A Study on Carp Polyculture in an Earthen pond

TABLE OF CONTENTS

ACKNOWLEDGEMENT

TABLE OF CONTENTS

LIST OF TABLES

LIST OF FIGURES

LIST OF APPENDICES

ACRONYMS

ABSTRACT

1. INTRODUCTION
1.1 Background
1.2 Objectives
1.3 Limitations of study

2. LITERATURE REVIEW
2.1 Carp polyculture
2.2 Species for carp polyculture
2.2.1 Rohu (Labeo rohita)
2.2.2 Grass carp (Ctenopharyngodon idella)
2.2.3 Bighead carp (Hypophthalmichthys nobilis)
2.2.4 Silver carp (Hypophthalmichthys molitrix)
2.2.5 Common carp (Cyprinus carpio)
2.2.6 Mrigal (Cirrhinus mrigal mrigala)
2.3 Stocking density of carps
2.4 Water quality requirements for carp
2.5 Bleaching
2.6 Fertilization
2.7 Feed and feeding
2.8 Overall carp production

3. MATERIAL AND METHODOLOGY
3.1 LEE site
3.2 Pond preparation
3.3 Stocking of fingerlings
3.4 Feeding
3.5 Water quality analysis
3.6 Fish sampling
3.7 Fish harvesting
3.8 Marketing
3.9 Analytical methods
3.9.1 Fish growth parameter
3.10 Gross margin analysis
3.11 Statistical analysis

4. RESULTS
4.1 Water quality
4.2 Growth and yield of carps
4.2.1 Silver carp
4.2.2 Bighead carp
4.2.3 Grass carp
4.2.4 Rohu
4.2.5 Common carp
4.2.6 Naini
4.3 Combined yield of carps
4.4 Marketing
4.5 Gross margin

5. DISCUSSION
5.1 Growth and production
5.1.1 Growth, survival and production of Silver carp
5.1.2 Growth, survival and production of Bighead carp
5.1.3 Growth, survival and production of Grass carp
5.1.4 Growth, survival and production of Rohu
5.1.5 Growth, survival and production of Common carp
5.1.6 Growth, survival and production of Naini
5.1.7 Combined yield of carps
5.2 Water quality

6. CONCLUSIONS

LITERATURE CITED

APPENDICES

ACKNOWLEDGEMENT

Any accomplishment requires the effort of many people and this work is no different. Foremost, I would like to express my sincere gratitude to my advisor Prof. Dilip Kumar Jha, Ph.D., for the continuous support of my LEE work, for his patience, motivation, enthusiasm, and immense knowledge and invaluable suggestions. His guidance helped me in all the time of work and writing of this thesis. I could not have imagined having a better advisor and mentor for my LEE work. It was a great privilege an honour to work under his supervision.

I would like to acknowledge and express my sincere gratitude to Prof. Sunila Rai, Ph.D, Head of the Department; Prof. Dilip Kumar Jha, Ph.D.; Prof. Madhav Kumar Shrestha, Ph.D.; Adjunct Prof. Jay Dev Bista; Asst. Prof. Kamala Gharti; Asst. Prof. Rahul Ranjan; Asst. Prof. Neeta Parajuli karki; Faculty of Animal Science, Veterinary Science and Fisheries, AFU, Rampur, Chitwan for providing an opportunity of LEE and for the financial support during our LEE work.

I would especially like to thank my colleagues, Ashish Shrestha, Suhaib Khan, Ajit Acharya, Yubaraj Neupane, Kishor Baduwal, and Bimarsha Gyawali for their help and cooperation during the work period which was instrumental for completing my LEE work easily.

I am indebted to my juniors, Rahul Chaudhary, Dibyanshu Shrestha, Shiva Poudel, Gopal Chaudhary, and respected seniors, Salin Kumhal, Ratan Saud, Pancham Lodh for helping me during data tabulation, analysis and for the preparation of this manuscript.

I could not forget staffs of the Fisheries Program Pancha Gurung, Tulsi Adhikari, Arpan Malla and Surya Kumar Gurung for their continuous support during my study period. Last but not the least, I am extremely grateful to my parents Mr. Anirudra Yadav Ahir and Mrs. Rambha Devi Yadav for their love, prayers, caring and sacrifices for educating and preparing for my future. Also I am very much thankful to my brothers Ramavtar Yadav, Ramanand Yadav and sister Angira Yadav for their encouragement and financial support and for the keen interest shown to complete this thesis.

