Chinese integrated fish farming: a comparative bioeconomic analysis

This paper provides an overview of the structure and performance of Chinese integrated pond fish farming systems, based on analysis of survey data for 1013 ponds on 101 farms in eight Chinese provinces. A province-by-province examination of gross and net fish yields supports the traditional Chinese classification of provinces into high, medium and low productivity classes according to fish farm output: average net fish yields for surveyed ponds in each class were 7958,4981 and 3321 kg ha^?1 year^?1 respectively. The paper includes summaries and analyses of data on fish stocking and harvesting, use of feeds and fertilizers, fish-animal integration, capital inputs, and the overall cost and revenue structure in each productivity class. In addition to variations in aggregate input and output levels, a key difference between productivity classes is seen to lie in the stocking model utilized: filter-feeding fish dominate in poorer areas, while ‘feeding fish’ (grass carp, Ctenopharyngodon idella (Valenciennes), black carp, Mylopharyngodon piceus (Richardson), and omnivorous carps) dominate in high-productivity provinces. These results are examined in light of regional differences in culturing tradition, socio-economics, infrastructure, climate and geographical factors.     

Effects of adding different proportions of the small fish punti (Puntius sophore) and mola (Amblypharyngodon mola) to a polyculture of large carp

This experiment was carried out in the framework of a project to develop a viable fish polyculture technology under Bangladeshi conditions that allows simultaneous fish production of small indigenous species for the farmers' family consumption and of large carp species as a cash crop. The objectives of this experiment were to assess the effects of adding punti and mola in different proportions on the large carp and on the environment, and to assess the effects of punti on mola and mola on punti. The polyculture included the large carp rohu, catla and common carp (as cash crop fish), and the small indigenous fish punti and mola (as food for the small‐scale farmer family). The total large carp stocking density was 10 000 fish ha^?1, at a species ratio of 1:1:1. The total small fish stocking densities were 0 in the control and 30 000 punti and mola ha^?1 in the treatments, these at rates 2:1, 1:1 and 1:2. Stocking punti and mola at the density and all ratios tested were viable solutions to obtain simultaneously large carp cash crops and small fish to feed the farmer's family. Statistically marginal differences in large carp production were obtained in stocking small fish in the different proportions. These marginal differences could be explained by food competition between punti and common carp and between mola and rohu, which had different outcomes depending on the proportions of the small fish stocked. Stocking punti and mola at a 1:1 ratio would result in more small fish for the farmer's family, while the individual size of rohu, the most expensive large carp, would be somewhat smaller, but not necessarily small enough to decrease its selling price. Stocking one of the small fish in higher proportion than the other (2:1 or 1:2) would result in less mola for the family consumption, while harvesting of common carp would be somewhat lower and of smaller fish. Since common carp is the cheapest of the large carps, this small reduction would not necessarily affect the family income in an important way. With these results, farmers would now be able to reorganize their stocking practices with large carps and small fish and decide the appropriate small fish stocking ratios to meet their needs.     

Effects of increasing the stocking density of large carps by 20% on 'cash' carp–small fish polyculture of Bangladesh

