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The Tamas River is a right-bank tributary of the River Ganga, originating from Jhukehi village in Madhya Pradesh and meeting up with the Ganga at Sirsa, Prayagraj, Uttar Pradesh, India. An investigation was carried out in six sites at (Itahara, S1), (Madhavgarh, S2), (Bakiya upstream, S3), (Bakiya downstream, S4), (Chakghat, S5) and (Panasaghat, S6) of the river to document the fish diversity, seasonal variability, and impact of environmental variables on fish species composition during the period 2017 to 2019. Altogether 75 fish species belonging to 54 genera, 23 families, and 10 orders were recorded. Fish species richness at (S1), (S2), (S3), (S4), (S5), and (S6) and was recorded as 9, 39, 38, 13, 61, and 49, respectively. Family Cyprinidae with 31 species contributing 41% was the most dominant family, followed by Bagridae (8%) and Schilbeidae (6.7%). Seasonal variation in fish species richness and diversity indices were observed in the river stretch. Maximum species richness (45) was observed at S5 during monsoon and a minimum (6) at S1 during post-monsoon. As per the International Union for Conservation of Nature categorization, 10 out of 75 fish species recorded from the river were considered to be threatened. Three exotic species, namely Cyprinus carpio, Oreochromis niloticus, and Hypophthalmichthys nobilis, were recorded at some stretches, which may be a concern for native fish diversity. Environmental variables like water temperature, pH, dissolved oxygen, water velocity, and alkalinity influenced the fish community structure. The selected (S1–S6) stretch of the river falls under the category of Slightly Impacted River based on the Shannon Index (H'>3). The present investigation was the first assessment of rich fish diversity covering the maximum stretch of river, which supports many important and small indigenous fishes for conservation. [ABSTRACT FROM AUTHOR]

Inland open-access fisheries of India are important resources that contribute significantly to the national economy while providing livelihood to millions. The majority of these resources are suitable for aquaculture, with a high potential for enhanced inland fish production. Enclosures (cages and pens) installed in such waters are useful for rearing fingerlings for enhancement programmes and table-fish production. Floating cages are most suitable for waterbodies vulnerable to occasional flooding, while pen enclosures installed in marginal areas of floodplain wetlands can be suitably reinforced to protect the fish during floods. Small indigenous fishes can be introduced into pens to increase their productivity. This paper reviews enclosure technologies in the inland open waters of India and discusses the socioeconomic benefits, ecological advantages, and climate resilience of these technologies. These factors may encourage their adoption and lead to an increase in fish production in the large inland waters of India. [ABSTRACT FROM AUTHOR]

This study assessed the vulnerability of 16 floodplain wetlands (beels) of the Lower Brahmaputra Valley, Assam, India, in relation to a range of natural and anthropogenic factors including climate change. The total water-spread area of the selected beels varied widely (8–50 ha), with 68.75% of the beels showing a reduction in water-spread area over the past 30 years. High levels of siltation and encroachment and detachment of marginal areas through the construction of roads were the major factors responsible for the reduction in the water-spread area of the beels. The reduction was observed to be in the range of over 33% in three beels (Raghunath Sora, Chulkani, and Dudua beel) to 83% in Bhoishpuri beel. In addition, one beel (Chulkani) experienced reduction in its deep pool area, which is an important wetland area that provides shelter to brood fishes during the dry season. Only 12.5% of the beels studied practiced enclosure (pen) culture for rearing fish. None practiced cage culture. Our study showed that only two beels (Bhoishpuri and Tariachora) were free from exotic fishes; the remaining surveyed beels reported exotic species such as, Cyprinus carpio (Common Carp), Ctenopharyngodon idella (Grass Carp), Hypophthalmichthys molitrix (Silver Carp), H. nobilis (Bighead Carp) and Piaractus brachypomus (Pacu). The prevalence of exotic fishes in the majority of the beels (due both to escape from nearby aquaculture ponds during floods and intentional stocking in certain beels) would have adversely affected the diversity of indigenous fishes in those wetlands. From discussion with the fishers, 50% of the beels surveyed experienced a reduction in the number of fish species from that recorded 10–20 years ago. In addition to climate change-related factors (e.g. abnormal rains, floods, or drought-like situations), other factors – both natural (e.g. hyper-nutrification) and anthropogenic (e.g. construction of roads, houses, and other structures) – also adversely affected the studied wetlands. To help cope with these factors and increase the adaptive capacity of fishers, four measures aimed at mitigation are suggested. These are: the practice of enclosure aquaculture in beels; the construction of floating macrophyte refuges (katal); deep pool refuges; and stock enhancement programmes with climate-resilient indigenous fishes. [ABSTRACT FROM AUTHOR]

