Aquacultural Engineering 41 (2009) 147–151

A mechanized harvest system for freshwater fishpond

K.K. Sharma *, Bikash Sarkar, S. Chand, S.K. Nayak

Central Institute of Freshwater Aquaculture, Indian Council of Agricultural Research, Kausalyaganga, Bhubaneswar 751002, Orissa, India

A R T I C L E I N F O

Article history:

Received 5 October 2008

Accepted 1 July 2009

Keywords:

Mechanized

Harvesting

Fish

Pond

Indian major carps

A B S T R A C T

Development of a prototype-mechanized fish harvesting system for carp from a rectangular shaped

fishpond is described in this paper. The system consists of motorized trolleys on the longer dykes of

fishpond, rail, boom pipe, netting arrangement and ON/OFF arrangements. The trolleys move on the rail

tracks with constant speed of 3 m/min and takes about 15 min to complete the harvesting operation. The

overall mean harvest efficiency of Indian major carps (IMC) with mechanized fish harvesting system has

been estimated to be around 80% per operation. The whole harvesting operation is done mechanically

except collection of harvested fishes at the end of operation, which presently requires two persons

getting into the pond and lifting out the fishes from the net.

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1. Introduction

Freshwater aquaculture production in India is dominated bycarp species viz., Labeo rohita, Catla catla and Cirrihinus mrigala,which contributes about 87% of the total freshwater production(ICLARM, 2001). These carps are widely cultured/reared through-out India owing to their high commercial value. The transforma-tion of small farm operation into aquaculture enterprises createdmany problems particularly in larger pond with bottom dwellingspecies. Most of these problems are related to the need for costreduction and improvement of production efficiency. Thus, newapproaches to the entire production process, with particularemphasis on mechanized systems, are required to make theindustry sustainable. Fish catching or harvesting is one of the mostcrucial factor determining the economic efficiency of commercialfish culture. A few authors reported on mechanized Seine harvestsystem or improved harvesting net for freshwater prawn but thereis no report on mechanized fish harvesting system for carps.

Gibson and Wang (1977) estimated that the traditional net-harvesting operation required 7.5 man-hour for 0.5 ha pond,accounting for approximately 9% of the total farm operating cost.While, the traditional net-harvesting operation is hard and tediouswork and also requires high labor involvement however it resultsin low capture efficiency. A mechanized Seine harvest system forfreshwater prawns reported by Losordo et al. (1986), in which, themean harvest efficiency of marketable prawns of the new systemin earthen production ponds was estimated to be 63.5%. Similarly,Williamson and Wang (1982) described an improved harvestingnet for freshwater prawns. They found that the harvest efficiencies

* Corresponding author.

E-mail address: kks8498@rediffmail.com (K.K. Sharma).

0144-8609/$ – see front matter � 2009 Elsevier B.V. All rights reserved.

doi:10.1016/j.aquaeng.2009.07.001

ranged between 56 and 60%. Peterson (1982) described twomethods of net-harvesting prawns from rectangular productionponds and harvest efficiencies ranged from 6 to 23% with an overallof 15%. In another study, Lam and Wang (1985) estimated harvestefficiencies from 2 to 46% with an average of 23%. Otherresearchers reported that the harvesting efficiency to be between50 and 75% (Gibson and Wang, 1977; Polovina and Brown, 1978;Williamson and Wang, 1982).

Williamson and Wang (1982) designed, fabricated and field-tested a first generation mechanized Seine harvest net system for theHawaiian Prawn Industry. The net system consisted of monofila-ment nylon Seine-net and a rigid PVC harvest grader box. The netsystem was pulled through the pond by prime movers. A secondgeneration mechanized net system was developed by AmfacAquatech-Hawaii. The system consisted of 18 twines multifilamentnylon Seine-net with a centre-mounted net-harvesting bag. Whilethe net achieved harvest efficiencies from 66 to 77%, it did not workwell in heavily silted ponds with eroded banks.

Keeping in view, the importance of the fish harvestingoperation, manpower requirements and lack of suitable mechan-ical methods tried or developed for harvesting of Indian majorcarps (IMC), and also considering the fact that aquaculture hascome to the stage of a industry and many entrepreneurs are takingup this activity to increase the production, the objective of thisstudy was to develop a prototype-mechanized fish harvestingsystem for freshwater pond and test its harvesting efficiency forIMC in a rectangular shaped fishpond.

