جستجوی مقالات مرتبط با کلیدواژه « fish diversity » در نشریات گروه « شیلات »

Nepal has a diverse geography, ranging from an altitude of 60 m to the world's highest peaks at 8849 m. Fish diversity has been observed to extend up to an elevation of 3600 m. With its intricate topography, fluctuating climatic conditions, and abundant water resources, the region exclusively comprises freshwater habitats spanning 745,000 ha. These habitats include rivers, lakes, ponds, marshes, reservoirs, and irrigated rice fields. There are roughly 6,000 rivers and creeks in the country (194,471 km² drainage area). Four major river systems, namely Koshi, Gandaki, Karnali, and Mahakali, originate from the upper Himalayas at an altitude greater than 5000 m above sea level and drain about 75% of the country. Freshwater fishes are often overlooked in biodiversity conservation efforts, leading to a significant decrease in fish diversity, particularly in densely populated urban areas and wetlands in the southern plains of Nepal. The decrease in fish diversity is likely linked to inadequate prioritization, funding, and human resources allocated to fish conservation. According to the literature and FishBase database records, the freshwater river system in Nepal contains a total of 255 fish species from 12 orders, 41 families, and 124 genera. This includes 15 fish species that are unique to Nepal and 15 that are not native to the region. Additionally, 34 fish species in this system are considered threatened and have been listed under the IUCN Red List. These fish have pronounced vertical dispersion throughout the country and horizontal distribution within the area and continent, displaying diverse adaptations. This research specifically examines the fluctuations in water quality and the range of fish species, together with their conservation status in the rivers of Nepal.

Regional study on the status of fish communities facilitates assessment procedures and conservation measures of fishes. Therefore, the present study investigated the impact of prevailing factors on the distribution pattern and status of freshwater fish fauna from River Song in the Lower Himalaya. In nine sampling sites under three sections (upper, middle, and down), 268 fish specimens were collected, 20 fish species belonging to 4 orders, 6 families and 12 genera were identified. Barilius bendelisis and Noemacheilus rupicola (upstream), B. bendelisis (midstream), and Glyptothorax pectinopterus (downstream) section constituted a high percentage of fish composition. The upper section was a relatively less disturbed section than other sections of the River Song. The upper section had good water quality, ample riparian vegetation, and a sufficient amount of food may affect the fish communities. However, many fish populations were declined in middle and down sections due to the disturbance through anthropogenic activities (i.e., channelization, construction, and municipal wastewater) removal of vegetation in the riparian zone by local people affect the abundance and distribution of fish species. 80% of fish species have been forced into decline and need to protect their natural habitats, execute policies, and motivate people for management and conservation.

This study was undertaken to investigate the diversity, abundance ratio, and distribution of the fish species and to record the water quality of Konhaye Stream, district Dir Lower, Pakistan. A total of 16 fish species were recorded, belonging to 4 orders (Cypriniformes, Channiformes, Siluriformes and Mastacebilformes), and 5 families including Cyprinidae (Schizopyge esocinus, Racoma labiata, Cyprinion watsoni, Cyprinus carpio, Barilius pakistanicus, B. vagra, B. modestus, Crossocheilus diplocheilus, Garra gotyla, Puntius ticto, and P. sophore), Channidae (Channa punctatus and Channa gachua), Nemacheilidae (Schistura macrolepis), Sisoidae (Glyptothorax punjabensis), and Mastacembelidae (Mastacembelus armatus). Different ichthyo-diversity indices [Simpson’s biodiversity index (D=0.918), Simpson’s reciprocal index (1/D=1.088), Simpson’s evenness index (E1/D=0.068), species richness (S), Shannon-Weiner’s index (H′=3.775), Menhinick’s index (Dmn=0.804), and Margalef’s index (Dmg=2.510)] were calculated for the stream. The physicochemical parameters [temperature (23.125±3.514℃), dissolved Oxygen (9.003±0.627 mg L-1), pH (7.333±0.201), turbidity (76.5±6.403 NTU), electric conductivity (201.68±11.31 µs cm-1), free CO2 (124.75±9.912 ppm), total dissolved solids (126.1±9.477 ppm), total alkalinity (4.325±0.171 mg L-1), total suspended solids (127.1±6.864 ppm), total hardness (5.225±0.341 mg L-1), salinity (42.25±6.292 ppt), calcium hardness (2.975±0.670 mg L-1), magnesium hardness (105±9.954 mg L-1), potassium (0.0145±0.001 mg L-1), sodium (16.55±3.861 mg L-1), chloride (1.825±0.727 mg/l), and nitrate (0.053±0.006 mg L-1) level] were monitored and found to be in varying but permissible ranges. The stream was found to be harboring a number of economically valuable fish species. An exotic fish species, C. carpio, was found well flourished, indicating the potential of the stream to be used for mitigating the declining ichthyofaunal diversity in the main nearby rivers. Two species, P. sophore and P. ticto, were recorded for the first time from the district. Proper management, appropriate fish stocking, and implementing environmental/fishing laws are suggested for the maintenance of the diversity and alleviating anthropogenic stress/threats.

Occurrence and distribution of larval and juvenile fish was investigated in nearshore waters of the southeastern Caspian Sea including the Gorgan Bay. Samples were collected during seven surveys using a fine mesh beach-seine in five sampling sites from July 2014 to June 2015. A total of 15500 individuals mostly juvenile were captured, representing 18 species from 8 families. Most juveniles belonged to Liza saliens, Atherina caspia, Neogobius pallasi and Neogobius melanostomus. The juveniles of Alburnus chalcoides, Vimba persa, Syngnathus caspius and gobies Neogobius caspius and Ponticola syrman occurred in low number (relative abundance 0.1% - 9.3%). Highest number of juveniles were caught in summer season. The occurrence of larval fish in coastal waters of southern Caspian was recorded for the first time (Atherina caspia with minimum length of 12 mm in Caspian and 9.5 mm in Gorgan Bay). In spring, early juveniles of mullet, Liza aurata, increased in the Caspian sites but they moved up to deeper waters by the end of the season. Based on results, the density of juvenile fish (specially Liza saliens) in Gorgan Bay was several times more than Caspian sites so it could be considered an important nursery ground in the region

Snow-fed River Pinder -a tributary of River Alaknanda in central Himalaya was explored for fish assemblages and habitat specificity. Altogether 27 fish species were reported from three orders, four families and nine genera. Cypriniformes order was dominating followed by Siluriformes and Salmoniformes. Shannon-Weiner diversity index (3.09 to 4.10) and Simpson index of diversity (0.81 to 0.92) of four sites specified strong relationship with species richness. The distribution of fish species showed interesting patterns, 33% species were common to all four sampling sites while 14.80% were restricted to single site and the remaining species were randomly distributed among two or three sampling sites. Habitat variability in the river significantly influenced the species assemblage structure. About 7.40% species were found common to all habitats while 3.70% species were restricted to only single habitat type. The remaining 88.90% of species were dwelling between two to three habitat types. Deep pools recorded maximum species richness followed by shallow pools, while least species richness was recorded in cascade habitats. The conservation status of fish fauna of the river was ascertained by CAMP (Conservation Assessment and Management Plan). Out of 27 species, the status of 8 species was not assessed due to data being deficient, 7 species were categorised as lower risk near threatened, 6 as vulnerable, 5 as endangered while 1 species was exotic.