The effect of integrating rice field fish culture with rodent pest management was examined. The use of rodent pest management was effective for controlling rodent pests as well as containing fish within the rice field while potentially providing a free source of dietary protein (captured rats) to feed fish. The growth of fed (captured rats or dried fish) walking catfish hybrids (Clarias batrachus x Clarias macrocephalus) in the rice field over 3 months was significantly higher (51.5g, 7.8cm) than a treatment of unfed walking catfish hybrids (26.4g, 4.5cm) in the same rice fields. Fish culture was shown to contribute to a farmer's income (68,800 Riel) and provided a source of protein for the family's consumption. Both the fed and unfed products were found to be palatable and accepted by a test group with 24% of the test group selecting fed fish and 21% selecting unfed fish as their first choice from 5 fish products. This pilot study and a preliminary survey in Kampong Cham province indicate that this technology will be useful for farmers to improve rodent management practices while supplementing income through fish sale and providing a high protein diet for their families

Leung, L.

Phaloeun, C.

Smith, E. G.

Sopheap, U.

University of Queensland eSpace

Cambodian Journal of Agriculture: Volume 6, 2002 Edition 
 9
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RICE FIELD FISH FARMING INTEGRATED WITH RODENT PEST  
MANAGEMENT IN CAMBODIA 
 
E.G. Smith1,3, L. Leung2, C. Phaloeun3, U. Sopheap3 
 
                                                           
1Cambodia-IRRI-Australia Project (CIAP), Phnom Penh, Cambodia.  
2University of Queensland (UQ), Australia. 
3Cambodian Agricultural Research and Development Institute (CARDI), Phnom Penh, Cambodia. 
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BaküKnwøH ³  Clarias batrachus, Clarias macrocephalus, 
karRKb;RKgstVkekr/ dMNaMRsUvcMruH    
 
ABSTRACT 
The effect of integrating rice field fish culture with 
rodent pest management was examined. The use of 
rodent pest management was effective for controlling 
rodent pests as well as containing fish within the rice 
field while potentially providing a free source of 
dietary protein (captured rats) to feed fish. The 
growth of fed (captured rats or dried fish) walking 
catfish hybrids (Clarias batrachus ♀ x Clarias 
macrocephalus ♂) in the rice field over 3 months was 
significantly higher (51.5g, 7.8cm) than a treatment 
of unfed walking catfish hybrids (26.4g, 4.5cm) in 
the same rice fields. Fish culture was shown to 
contribute to a farmer's income (68,800 Riel) and 
provided a source of protein for the family's 
consumption. Both the fed and unfed products were 
found to be palatable and accepted by a test group 
with 24% of the test group selecting fed fish and 21% 
selecting unfed fish as their first choice from 5 fish 
products. This pilot study and a preliminary survey in 
Kampong Cham province indicate that this 
technology will be useful for farmers to improve 
rodent management practices while supplementing 
income through fish sale and providing a high protein 
diet for their families. 
 
Keywords; Clarias batrachus, Clarias 
macrocephalus, rodent management, integrated rice 
field fish culture, carnivorous, hybrid 
 
Cambodian Journal of Agriculture: Volume 6, 2002 Edition 
 10
INTRODUCTION 
Wild fisheries provide the farm household in 
Cambodia with a free source of dietary protein, 
equivalent to more than 35% of animal protein 
consumption (Subasinghe, et al., 1998), and are a 
simple alternative to culturing fish. However in some 
areas the supply of wild rice field fishes has been 
degraded to the extent that fish culture is the only 
alternative for a sustainable fish supply (Bunra and 
Gregory, 1995). The demise of this natural resource 
has come about largely because of the intensification 
of agriculture, population growth, over-harvesting 
and the use of destructive fishing gear. These 
problems are likely to worsen with rapidly increasing 
population (Sihapitakgial, 2000) and increased fish 
demand for local and export markets (Gregory, 
1997).  
Rice field fish culture is not a new concept 
and has been widely trialed and used throughout 
Cambodia. Not only does the fish harvest add to the 
rice farmer’s income, it provides a source of dietary 
protein. Dual cropping, rice and fish, helps manage 
economic uncertainty better, fish are believed to 
manage insect pests and accelerate nutrient recycling 
and the simple fact that farmers frequent the rice field 
more often to manage fish results in improved rice 
husbandry (Gregory, 1997). Despite these benefits 
there are many problems that have and continue to 
inhibit the success of rice field fish culture. The most 
common problems reported are that natural flooding 
and drought can result in the loss of an entire fish 
crop and that fish predators such as carnivorous wild 
fish can significantly reduce the harvest (Gregory, 
1997).  
These problems are currently being 
addressed by CARDI through a novel approach to 
introduce rice field fish culture to rural Cambodia. 
This pilot project has been designed to value-add 
work on the ACIAR funded Farmer-based Adaptive 
Rodent Management, Extension and Research 
System (FARMERS) project by linking rice field fish 
culture with rodent pest management. 
Implementation of a community-based project has 
been secured from the AusAID funded Community 
Development Fund and will be initiated in March 
2002.  
 