Subash Yadav Ahir

LIST OF TABLES

Abbildung in dieser Leseprobe nicht enthalten

LIST OF FIGURES

Abbildung in dieser Leseprobe nicht enthalten

LIST OF APPENDICES

Abbildung in dieser Leseprobe nicht enthalten

ACRONYMS

$ : Dollar

˚C : Degree Celsius

ADB : Asian Development Bank

AFCR : Apparent Feed Conversion Ratio

AFU : Agriculture and Forestry University

AGDP : Average Gross Domestic Products

B:C : Benefit Cost

CABI : Centre for Agriculture and Bioscience International

CBS : Central Bureau of Stastistics

CFPCC : Central Fisheries Promotion and Conservation Center

cm : Centimeter

DAP : Diammonium Phosphate

DO : Dissolved Oxygen

FAO : Food and Agriculture Organization

FAVF : Faculty of Animal Science Veterinary Science and Fisheries

FCR : Feed Conversion Ratio

FGR : Fish Growth Rate

FY : Fiscal Year

g : Gram

GDP : Gross Domestic Products

GFY : Gross Fish Yield

GoN : Government of Nepal

ha : Hectare

kg : Kilogram

L : Liters

LEE : Learning for Entrepreneurial Experience

m : Meter

mg : Milligram

MOC : Mustard Oil Cake

mt : Metric tonnes

NARC : Nepal Agricultural Research Centre

NFY : Net Fish Yield

PER : Protein Efficiency Ratio

ppt : Parts Per Thousands

UNDP : United Nation Development Programme

Wt. : Weight

yr : Year

ABSTRACT

Carp polyculture in an earthen pond was practiced at Fisheries Farm of Agriculture and Forestry University, Rampur, Chitwan from 31st August to 28th November, 2022. Growth and production parameters of different fish species were assessed along with the regular monitoring of water quality parameters, namely water temperature, DO, pH and water transparency. Gross margin and B:C ratio of carp polyculture were calculated. The stocking weight of 6 species of carp were: silver carp (12.64±2.21 g), bighead carp (11.53±2.24 g), grass carp (34.87±3.34 g), rohu (6.38±1.29 g), common carp (10.36±1.03 g) and mrigal (7.1±2.14 g) and stocked in the ratio of 4:2:3:5:5:1, respectively. The stocking density was 2 fish/m². Fishes were fed with dough feed (mustard oil cake and rice bran in the 1:1 ratio) of 21% CP twice a day at the rate of 5% of body weight per day. The feeding rate was adjusted on the basis of monthly sampling. Fertilization of pond was done using urea (4.7g/m[2]/week) and DAP (3.5g/m[2]/week) before stocking and to maintain the plankton according to record of transparency. Water depth was on average 0.64 cm throughout the culture period. Temperature of water ranged between 20.2 °C and 35.3°C throughout culture period. Average temperature at morning (6-7 am) was 26.61±2.66°C and at afternoon (2-3 pm) was 30.53±2.33°C. The average DO at morning and afternoon were 2.18±0.54 mg/L and 5.06±1.24 mg/L respectively. Similarly, the average pH at morning and afternoon was 8.01 and 9.21 respectively. After 90 days of culture period, the overall extrapolated GFY and NFY were 2.031 and 1.258 t/ha/yr, respectively. The highest growth rate was seen in grass carp which was 0.863 g/fish/day. The overall survival rate of all species was 51.33 % and AFCR 1.97. The net profit was NRs. 526 with BC ratio 1.17. Harvested fish were sold at the rate of NRs. 300 per kg. From LEE work, we can conclude that this is great opportunity to learn, experience and enriched our knowledge by maximum exposure to field.

1. INTRODUCTION

1.1 Background

Fish farming is currently one of the popular agriculture enterprises among Nepalese farmers. The growth rate of fisheries and aquaculture sector is more than 9 % in the last decade (CFPCC, 2019). Fisheries contributed 1.59 % to Gross Domestic Product (GDP) and 4.22 % to Agricultural Gross Domestic Product (AGDP) in the Fiscal year (FY) 2077/2078 (CFPCC, 2021). Polyculture is a production system where two or more species of fish with different ecological habitat and food preferences are cultured together in such densities that there will be almost no competition for space and food (Shrestha and Pandit, 2012). Actually, development of carp polyculture was noticed from the beginning of the 1980s with the execution of the Aquaculture Development Project supported by the Asian Development Bank (ADB) and the United Nations Development Programme (UNDP). Carp polyculture has developed as the most viable and popular aquaculture production system in Nepal and accounted for over 90 percent of the total production of 20,000 tonnes in 2003/2004 (FAO, 2014). Terai of Nepal has sub-tropical climate which is suitable for carp. Therefore, carp polyculture is commonly done in in this region (FAO, 2014).

The species chosen should have different food spectrum and habitats. Carp polyculture practice has been increasing since low income people favor carp because of their high price and good taste and important source of protein for the poor people. Polyculture system requires less resources, utilizes available nutrients better, yields higher and provides variety of products to consumers. It is considered as economical and environment friendly approach (FAO, 2020). Carp polyculture can be practiced extensively, semi-intensively and intensively. However, semi-intensive carp polyculture is a common practice in Nepal because majority of farmers are small scale farmers and they have less resources. Semi-intensive carp polyculture utilizes limited resources like labor, material, money efficiently and results in higher production per unit area. Yields obtained from polyculture are usually much higher than those obtained from monoculture, especially if the right species have been chosen. Also oxygen of culture environment is balance in polyculture because excess plankton is consumed by Silver carp and Bighead carp and detritus is consumed by Rohu (UNDP, 2008). Learning to produce indigenous major carps and exotic Chinese carps and common carp in polyculture will help to understand semi-intensive fish farming systems and become self-employed in Nepal. Polyculture enables the maximum production of fishes by optimum utilization of available natural feeds as well as ecological niches in the same pond.

1.2 Objectives

General objective

- To learn the production of carps under polyculture system in an earthen pond.

Specific objectives

- To access the growth and yields of different carps in polyculture system.
- To calculate gross margin, B:C ratio and apparent FCR of carp polyculture.
- To monitor the water quality parameters required for carp polyculture.
- To learn about the marketing of carps.

1.3 Limitations of study

a. Time and resource constraints limited the LEE work. Culture period was short and fish could not attain the suitable market size which created problem in marketing.
b. Pond bottom and dyke conditions, which encounters maximum fish loss during harvesting.
c. Similarly, instrumental faults brought challenge to daily recordings of DO, pH and temperature of pond water.

2. LITERATURE REVIEW

2.1 Carp polyculture

The most common aquaculture practiced in Nepal is carp polyculture in ponds (FAO, 2005). Increase in the cost of production is due to the pond enrichment with fertilizer, manuring and the feeding practice. Feed cost generally covers 76 % of the total operational cost in intensive culture and 69 % in semi-intensive culture and usually carp are grown in semi-intensive culture (Ahmed, 2007). The carp polyculture has an advantage by covering certain percent of the feed cost because in the pond where fertilization, manuring is done so there is an abundant amount of natural food as well and species will be added in such manner they will have different feeding habit and in such proportion that optimum utilization of natural food occurs.

Selection of the species for the carp polyculture can be done based on the feeding habit which is categorized as plankton feeder (Hypophthalmichthys molitrix, Hypophthalmichthys nobilis, Labeo catla), herbivorous fish (Ctenopharyngodon idella, Labeo rohita) and detritus feeder (Cyprinus carpio, Cirrhinus mrigala mrigala) and feeding niche such as surface feeder (Hypophthalmichthys molitrix, Hypophthalmichthys nobilis, Labeo catla, Ctenopharyngodon idella), Column feeder (Labeo rohita, Ctenopharyngodon idella), bottom feeder (Cirrhinus mrigala mrigala, Cyprinus carpio) (Rahman, Varga, & Chowdhury, 1992). In China polyculture is done with silver carp, bighead carp, grass carp with combination of other species where stocking density is determined by the condition of the pond, cultured species, availability of fry, managing technique and production planning (Milstein 1992), stocking density of 10,500-21,000 per ha is found to be suitable in the pond depth of 1.8-3 m (Ren, 2011).