2. Design criterion/requirements

For developing any system, the design of different parts ormechanism of the system is a pre-requisite. The designs are madeon the basis of standard engineering principles and requirements

K.K. Sharma et al. / Aquacultural Engineering 41 (2009) 147–151148

of jobs to be performed by the system. The selection of suitablematerials and its locally availability is also an important factor tobe considered while designing. The environment in which thesystem will work and kind of operation performs would determinethe material to be used for product development.

2.1. Electric motor

Induction type 2 h.p. motor was selected for each trolley. Thepower of the motor was decided based on manual force requiredfor pulling the net in similar size pond. For manually pulling the netof similar size of pond the total number of manpower requirementis 8 persons based on practical experiences. The standard power ofa person on an average is 0.1 h.p. for all practical purposes. Hencetotal requirement of power is 0.8 h.p. The efficiency of the motorwas taken 60%. After considering all the losses through transmis-sion, the net power available in each trolley is about 1.2 h.p. Thedesign load was taken higher than the actual load to avoid failure ofthe motor.

2.2. Gearbox

A basic requirement of mechanically operated harvestingequipment is its ability to transmit or receive motion from onepart to another to overcome friction. Gear reduction in the contextrefers to speed reduction in general whether it is traditional gear orchain. The advantage of using gear reduction is to reduce the speedup to desired one. The constant speed of 3 m/min was selectedbased on experiences of manual netting. Measurements takenduring harvesting operations indicated that even in moderatelysilted ponds, the ideal speed of pulling the net is around 3.0–3.5 m/min at which maximum catch efficiency is obtained. Accordinglythe standard gear ratio was selected, i.e. 50:1. The determination ofthe proper gears for a particular application is a complexphenomenon. In this case, spur gear was selected, as the pinionspeed is less than 3600 rpm. The gears are made of plain carbonsteel with the degree of accuracy (6–9).

The design speed of trolley is calculated as follows:

Motor speed—1440 rpmGear ratio—50:1Calculated pinion speed—28.8 rpmAssume power transmission losses 30% hence,Actual pinion speed—20.16 rpm

The velocity of the chain sprocket was calculated using thefollowing equation:

V ¼ Pzn

1000m=min (i)

where P is the pitch of chain, mm; z is the number of teeth on thesprocket, n is the speed of the pinion/sprocket.

The values of P, z and n for developed system are 15 mm, 17 and20.16 rpm, respectively.

Hence, the calculated velocity of chain is 5.14 m/min.Assuming that the efficiency of the chain sprocket mechanism

is 70%, the velocity of the mechanized trolley is approximately3.6 m/min.

As the speed of the system is low, the transmission steel rollerchain (single) conforming to IS: 2403-1975 was used, which is alsocomparatively cheaper.

The measured velocity of trolley during operation was 3 m/min,which is lower than the calculated velocity (3.6 m/min). This maybe because of variable load applied on it caused by uneven bottomsurface and non-uniform silt at the bottom.

2.3. Net

The sizes of mesh are used according to the type of fishing andspecies to be harvested. Several types of twine are available and thechoice is a compromise between stiffness for ease of handling andsoftness for catching efficiency. Among them, Nylon twine oftencolored white is the popular material for fish net, which ispractically invisible under water under most condition. Othermaterials like high-density polyethylene and polypropylene arenot suitable because they have tendency to float on water due to itslower density (<1). Whereas incase of Nylon twine the density is>1 so that it can maintain a good seal between bottom net line andpond bottom. The less number of lead weight or sinkers are alsorequired in case of Nylon twine. However the cost of Nylon isslightly higher.

2.4. Material for manufacturing

There are many factors involved while selecting the material formanufacturing a particular product. During conceptual designstage due considerations are given particularly for properties of thematerial, local availability and their cost. The cost of the material inmachine component consists of the initial cost, processing cost andmaintenance cost. The developed mechanized fish harvestingsystem was obtained by a combination of various machinecomponents right from nut and bolts to motor, gear, chain andsprocket mechanism, etc. For manufacture of mechanized fishharvesting system, most of the standard components (motors,gear, chain sprocket mechanism, rails, etc.) were purchased fromlocal market and some of parts (boom mechanism, housing box,electrical fittings, nets, etc.) were fabricated in the workshop.Therefore during designing and manufacturing due considerationswere given to the assembly aspect of the design. While systemmanufacturing, proper care must be given to the performancerequirements, appropriate material, etc. Since this device isexposed to the outdoor environment, due care was takenparticularly in dimensional stability and environmental resistance.The most important aspect of this system is fabricability ofdifferent materials. The product is a job type work and 90% of workwas either fabricated or assembled. Therefore during fabricationimportant criteria for system manufacturing like weldability,machinability, ease of joining and response to heat treatment wastaken into consideration.