This experiment was carried out in the framework of a project to develop a viable fish polyculture technology under Bangladeshi conditions that allows simultaneous fish production of small indigenous species for the farmers' family consumption and of large carp species as a cash crop. The objectives of this experiment were to assess the effects on fish performance and on the environment of adding 20% large fish to the basic ‘cash crop’ carp–small fish polyculture consisting of 10 000 fish ha^?1 of the large carp rohu Labeo rohita (Hamilton), catla Catla catla (Hamilton) and common carp Cyprinus carpio (L.) at a species ratio 1:1:1, and 15 000 fish ha^?1 of each small indigenous fish punti Puntius sophore (Hamilton) and mola Amblypharyngodon mola (Hamilton) (control). The treatment ponds were stocked with additional 2000 large fish ha^?1, either all rohu, or all catla, or all common carp, or half rohu and half common carp, or half catla and half common carp. The results obtained and the analysis of interactions through the food web that affect food resource availability of the different fish species and account for the trends and differences observed among treatments confirm the positive effect of common carp on rohu reported in previous experiments and show that a 20% increase in large carps stocking neither affect the survival of the large carps nor reduce harvesting biomass of the small fish for the farmer's family consumption. Increased stocking densities of each large carp species did not significantly reduce its own harvesting weight and mean growth rate, while significantly increased rohu and catla (but not common carp) harvesting biomass and yield. The complex relations between species led to inter‐ and intraspecific competition, which in some treatments increased growth or yield of one species and in other treatments of other species, so that the gains on one species and the losses on the other led to no significant total harvested biomass differences between treatments. Yet, the results herein reported may help farmers to select their species stocking ratios. Thus, if the main target of the farmer is rohu, then a stocking density increase of 10% common carp and 10% rohu would improve rohu growth rate (due to common carp) and result in 50% higher rohu harvesting biomass and yield. If the main target of the farmer is catla, then a 20% increase in catla stocking density would lead to 20% higher catla harvesting biomass.     

Technical efficiency of carp production in India: a stochastic frontier production function analysis

This paper aims to examine the levels and determinants of technical efficiency in carp pond culture in India. The stochastic production frontier technique involving the model for technical inefficiency effects is applied separately to samples of semi‐intensive/intensive and extensive carp producers interviewed during 1994–95. The results showed significant technical inefficiencies in carp production in India, especially among extensive farms. The mean technical efficiencies for semi‐intensive/intensive and extensive sample farms were estimated to be 0.805 and 0.658 respectively. By operating at full technical efficiency levels, the semi‐intensive/intensive farms could, on average, increase their production from about 3.4 Mt ha^?1 to 4.1 Mt ha^?1. Likewise, the extensive farms could increase their production from 1.3 Mt ha^?1 to 1.9 Mt ha^?1. Much of these efficiency gains would come from improvement in the adoption of recommended fish, water and feed management and monitoring practices. Besides expanding production area, the results indicated several other possibilities for increasing carp production in India by increasing yields per hectare, such as: (1) increased intensification of carp culture (i.e. moving from extensive to semi‐intensive or intensive systems); (2) improvement in technical efficiency at the farm level; and (3) technological progress. However, the realization of these potentials will depend on continuous efforts by the government in ensuring an adequate supply of inputs, technology transfer and development and adequate provision of research, extension and credit services in aquaculture.     

The effects of partially substituting Indian carps or adding silver carp on polycultures including small indigenous fish species (SIS)

A sustainable semi-intensive pond aquaculture technology including major carp species (Indian, Chinese and common carp) as cash-crop and small indigenous fish species (SIS) as food for the farmers' families is being optimized in Bangladesh. Silver carp inclusion in the polyculture is now being considered, because this very efficient filter feeder has a strong impact on pond ecology and also on the farmers' family nutrition because it is a cheap fish that the family can afford to eat instead of selling. The present paper is centered on the reduction of silver carp negative effects on other species while keeping the advantages of increased total yield and income due to silver carp stocking. It presents the results of two experiments, one on-station and one on-farm, in which 3–5 silver carp/100 m² were added or partially substituted major carp filter feeders. The basic stocking density was 100 carps (rohu, catla and a bottom feeder, either mrigal or common carp, at a 1:1:1 ratio) and 250 SIS (punti and mola) per 100 m². In the on-station experiment silver carp density was 3 and 5 fish/100 m² and the large carp bottom feeder was common carp. In the on-farm experiment silver carp density was 5 fish/100 m² and the bottom feeder was either common carp or mrigal.Most of the water quality and fish performance parameters tested were not affected by the polyculture composition. Adding 3–5% silver carp or substituting 3–5% of the herbivorous fish species by this highly efficient filter feeder increased grazing pressure on the phytoplankton, which led to a 25–40% reduction of the chlorophyll concentration in the water column. The increased grazing pressure was not enough to affect other water quality parameters and fewer effects on the availability of food for the other fish species occurred than when the silver carp addition was 10% of the polyculture, as reported in a previous work. The strong negative effects of silver carp on the other species of the polyculture and the higher total yields and income recorded in previous experiments with the addition of 10 silver carp/100 m² were much weaker and their expression depended on other pond conditions when 3 or 5 silver carp/100 m² were added or substituted the same number of rohu or catla, either when the bottom feeder was mrigal or common carp. It was concluded that stocking 3 silver carp/100 m² over the usual 100 large carp and 250 SIS /100 m² can be considered a ‘no effect’ stocking density in relation to the control without silver carp, while stocking 10 silver carp/100 m² should be preferred by farmers to keep the option of selling or consuming the silver carp.     