In case of Nepal, combination of silver carp, bighead carp, grass carp, common carp, rohu, mrigal at the ratio of 4:1:4:3:5:5, the stocking density of 15,000 per ha was also found to give a better result (Jha, Rai, Shrestha, Diana, Mandal, & Egna, 2018). Whatever the selection criteria of the fish the only thing to be considered is species must meet the principal requirement of the different species according to Shrestha and Pandit (2017) is mentioned as follow:

- They should have complementary feeding habits
- They should occupy different ecological niches and be non-predatory
- They should tolerate each other and attain marketable size at same time

2.2 Species for carp polyculture

2.2.1 Rohu (Labeo rohita)

Rohu (Labeo rohita) is commonly called as Rohu is characterized by elongated and cylindrical body, small or pointed head, sub-terminal mouth and pairs of maxillary barbells, lips are thick and fringed (Mannan, Islam, Rimi, Meghla, & Suravi, 2012). Rohu is a column feeder which feeds on plant matter including decaying vegetation. It feeds on algae, periphyton (Rai & Yi, 2012), detritus and small proportion of crustaceans and rotifers. It is known that Rohu preferred plankton over artificial feed (Rahman, Nagelkerke, Verdegem, Wahab, & Verreth, 2008). Rice bran and ground nut oil cake in a ratio of 1:1 is prefered by Rohu, also potato starch as carbohydrate source and mustard oil cake are used as supplemental feed type (Mannan, Islam, Rimi, Meghla, & Suravi, 2012). For fingerling rearing, the feeding rate of 6.5–7.0 percent body weight per day, with a 26-28 percent protein diet is optimum for growth and efficient feed utilization and later for grow out the supplementary feed is provided once or twice a day at a daily ration of 3-5 percent of the biomass in the first month and then reduced to 1-3 percent of fish biomass per day (Ahmed & Maqbool, 2016).

The fish attains 1.0-1.5 kg after a culture period of 10-12 months (FAO, 2020). Chondar (1999) reported that in well prepared ponds, Rohu attains 700-1000 g in the first year, 800-2000 g in the second year and 2000-4000 g in the third year. The growth of Rohu was found to be highest when stocking with common carp at the rate of 0.5 common carp m-[2] with the supply of feed. It was found that average individual harvesting weight, 191.1 gm highest specific growth rate, 1.62% body wt. day−[1] and highest total production of 2860 kg ha-[1] in 137 days (Rehman, et al., 2006). Production levels of 6-8 t/ha could be obtained in properly managed pond in which Rohu contributing about 70-80 percent of the biomass (FAO, 2020). Survival rate of 68.3% and 79.4% when fed at twice a day and thrice a day respectively were recorded (Bishwas, Jena, Singh, Patmajhi, & Muduli, 2006).

2.2.2 Grass carp (Ctenopharyngodon idella)

Grass carp were brought to Nepal from India and Japan in 1967 and 1968 simultaneously (Shrestha & Pandit, 2017). It is cultivated for food as well as for the control of aquatic weed in the lakes pond and is reported the maximum produced fish in the word 5,704 thousand tones (FAO, 2020). The body is elongated, torpedo-shaped with terminal mouth slightly oblique, upper jaw slightly longer than the lower jaw. It has a complete lateral line, ridged pharyngeal teeth are arranged in a 2,4,4,2 formula. Body coloration with dark olive, shading to brownish-yellow on the sides, with a belly and slightly outlined greenish scales.

Grass carp is column/marginal feeder, herbivorous which feeds on different aquatic macro-vegetation including certain terrestrial plants as well. Hybrid Napier (a cross between elephant grass, Pennisetum purpureum and Sajje P. typhoideum) given to the fingerling of 30-50 g showed the best growth which was because of the development of proper digestion system to utilize the fibrous and tough nature of the grass (Venkatesh & Shetty, 1978)

2.2.3 Bighead carp (Hypophthalmichthys nobilis)

Bighead carp is an exotic fish that was introduced in Nepal from America and Hungary in 1969 and 1972 respectively. It can tolerate extremes in water temperature and high turbidity and can, therefore, be cultured in many areas (CABI, 1989). It ranks 5th among all cultured freshwater fish globally (FAO, 2020). The body of the fish is flat, laterally compressed and covered by small silvery scales brownish above, the head is long and massive, barbels are absent, mouth is large and upturned with lower jaw longer than upper and abdominal keel incomplete. The snout is short and blunt, eyes are small, projecting downward, and located anteriorly on the head, below the midline of the body (CABI, 1989). Bighead carp is a surface, zooplankton feeder (Shrestha & Pandit, 2017). Larvae feed mainly on unicellular phytoplankton, nauplii and rotifers. Fry and adults feed on diverse forms of planktonic life, mainly zooplankton as well as phytoplankton such as Bacillariophyceae, Flagellata, Dinoflagellata, Myxophyceae, etc. (Jhingran & Pullin, 1985). Feed Conversion ratio (FCR) for Bighead carp was better in summer than in winter and overall FCR was 4.24±1.74 (Afzal et al., 2008). Bighead carp were observed feeding on floating pellets at the pond surface, and its growth was 57% greater in the pond receiving supplemental feed than in ponds receiving fertilizer only. Bighead carp growth was 53% greater in the cage with feed than in cages without feed (Cramer & Smitherman, 1980).

It was found that the average initial weight of 11.40±3.25g Bighead reached to 902.00 ± 4.63g after 12 months of experiment using fertilizers alone (Afzal et al., 2008). Production of Bighead carp was 261 and 186 kg/ha when mixed stocked with Common carp, Silver carp and Grass carp respectively (Opuszynski, 1981). Bighead carp is hardy fish. The survival rates can be as high as around 90% (Sun et al., 2012).