3. Manufacturing and operational details of the system

A prototype-mechanized fish harvesting system has beensuitably designed, fabricated and installed in rectangular fishpondsat farm complex of Central Institute of Freshwater Aquaculture(ICAR). The system replaced the existing manual netting in thepond in order to increase the harvest efficiency and minimize themanpower requirement. The newly developed system consists of anetting arrangement, boom rods, motorized trolleys and railtracks. Motorized trolleys consist of an induction type electricmotor (1440 rpm 3 phase; 2 hp), gearbox (fixed type 50:1) andchain sprocket mechanism to provide four-wheel drive, which areplaced inside the housing box made of mild steel. Each trolley hasfour wheels of 90 mm diameter. The wheels are placed at a spacingof 940 mm and the distance between the rear and the front wheel isabout 1170 mm (Fig. 1). A starter (reverse and forward) was fittedwith a vertical mild steel pipe of 40 mm diameter and 0.4 m lengthat the end of housing box, which regulates/control the ON/OFF ofthe system.

The boom pipe was constructed of heavy gauge harden steel of42 mm diameter. The pipe has a total length of 3.65 m and extendsapproximately 0.2 m to the side of the housing box, which

Fig. 1. Front operational view of the mechanized harvesting system.

Fig. 3. Side operational view of the mechanized harvesting system.

K.K. Sharma et al. / Aquacultural Engineering 41 (2009) 147–151 149

facilitates upward or downward movements of the bottom dragnet, depending on the water depth. At the bottom of the boom pipe,a hollow mild steel (medium grade) bend pipe of 32 mm diameterwas welded to tie-up bottom drag net for free movements alongwith pond dyke. The boom pipe is coupled with universal joint, atthe base of the housing box. It can rotate/move in both directionseither horizontally or vertically depending upon the operationalrequirement (Fig. 2). Both the trolleys are placed/put on the railtrack; the rail tracks (32 LB rail of 200 m length and @ 20 kg/m)were laid at a spacing of 0.9 m on the pond embankment and fixedwith concrete grouting. A monofilament net of 20 mm mess sizeand length 20.5 m, width 8.0 m was used for effective catching offish (Fig. 3). Before fixing the net, multifilament polypropylenerope of 15 mm diameter and length of 25.5 m were twisted andstitched on both sides, i.e. bottom and upper side of the net. Thelength of the rope was allowed slightly larger than the actuallength of net for proper tension and tie-up of the net assembly withthe boom and trolleys, respectively. The bottom drag net wasattached by tubular cast iron sinkers (40 mm diameter � 100 mmlength) of weight of 500 g each. The sinkers were placed at thebottom drag side at 3 m intervals for maintaining good seal of thenet at the pond bottom. To hang the upper net, a steel wire rope of6.0 mm diameter, length 25 m was tied between the vertical stand/arms of the trolleys. A vertical clearance of about 1 m wasmaintained between the upper net rope and the water surface toprevent escape of fish through jumping. To hang the net in thepond the bottom of drag net was tied at the end of bend weldedwith boom pipe and the upper net with vertical arm (32 mmdiameter � 1000 mm) provided at the backside of the trolley. Adiagonal distance of 5.5 m was provided between bottom of boom

Fig. 2. Trolley showing different components of the system.

rod and top of vertical arm to create the pocket of net for effectivefish haul. For successful operation of the system, power supply wasprovided from electric pole to the trolley through a flexible cable(2.5 mm diameter 3 core water proof electrical cable). The powersupply of the second trolley was provided from first trolley. Thecable attached with a steel wire connected both the motors.

Before carrying out the operation, it should be ensured that thetrolleys are in the same position and direction. Once the system isready, the ON/OFF starter switch is pressed. The trolley moves/travels with a constant speed of 3 m/min. It takes about 15 mintravel time to complete the harvesting operation of a rectangularpond of size 40 m � 20 m.

Just before trolley touches the end of pond, the dowel pins ofboom to the universal joints are taken out to facilitate the freemovement of the boom rods in such a way that when the trolleysreach the end of the track, i.e. they are 2.5 m away from the end ofthe pond, the bottom rope of the net should come to above thewater surface. When the system reaches the end, the boom pipe isdetached from the universal joint and pulled towards theembankment side for closing of the net. The bottom net isdetached from the boom rods whereas the upper net remains fixedat the particular point. Two fishermen are required at both the endsto pull the bottom drag net for a pond of this size. When the net endis brought to the desired point, the fish may be collected manuallyor by hand net (Fig. 4). The entire operation usually requires 25–30 min (15 min for netting).