Growth, Yield, Dressout, and Net Returns of Bighead Carp Hypophthalmichthys nobilis Stocked at Three Densities in Catfish Ictalurus punctatus Ponds

Abstract— Alternative fish species that can be cultured together with catfish Ictalurus punctatus provide an opportunity to diversify caffish farms. A 2-yr study was conducted in 0.10-ha earthen ponds to evaluate the effect of bighead carp (BHC) stocking density on growth, yield, dressout yield, and net returns. Initially, bighead carp (average weight of 22 g) were stocked at rates of 380, 750, or 1,130 fishha in ponds with catfish. Caffish were cultured under commercial conditions by stocking caffish at a density of 12,500/ha, aerating nightly and feeding at an average rate of 82 kgha per d. Stocking rates for 2-yr-old fish were reduced to 77, 260, and 435/ha in the second growing season. There were no significant differences among treatments ( P > 0.05) in summer growth of bighead carp in either year. Bighead carp stocked at 1,130 fishha had significantly higher yields than those stocked at 380/ha, but did not reach minimum market size of 2.2 kg during the first year ( P > 0.05). There were no significant differences ( P > 0.05) in caffish growth, yield, survival, or feed conversion ratios due to the bighead carp stocking densities. Partial budget analysis indicated that net benefits were positive for all three treatments over a range of prevailing prices of bighead carp. Bighead carp production in catfish ponds is economically feasible over a wide range of prices. Given the market risk of producing smaller fish at the higher density, the medium density is the preferred stocking density of fingerling bighead carp in catfish ponds.     

主养草鱼池塘三种混养模式鱼类生长和效益的比较

为进一步提高我国广大池塘养鱼的产品质量、经济效益和改善其生态环境。本试验在武汉新洲973项目实验基地9个陆基鱼池中进行了三种不同混养模式鱼类生长和效益的比较研究,每种模式设3个重复。模式Ⅰ中放养草鱼、鲢、鳙和高背鲫;模式Ⅱ中放养草鱼、鲢、鳙、匙吻鲟和高背鲫;模式Ⅲ中放养草鱼、鲢和高背鲫。 结果表明：通过122d的养殖试验,模式Ⅱ中草鱼的生长不仅显著高于模式Ⅰ和模式Ⅲ（P<0.05）,而且其经济效益模式Ⅱ同样高于模式Ⅰ和模式Ⅲ。     

Fish-management relationships in Israeli commercial fish farming

To analyse the relationships among fish species performance and management procedures, a database was built up with data from 31 fish farms during the period 1976–1987 (1673 observations) and analysed through multivariate statistics (factor analysis). The data include nurseries, grow-out and operational ponds with mono- and polycultures of common carp, Cyprinus carpio, tilapia hybrid, Oreochromis niloticus × O. aureus, silver carp, Hypophthalmichthys molitrix, and mullet, Mugil cephalus. The main conclusions include the following. (1) The highest total yields and best tilapia performances were obtained in polyculture ponds where tilapia was the main species. (2) The best carp performances occurred in grow-out polyculture ponds where carp was the main species. Carp performance was improved in polycultures with mullet and silver carp, irrespective of whether tilapia were present or not. (3) Carp and tilapia yields increased as the nutritional inputs (feed pellets, sorghum pellets, manure), pond size and culture duration increased. The effect of the nutritional input was not linear, but logarithmic. (4) Growth rate of common carp was more affected by total density and stocking size than that of tilapia. Better carp and tilapia growth occurred in grow-out ponds when stocked at large sizes and cultured during short periods, mainly when both species were present. (5) Carp growth varied with the geographical region and size of fish pond, being better in smaller than in larger ponds due to reduced access to natural benthic food in deep ponds.     

