PRODUCTION OF PRAWN (Penaeus monodon Fabricius) Using the Modular Pond System

by

Pudjiatno
Dan B. Baliao

Network of Aquaculture Centres in Asia
Bangkok, Thailand
June 1987

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PRODUCTION OF PRAWN (Penaeus monodon Fabricius)
USING THE MODULAR POND SYSTEM

Pudjiatno¹
Dan D. Baliao²

ABSTRACT

This study was conducted to evaluate survival, growth, production, food conversion and economic feasibility in the monoculture of prawn (Penaeus monodon) at two stocking densities (15,000 juv/ha and 20,000 juv/ha) following modular pond system. Four sets of existing modular ponds at SEAFDEC, Leganes Research Station were used for this study. Each set forms a three-stage link-up. The area of each set is increasing progressively in a ratio of 1:2:4 proportion or a corresponding ratio of 550, 1100 and 2,200 m² respectively. Using this method, prawns were grown and were provided a better utilization of space and increased number of croppings (six crops a year) than previously realized in straight-run culture. On Treatment 1 and Treatment 2 growth, survival rate and final body weight of the prawn showed that there were no significant differences between the two treatments. Observed significant differences was on greater average production of the prawn achieved which was 533 kg/ha in Treatment 2 than 404 kg/ha production in Treatment 1. Economic analysis for Treatment 1 and Treatment 2 showed that returns on investment were 69.5 and 72.0%; the payback periods were 1.4 and 1.3 years, respectively.

¹ Brackishwater Aquaculture Development Centre, Jepara, Indonesia

² SEAFDEC researcher

INTRODUCTION

Brackishwater prawn (Penaeus monodon) culture has developed tremendously in the past few years due to a constant increase in prawn demand and limited supply in the world market. Aquaculturists have tried to increase the production of prawn. Improvements in pond design and layout for prawn culture, have gradually evolved. Thus, stocking density could be increased with the aid of aeration. Therefore, growth rates of the prawn could be increased and production can also be raised.

The modular system is an advanced method in prawn culture and it has potential in the development of prawn culture. Usually, the modular or progressive pond culture system has been identified only with milkfish (Chanos chanos), like culture of milkfish in Indonesia, Philippines and Taiwan (Lijauco et al, 1979).

Parker (1974) reported a production module designed to provide a maximum member of crops per season and more efficient utilization of space than previously realized in single pond units. Chamberlain (1981) found that comparison of survival, growth, production and value in the three-phase system (modular system) versus single-phase system (straightrun system) to be similar between systems. Baliao (1985) observed that by following the modular systems, prawn production would be increased by 6 crops a year. In the same process, there was accurate accounting of stock and computation of feeding rates. Also, limitation of unwanted species was facilitated.

This study was conducted to evaluate survival, growth, production. feed conversion and economic feasibility in the monoculture of prawn (P. monodon) at two stocking densities (15,000 juveniles/ha and 20,000 juveniles/ha) following the modular pond system.

MATERIALS AND METHODS

This study was conducted from July 20 to November 10, 1986 at Leganes Research Station, SEAFDEC Aquaculture Department, Iloilo, Philippines.

MODULAR DESIGH AND OPERATION

Four sets of existing modular ponds at SEAFDEC-LRS were used for this study. Each set forms a three-stage link-up. The area of each set is increasing progressively in a ratio of 1:2:4 proportion or a corresponding ratio of 550,1100 and 2200 m², respectively. A completely randomized design with 2 treatments and 2 replicates was followed (Table 1).

Table 1. Random selection of 2 treatments and 2 replicates on the modular experiment pond.

The modular experimental ponds were constructed with peripheral canals (150 cm wide and 20 cm deep) for refuge during warm water condition, transfer and harvesting of stock and ease in water management. Standpipe gates (16 cm diameter) and concrete slices were provided with fine mesh (1 mm) nylon and bamboo screens. Feeding trays (80 × 80 cm) made of nylon screen (1.5 mm mesh size) and frame with bamboo splits were provided. Also, wooden catwalks were installed at strategic corners or sides of the pond to facilitate feeding.

Prawns were grown and moved periodically from one module to the other, taking 4 to 6 weeks in each module until they reached marketable size within 12 to 18 weeks.

EXPERIMENTAL METHODS

All activities in the modular pond culture experiment are shown in Table 2.