2.2.4 Silver carp (Hypophthalmichthys molitrix)

Silver carp is ranked second among cultivated fish in world (FAO, 2020). It is an exotic fish introduced to Nepal from India and Japan in 1967 and 1968 respectively (Shrestha & Pandit, 2017). Silver carp is characterized by the flat and laterally compressd body covered by silvery scales. Head is small, barbells are absent, mouth is upturned with lower jaw longer than upper jaw and abdominal keel is complete, gill rakers are long and dense, interlaced, connected and covered with spongy sieve membrane (Shrestha & Pandit, 2017).

Silver carp consumed leaves of vegetable such as cauliflower, cabbage, and radish directly and other carps perhaps grew on the semi-digested food which serves both as feed for bottom-dwelling fishes and pond fertilizer when Grass carp were fed daily at the rate of 50% of body weight for first four months and at the rate of 25% of body weight for rest four months of culture period (Roy, Rai, Datta, Das, & Ghosh, 1996). One to three-day old fry feed mainly on zooplankton, rotifers and copepod nauplii and diet expands as the fry grow to include copepods, cladocera and phytoplankton. Flagellata, Dinoflagellata, Myxophyceae, Bacillariophyceae, etc., are the best food for larger fry and adult so Silver carp is primarily phytoplankton and secondarily zooplankton feeder (Jhingran & Pullin, 1985). Silver carp is able to collect the food particles smaller than distance between its gill rakers like Cyclotella and collecting such small particles is assisted probably by secretion of mucus (Esmaeili & Singh, 2015). It is found that there is no need to provide formulated feed in the culture of Silver carp (FAO, 2009). Absolute weight increases at a rate of 4.2 g/day during the fingerling stage. Highest growth rate in length and maximum growth rate in weight of Silver carp is attended in the second and third year of life respectively. Growth in both length and weight declines sharply after the third year, by which period the fish may weigh as much as 2780g, gaining weight at the rate of 6.3 g/day (Jhingran & Pullin, 1985). Production of silver carp averaged 130 and 120 kg/ha in mixed stocks with Common carp, Bighead carp and Grass carp (Opuszynski, 1981). The survival rate of Silver carp was found to be 79.23% when Silver carp was stocked at rate of 20 piece/m[3] and 70.7% when stocked at rate of 40 piece/m[3] (Jui, Haque, & Rahmahatullah, 2018).

2.2.5 Common carp (Cyprinus carpio)

Common carp (Cyprinus Carpio) is the fourth highest fish cultivated in the world (FAO, 2020) which was introduced in Nepal in 1956 and 1960 from India and Israel, respectively (Shrestha & Pandit, 2017). Two varieties: the scale carp or German carp (Cyprinus carpio var. communis), with body completely and uniformly covered with golden scales in regular rows; and the mirror or Israeli carp (Cyprinus carpio var . specularis with body covered unevenly with few large shiny scales are culture in Nepal (Shrestha & Pandit, 2017). It is said that Common carp enjoys the status of a virtually global fish and its culture is very widespread (Jhingran & Pullin, 1985). Common carp is characterized by a flat and deep body, short and small head, protractile mouth and two pairs of maxillary barbells, dorsal fin long with sharp spine (Shrestha & Pandit, 2017). There are 5–5 molar-like pharyngeal teeth serving to grind the food (FAO, 2008). Common carp is a bottom dweller which digs and burrow into pond embankments and sides in search of organic matter, the fish gulp in mud from which digestible matter is sifted and the rest rejected, this habit which often makes pond water turbid (Jhingran & Pullin, 1985).

This carp is an omnivorous, flexible and opportunistic feeder which feed on varieties of natural foods, including planktonic crustaceans, insects (including their larvae and pupae), the tender parts and seeds of water plants, and also fish eggs and larvae, and can switch to alternative diets according to food availability (FAO, 2008). Mouth of the Common carp is relatively large and protusible fashion which enable the fish to dig in the mud of the bottom, two pairs of barbells function as feelers for searching for food; 5–5 molar-like pharyngeal teeth which serve to grind the consumed food and feeds (Froese & Pauly, 2011). Common carp readily feeds on grains, supplementary or commercial feeds (FAO, 2008).

An individual weight of about 0.2–0.3 kg, 1–1.2 kg and 2.5–3.5 kg is attained by Common carp within about 2–3, 5–7 and 10–14 months, respectively (Jhingran & Pullin, 1985). The total yield in treatments with feed was 2.1 times higher than in treatments without feed (Rehman et al., 2006).

2.2.6 Mrigal/ Naini (Cirrhinus mrigala mrigala)

Among indigenous fish mrigal is next in importance to rohu and Catla for culture. This fish is characterized by elongated and cylindrical body, small head and sub-terminal mouth with thin non-fringed lips. One pairs of small barbels are present. The Upper jaw is longer than the lower jaw. The body color is Grayish on dorsal side and whitish on belly but is not pinkish as Rohu. Mrigal is a bottom feeder, omnivorous and feeds on detritus, Mud organisms, decaying plant and animal matter, however, young ones feed on zooplankton. Mrigal grows slower than catla and rohu. The growth in the fry of mrigal was significantly higher at 33°C and 30°C when compared to treatment 36°C. Probable explanation of improved feed efficiency of fish maintained at higher temperature might be the increased feed intake of the fish with increase in water temperature, which resulted in better growth of the fish, leading to better feed conversion ratio. The preferred temperature is considered to coincide with the optimum temperature for growth (Brett, 1971; Kellog and Gift, 1983). An increase in temperature increases the activity of digestive enzyme, which may accelerate the digestion of the nutrients, thus resulting in better growth (Shcherbina and Kazlauskene, 1971). Largest size attains is 90 cm and 30 kg. Time to maturity and breeding behavior is similar to Rohu and Catla.

2.3 Stocking density of carps

Stocking densities and species combinations are the two important aspects greatly influencing the level or intensity of operation in polyculture systems. Stocking combination adopted by farmers in Nepal as per recommendation from CFPCC is shown in table no. 1.

Table 1. Stocking ratios of carps in polyculture

Abbildung in dieser Leseprobe nicht enthalten

Source: (CFPCC, 2019)

Mandal, Rai, Shrestha, Jha and Pandit (2018) evaluated carp polyculture systems using Silver carp, Bighead carp, Grass carp, Common carp, Rohu, and Mrigal at a ratio of 4:1:4:3:5:5 with a rate of 1.5 fish/m[2] and at a ratio of 3.5: 2.5: 1.5: 1:1:0.5 with a rate of 1 fish/m[2], respectively. The ponds were stocked with six carp species, viz., Catla, Rohu, Mrigal, Silver carp, Grass carp and Common carp in the ratio of 2:2:2:2:0.5:1.5, at a combined density of 10,000 fingerlings (Jena, Ayyaappan, & Aravindakhshan, 2002).

