Impact of stocking on yield in small reservoirs in Andhra Pradesh, India

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.

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 harvest of microalgae from the effluent of a sewage fed high rate stabilization pond by Tilapia nilotica

Background: The water resources of Northeast (NE) Indian reservoirs have been largely overlooked, despite their immense potential in various aspects. A comprehensive analysis of water quality parameters was conducted to assess the physio-chemical changes and health status of Maphou or Mapithel reservoir, Manipur, NE, India. Methods: Sub-surface water samples were collected from June 2021 to May 2022 to assess the spatio-temporal changes. Trophic State Index (TSI), Morpho Edaphic Index (MEI), Maximum Sustainable Yield (MSY) and fish yield potential were calculated. The average water spread area was calculated through Normalised Difference Water Index (NDWI) method. Result: A total of eighteen (18) water quality parameters were examined following Standard Methods. ANOVA analysis indicated that all water quality parameters, except total alkalinity, exhibited significant seasonal variations (p less than 0.05). Spatially, most of the water quality was found to be insignificant, except for Chl-a and depth (p less than 0.05). All the water quality parameters were within acceptable ranges for the growth and survival of aquatic biotic resources. No signs of pollution were observed. The trophic status of the reservoir was found in an oligotrophic state. The MEI was estimated as 8.55 and the average fish yield for the reservoir was 14.98 kg ha-1, which is below the national average yield of small reservoir (49.9 kg ha-1). The MSY was estimated to be 21.46 kg ha-1. Heatmap cluster analysis revealed three distinct clusters of months. The actual average water spread area was determined to be 852.62 ha, hence the reservoir can be categorised as small reservoir.

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.

Indian reservoirs offer tremendous scope but fish production remains below potential. The present study evaluates the effectiveness of fish seed stocking on the yield of 62 reservoirs of Tamil Nadu, India during 2011–2020. The results indicate that all large (&gt;50 km 2 ), 64.1% of the medium (10−50 km 2 ) and 50.7% of small (&lt;10 km 2 ) reservoirs are under-stocked with less than &lt;50% of the recommended stocking density. The stocking efficiency was found to be lowest in large (0.05), medium (0.11) and highest in small reservoir (0.26). The regression analysis showed significant positive associations between stocking density and yield in small ( R 2 =0.05), medium ( R 2 =0.31) and negative in large ( R 2 =0.008) reservoirs. The mean annual yield during the studied period was highest in small (137 kg ha −1 yr −1 ), followed by medium (86.64 kg ha −1 yr −1 ) and, large (46.1 kg ha −1 yr −1 ) reservoirs. The study indicated that insufficient availability of fingerlings and inconsistency in the seed quality as the major stumbling blocks in achieving the estimated production potential. It is suggested to improve the hatchery facility, adoption of enclosure culture for rearing fish fingerlings, creating awareness among the stakeholders to optimize the fish production from these resources and also for ensuring improved livelihood of the fishers dependent on this sector. This is the first long-term, state level evaluation of reservoir stocking in Tamil Nadu, complementing past national studies. These findings highlight the importance of optimal stocking density, advanced fingerling use, and cooperative-based management for sustaining fish production and fisher livelihoods in Tamil Nadu.

Fingerlings of common carp (Cyprinus carpio), Thai silver carp or tawes (Puntius gonionotus), Nile tilapia (Oreochromis niloticus) and mrigal (Cirrhinus mrigala) were stocked in rainfed lowland riceflelds in Northeast Thailand in 1986 and 1987. In both years, farmers harvested on average 50 kg•ha·1 of stocked fish species. Farmed fish yields were corelated with stocking densities. Feeding practices did not contribute to fish yields. Average recovery rates in both years were about 16%, but recovery of tawes was much better than of the other species. Nursery-paddies to increase recovery rates were not successful. The fingerling costs exceeded the market value of the fanned fish with 40% of the farmers. The average wild fish yield over both years was 209 kg 0ha·1, mostly snakehead (Channa striata) and catfish (Clarias batrachus and C. macrocephalus), with some climbing perch (Anabas testudineus ). Wild fish yields in both years were corelated with water depths in the field. The market value of the wild fish equalled the market value of the rice crop. Wild fish caught by household members from ricefields were the most important source of animal produce consumed during the rice-growing season (68%).

Pahuj, a small reservoir, located at Jhansi in Uttar Pradesh was investigated during April 2006 to March 2009 for evaluating fish yield potential. The reservoir receives a portion of Jhansi city sewage through Pahuj River. As per the physico-chemical parameters, the reservoir has been categorized as eutrophic. Average fish yield during 1994-95 to 2008-09 was 142.03 kg ha-1year-1, whereas during study period (2006-07 to 2008-09) it was 286.43 kg ha-1year-1. The potential fish yield was estimated using morpho-edaphic index, which revealed that the reservoir have potential to produce up to 560.78 kg ha-1year-1. Thus, there is scope for enhancing the fish yield in the reservoir if proper management measures are adopted. Key words: Small reservoir, eutrophication, production potential, fish yield

Pond water quality and its relation to fish yield and disease occurrence in small-scale aquaculture in arid areas

