected, where Cyprinidae was found to be the most abundant fish family followed by Channidae and Mastacembelidae and the fish assemblage was found to be most diverse at the plains compared to hilly terrains. Whittaker’s β diversity showed highest value between the sites situated at highest and lowest altitude. Four species namely Neolissochilus hexagonolepis (McClelland, 1839),Garra gotyla gotyla (Gray, 1830), Acanthocobitis botia (Hamilton, 1822) and Danio dangila (Hamilton, 1822)were found to prefer four different sites and may be termed as habitat specialists. Such thorough understanding of this aquatic system and its biodiversity may assist in decision making and policy framing that lead to sustainable water use practices

Estimation of length-weight relationship and condition factor of the mahseer fingerlings, Neolissochilus hexagonolepis (McClleland, 1839) of River Ghish in Darjeeling Himalaya of West Bengal, India

A Length-Weight Relationship (LWRs) and Condition Factor (K) of Neolissochilus hexagonolepis (McClelland, 1839) fingerlings collected from three adjoining sites of River Ghish, Darjeeling Himalaya, West Bengal, India was studied. A total of 90 specimens were collected during November 2019 and total length-weight data was measured. The total length of specimens studied ranged from 4.0 to 5.9 cm while, the total weight ranged from 0.54 to 1.92 g. Linear regression analysis was used to calculate the degree of relationship between total length and total weight. The Coefficient of Determination (r2) value ranged from 0.976 to 0.974 exhibiting a highly significant correlation (p≤0.001) between length and weight. Estimates of parameter b ranged from 2.893 to 2.926 suggesting negative allometric growth, while estimates of parameter a ranged from 1.12 x 10-5 to 1.29 x 10-5, for three river sites. The overall estimate of Condition Factor (K) indicated increasing growth pattern along with the length of fingerlings. Thus, the data obtained will complement the efforts to understand the biology of these stage specific fish species and will provide useful information for its culture in confined condition.

Trace elements in fish species: Schizothorax richardsonii, Salmo trutta and Neolissochilus hexagonolepis in relation to sizes and tissues of Punatsang Chhu

Three fish species ( Schizothorax richardsonii, Salmo trutta and Neolissochilus hexagonolepis ) were collected from Punatsang Chhu river and sample tissues of muscles and gills were analyzed for Al, As, Ba, Cd, Co, Cr, Cu, Fe, K, Mn, Mo, Ni, Pb, Se, Sr and Zn using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). Principal Component Analysis (PCA) for each species grouped elements with higher concentration in gills compared to muscle tissues. The Man-Whitney test revealed significant difference between tissues sources and concentrations of Al, Ba, Cd, Co, Fe, K, Mn, Mo, Ni, Sr and Zn in S. richardsonii , Al, Ba, Co, Fe, K, Mn, Ni, Sr and Zn in S. trutta and Al, Ba, Co, Cr, Fe, K, Mn, Sr and Zn in N. hexagonolepis. The Kruskal-Wallis test for inter-species variation revealed significant difference in concentration of As, Cr, Cu, Fe, Mn, Ni and Zn in muscle tissues and Ba, Cr, Cu, Mn, Sr and Zn concentrations in gills of three species. Spearman correlation between levels of elements and fish size (weight and length) revealed positive and negative relationships for concentrations of As, Ba, Cd, Co, Cr, Cu, Fe, K, Mn, Ni, Pb, Sr, and Zn and concentrations of Al, Ba, Cd, Co, Fe, K, Mn, Mo, Ni, Sr and Zn respectively, both at p < 0.001 and p < 0.005. • Sixteen trace elements analyzed in tissues of the three fish species using ICP-OES. • Significant differences in concentration of trace elements in gills and muscle tissues of three fish species. • Strong to moderate of both positive and negative correlations between fish sizes and concentration of trace elements. • Interspecies concentration significantly different for most of the trace elements. • MPI observed highest in Schizothorax richardsonii for both gills and muscle tissues compared to other two species.