2.4 Water quality requirements for carp

Efficient production of aquaculture is directly related to the suitable water quality management in culture units. Temperature, transparency, dissolved oxygen (DO), carbon dioxide (CO2), ammonia, nitrite, soluble reactive phosphorus, abundance of algae and macrophytes in culture system are important (Boyd & Tucker, 2014). Temperature determines the growth, production and reproductive activity of all aquatic organisms. During winter, fish stop feeding, they hibernate and remain dormant at the pond bottom because temperature lowers down below suitable range (Woynarovich, Poulsen, & Peteri, 2010). The acceptable range of temperature for efficient growth of fish ranges from 25[0] C and 32[0] C for warm water fish (Boyd & Tucker, 2012). Below 12[0]C death of fish occur and feeding usually decline when temperature falls below 20 [0]C (Shrestha & Pandit, 2017). Turbidity is caused rendered by suspended matter such as clay, silt, and organic matter and by plankton and other microscopic organisms that plug the passage of light through the water (P´erez-Sicairos, Morales-Cuevas, F´elix-Navarro, & Hern´andez-Calder´, 2011). The acceptable range for transparency is 20-40 cm (Mustapha, M., 2017)

To ensure efficient respiration and feed intake, sufficient dissolved oxygen in pond water is required. DO in pond water is mainly produced by phytoplankton photosynthesis. DO is maximum in early afternoon and minimum is at daybreak (Woynarovich, Poulsen, & Peteri, 2010). Carp grow well in dissolved oxygen levels above 5 mg/L (FONDRIEST, 2020). Carp are unable continue their normal physiological activities, if dissolved oxygen content in pond water drops below 2.0 mg/L. According to Hepher and Pruginin (1981) water ranging in pH between 6.5 and 9.0 is most suitable for pond fish culture, at pH 6.5–5.5, fish production will be less, either because of the direct effect on the fish and/or on the growth of fish food organisms, acid water with pH 5.0–5.5 can be harmful to fish. Diurnal variation in pH is caused by photosynthesis and respiration. During daytime CO2 is consumed therefore pH increases, at night plant consumes oxygen and produce CO2, this decreases the pH of the water (Woynarovich, Poulsen, & Peteri, 2010). Total amount of base present in water is known as total alkalinity. A desirable range of total alkalinity for carp culture is between 75 and 200 mg/L CaCO3 and there is no maximum acceptable alkalinity for but productivity probably begins to decline above 200 to 300 mg/L CaCO3 (Boyd & Tucker, 2012). Ammonia is produced by fish as the end product of their metabolism. Fish excretes through the gills about one-third of the consumed nitrogen in the form of ammonia. The optimum level of NH3 for pond culture is 0.3 to 1.3 ppm. Carp culture can go smooth on waters up to 0.3 mg/L nitrite (Eddy & Williams, 2013). The presence of right amount of organic matter ensures the continuous supply of easily accessible phosphorus. About 10 - 15 mg phosphate per 100 g soil is required for carp culture (Islam, Rahman, & Rahman, 2011). The desirable Chlorophyll-a concentration for carp polyculture is 80-100 g/L (Boyd, 2009).

Table 2.Water quality parameter for carp polyculture

Abbildung in dieser Leseprobe nicht enthalten

Source: (Wahab, Ahmed, Islam, Haq, & Rahmatullah, 1995)

2.5 Bleaching

Pond bleaching kills all the organisms in the pond such as parasites, mollusks, crustaceans, fishes etc. If bleaching powder is applied to the pond, then liming is not required. The toxicity of the bleaching powder lasts for about 6-7 days (Kunwar, Karim & Nandi, 1992)

2.6 Fertilization

Combined application of inorganic and organic fertilizer are preferred to enhance a wide variety of both autotrophic and heterotrophic organisms (Das & Jana, 1996). Mortimer (1954) reported that the production of carps in fertilized pond was 2 to 10 times higher than that of unfertilized ponds in temperate region. Organic manures contribute a great amount of combustible matter, which is oxidized and produce carbon dioxide that helps in the algal photosynthesis. Organic fertilizer decomposition is carried out by bacteria, fungi, actinomycetes as a result, the released essential nutrients help to sustain the biological productivity of pond (Bhakta, Bandyopadhyay, & Jana, 2006). Application of inorganic fertilization is known to accelerate the mineralization. The advantages of inorganic fertilizers are that they have a definite chemical composition of nutrient elements and are instantly soluble in water. Biweekly application of urea and DAP at of 9.4 g/m[2] and 7 g/m[2] respectively to maintain N:P ratio of 4:1 (Knud-Hansen, Batterson, & McNabb, 1993) and organic manure at the rate 4.5 kg/100 m[2] (CFPCC, 2019) can enhance pond productivity.

2.7 Feed and feeding

Carps are fed with dough of rice bran and mustard oil cake mixed at ratio of 1:1 in Nepal. However, nowadays farmers have started to use pellet also. Floating (24% CP) was fed at 3% body weight per day to carp except Grass carp. According to Mandal et al., 2018 Grass carp was fed with Grass on wet weight basis of 50 % body weight. Mandal et al., 2018 said that proximate analysis showed that pellet contained 91.5% dry matter, 24.0 % crude protein, 5.5% crude fiber, 5.6% ether extract, 5.3% total ash and 51.0% nitrogen free extract is also good for carps.

2.8 Overall carp production

According to FAO (2012) Carp contributes 95 % of total fish production in Nepal. The overall carp production in Nepal is about 29,689 Metric Ton (FAO, 2012). The NFY of carp under control was found to be 4.36± 0.47 t/ha/yr (Jha, Rai, Shrestha, Daina, & Mandal, 2018).