A new high in fish production in India with record yields by composite fish culture in freshwater ponds

Composite fish culture of the Indian major carp, Catla catla, Labeo rohita and Cirrhinus mrigala together with the Chinese silver carp Hypophthalmichthys molitrix and grass carp Ctenopharyngodon idella and the Indonesian strain of common carp (Cyprinus carpio communis) was carried out in experimental ponds in 1971–1972 and 1973–1974. The management techniques adopted aimed at high yields of marketable fish (around 1 kg) in 1 year.In the first year, production varied from 3 889 to 5 600 kg/ha/year and this rose to an average of 8 200 kg/ha/year with a maximum of 9 389 kg/ha/year in the second year. The important changes made to the management schedule in 1973 were increased stocking density, greater use of feed and fertilizers, and provision of more weeds for grass carp.The experimental studies demonstrate the practicability of raising large crops of healthy marketable fish in India.     

Production economics of the emerging private fish farming industry in Bulgaria

The production economics of the emerging Bulgarian private carp and trout farming industry were assessed by surveying a representative sample of 20 private and state-controlled farms as well as visiting the National Fresh Water Fish Research Institute, the state-owned fish feed production plant and a fish processing plant.The major constraints for the development of profitable fish farming were found to be the lack of capital and the insecurity of tenure, which nonetheless, do not serve to discourage new entrants into the industry. The expected gross margin per tonne of carp produced in reservoirs or earth ponds is USD 487, while a tonne of trout farmed in concrete raceways shows a gross margin figure of USD 525. State-owned trout farms are only available for outright purchase at auctions, whereas carp farms may be rented, but only for a short term.Fish farmers could benefit from organizing themselves into producer groups in order to improve marketing and secure quality inputs. In particular, there is scope to source quality dry fish diets on both economic and environmental grounds.An extension advisory service is needed to support inexperienced new entrants and researchers should urgently evaluate what seem to be the most cost-effective methods of production.     

Effects of adding the small fish punti (Puntius sophore Hamilton) and/or mola (Amblypharyngodon mola Hamilton) to a polyculture of large carp

Abstract This experiment was carried out in the framework of a project to develop a viable fish polyculture technology under Bangladeshi conditions that allows simultaneous fish production of small indigenous species for farm families' consumption and of large carp species as a cash crop. The polyculture included the large carp rohu, catla and mirror carp as cash crop fish, and the small indigenous fish punti and mola as food for the small‐scale household. Total large carp stocking density was 10 000 fish ha^?1, at a species ratio 1:1:1. Total small fish stocking densities were 0, 25 000 or 50 000 fish ha^?1. The objectives were to assess the effects of adding 25 000 punti and/or mola ha^?1 on the large carp and environment, and to assess the effects of punti on mola and mola on punti. It was found that catla was not affected by the addition of small fish in any of the combinations tested; rohu was not affected by punti, and mola reduced rohu performance by 30–40% only when punti was not present; mirror carp was not affected by punti, and mola increased mirror carp growth rate and harvesting weight by 25–30% whether punti was present or not; small fish did not significantly affect total yield and food conversion ratio; punti performance was not affected by mola; mola harvesting weight was not affected by punti, while mola harvesting numbers and biomass were reduced by 55–65% by punti. Factor analysis of water quality data identified photosynthesis–respiration and algal biomass– temperature as the main processes governing water quality. Effects of treatment on those water quality factors are analysed, and the fish–water quality relationships discussed. In a parallel polyculture experiment in 25 farm ponds, the performance of large carp species was found to be unaffected by the addition of punti and/or mola. The results indicate that, at the densities tested, punti and mola addition to the large carp polyculture is viable as they do not reduce cash crop production and might be a good food source for the farmer's family.     