Fig. 4. View of the lifting of fish at the end of harvesting.

Table 1Comparison of harvest yield and catching efficiency.

Carps species Manual netting Mechanized netting

Harvest yield (kg) Harvest efficiency (%) Harvest yield (kg) Harvest efficiency (%)

Rohu (Labeo rohita) 65.25� 0.77 56.25� 0.76 112.64� 0.39 80�0.78

Catla (Catla catla) 114.55� 0.95 65.83� 0.91 183.04� 0.92 99.05�0.38

Mrigala (Cirrihinus mrigala) 53.65� 0.77 37.00� 0.88 88.00� 0.55 70.42�0.80

Table 2Techno-economic analyses of mechanized fish harvesting system.

Sl. no. Items Annual expenditure

(Rs.)

1 Initial investment (Rs. 2,10,000) –

2 Operation and maintenance cost (O&M)

Fish nets 2,000.00

Manpower (2 man-hour) 13,200.00

Repair 1,000.00

Electricity 301.00

3 Interest at 5% per annum 10,500.00

4 Salvage value 31,500.00

5 Depreciation 11,900.00

K.K. Sharma et al. / Aquacultural Engineering 41 (2009) 147–151150

4. Results and discussions

4.1. Experimental trials

Several trial runs in a 0.08 ha (40 m � 20 m) pond wereperformed with the developed prototype-mechanized system.The system was compared using harvest yield and the estimatedharvest efficiency of the mechanical system versus manual nettingoperation. The capture efficiency or the number of fish caught on asingle operation, was expressed as a percentage of the totalnumber of fish in the pond prior to the run, and was in the range of70–99%. Prior to the operational trial, the pond was stocked withIndian major carps viz., Labeo rohita, Catla catla and Cirrhinus

mrigala with predetermined quantity. The depth of water in thepond was maintained about at 1.5 m. The results of the harvestyield and harvest efficiency estimations are presented in Table 1.The overall harvest efficiency was 53.03 � 0.72 and 85.15 � 0.59%in manual and mechanized netting operation respectively. In all theoperations, the results of harvest yield and efficiency indicate that thismethod is more efficient in capturing the fish than the traditionalnetting. However, Cirrihinus mrigala showed a lower harvest yield andharvesting efficiency in all the operations, as this species is bottomdweller in nature. The highest harvest yield and harvest efficiency(99%) were obtained in case of Catla catla followed by Labeo rohita andCirrhinus mrigala in all the operations due to the fact that theirhabitation follows that order from the top. Only few authors reportedabout the harvesting using mechanized seine and boat from marinesources. There is no report on mechanized harvesting system forfreshwater aquaculture. Therefore, the data generated in the presentexperiment could not be compared with due to lack of similar studies.

The mechanized netting was also compared with manualnetting in respect of man-hour requirement in each operation. Theresults revealed that the manual netting required around 8.33man-hour to complete the harvesting operation of 0.08 ha pondwhereas mechanized system took around 1.33 man-hour. Theman-hour requirement for manual netting is comparatively moreas reported by Gibson and Wang (1977). The mechanized nettingoperation produced encouraging result and saves about 84% man-hour compared to the manual operation.

4.2. Techno-economic analysis

Techno-economic analysis of a newly developed mechanizedsystem is the area, wherein technical feasibility and economicalviability of the system is assessed based on engineering judgmentand experience. As mechanized fish harvesting technology ismeant for aquaculture enterprise, it is necessary for any newtechnology to be technical feasible and economically viable so that,it can penetrate to the users for its adoption. For any technology tobecome popular and attractive among the farmers and users, itshould be economical, user friendly and easy to maintain. Theusers should be convinced then only they can utilize in a bestpossible manner to get maximum return. The mechanized harvesttechnology is capital-intensive in term of initial investment but itsoperational cost is quite low as it is run by electricity. The totalbudgets includes capital investment, operation and maintenance

costs (O&M), salvage values, depreciation cost, etc. The item wisecost analysis is given in Table 2.

The economic model is based on 15 years lifetime with average10 operations in a month. Initial investment, i.e. system manu-facturing cost, which includes both trolleys, motors, gears, chaindrive, boom assembly, starters, cables and rail tracks: Rs. 2,10,000;fish harvesting net (generally, the life of nylon net is 3 years): the costof single piece net is approximately Rs. 6000. Hence, it is assumedthat Rs. 2000 is required annually for replacement of net;manpower: 2 man-hour is required in each operation and hencetotal man-hour cost involves in one year is Rs. 13,200 (labors cost at55 per hour); repairs and related day-to-day expenses are estimatedat Rs. 1000 annually; electrical costs: Rs. 301/annum. The simpleinterest was calculated based on prevailing agriculture interest rate5%, which is a subsidized rate using standard formula. It is assumedthat after 15 years of service life, the salvage value is approximately15% of the initial cost, i.e. Rs. 31,500. Every product eithermechanical or electrical is having depreciation value except glass.It comes for this system Rs. 11,900/annum.