Trade Potential of Indigenous Ornamental Fishes of Arunachal Pradesh, India

Arunachal Pradesh is rich with networks of drainage systems with enormous wild fish diversity due to varied climatic and topographical features. Most of the streams harbour very alluring small indigenous minnows, loaches, catfishes and barbs that have hardly been exploited for the ornamental fish market. If these aquatic resources are sustainably utilised as a trade commodity, then the pattern of livelihood of the local populace may be uplifted economically. The present investigation was undertaken to establish the market potential of certain indigenous ornamental fishes of Arunachal Pradesh. The survey was conducted during 2019–2020 for 6 months (October–March) based on the feasibility of accessible collections. A total of 52 ornamental fish species under 6 orders and 15 families were documented and collected during the surveys in various streams and rivers. The collection showed that 4 species namely Balitora brucei Gray, 1830, Aborichthys kempi Chaudhuri, 1913, Schistura devdevi Hora, 1935, and Neolissochilus hexagonolepis (McClelland, 1839) were recorded under near threatened; Lepidocephalichthys arunachalensis (Datta &amp; Barman, 1984) and Botia rostrata Günther, 1868, under endangered and vulnerable categories, respectively as per International Union for Conservation of Nature (IUCN) status. The species documented exhibiting natural ornamental features herein considered an indigenous ornamental fish (IOF) for depicting their market demand showing the minimal price of each individual species towards the development of organised trade in Arunachal Pradesh.

A karyotype study in two fish species belonging to Genus Neolissochilus found in Meghalaya, India

The karyomorphological study of two species of Mahseer belonging to the genus Neolissochilus, namely Neolissochilus hexagonolepis and N. hexastichus were carried out. The study revealed the basic chromosome number in both the Masheer species was observed to be 100. However, the karyotype formula number varied among the species. N. hexagonolepis had a diploid chromosome number of 42 metacentric (m), 20 submetacentric (sm), 8 subtelocentric (st) and 30 telocentric (t) and N. hexastichus had a karyotypic formula of 32 metacentric (m), 22 submetacentric (sm), 4 subtelocentric (st) and 42 telocentric (t). This finding removed taxonomic confusion due to the differences in the chromosome number, the morphology of the chromosomes and chromosome formula between the two fish species of the genus and helped in distinctive and unblemished identification of the two species belonging to the genus Neolissochilus from Meghalaya, though they have a morphological similarity.

Spawning substrate preference and spawning behavior of chocolate mahseer, Neolissochilus hexagonolepis

Captive breeding programs for Neolissochilus hexagonolepis are essential for population restoration. To develop an efficacious method for enhancing N. hexagonolepis spawning in captivity, there was examination of: (1) different types of spawning substrate and (2) area of spawning in the substrate. The study was conducted to describe spawning behavior of males and females. There was a choice of three substrates in which to spawn: gravel, small cobble, and coarse sand. There was preferential choosing of gravel followed by cobble with there being no use of sand for spawning. Behavior of N. hexagonolepis included preparation of a spawning pit by females, a behavior that has not been previously ascertained for cyprinids. Males expressed courting behaviors, including chasing, nudging, and quivering. Courting males expressed aggressive behaviors towards other males. Results from the present study are the first on the volitional spawning of N. hexagonolepis in captivity using spawning substrate. It was further revealed that using a gravel substrate tray would also be a feasible approach for egg production. Mean total eggs per female and mean fertilized eggs collected were less when there was siphoning used for egg collections in the preference study. Hence, stripping was implemented to increase the egg collection when spawning behaviors were observed. Total eggs collected were 40,540 with 3685 eggs per female, 90.3% fertilization rate, 82.8% hatching rate, and 97.4% free-swimming larvae survival rate. The implications of this study could be beneficial for enhancing the natural population through environmental management and developing a viable egg production technique in captivity.

Modeling the climate change impact on the habitat suitability and potential distribution of an economically important hill stream fish, Neolissochilus hexagonolepis, in the Ganges–Brahmaputra basin of Eastern Himalayas

Modeling the climate change impact on the habitat suitability and potential distribution of an economically important hill stream fish, Neolissochilus hexagonolepis, in the Ganges–Brahmaputra basin of Eastern Himalayas

Effects of rearing temperature on egg incubation, growth, standard metabolic rate, and thermal tolerance of chocolate mahseer, Neolissochilus hexagonolepis.