Factors contributing to the outcome of stocking programmes in Cuban reserviors

Abstract In less-developed countries, fisheries enhancement using stocking is a common practice to manage reservoirs for biomass production. In many cases, there appears to be little control over whether the stocking activity is appropriate or necessary. Cuban reservoir fisheries have been usually managed to maximize fish biomass. Blue tilapia have been introduced and supplemented in reservoirs, and Chinese carp are introduced and maintained in reservoirs throughout the entire island. Supplemental stocking with introduced fish species is a usual practice to manage large and medium-sized reservoirs. Small and very small reservoirs have been managed as semi-intensively enhanced fisheries with carp and tilapia stocking. The main purposes of the present paper are to study the factors contributing to the outcome of stocking programmes in reservoirs and to test the hypotheses that supplementary stocking for self-sustained fish populations usually cannot contribute to increase fish yield. Yield and stocking data by groups of fish species were available for Cuban reservoirs. Total fish yield was only slightly related to total fish stocking density for the complete set of reservoirs. However, this result was mainly because of the relationship between total yield and cyprinid stocking for semi-intensively-used reservoirs. Tilapia yield was not significantly related to tilapia stocking for both extensively and semi-intensively-used reservoirs. However, yield and stocking for cyprinids were highly related for both reservoir subsets. Therefore, cyprinid stocking was effective in certain reservoirs, but tilapia stocking was not effective in any reservoir. Moreover, tilapia stocking was a superfluous activity for reservoirs where tilapia have an adequate natural reproduction cycle.     

Quantitative estimates of freshwater fish stocking practices by recreational angling clubs in France

Although freshwater fish stocking is widely used by managers, quantitative assessments of stocking practices are lacking in many countries. The general objective of the present study was to determine the quantity and characteristics of fish stocking in metropolitan France. Using a survey-based approach, stocking practices for 2013 by recreational angling clubs in France were quantified, which represented the bulk of fish stocking undertaken in that year. Stocking was found to be practiced by 88.6% of angling clubs in France, representing, on average, 65% of their annual budget. Overall, 22 species were stocked, including 13 native and nine non-native species, with strong variations among species in terms of life stages and body sizes used for stocking. Using Bayesian modelling, a total biomass of 2.029 t, representing approximately 90 million fishes, was estimated to be stocked in France in 2013. In terms of biomass, the most widely stocked species were rainbow trout Oncorhynchus mykiss (Walbaum), brown trout Salmo trutta L., roach Rutilus rutilus (L.), common carp Cyprinus carpio L. and northern pike Esox lucius L. A stocking volume of approximately 60 fishes or 1.5 kg of fish biomass per angler per year seems commonplace in industrialised countries for which data are available.     

Factors affecting fish yield and profit in fish pen culture in flooded ricefields

In recent years, a rotational system consisting of two rice crops followed by a fish pen culture during the monsoon flood period was adopted in parts of the flood-prone region of the Mekong Delta. In this paper, we use the survey data from 51 fish pen farmers at Co Do and Vinh Thanh district, Can Tho City, to investigate the factors affecting fish yield and profit in such fish pen culture system. The net yield of all stocked fish varies from 377 to 3,782?kg/ha/crop while the return above variable costs varies from ?5.3 to 9.8 million VND/ha/crop. Low fish price at harvest and the difficulty to sell below market sized fish at a period of oversupply are the main problems for fish pen culture. Fish net yield significantly increases with stocking density and is linked with specific polycultures. Common carp and bighead carp perform best in fish pen culture, both in production and profit considerations. Harvest body mass of common carp is mainly limited by increasing common carp stocking density. Therefore, a stocking density of common carp of about 6,000 fish/ha is recommended to obtain the optimum combination of reasonable body masses, and a good price, as well as a high return above fingerling costs.     