Benefit–cost analysis. Benefit–cost ratio (B/C ratio) is a tool toselect the right technology based on advantage versus disadvan-tage analysis. A technology is considered to be attractive when thebenefits derived from its execution exceed its associated costs. It isestimated that for manual netting of similar pond size approxi-mately 8.33 man-hour is required in single operation and alsoassuming 10 operations may be required in a month, total benefitsmay be derived in 10 years is Rs. 4,99,800. The benefit–cost ratio(B/C) was calculated to be 1.14.

Payout time. The pay back period, which is a powerfull tool forsuccess of any project or technology. It is the number of yearsnecessary to exactly recover the initial investment, which iscomputed by summing the annual cash flow values and estimatingthrough the relation. Based on estimated initial investment costs,operation and maintenance costs and prevailing 2008 market price,it is calculated that initial investment will be recovered in 5.4 year.

4.3. Problems encountered during the operation

� It has been observed that due to improper alignment of track, thetrolley’s forward movement is not smooth and need frequentadjustment of trolley on the track. Sometimes due to presence of

K.K. Sharma et al. / Aquacultural Engineering 41 (2009) 147–151 151

huge mud in the pond bottom, the trolleys get slipped because ofexcess load of mud with fishes on net. Hence care should be takenfor making proper alignment of tracks and also design of powerof the prime mover.� The developed system has been designed for fixed speed, i.e. 3 m/

min, which was made possible by having fixed gear ratio, i.e. 50:1.It creates problems during partial harvesting operation, whenhigher speed is required. Hence, the incorporation of variablespeeds is recommended in the system for further development.� Another major constraints for the developed system becoming

popular and economical is that for using this system, thefishponds need rail track on both the dykes of the pond, whichreduces scope for its wider application. Alternate design in whichrail track requirement can be eliminated would be very goodimprovement to make this system more adoptable, popular andeconomical.� At the end of harvesting operation fishes are lifted manually for

which two person need to go inside the pond and collect thefishes. The collection and lifting of harvested fishes remains aproblem. A suitable lifting system required be designed andincorporated, which would make the process of lifting theharvested fishes much easier/efficient.

5. Conclusion and recommendations

A prototype-mechanized harvesting system was designed,developed and installed for use in rectangular fishpond. Thesystem has indicated promising results in silted laterite stonelining pond for harvesting of IMC. The newly developed mechan-ized fish harvesting system, with suitable modifications, could behighly useful in commercial fish farming activity with maximumefficiency (>80%) of fish harvest per operation. The systemsignificantly reduces required time for harvest; minimize nettingstress to the fishes and fishermen fatigue.

For further development, the following recommendations aremade from the present study:

(i) The pond dyke may be designed to suit the mechanizedharvesting.

(ii) Preferably the ponds should be similar in shape and size witheither square or rectangular geometry.

(iii) Incorporation of fish lifting device at the end of harvestoperation may reduce both time and effort required by thetraditional harvesting method currently practiced by thefishermen.

Acknowledgements

The authors are grateful to Dr. Mangala Rai, DG (ICAR) andSecretary (DARE), Govt. of India, Dr. S. Ayyappan, DDG (FY), ICARand Director, CIFA Bhubaneswar for their kind encouragement,support and guidance to undertake the work.

References

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Lam, C.Y., Wang, J.K., 1985. Estimating harvest efficiency of freshwater prawns.Presented at the Summer Meeting of the American Society of AgriculturalEngineers, East Lansing, Michigan, 23–26 June, 1985.

Losordo, T.M., Wang, J.K., Brooks, M.J., Lang, C.Y., 1986. A mechanized seine harvestsystem for freshwater prawns. Aquacult. Eng. 5, 1–15.

Peterson, J.J., 1982. Freshwater prawn harvesting a comparison of three methods.Proc. World Mariculture Soc. 13, 104–119.

Polovina, J., Brown, H., 1978. Population dynamics and production economics. Proc.World Mariculture Soc. 9, 393–404.

Williamson, M.R., Wang, J.K., 1982. An improved harvesting net for freshwaterprawns. Aquacult. Eng. 1 (2), 81–91.