Table 2. Description of activities on the modular culture experiment

1 Monitoring of water quality parameters (salinity, temperature, pH, dissolved oxygen and water depth) was done on Tuesday and Friday at 7:00–8:00 A.M.

Pond Preparation

Prior to stocking, renovation of peripheral canal in each module was made. The canal system facilitates harvest or transfer of stock and likewise renders ease in water management. All compartments were prepared following the “lab-lab” method of growing natural food in pond. Levelling, draining and drying the pond bottom to crackness was done in order to maximize production area and to release obnoxious gases, respectively. Application of a combination of lime (CaO) at 1000 kg/ha and ammonium sulfate (21-0-0) at 200 kg/ha was followed in order to get rid of unwanted species. Also, chicken manure as organic fertilizer was broadcasted on the pond bottom about 2000 kg/ha.

Artificial substrates (Aviscennia spp.) twigs were installed across the pond bottom to increase surface area for attachment of fry and natural food organisms. A week before stocking, the ponds were filled with seawater gradually to allow for growth of “lab-lab” as a natural food.

Stocking

Juveniles that had been cultured for 30 days in the adjacent nursery pond were used in this study. Before stocking, the juveniles were placed in plastic basins to facilitate counting or sorting out unwanted species. It was not necessary to acclimate that juveniles from nursery to modular pond because both water temperature and salinity were the same at 27°C and 200 ppt. The juveniles were stocked directly into the pond early in the morning of July 20, 1986. Ponds B and C were stocked with 5775 juveniles each, which was assigned with 15,000 juv/ha (Treatment 1). Ponds A and D were stocked with 7000 juveniles each which was assigned with 20,000 juv/ha (Treatment 2).

Water Management

After stocking, the primary concern was to keep the water condition favorable for both the fry and the natural food particularly in the first module. Dikes, gates and screens were regularly inspected to prevent excessive loss of water due to leaks and seepages. Whenever possible, water was renewed specially during long summer months to prevent salinity increase to unfavorable levels. Prawns are observed to grow faster in warm water between 26 to 30°C and water salinity of 6 to 33 ppt (Motoh, 1981).

Water renewal was performed by draining about one third during low tide and reflooding gradually during spring tide. It was done about 3 to 4 times every spring tide. Low saline water was drawn from the drain canal that was connected to the Jalaur River.

Feeding

Prawns were fed with frozen trash fish (wet weight) twice a day. It was chopped and given by tray and broadcast methods. Feed amounts for each module at 30, 24 and 18% of total body weight were adjusted after each sampling period based on new survival and growth of the prawn. One half of the feeding requirement was given early in the morning (7:00 to 8:00 AM) and the other half in the evening (5:00 to 6:00 PM).

Sampling, Transfer and Harvest

Salinity, temperature, pH, dissolved oxygen (DO) and water depth were recorded twice a week between 7:00 and 8:00 AM.

Survival was determined by collecting and counting all prawn individually harvested from 1st, 2nd and 3rd modules. The growth of the prawn was determined as described for the straight-run culture. Thirty prawns were taken from each pond and total length and weight measured. On the other hand, average weight was taken and multiplied by the number of prawns stocked in the pond in order to get total biomass for estimating daily feed allowance.

For transfer, collecting the prawns was done late at night or early in the morning when the temperature was low. The prawns were led into the catching net (hapa) by draining or attracting them against the current. From there, they were held temporarily in a hapa net set inside the canal near the mouth of a gate. The prawns were scooped out, counted and transferred. After transfer, vacated compartments were readied or prepared for the incoming stock. After collecting in the hapa net, the prawns were scooped out, counted and put in the styrofoam boxes.

STATISTICAL ANALYSIS

Analysis of variance (ANOVA) was used to detect differences in production and value between treatments. For detecting differences on growth and survival, comparison of regression lines on analysis of covariance (Swedecor and Cochran, 1979) was used. Differences were considered significant at the 0.05 level.

RESULTS AND DISCUSSION

Water Quality Parameters

Water quality conditions were similar among ponds and between treatments (Table 3). Salinity ranged from 5.0 to 30.0 ppt and averages were 12.8, 23.6 and 22.5 ppt for the 1st, 2nd and 3rd modules, respectively. Low saline water was drawn from the drain canal into the 1st module compartments. Therefore average water salinity in the 1st module was 12.8 ppt with a minimum of 5.0 ppt.