Effect of density on survival and growth of cyprinid fish fry

One of the bottlenecks in Israel's cold water ornamental fish industry is the large loss of fish during the post-larval stage. As a first step towards increasing survival rates, the optimal stocking density in earthen ponds for fry of each species should be determined. The results of five consecutive experiments with fry of goldfish (Carassius auratus), common carp and koi (respectively, edible and ornamental morphotypes of Cyprinus carpio) are presented here. The experiments were run in 18 cages of 1 m³ and 0.8 mm mesh size placed in a 0.02 ha earthen pond, stocked at 50,100 and 200 fry per cage. The variables analyzed were growth rate, harvesting weight, biomass and survival. Equations to estimate growth rates under different conditions are given. The three fish types present different growth rates and survival patterns in relation to stocking density and season, which lead to different management implications. Koi can be stocked up to 2 million fry per ha without showing negative density effects. Goldfish should be stocked at low density (500,000–1 million fry per ha) in spring and at higher rate (2 million fry per ha) in summer. Common carp stocking density should be adjusted to obtain the required fish size at harvest.     

Intensive polyculture of fish in freshwater ponds. I. Substitution of expensive feeds by liquid cow manure

In 1974 and 1975 nine experimental treatments of fish polyculture in stagnant water ponds without aeration were conducted at Dor. The polyculture was composed of common carp, silver carp, white amur (grass carp) and Tilapia. The treatments differed in stocking densities, feeding and manuring levels. The most productive treatment of the experiment, in which the fish were fed with protein-rich pellets, produced 50 kg/ha per day, probably a record for unaerated ponds of stagnant water. Two treatments (low and high stocking densities) fed exclusively with liquid cow manure produced an average yield of around 32 kg/ha per day. The yields of the treatments receiving high-protein pellets exceeded those of the treatments receiving grain pellets by 20 and 9.6 kg/day per ha, at high and low stocking densities, respectively, and in both cases the yield increments justified the extra cost of high-protein feed. The responses of the four fish species to the different levels of feeding and stocking densities were widely different. The common carp and white amur showed the greatest responses to increased feeding inputs while the silver carp and Tilapia, even at high densities, have done equally well at low feeding levels. Total body fat contents of the common carp were 20%, 15% and 6.2% when fed with high-protein pellets, grains pellets and liquid cow manure, respectively. Intermittent harvesting did not result in increased yields.     

Optimization of fish to mussel stocking ratio: Development of a state-of-art pearl production mode through fish–mussel integration

Integrated aquaculture has been widely used for pearl production in the freshwater pearl mussel Hyriopsis cumingii farming in China, but the production technology has not reached the state of the art. This study explored the optimal stocking ratio of fish to mussel (fish–mussel) through a 90-day experiment conducted in land-based enclosures. The integrated system included pearl mussel, grass carp, gibel carp, silver carp and bighead carp, with four fish–mussel stocking ratios by number: 1:1 (R1), 2:1 (R2), 3:1 (R3) and 4:1 (R4). The pearl yield was higher in the R2 enclosures than in the R1 and R4 enclosures, whereas the fish yield was higher in the R3 and R4 enclosures than in the R1 and R2 enclosures. The phosphorus (P) utilization efficiency was higher in the R2, R3 and R4 enclosures than in the R1 enclosures. The wastes of nitrogen (N) and P enhanced with the increase of fish–mussel ratio. Regression analyses indicated that the fish–mussel ratio was 2.3:1 for the maximal pearl yield, and 3.6:1 for the maximal fish yield, and 1.6–2.3:1 for the minimal N waste, and 1.9–2.9:1 for the minimal P waste. This study indicated that the suitable fish–mussel stocking ratio was 2:1 in the integrated culture of H. cumingii, grass carp, gibel carp, silver carp and bighead carp.     

