Assessment of fish stock supplementation for sustainable production from reservoirs of Tamil Nadu state, India

India has 19 370 small reservoirs with a total water surface area of 3 153 366 ha. At least 100 of them have been subjected to scientific studies. Habitat variables responsible for a reservoir's productivity can be summed up into climatic, morphometric and hydro-edaphic factors. The peninsular reservoirs are characterized by a narrow range of fluctuations in water and air temperature across seasons, a phenomenon which prevents the formation of thermal stratification. Many reservoirs in the upper peninsula show thermal stratification during summer. Wind-induced turbulence facilitates the return of nutrients to the trophogenic zone. Most reservoirs on the mountain slopes of Western Ghats, Himalayas and the other highlands are deeper, with steeper basin walls, compared to irrigation impoundments. Mean depth does not show any direct correlation with productivity, either at primary or fish level. A high shoreline development index gives a better indication of productivity. Plankton, benthos and periphyton pulses of Indian reservoirs coincide with the months of least level fluctuations. Oligotrophic tendencies shown by some reservoirs are mainly due to poor nutrient status and other chemical deficiencies. In most cases, poor water quality is accountable to poor catchment soil. Low levels of phosphate and nitrate are not indicative of low productivity due to quick recycling of these nutrients. Specific conductivity reflects the production propensities of reservoirs satisfactorily. Almost all productive reservoirs have a klinograde oxygen curve and a vertical stratification of chemical variables such as pH, carbon dioxide, total alkalinity and specific conductivity. High seasonal rainfall and discharge of water during monsoon result in high flushing rates, which do not favour colonization by macrophytic communities. Similarly, inadequate availability of suitable substrata retards the growth of periphyton. Plankton constitutes the major link in the trophic structure. A rich plankton community with well-marked succession is the hallmark of Indian reservoirs with blue-green algae as the major component. The main factors that retard the growth of benthos are a rocky bottom, frequent water level fluctuation and rapid deposition of silt and other suspended particles. Large reservoirs, on average, harbour 60 species of fishes, of which at least 40 contribute to the commercial fisheries. Fast-growing Indian major carps are the prominent commercial fishes. Dam construction has adversely affected populations of many other species such as Tenualosa ilisha, Torspp. and Cirrhinus spp. Formulae for estimating fish yield potential and stocking density are described. While culture-based fisheries have been successfully practiced in many small reservoirs, the management norm followed in medium and large reservoirs is primarily on capture fishery. In large and medium reservoirs, stocking was successful only when stocked fishes bred. Indian experience on species enhancement and introductions is described. Environmental enhancement of small reservoirs has been attempted in some reservoirs of Tamil Nadu. Modeling, using standard population parameters, such as the density-dependent growth, size dependent mortalityand weight–length relationshipis discussed. Two exotic fishes viz., Oreochromis mossambicus and Cyprinus carpio have been introduced into Indian reservoir with discouraging results. Hypophthalmichthys molitrix, after an accidental introduction, has performed well in Gobindsagar, a reservoir with a distinct cold water regime. Reservoir fisheries in India are well poised for development, provided scientific management norms are adopted.

The present study investigates the success of stocking fingerlings of Indian major carps ‐Gibelion catla (Hamilton), Labeo rohita Hamilton and Cirrhinus mrigala Hamilton – to enhance fish yield in 58 small reservoirs in Odisha State, India. Fish stocking and yield data were collected from State Fisheries Department, Odisha. The relationships between area, stocking density and fish yield of different size groups of reservoirs were assessed using the Pearson correlation coefficient (r). Fish yield increased significantly (p < 0.05, t‐test) from 204 kg/ha/year in 2012–13 to 323 kg/ha/year in 2013–14 due to adoption of CBF. The corresponding per capita fish production increased from 398 kg fisher−1 year−1 to 702 kg fisher−1 year−1 benefitting more than 8,000 fisher households. Reservoirs in the size group 100–500 ha showed the highest response of fish yield with respect to stocking of fingerlings. The size of fingerlings at stocking and area of the reservoir had greater impact on enhancing fish yield. Stocking had a profound positive impact on fish yield. This study forms a baseline evaluation of the impact of stocking on small tropical reservoirs in India. It also recommends management measures and discusses issues, and the way forward for sustainable fisheries enhancement in small tropical reservoirs in eastern India.