Temperature ranged from 26.4 to 28.7 and averages were 27.5 27.8 and 28.0°C for the 1st, 2nd and 3rd modules, respectively. Water temperature increased rapidly in the morning (28.7°C), because the experiment ponds were shallow especially in the 1st module (average 41 cm water depth). When the air temperature drops (cloudy) water temperature also decreases rapidly.

pH ranged from 6.9 to 9.2 and averages were 8.3, 7.7 and 8.1 for 1st, 2nd and 3rd modules, respectively. DO ranged from 3.2 to 5.9 ppm and averages were 4.7, 3.8 and 4.1 ppm for the 1st, 2nd and 3rd modules, respectively. The maximum range of DO was only 5.9 ppm, because DO was measured in the morning. Water depth ranged from 30 to 70 cm and averages were 41, 51 and 63 cm for the 1st, 2nd and 3rd modules, respectively. Maximum capacity of the ponds to keep water were 50, 60 and 70 cm for this 1st, 2nd and 3rd modules, respectively.

Table 3. Modular averages and ranges of various water salinity, temperatures, pH DO and water depth of the experimental ponds.

Growth and Feed Conversion

After 38, 40 and 34 culture days in the 1st, 2nd and 3rd modules, the body weight of prawn in Treatment 1 were 3.6, 12.6 and 30.6 g, and in Treatment 2, 3.4, 15.1 and 29.4 g, respectively (Fig. 1). Final body weight of the prawn varied; for Treatment 1 30.6 g; and for Treatment 2, 29.4 g (Table 4). However, there is no significant difference between treatments (P < 0.05).

Growth of the prawn among the treatment mean ranged from 0.25 to 0.2 g/day giving an average growth rate of 0.27 g/day for Treatment 1 and 0.25 g/day for Treatment 2. Baliao (1985) reported that growth rate of prawn with stocking density of 5,000 and 10,000 juv/ha following modular system was 0.43 and 0.41 g/day, respectively. Average final body weight of the prawn in his report were 93.7 and 38.4 g. Liao (1977) reported that in a straight-run culture of grass prawn (P. monodon), 16,596 juv/ha would grow 28.3 to 32.5 g in 4 months. Delmendo and Rabanal observed that jumbo tiger prawn (P. monodon) growths were 14.5, 22.3 and 25.1 g on culture of 4, 6, and 7 months.

Feed conversion ratio (FCR) of prawn using fresh chopped trash fish (wet weight) varied from 3.2 to 5.0 to 5.0; averaging 4.0 in Treatment 1, and 4.6 in Treatment 2. It is apparent that FCR increased with increasing stocking density levels. A theoretical consideration would be that in the 1st module natural food (“lab-lab” or plankton) available may be used for the growth of juveniles as minimal feeding and increase supplementary feed at the later part of the culture period.

SURVIVAL

Average percentage survival rate of Treatment 1 was 95.93 and 88% for the 1st, 2nd and 4rd modules respectively, while those of Treatment 2 was 99, 97 and 91% for the 1st, 2nd and 3rd modules, respectively (Fig. 2). Survival rates at the end of culture between 2 treatments were not significantly different (p 0.05) from each other.

Parker (1974) observed that survival rate of P. monodon and P. stylirostris were 86 and 33% using the modular system. Chamberlin (1981) reported that survival rates of both P. vannamei and P. styliros- tris varied from 18 to 74% using three-phase system (modular system). Balio (1985) observed that survival rate of P. mondon were 96.5 and 90.6% using modular system.

Production

Average production of prawn of Treatment 1 was 404 kg/ha and that of Tratment 2, 533 kg/ha and highly significant (P 0.05). It was apparent that high stocking density, production of treatment 2 (20,000 Juv/ha) was 32% higher than treatment 1 (15,000 juv/ha).

Baliao (1985) reported similarly that production levels of prawn at stocking density of 5,000 juv/ha and 10,000 juv/ha were 193 and 348 kg/ha crop. With all the production functions not significantly different, it would be possible to further increasethe density higher than what this study had tried by simply following the modular system.

Economic Analysis

In Treatment 1 the major cost items were fry, trash fish and interest, accounting for about 27.6, 26.0 and 13.3% respectively of the total cost. In Treatment 2, the same cost items accounted for about 29.2, 31.4 and 11.2% respectively of the total cost (Table 5).