3. MATERIALS AND METHODS

3.1 LEE site

The selected carp species were cultured in D-2 series earthen pond of Fisheries farm, Agriculture and Forestry University, Rampur, Chitwan. The area of pond is about 145 m[2] and the depth was 0.64 m. Similarly, culture period was of 90 days starting from 31st August to 28th November, 2022.

3.2 Pond preparation

Preparation of the pond was started on 18th August, 2022. The dyke of the pond was cleaned for easy administration of the work. Pond bleaching was done at the rate of 300 kg/ha to kill potentially harmful organisms in the soil and speed the breakdown of excessive organic matter using bleaching powder (CaOCl2). After 3 days of bleaching, organic fertilization with cow dung at the rate of 3000kg/ha (CFPCC,2021). And on the next day, inorganic fertilization with urea and DAP will be done at the rate of 4.7 g/m² and 3.5 g/m² respectively (Knud-Hansen, Batterson, & McNabb, 1993).

3.3 Procurement and Stocking of fingerlings

Fingerlings of carps were procured from Hira Matsya Farm, Tandi, Chitwan. Plastic bags containing fingerlings were floated on pond surface to acclimatize them for 15 minutes prior releasing to the pond. Fingerlings of carp were stocked in pond at the rate of 2 fish/m[2] on 31st August, 2022. About 10% of all carp fingerlings were weighed individually and mean weight was noted. Six species of carp were stocked in the following proportion given below:

Table 3. Stocking number of carps in the pond.

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3.4 Feeding

Dough was prepared from locally available ingredients i.e., rice bran (dhuto) and mustard oil cake (pina) in the ratio of 1:1 which contains about 20-25 % CP. Fishes were fed twice daily. Once in morning between 9-10 am and next in the evening between 3-4 pm with the aid of feeding tray. Feeding rate was 5 % of the body weight per day and this rate was adjusted based on monthly sampling of the fish. For grass carp, locally available chopped grasses were fed at the rate 50% of body weight twice daily just before dough feeding (8-9 am in the morning and 2-3 pm in the afternoon).

3.5 Water quality analysis

Water quality parameters, such measurement of water temperature, DO and pH were done twice daily, first at 6-7 am in the morning and next at 2-3 pm in the afternoon by using thermometer, DO meter and pH meter, respectively.

Table 4. Water quality parameters and method used during culture period

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3.6 Fish sampling

Fish Sampling was done monthly in order to address the growth of the fishes and to calculate the amount of the feed to be given the next month. Sampling was done using the dragnet, 10% of each species of fishes were sampled.

3.7 Fish harvesting

Harvesting of fish was done after 90 days of culture period on 28th Nov, 2022. For the final harvest, pond was drained using pump set and fish were handpicked. About 10 % of population of each species was weighed individually for assessing mean weight and rest were counted and weighed in batches for assessing survival, growth and yields.

3.8 Marketing

After harvesting, fish were sold to nearby canteens and hostels of Agriculture and Forestry University at the rate of NRs. 300 per kg.

3.9 Analytical methods

3.9.1 Fish growth parameter

To determine the growth and maintain feed ratio, sampling of fish was done fortnightly. Netting for a single time was done and fish caught was weighed and noted. Growth and production was calculated using the following formulae:

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3.10 Gross margin analysis

According to Shang (1980), the gross margin and rate of return was analyzed deducting total variable costs from total income from fish sale. The variable cost items included were the cost of fingerlings, feed, fertilizer, agricultural lime required for the production at local price. Gross margin and rate of return was calculated based on the product sold at the farm get price.

Gross Margin analysis can be done by using a simple formula:

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3.11 Statistical analysis

All data collected during LEE work such as fish growth data, water quality data and pond inputs data were entered in the MS-Excel sheet. Data were analyzed by calculating mean and standard deviation. Suitable tables, graphs and diagrams were used to present the collected data by using MS-Excel Version 2021.

4. RESULTS

4.1 Water quality

Environmental parameters play imperative role on the production of fish. Suitable water quality parameters are pre-requisite for a healthy aquatic environment and for the production of sufficient fish and fish food.

Water depth was on average 0.54 cm throughout the culture period. Temperature of water ranged between 20.2 oC and 35.3 oC during culture period. Average water temperature at morning (6 -7 am) was 26.6±2.66 oC and 30.5±2.33 oC in the afternoon (2-3 pm). The average DO at morning and evening was 2.1±0.54 mg/L and 5±1.24 mg/L respectively. Similarly, the average pH at morning and evening was 8.01 and 9.21 respectively.

Table 5. Daily water quality parameters recorded at morning and afternoon

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Figure 1. Daily recorded water temperature of pond during culture period

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Figure 2. Daily recorded dissolved oxygen of pond during culture period

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Figure 3: Daily recorded pH of pond during culture period

4.2 Growth and yield of carps

The growth and yield of carp species during culture duration of three months is well summarized in table no. 6.

Table 6. Growth and yields of fishes during culture period

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4.2.1 Silver carp (Hypophthalmichthys molitrix)

The average weight of Silver carp during sampling period is shown in figure 4, it shows normal trend from average stocking weight of 12.64±2.77 g/fish to average harvesting weight of 41.89±5.88 g/fish.

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Figure 4. Average weight (g/fish) of Silver carp during culture period

From table 6, it shows that the daily weight gain is 0.325 g/fish/day and total weight gain is 0.67 kg/pond. The survival rate for Silver carp is 61.66%, extrapolated GFY is 0.312 t/ha/yr and extrapolated NFY is 0.148 t/ha/yr.

4.2.2 Bighead carp (Hypophthalmichthys nobilis)

The average weight of Bighead carp during sampling period is shown in Figure 5, it shows normal trend from average stocking weight of 11.53±2.43 g/fish to average harvesting weight of 36.37±6.55 g/fish

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Figure 5. Average weight (g/fish) of Bighead carp during culture period

From Table 6, it shows that the daily weight gain is 0.276 g/fish/day and total weight gain is 0.15 kg/pond. The survival rate for Bighead carp is 43.3%, extrapolated GFY is 0.103 t/ha/yr and extrapolated NFY is 0.36 t/ha/yr.

4.2.3 Grass carp (Ctenopharyngodon idella)

The average weight of Grass carp during sampling period is shown in Figure 6, it shows normal trend from average stocking weight of 34.87±9.38 g/fish to average harvesting weight of 112.54±21.23 g/fish.