The present study assessed the impact of fingerling stocking of Indian major carps (Gibelion catla, Labeo rohita, and Cirrhinus mrigala) on fish yield in 24 small reservoirs of Central India. The time series data on fish stocking and yield were collected from the State Fisheries Department, Govt. of Chhattisgarh, for the year 2008 to 2016. The fish yield increased significantly (p < 0.05) from 87.11 to 379.13 kg/ha/year due to stocking indicating significant impact on fish production. The relationships between area, stocking density, and fish yield of reservoirs were also assessed. Stocking had a significant positive impact on fish yield (t test, p < 0.05). The important water quality parameters were also studied to have a conspicuous picture of eco-hydrological characteristics of these selected small reservoirs. The study forms a baseline for the small tropical reservoir fisheries of Central India (Chhattisgarh state) and suggests regional strategies for sustainable fisheries enhancement and management, employment generation, and nutritional security of a large number of fish-eating population.

Sediment organic carbon and nitrogen trapping in a small reservoir within a typical agricultural granite catchment

ABSTRACTThe fisheries sector plays a vital role in the food, nutritional and livelihood security of people, especially in the rural regions of India. Reservoirs, the man made impoundments built on rivers/streams obstructing the surface flow, form an important resource for the fish production besides holding up economic growth through various cultural and ecological services. India has enormous reservoir resources to the tune of 3.42 million ha (19,386 numbers). The distribution of reservoirs is quite uneven and most of the reservoirs are located in the southern and central Indian states. In the last few decades, India has made tremendous progress in reservoir fisheries and overall management strategies have been considerably innovated. The average annual fish productivity realized from reservoirs was very low (small: 49.9, medium: 12.3 and large: 11.4 kg ha−1yr−1) against the annual potential yield of 100, 75, and 50 kg ha−1yr−1. The fish yield from Indian reservoirs has enhanced through fingerling stocking and adoption of improved management practices and the average productivity increased to 33, 94, and 174 kg ha−1yr−1 from large, medium, and small reservoirs respectively. The production potential has been re-casted to a level of 100, 200, and 500 kg ha−1yr−1 from large, medium and small reservoirs, respectively. The increase in fish productivity is about one third of the present production potential and there exists scope for developing effective and sustainable strategies for further enhancing the fish yield. The present review synthesizes the updated information available on Indian reservoirs and the developments during the last decade with reference to fisheries, biodiversity, potential, threats, and recommends strategies for sustainable management of the reservoir fisheries in India.

The present study is an attempt to document production trend and marketing channels in Aliyar reservoir. Secondary data were analysed and reported that the Annual Growth Rate of stocked fish production (IMC and Common carp) decreased by 16%, but an attractive issue was that AGR of non-stocked fish production (exotic and indigenous species) increased by 49%. Mrigal was observed to dominate in total fish production. The study revealed that negative relationship (r -0.4416) existed between total seeds stocked and fish production, while positive relationship was observed in species wise fish production of Rohu (r 0.6557), Mrigal (r 0.8736) and Common carp (r 0.5991) except Catla which proved that stocking density influences production of these fish species. Catla production was negatively (r -0.2141) correlated with stocking density. Hence, this study recommends that reduction in stocking density of Catla seeds may help improve total fish yield. The present study revealed that the reservoir has well organized marketing system with 31 fresh fish marketing stalls.