In Treatment 1, the average selling price was P101.05/kg and the production cost was P53.80/kg resulting to a net profit of P47.20/kg. In Treatment 2, the average selling price was P92.74/kg and the production cost was P51.31/kg resulting to a net profit of P41.43/kg. The higher net profit/kg in Treatment 1 was primarily due to the bigger sizes and better quality prawns produced. However, Treatment 2 had a higher return on investment of 72.0% and shorter payback period of 1.3 years compared to Treatment 2 with 69.5% and 1.4 years respectively. This was due to the fact that the difference in the investment requirement was about P18,000 whereas the resulting difference in net income for one year was about P17,100 in favor of Treatment 2.

In general, the use of the modular culture system for prawn production is economically viable, and profitable due to more croppings per year (6 croppings) compared to the three cropping for straight -run culture method. (Fig. 3).

ACKNOWLEDGEMENT

This study was partly funded by FAO-NACA under the Training Programme on Secondment of Junior Scientists to the Aquaculture Department of SEAFDEC. Thanks are due to Mr. Romulo Ticar, Nicolas Guanzon, Ulderico Derotas, Butch Juangga, record assistants and Jesus Amilan, technician, for their significant contributions to the conduct of these experiments. Thanks are also due Mr. Rene Agbayani for his assistance in the economic analysis.

The authors are also indebted to Dr. Felicitas Pascual for reading and editing the paper.

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Table 4. Summary of harvest and economic data for prawn.

¹ Treatment means with the same superscript are not significantly different (P<0.05).

Table 5. Cost and return of prawn culture at two stocking densities

Items		Treatment 1			Treatment 2
		Quantity	Total Value	%	Quantity	Total Value	%
A.	SALES	404 kg	40,825		533	49,431
B.	VARIABLE COST
	1. Fry	15,000 pcs	6,000	27.6	20,000 pcs	8,000	29.2
	2. Fertilizer and Feed
	- Lime	1,000 kg	520	2.4	1,000 kg	520	1.9
	- (20-0-0)	200 kg	890	4.0	200 kg	890	3.2
	- Chicken manure	2,000 kg	800	3.6	2,000 kg	800	2.9
	- Trash Fish	1,616 kg	5,656	26.0	2,452 kg	8,582	31.4
	3. Aviscennia spp twigs	500 pcs	700	3.2	500 pcs	700	2.6
	4. Ice	2 blcs	140	0.6	2 blcs	140	0.5
	5. Casual Labour	25 man-days	750	3.4	25 man-days	750	2.7
	6. Miscellaneous (10%)		1,545.6	7.1		2,038.2	7.4
		Total	17,001.6		Total	22,420.2
C.	FIXED COST
	1. Depreciation		666.7	3.0		666.7	2.4
	2. Interest		2,885.2	13.3		3,061.8	11.2
	3. Salaries		1,200	5.5		1,200	4.4
			4,751.9			4,928.5
	Total Cost		21,753.5			27,348.7
	Net Profit before Tax		19,071.5			22,082.3
	Income Tax (5%)		953.6			1,104.1
	Net Income after Tax/Corp		18,117.9			20,978.2
C.	NET INCOME AFTER TAX/YEAR		108,707.4			125,869.2

D. ECONOMIC PARAMETERS
1. Cost/kg	53.8		51.31
2. Net Profit/kg	47.2		41.43
3. Return on Investment	69.5 %		72.0 %
4. Pay Back Period	1.4 years		1.3 years
INVESTMENT REQUIREMENT
1. Pond Acquisition		100,000	100,000
2. Pond Development		20,000	20,000
3. Operating Capital (2 croppings)		36,403.2	54,697.4
		156,403.2	174,697.4
SOURCE OF FUNDS
1. Equity		78,201.6	87,348.7
2. Loan (20% interest/year)		78,201.6	87,348.7
3. Interest per year		15,640.3	17,469.7
4. Interest per crop		2,606.7	2,911.6

Figure 1. Mean weight of prawns at two stocking densities versus number of days from stocking until harvest.

Figure 2. Mean percentage survival rate of prawn at two stocking densities.

A1, B1 and C1: Pond Preparation of 1st, 2nd and 3rd modules
A2, B2 and B3: Culture of prawn in 1st, 2nd and 3rd modules

Fig. 3 Six crops culture of prawn a year following modular pond system.

1st M = 550 m²
2nd M = 1100 m²
3rd M = 2200 m²

Fig. 4 The modular pond system (Experimental) SEAFDEC AQD, Leganes Research Station