Assessment of impact of the introduction of exotic fish species in north-east Thailand

Abstract. Within the framework of a fisheries project in north-east Thailand, project MK/FSPC/069 entitled ‘The Fish Seed Production Centre, North East Thailand’, an assessment was carried out of the ecological impact of introducing exotic fish species (common carp, Cyprinus carpio L., Nile tilapia, Oreochromis niloticus (L.), and Chinese and Indian carps). For the assessment, the protocol of Kohler & Stanley (1984) was followed, covering feasibility of introduction, acclimatization potential, potential impact, and control potentials. Regarding the (ongoing) use of the proposed exotic species in aquaculture, it was concluded that so far no clear ecological impact has been reported from escapes to open water; the use of the exotic species has shown to be highly beneficial from a 9 socio-economic point of view. Regarding the proposed introduction of the exotic species into public waters (natural lakes and man-made reservoirs), it was concluded that earlier releases of these species in north-east Thailand did not provoke severe ecological impact in terms of deterioration of aquatic ecosystems. Incidental cases of minor ecological impact were reported for common carp and nile tilapia. Indications were obtained for niche competition between Chinese and Indian carps and indigenous carps, while similar niche competition was concluded for bighead carp, Aristichthys nobilis (Richardson), and indigenous pelagic zooplankton feeders. Observing the prolific development of the Nile tilapia in a number of reported cases, it was recommended not to include this species in stocking programmes for public water bodies, until more risk assessments are available.     

Rearing advanced fry of major Indian carp species in recirculatory-filtering ponds at Barrackpore,West Bengal

This paper describes an experiment using a recirculatory-filtering system operating in two rectangular cemented ponds (160 and 190 m², 1.5 m deep) to rear fry (25 mm–50 mm) of the major Indian carp species Labeo rohita (Hamilton) and Catla catla (Hamilton) to fingerlings (100 mm–125 mm). These operations were concluded in both the species in 32 days at stocking densities of 0.46 million/ha and 0.55 million/ha, and showed survival rates of 96.6% and 84.4% respectively. In the presently followed practices of modern fish culturists, corresponding operations in earth ponds usually take 90 days and have a stocking density of 0.2 million/ha with survival rates more or less similar to those obtained in the recirculatory-filtering system. If followed by industry, the technique described will enable production of major Indian carp fingerlings with great saving in time, the use of water and the space occupied by the production system. These advantages greatly enhance the economic viability of rearing carp fingerling in India.     

Polyculture of silver barb, Puntius gonionotus (Bleeker), Nile tilapia, Oreochromis niloticus (L.), and common carp, Cyprinus carpio L., in Vietnamese ricefields: fish production parameters

The fish production parameters of five polyculture combinations, consisting of small and large silver barb, Puntius gonionotus (Bleeker), small and large Nile tilapia, Oreochromis niloticus (L.), and small common carp, Cyprinus carpio L., fingerlings in three replicates, were investigated in a rice-fish culture experiment (duration 149 days) conducted in the Mekong Delta, Vietnam. The survival rate was not significantly (P > 0.05) affected by the polyculture combination, but when grouped according to species, the mean survival of silver barb and tilapia was 64.3% and 63.7%, respectively, significantly higher than the mean common carp survival rate (33.4%). The growth of silver barb and tilapia was proportionally related to the stocking density, probably because of intraspecific competition and a synergistic interaction between silver barb and tilapia. The growth of common carp was not significantly different among the polyculture combinations. The highest net production (474.1 kg ha^?1) was obtained in the polyculture combination consisting of 80% small-sized silver barb fingerlings, but the fish was not marketable at that time. In concurrent rice-fish culture, it is recommended to raise large silver barb fingerlings. Small tilapia can be polycul-tured with silver barb, provided a stocking density lower than 1400 ha^?1. Common carp is considered less suitable because of a limited tolerance for the water quality conditions in the ricefield and the large size required by the market.