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Figure 6. Average weight (g/fish) of Grass carp during culture period

From Table 6, it shows that the daily weight gain is 0.863 g/fish/day and total weight gain is 2.10 kg/pond. The survival rate for Grass carp is 71.11%, extrapolated GFY is 0.758 t/ha/yr and extrapolated NFY is 0.487 t/ha/yr.

4.2.4 Rohu (Labeo rohita)

The average weight of Rohu during sampling period is shown in Figure 7, it shows normal trend from average stocking weight of 6.38±1.67 g/fish to average harvesting weight of 33.55±5.08 g/fish.

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Figure 7. Average weight (g/fish) of Rohu during culture period

From Table 6, it shows that the daily weight gain is 0.295 g/fish/day and total weight gain is 1.01 kg/pond. The survival rate for Rohu is 57.33 %, extrapolated GFY is 0.332 t/ha/yr and extrapolated NFY is 0.228 t/ha/yr.

4.2.5 Common carp (Cyprinus carpio)

The average weight of Common carp during sampling period is shown in Figure 8, it shows normal trend from average stocking weight of 10.36±3.01 g/fish to average harvesting weight of 80.42±6.22 g/fish.

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Figure 8. Average weight (g/fish) of Common carp during culture period

From Table 6, it shows that the daily weight gain is 0.745 g/fish/day and total weight gain is 1.52 kg/pond. The survival rate for Common carp is 34.66%, extrapolated GFY is 0.483 t/ha/yr and extrapolated NFY is 0.344 t/ha/yr.

4.2.6 Naini (Cirrhinus mrigala mrigala)

The average weight of Naini during sampling period is shown in Figure 9, it shows normal trend from average stocking weight of 7.16±2.02 g/fish to average harvesting weight of 36.26±7.26 g/fish.

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Figure 9. Average weight (g/fish) of Naini during culture period

From Table 6, it shows that the daily weight gain is 0.314 g/fish/day and total weight gain is 0.06kg/pond. The survival rate for Common carp is 20 %, extrapolated GFY is 0.043 t/ha/yr and extrapolated NFY is 0.015 t/ha/yr.

4.3 Combined yield of carps

Overall yield of carp in the pond of 145 m[2] is illustrated in Table 7. The extrapolated GFY and NFY were 2.031 t/ha/yr and 1.258 t/ha/yr respectively. The overall survival rate and AFCR was 51.33 % and 1.97 respectively during present work.

Table 7. Combined yield of carps

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Figure 10. Growth trend of all carps during culture period

4.4 Marketing

Due to shorter culture period i.e. three months, fish could not reached to suitable marketable size. However, all the species of fish were sold at the rate of NRs. 300/kg and all extra biomass (weed fishes and shellfish) harvested from pond were sold at NRs. 500.

4.5 Gross margin

The total variable cost was NRs. 3019 and gross return was NRs. 3545. The net profit was NRs. 526. The benefit cost ratio (B/C) was 1.17. Details of variables cost and return is given in Table 8.

Table 8. Details of variables cost and return

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5. DISCUSSION

5.1 Growth and production

5.1.1 Growth, survival and production of Silver carp

Present result showed that the daily weight gain of Silver carp was 0.32 g/fish/day which is too lower than result mentioned by Jhingran & Pullin (1985) and by Mandal et al. (2018). The reason for the low growth rate of Silver carp may be due to lower production of phytoplankton. High transparency in the pond indicates that there was lower amount of phytoplankton which affected the growth of Silver carp. Survival rate of Silver carp during present study was 61.6% which was too low as stated by Jui et al. (2018) where survival was 70.7 %. Lower survival may be due to escape of fish from dyke`s hole and also loss inside bottom mud while harvesting. The extrapolated gross fish yield 0.31 t/ha/yr which is lower than other studies. Net fish yield was 0.14 t/ha/yr which is comparatively lower than as mentioned by Mandal et al. (2018).

5.1.2 Growth, survival and production of Bighead carp

In a present study, the daily weight gain of Bighead carp was 0.27 g/fish/day which is lower than the report studied by Afzal, et al. (2008). The reason might be due to lower zooplankton density in the pond since the pond bottom harbours large number of shellfishes. During the present study the survival rate of Bighead carp was 43.33% which is comparatively lower in accordance to reported by Sun et al. (2012). This may be due to loss of fish from dyke`s failure and bottom mud. The extrapolated gross fish yield and net fish yield was 0.1 and 0.03 t/ha/yr respectively in the present study which was comparatively lower as reported by Jha et al. (2018). This may be due to lower survival and growth rate in present study than their study.

5.1.3 Growth, survival and production of Grass carp

Result of present study showed that the daily weight gain of grass carp was highest among other fish species which was 0.86 g/fish/ day which is comparatively similar as reported by (Jha et al., 2018). The reason might be due to higher average stocking weight and also bloom of nymphoides in the pond basin for grass carp. During the present study the survival rate of grass carp was 71.1% which is very high as reported by Roy et al. (1996). This may be due better environmental conditions, hardy nature and adaptability. The extrapolated GFY and NFY were 0.75 and 0.48 t/ha/yr respectively in the present study.

5.1.4 Growth, survival and production of Rohu

Daily weight gain of Rohu was 0.22 g/fish/day which was lower than reported by Jha et al. (2018), Jena et al., (2002 a; 2002 b). The reasons for the low growth rate of rohu in comparison to bighead carp and common carp may be due to low availability of periphyton in the pond because it has been known that rohu preferably feeds on periphyton resulted high growth rate (Rai & Yi, 2012). On the other hand, rohu prefered plankton over artificial feed Rayman et al. (2008). During present study low available of phytoplankton might have resulted lower daily weight gain of rohu. Survival rate of rohu during the present study was 57.3% which is lower than the studies of Jena et al. (2002 a; 2002 b). The Extrapolated gross fish yield was 0.33 t/ha/yr which was lower in comparison to study done by Jha et al. (2018) and net fish yield was 0.22 t/ha yr which was lower in accordance with result of Mandal et al. (2018). Lower extrapolated GFY and NFY in present study may be due to lower survival.