The present study was aimed to assess the effect of temperatures on egg incubation, growth, standard metabolic rate (SMR), and thermal tolerance of a near threatened Himalayan hill stream chocolate mahseer (Neolissochilus hexagonolepis). For the hatching study, eggs were incubated in four temperatures (17, 20, 23, and 26°C). The total hatching and free-swimming larvae percentage were higher at 23°C (p<0.05). Experiment I (for validation of the CTmax method) was carried out by incubating eggs at 17°C and 23°C. The CTmax was estimated in response to different warming rates (1-18°C h-1), acclimation temperatures (17 and 23°C), and the age of fishes (8, 15, 35 dph). The results suggested that a warming rate of 18°C h-1 could be used for the thermal tolerance study of yolk-sac larvae (8 dph) and 35 dph larvae, but for free-swimming larvae (15 dph) up to 3°C h-1 is suitable. Experiment II (for growth, SMR and thermal tolerance) was carried by acclimatizing 15 dph larvae in five temperatures (15, 19, 23, 27, and 31°C) for 60 days. The mean growth rate increased with the increase in temperature from 15°C to 27°C (1.30-3.58% day-1) and decreased at 31°C. The mean SMR of the chocolate mahseer in the above acclimation temperatures was ranged from 1.14±0.36 to 2.81±0.15 μgO2h-1mg-1 and were significantly different (p<0.01). The Q10 with the SMR of the fish suggested the preferred temperature ranged between 23 and 27°C, and the optimum temperature for growth (ToptG) was estimated to be 25°C. Chocolate mahseer is an eurythermal species which is advantageous for aquaculture practices due to its wide thermal tolerance zone (411.68°C2 in 15 to 31°C acclimation temperature range) and high ARR values (0.49 - 0.54).

Species composition and longitudinal patterns of fish assemblages in the middle and lower Yarlung Zangbo River, Tibetan Plateau, China

The Yarlung Zangbo River is the largest river on the Tibetan Plateau, which is considered a hotspot of biodiversity conservation efforts. In this study, the fish fauna of the middle and lower Yarlung Zangbo River was investigated, to explore the species composition and spatial patterns of fish assemblages as well as the associated environmental factors. Thirty-four sites across an elevation of 589 to 3410 m were sampled in 2015 and 2016. A total of 35 species—28 native and seven exotic—was collected. Of these species, four were described for the first time, 14 were endemic to the Yarlung Zangbo-Brahmaputra River drainage and five are considered endangered. Cluster analysis revealed significant spatial changes in fish assemblages along the longitudinal gradient. Two site-groups separated by the Yarlung Zangbo Grand Canyon were identified, corresponding to midstream and downstream. In the midstream, fish assemblages were characterized by typical plateau fish species (e.g., Schizopygopsis younghusbandi, Schizothorax oconnori, Triplophysa stenura, Triplophysa brevicauda, Schizothorax macropogon, Triplophysa tibetana and Ptychobarbus dipogon), while in the downstream fish assemblages were characterized jointly by plateau species (e.g., Schizothorax curilabiatus and Schizothorax molesworthi) and oriental species (e.g., Garra tibetana, Psilorhynchus homaloptera, Pseudecheneis sulcata, Exostoma tenuicaudata, Parachiloglanis hodgarti, Neolissochilus hexagonolepis and Garra yajiangensis). Canonical correspondence analysis (CCA) showed that altitude, channel width and the density of macroinvertebrates were the main environmental factors determining the spatial distribution of fish assemblages. This study is an important step towards understanding fish assemblages in the middle and lower Yarlung Zangbo River and will help with future efforts to protect aquatic communities and their habitats.