Sustainable integrated farming involving the combination of rice-fish-vegetables requires advanced technology to be adopted in crop production in arid zones characterized by red or yellow soil. In the present study, we used suitable and varying stocking densities of Silver barb (Barbonemus gonionotus) and evaluated in a structured production and economic framework under four treatments (T1, T2, T3, and T4) assigned with a stocking density of 10, 20, 30 and 40 fish/decimal, respectively. We used standard methods of water, soil, and plankton monitoring of the rice field. The study showed that lower stocking density provided the fish with more spaces and less competition for food resulting in higher growth performance in T1 compared to other treatments. Although stocking density did not show any significant (P>0.05) effect in rice, straw and vegetable production in all the treatments, the highest rice and straw production at T4 could be ascribed to the improvement in soil fertility by the accumulation of fish excreta and subsequent release of nutrients from the soil by the higher number of fish in that treatment. The best fitted polynomial regression line obtained between gross yield and net yield with different stocking densities of Silver barb described an inevitable fluctuation in net yield of fish with increasing stocking density. Despite the stable growth performance of fish in T1, a combined effect of lower total input cost, higher yield of fish and rice, and economical vegetable production, T2 showed a significantly (P<0.05) higher total return. Furthermore, the benefit-cost ratio (BCR) for rice-fish-vegetables integrated culture system in the rain-fed rice field was also high. In conclusion, this study revealed that maintaining a stocking density of 20 fish/decimal was economically profitable for rice-fish-vegetables integrated culture systems in arid zones on a global scale.

To quantitatively define relationships among stocking densities, feeding rates, water quality, and production costs for channel catfish, Ictalurus punctatus, grown in multiple‐batch systems, twelve 0.1‐ha earthen ponds were stocked at 8,600, 17,300, 26,000, or 34,600 fingerlings/ha along with 2,268 kg/ha of carryover fish. Fish in all ponds were fed daily to apparent satiation using 32% protein floating feed. Temperature and dissolved oxygen in each pond were monitored twice daily; pH weekly; nitrite‐N, total ammonia nitrogen, and Secchi disk visibility every 2 wk; nitrate‐N, chlorophyll a, total nitrogen, total phosphorus, and chemical oxygen demand monthly; and chloride every other month. The costs of producing channel catfish at different stocking densities were estimated. There were no significant differences (P &gt; 0.05) as a result of stocking density among treatment means of (1) gross or net yields, (2) mean weights at harvest, and (3) growth or survival of fingerlings (24–36%) and carryover fish (77–94%). Mean and maximum daily feeding rates ranged from 40 to 53 kg/ha/d and 123 to 188 kg/ha/d, respectively, and feed conversion ratios averaged 1.75. There were no differences in any feed‐related parameter as a result of density. Water quality variables showed few differences among densities at samplings and no differences when averaged across the production season. Yield of fingerlings increased as stocking density increased with significant differences between the two highest and the two lowest stocking densities. Breakeven prices were lower at the higher stocking densities as a result of the higher yield of understocked fish and similar mean individual fish weights produced at these higher stocking densities. Overall, varying stocking densities of fingerlings in multiple‐batch systems had little effect on production efficiency and water quality. Additional research on managing the population structure of carryover fish in commercial catfish ponds may be warranted.

Effect of stocking density and source of animal protein on growth and survival of rainbow trout fingerlings in flow-through system at Nuwakot, Nepal

Biological manipulation of eutrophication in West Yangchen Lake

In Sri Lanka, there is a great potential for the development of culture‐based fisheries because of the availability of around 12 000 non‐perennial reservoirs in the dry zone (&lt;187 cm annual rainfall) of the island. These reservoirs fill during the north‐east monsoonal period in October to December and almost completely dry up during August to October. As these non‐perennial reservoirs are highly productive, hatchery‐reared fish fingerlings can be stocked to develop culture‐based fisheries during the water retention period of 7–9 months. The present study was conducted in 32 non‐perennial reservoirs in five administrative districts in Sri Lanka. These reservoirs were stocked with fingerlings of Indian (catla Catla catla Hamilton and rohu Labeo rohita Hamilton) and Chinese (bighead carp Aristichthys nobilis Richardson) major carps, common carp Cyprinus carpio L., genetically improved farmed tilapia (GIFT) strain of Nile tilapia, Oreochromis niloticus (L.) and post‐larvae of giant freshwater prawn, Macrobrachium rosenbergii De Man, at three different species combinations and overall stocking densities (SD) ranging from 218 to 3902 fingerlings ha−1, during the 2002–2003 culture cycle. Of the 32 reservoirs stocked, reliable data on harvest were obtained from 25 reservoirs. Fish yield ranged from 53 to 1801 kg ha−1 and the yields of non‐perennial reservoirs in southern region were significantly (P &lt; 0.05) higher than those in the northern region. Naturally‐recruited snakehead species contributed the catches in northern reservoirs. Fish yield was curvilinearly related to reservoir area (P &lt; 0.05), and a negative second order relationship was evident between SD and yield (P &lt; 0.05). Chlorophyll‐a and fish yield exhibited a positive second order relationship (P &lt; 0.01). Bighead carp yield impacted positively on the total yield (P &lt; 0.05), whereas snakehead yield impact was negative. Bighead carp, common carp and rohu appear suitable for poly‐culture in non‐perennial reservoirs. GIFT strain O. niloticus had the lowest specific growth rate among stocked species and freshwater prawn had a low return.