5.1.5 Growth, survival and production of Common carp

Daily weight gain of common carp was 0.74 g/fish/day which is relatively similar as the study of Mandal et al. (2018). The reason for the good growth rate of Common carp may be due to higher average stocking size, its feeding behaviour as omnivorous and readily acceptance of formulated pellet feed. Survival rate of Common carp in the present study was 34.6% which is very lower to the studies of Mandal et al. (2018). Lower survival in Common carp may be due to higher mud sediment and dyke`s hole that results loss of fish. The extrapolated gross fish yield and net fish yield were 0.48 and 0.34 t/ha/yr respectively, which is comparatively lower than reported by Jha et al. (2018) which is probably because lower survival and harvest.

5.1.6 Growth, survival and production of Naini

Daily weight gain of Naini was 0.31 g/fish/day which is comparatively as the study of Mandal et al. (2018). The reason for the poor growth rate of Naini may be due to higher mud sediment and lower pond depth (0.54 cm). Survival rate of Naini in the present study was 20% which is very lower to the studies of Mandal et al. (2018). Lower survival in Naini may be due to higher mud sediment at pond bottom and dyke`s hole that results loss of fish. The extrapolated gross fish yield and net fish yield were 0.04 and 0.01 t/ha/yr respectively, which is comparatively lower than reported by Jha et al. (2018) which is probably because of lower survival and harvest.

5.1.7 Combined yield of carps

Overall extrapolated GFY and NFY of carps were 2.03 t/ha/yr and 1.25 t/ha/yr respectively which is lower than reported by (CFPCC 2019/2020). Lower GFY and NFY is due to loss of fish due to poor pond condition. The overall survival rate was 51.33% and overall AFCR was 3.83.

5.2 Water quality

The water depth was 0.64 m throughout the culture period, is the main reason behind lower weight gain of carps. Pond bottom was clearly visible which may be due to lower plankton density in water. The presence of enormous number of bivalves (filter feeder) may be a reason behind lower plankton density and clearly visible pond bottom. The water temperature ranged from 20.2°C to 35.3°C and the average water temperature was within the desired level for fish culture.

The mean DO at morning and afternoon were 2.1 mg/L and 5.06 mg/L, which were within desired level during the culture period. The concentration of DO under this study fell to a critical level, sometimes in the morning. This may be due to higher amount of dead or decaying organic matter as well as nymphoides bloom.

The value of mean temperature, pH and DO was 27.7 °C, 7.63 and 4.82 mg/L which was within desirable level for fish growth.

6. CONCLUSIONS

Present study showed that the production of carp polyculture in an earthen pond is an easy, productive and profitable aquaculture system. Water quality was optimum and there was no such major problem in water quality management to affect fish growth. But pond bottom condition was troublesome in production and harvesting of fishes. The benefit cost ratio was not so satisfactory because most of the fishes were lost while harvesting primarily due to dyke hole and also bottom mud, but it was positive and the harvesting yield was promising which concludes that carp polyculture is most profitable and easily adopted by middle to small scale farmer with a limited resource. From LEE work, we can conclude that this is a great opportunity to learn, experience and enriched our knowledge by maximum exposure to field. We were able to learn the production of carp polyculture along with water monitoring ability was built. Also we learn marketing and selling of undersized produced fish.

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APPENDICES

Appendix 1. Stocking data sheet

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Appendix 2. First monthly Sampling data sheet

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Appendix 3. Second monthly sampling data sheet

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Appendix 4. Harvesting data sheet

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Appendix 5. Daily water quality parameters during culture period

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Appendix 6. Feeding data sheet

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Frequently asked questions

What is the purpose of this document?

This document serves as a language preview, encompassing various aspects of a study related to carp polyculture. It includes the table of contents, objectives, key themes, chapter summaries, and a glossary of key words.

What is Carp Polyculture?

Carp polyculture is a production system where two or more species of fish with different ecological habitat and food preferences are cultured together in such densities that there will be almost no competition for space and food.

What carp species are typically used in polyculture, according to this document?

The document discusses several carp species used in polyculture, including Rohu (Labeo rohita), Grass Carp (Ctenopharyngodon idella), Bighead Carp (Hypophthalmichthys nobilis), Silver Carp (Hypophthalmichthys molitrix), Common Carp (Cyprinus carpio), and Mrigal (Cirrhinus mrigala mrigala).

What are the objectives of the LEE (Learning for Entrepreneurial Experience) work described in this document?

The general objective is to learn the production of carps under a polyculture system in an earthen pond. Specific objectives include assessing growth and yields, calculating gross margin and B:C ratio, monitoring water quality, and learning about carp marketing.

What are the limitations of the study as outlined in the document?

The limitations include time and resource constraints, pond bottom and dyke conditions leading to fish loss, and instrumental faults affecting water quality recordings.

What water quality parameters are important for carp polyculture, according to this document?

Key water quality parameters include water temperature, dissolved oxygen (DO), pH, and water transparency.

What is the role of fertilization in carp polyculture, according to this document?

Fertilization, using both organic and inorganic fertilizers, enhances the production of autotrophic and heterotrophic organisms, promoting the biological productivity of the pond.

What kind of feed is provided to the carps?

Carps are fed with dough prepared from rice bran (dhuto) and mustard oil cake (pina) in the ratio of 1:1 which contains about 20-25 % CP. For grass carp, locally available chopped grasses were fed.

What were the growth and yield results of the study?

After 90 days, the overall extrapolated GFY (Gross Fish Yield) was 2.031 t/ha/yr, and the NFY (Net Fish Yield) was 1.258 t/ha/yr. The highest growth rate was observed in grass carp (0.863 g/fish/day).

What was the survival rate, AFCR, and profit reported in the study?

The overall survival rate was 51.33%, the Apparent Feed Conversion Ratio (AFCR) was 1.97, and the Benefit Cost (B:C) ratio was 1.17.

What were the marketing aspects discussed?

Harvested fish was sold at a rate of NRs. 300 per kg to nearby canteens and hostels. The total amount of profit was NRs. 526.

What are the conclusion derived from the LEE work?

The production of carp polyculture in an earthen pond is an easy, productive, and profitable aquaculture system, but pond condition and short culture period creates some challenges in production and harvesting of fish.