Reservoirs are aquatic resources with the potential to increase India's fish production through inland fisheries. Thippagondanahalli is a medium-size reservoir on Arkavathy River, a tributary of the Cauvery. It is located in Bangalore rural district of Karnataka (12°58′24″ to 12°96'49" N 77°20′33″ to 77°35′63″ E) and has a water surface area of 1162 ha at full reservoir level and 784.55 m at full supply level. Fish diversity studies were conducted to examine the spatial and temporal variations in fish diversity in relation to habitat parameters. A taxonomic abundance of 25 fish species (80% of them native) belonging to 14 families and 4 orders was recorded. A range of statistical estimators such as Chao 1, Jack 1, and Bootstrap were used to assess the expected species richness. The Jack 1 method showed the highest abundance with 28 species. The littoral zone, dominated by small indigenous species, was found to have relatively higher fish diversity (Shannon index-1.86) compared to the limnetic zone of the reservoir. Shannon diversity was higher in the monsoon season (1.76) compared to other seasons. Physico-chemical parameters revealed that this waterbody is highly eutrophic. Canonical correspondence analysis between seasonal habitat characteristics and seasonal species abundance showed the abundance of the small indigenous fish Amblypharyngodon mola during the post-monsoon season, the bottom feeder Cirrhinus mrigala and the surface feeder Rasbora daniconius during the monsoon season, and the carnivores Mystus malabaricus and Channa orientalis as well as the planktivore Puntius sarana during the pre-monsoon season. This study suggests the use of fisheries management and conservation measures such as fish-aggregating devices, stocking of certified seed, and impact assessment of exotic species. [ABSTRACT FROM AUTHOR]

The catch pattern of the exotic Common Carp (Cyprinus carpio) and their relationship with water quality along with maturity status of fishes were assessed during 2017-2019 to understand overall establishment and impact of the species in Buxar stretch of River Ganga in West Bihar, India. A total of 64 fish species were recorded including two exotic fishes (C. carpio and Oreochromis niloticus) from the river stretch during the study period. The annual production data depicted Cyprinus carpio to be the most dominating fish species encountered from the study area sharing 57.07% (by weight) during the period 2017-19. Calculated average 'Invasion coefficient index (Ix)'of 0.25 in entire three-year study period revealed that the invasion has moderately impacted the indigenous fish diversity. Landing of Indian Major Carp (IMC) indicated severe decline (76.4 - 95.6%) in comparison to the catch data recorded earlier from Buxar. Data generated on sex structure of Common Carp indicated that the overall sex ratio showed positive recruitment within the smaller size range of 282-307 mm and thus avails a competitive breeding advantage over other carp fishes. Gut content of Common Carp from the stretch observed major share of phytoplankton (81.04%) and zooplankton (17.18%) and thus there are significant dietary overlap of Common Carp with other valuable species. The stretch has been impacted with anthropogenic loading as identified through significantly higher water specific conductivity (580 µScm-1), Biochemical Oxygen Demand (3 mgl-1), etc. in drastically reduced water discharge regime. Among different water parameters, river flow, Biochemical Oxygen Demand and Total Phosphate showed positive whereas specific conductivity showed negative correlation with Common Carp seasonal abundance. Future conservation management measures may be formulated keeping in view of the identified factors through the present study for reducing the impending risks of the invasive fish species in Buxar stretch of River Ganga. [ABSTRACT FROM AUTHOR]