FOOD AND FEEDING OF CHOCOLATE MAHSEER (NEOLISSOCHEILUS HEXAGONOLEPIS) FROM FRY TO JUVENILE STAGES IN CAPTIVITY

Chocolate mahseer, Neolissochilus hexagonolepis was reared from the juvenile stages in captivity to establish it as a new candidate species in hill aquaculture. Gut content analysis of fry showed that the food consisted of 50.48 % zooplankton, 29.72 % phytoplankton, unidentified matter 14.09 % and 5.71 % sand and mud. In fingerling stage, 56.33 % phytoplankton and 24.07 % zooplankton was recorded from the gut. Maximum phytoplankton percentage (60.65) was recorded during juvenile stage. The RLG (1.048 to 2.72) and GSI (3.92 to 9.65) accessed from fry till juvenile stage indicated the changing feeding habits from carni-omnivorous to herbi-omnivorous. Key words: Chocolate mahseer, food and feeding, captive rearing, Himalaya

Fish communities and associated habitat variables in the upper Subansiri River of Arunachal Pradesh, eastern Himalaya, India

Ecological information on the rivers of eastern Himalaya, specifically the state of Arunachal Pradesh is not studied well. The present study describes fish assemblage patterns and deriving relationships between local habitat variables in the upper reaches of Subansiri River, Arunachal Pradesh. This study was carried out during October to November 2014 and February to March 2015. A total of 26 fish species belonging to eight families were recorded, in which eight species are endemic to the eastern Himalayan region. Fish species richness varied from two to 18 species in the upper reaches of Subansiri River and high species diversity was recorded in Sigin Stream (H’=2.76). Based on the seven habitat variables (water velocity, depth, channel width, percentage of substrate composition, percentage of riparian vegetation, altitude, and water temperature) then streams were categorized into lower-order and higher-order streams using principal component analysis (PCA). The site-wise fish abundance data along with habitat variable information was then subjected to the canonical correspondence analysis (CCA) for testing the association of habitat variables on fish abundance. The CCA results revealed that the abundance of large-size barbs, Neolissochilus hexagonolepis, N. nigrovittatus, Schizothorax progastus, and S. richardsonii were strongly associated with high altitude, water velocity, rich dissolved oxygen, and good riparian vegetation. On the other hand, Channa gachua, Botia rostrata, Danio rerio, Devario aequipinnatus, and Garra nasuta showed strong association with warm water streams with more conductivity.

Spatial and Temporal Variation of Fish Assemblages in Seti Gandaki River, Tanahu, Nepal

The space and time variations of the fish community structure in hill streams of Nepal are poorly understood. This research aims at studying the space and time variation of fish community structure in the Seti Gandaki River, Tanahu, Nepal. The field survey was conducted from July 2017 to June 2018 and the fishes were sampled from six sites using a medium size cast net of mesh size ranging from 3 mm to 6 mm mesh size, 25-33 feet length and 3.5-5 feet width, with the help of local fisher man. A total of 1,440 individuals were caught representing 46 species belonging to three order, nine families and 23 genera. The analysis of similarity (ANOSIM) showed significant difference in space (R = 0.824, P = 0.001) but not in time (R = 0.135, P = 0.021). On the basis of similarity percentage (SIMPER) analysis, 85.43% similarity was found among the seasons and major contributing species were Barilius bendelisis (8.44%) followed by B. vagra (7.79%), Tor putitora (7.27%), Garra gotyla (7%), Acanthocobotis botia (6.7%), Neolissochilus hexagonolepis (6.64%), Barilius shacra (6%), B. barila (4.5%) and Opsarius barna (4.37%). On the other hand, 85.24% similarity was found among the sites and major contributing species were B. bendelisis (8.8%) followed by B. vagra (7.6%), G. gotyla (7.27%), T. putitora (7.17%), A. botia (6.97%), N. hexagonolepis (6.7%), B. shacra (6.34%), B. barila (4.7%) and O. barna (4.39%). Results from the Canonical Correspondence Analysis indicated that the environmental variables, such as pH, total hardness, alkalinity, dissolved oxygen and water temperature have shown to determine the fish community structure of Seti Gandaki River.&#x0D; Keywords: Fish diversity, freshwater, habitat, spatio-temporal, stream