Man-made lakes are abundant in Guangdong province (South China) but are distributed irregularly. Since 1950s, about 6700 reservoirs (>106 m3) with total volume 39.8×109m3 have been built. The largest one, Xinfengjiang reservoir, contributes one third to the total volume. Half of the reservoir storage is situated in the Dongjiang river watershed in which the designed capacity is low, only 1.82×109 m3. In 1998, water demand in Guangdong was 44.7×109 m3, with one third coming from reservoirs. In total, 75% of reservoir water supply was contributed by small (<107 m3) and very small reservoirs, and 25% by large and medium reservoirs. An annual amount of 1.1×109 m3 is supplied to Hong Kong by one medium-sized reservoir (Shenzhen reservoir), and 8.31×106 m3 to Macau by four small reservoirs. In spite of the importance of reservoir water, the protection of this resource remained largely ignored prior to 2005. The deterioration of reservoir water quality stimulated the local government to initiate the first program for a systematic survey of the eutrophication of 20 typical and important reservoirs used for drinking water supply in 2000. The trophic state index (TSI, Carlson index) was calculated on the basis of TP, TN, SD and chlorophyll-a concentration. The index showed that most reservoirs were mesotrophic, tending towards eutrophy. Only few reservoirs (two) situated in the upstream zone were oligotrophic. Four reservoirs located near towns in the downstream zone were eutrophic. Compared with the data of a fishery survey in the 1980s, the trophic level over the past 20 years had significantly increased. After a first water bloom observed in Tangxi reservoir in 1997, the fact that Cyanobacteria bloomed in seven large reservoirs indicated a rapid deterioration of water quality. Besides the common domestic waster water and fertilizers lost from agricultures, fish production through fertilization and ice-fish introduction is another factor leading deterioration of water quality and eutrophication.

Changes in mucosal nutrient transport in small and large ileal reservoirs after endorectal ileal pullthrough

The carbon dioxide content of the atmosphere affects life, climate, and the chemistry of oceans and sedimentary rocks. The processes that control atmospheric carbon dioxide can be analyzed in terms of biogeochemical cycles that transfer carbon between reservoirs. The small atmospheric reservoir is closely linked to other small reservoirs, shallow sea and biota. Transfer of carbon between these small reservoirs is rapid; residence times are short. The small reservoirs are connected by slower transfers to a much larger deep sea reservoir, and the coupled reservoirs of ocean, atmosphere, and biota are coupled, in turn, to very much larger reservoirs in sedimentary rocks. The exogenic reservoirs of sedimentary rocks, ocean, atmosphere, and life are coupled, in turn, by the very slow exchange of carbon with a large mantle reservoir. This hierarchy of interacting reservoirs controls atmospheric carbon dioxide on all time scales. Particular problems with restricted time scales can be analyzed in terms of a subset of the total system. Observations that illustrate interactions on different levels of the hierarchy include the seasonal change of carbon dioxide partial pressure, the glacial to interglacial change, and the evolving distribution of carbonate sediments.

Increasing water demand and climate change exacerbate water management challenges in arid and semi-arid regions experiencing water scarcity resulting from low and irregular precipitation and high evapotranspiration. These regions rely on substantial water storage capacity, typically provided by large multi-purpose public reservoirs and small private reservoirs. While public reservoirs are typically monitored, the number, size, and private ownership of small reservoirs complicate effective storage monitoring, hindering efforts to assess water availability during droughts and to allocate water efficiently and equitably. Remote sensing provides a solution to complement existing monitoring systems by offering high spatial and temporal resolution observations. This study introduces a methodology for monitoring the surface area of large and small reservoirs based on optical and radar images from Sentinel-1 and Sentinel-2 satellites. The Normalized Difference Water Index (NDWI) and the Otsu image segmentation method are employed to identify and estimate water body areas, and the Google Earth Engine and programming languages are used to automate the process. The validation results demonstrated correlation for most reservoirs, with slight underestimations at flood peaks. Among the 17 large reservoirs, 16 had an R2 value above 0.82, 12 had an RMSE value below 0.8, and 14 had a KGE value above 0.7. For the small reservoirs, the method correctly identified 3224 of the 6370 reservoirs recorded in situ, with greater accuracy in the classes of reservoirs with elevation above 10 m. A total of 7251 reservoirs were mapped, including 4027 not present in the database of the responsible regulatory entity, most with an area of less than 1.8 ha. Performance was better for larger areas (&gt;3 ha), while small areas were underestimated. This methodology offers a practical water management tool adaptable for various-sized surface water bodies, including small, unmonitored water bodies.

Development and application of a method for quantifying factors affecting chloramine decay in service reservoirs

The relationships between surface area, stocking density and fish yield in 40 small reservoirs in India between 1994 and 1999 were examined. A significant positive correlation (r = 0.6) was found between stocking density and fish yield. Area was negatively correlated with stocking density (r = −0.57) and fish yield (r = −0.62), but its correlation with efficiency of stocking was not significant for all the size groups of small reservoirs.

The Mediterranean water sector faces multiple challenges. Climate change not only drives future water shortages but also drastically affects the effectiveness of water storage strategies, such as small and large reservoirs. Furthermore, the limited involvement of local actors often hampers the success of implemented solutions. We apply a co-modeling approach within the Val d'Orcia Rural Living Lab, to inform water planners about the potential impacts of climate change on reservoir water dynamics and to nourish the discussion on climate change adaptation. Specifically, we simulate various water storage strategies by alternatively considering existing small agricultural reservoirs (SmARs) and a planned large dam under current and projected future climates considering five climate models under the Shared Socioeconomic Pathway 585. Due to the reduced precipitation and increased temperature, future annual average water stored in both types of reservoirs is expected to decline (−6.3%) as a result of limited inflows (−30%) and enhanced evaporation (8.7%) by the end of the century. Moreover, seepage losses decrease (−9.8%) reducing aquifer recharge. While the trends in these key variables are consistent across storage types, SmARs are more susceptible to climate change, with water storage reductions of up to −21%. Evaporation losses increases are a major concern for the dam, whereas the reduction of inflows poses a major threat to the reliability of the smaller SmARs. Still, SmARs have several advantages and a more comprehensive and participatory analysis is important for appropriate decision-making. By involving local actors from the early stages, this research poses the basis for developing future best watershed management practices within a representative Mediterranean catchment.

The current study, which is based on data collected over a five-year period, examines the role of a minor reservoir in fish production as well as the impact of stocking densities on fish output. Nagulakunta is a small reservoir in Siddipet District's Vinjapally village with a water spread of 10 acres. The tiny reservoir is used as a stocking and capture system for fisheries growth. The overall major carp production is 465.88kg/ha/yr, and that of the rest being 56.25kg/ha/yr. The total fish production is 513.13kg/ha/yr. The output of big carp increased greatly from 13.43 to 98.02 percent, while the production of other carp declined dramatically from 86.57 to 1.98 percent. The reservoir was filled with only the main carp seed (20-40mm fry), with an overall stocking rate of 5892 fry/ ha/ yr. The maximum yield of carps was reported at a stocking density of 8500 fry/ha/yr, indicating that major carp production increased significantly with stocking. Nagulakunta has been determined to be a productive reservoir in terms of fish production.

To evaluate the importance of dispersal by water transportation in structuring phytoplankton community, we compared phytoplankton composition and succession between two connected tropical reservoirs: a large reservoir with a bottom outlet that periodically feeds a small reservoir via a 40 km open channel. Multivariate analysis was carried out on datasets of phytoplankton for exploring the relationship between phytoplankton and environmental variables. Differential survival of phytoplankton taxa during long channel transportation contributed to high dissimilarity of phytoplankton community between the two reservoirs. Local ecological filtering was mainly responsible for structuring the phytoplankton community with a few dominant functional groups in the large reservoir. Phytoplankton community succession in the large reservoir also showed a clear seasonal pattern. The community in the small reservoir had a more diverse functional group composition and did not show a clear seasonal succession because of strong hydrodynamic disturbance and phytoplankton inoculation with periodic water transportation. In conclusion, periodical transportation and mass effect by dispersal disturb succession and seasonal dynamics, and phytoplankton community assemblage depends on both environmental filtering (habitat selection) and dispersal in the small (receiving) reservoir. In addition, the dissimilarity of phytoplankton community between the connected waters was caused by both habitat difference and differential survival of phytoplankton taxa during transportation.