MATERIALS AND METHODS 
Field design for rice fish culture with rodent pest 
management 
The design of the Trap and Barrier System 
(TBS) is similar to that used for rodent pest 
management in the FARMERS project. The trap crop 
is a 20 x 20m rice plot with a bund and a fence placed 
around the perimeter. In addition for fish culture, a 
small pond (4 x 4 m x 1m deep) was incorporated 
into the corner of the rice field. This was to offer fish 
a localized site for supplementary feeding and refuge 
from heat and drought. This study made comparisons 
between the rates of growth of fish fed a 
supplementary diet (rats that are trapped or dried fish 
if no rodents are captured) and those that feed only 
on what is available in the rice field. To achieve this 
a division was incorporated into the rice field, rats 
trapped in the field were euthanised and minced with 
rice bran to feed fish on one side of the division 
(Appendix 1). For reproducibility of results two 
project sites were developed at CARDI. The project 
was implemented on 1st October 2001 when rice 
(IR66) was transplanted and hybrids of the walking 
catfish (average weight 10.93g ± 0.5, average total-
length 10.95cm ± 1.52) were released into the rice 
field on the 22nd October at 1.25 m-2. The catfish had 
previously been held in a harpa (holding cage) for 7 
weeks 
Catfish hybrid 
The species of fish to be grown is a hybrid of 
two native catfish species, the walking catfish (C. 
batrachus) and the broad head catfish (C. 
macrocephalus). These fish are a highly regarded 
table-fish in Cambodia, reaching market prices of 
4000 - 5000 Riel kg-1 (US$1- 1.25 kg-1). This group 
of catfish is very suitable for coupling with the TBS 
as they are resistant to desiccation, can breath 
atmospheric air, are highly carnivorous, have fast 
growth rates (200g in 3 months) and the hybrid has 
been shown to grow 20% faster (Dunham, et al., 
1990). Another characteristic of these catfish species 
is their ability to move across land with their pectoral 
spines (Pillay, 1990). In the past the mobility of this 
species has proven to be a problem for rice field 
culture, however the TBS will act as a barrier to 
contain these mobile fish. The hybrid cross used for 
this project was C. batrachus ♀ x C. macrocephalus 
♂. Tarnchalanukit (1986) found that this hybrid cross 
produces a 5% higher fertilization rate and surviving 
larvae than the inverse cross. Fish were stocked at 
1.25 m-2, or 500 per 400m2 trap plot. 
Product evaluation 
The final issue to be addressed by this study 
is taste and marketability of the fish product. 
Preliminary surveys identified that Cambodian’s have 
a preference for wild caught fish compared to 
cultured fish. Whether this is due to the taste of the 
fish or common perception that cultured fish are 
raised on low quality diets in poor water and previous 
experiences from bad quality products needs to be 
tested. To test whether there is a difference in taste, a 
taste test and product evaluation was conducted with 
CARDI staff to quantify their responses to wild 
caught versus cultured fish and different catfish 
species. Staff were asked to sample 5 different fish 
Cambodian Journal of Agriculture: Volume 6, 2002 Edition 
 11
(wild C. macrocephalus, wild C. batrachus, fed 
CARDI hybrid, un-fed CARDI hybrid and hybrid 
catfish from another farm) and given a survey to 
record their response to each product. 
Project potential 
A community project with farmers in the Som 
Rong Commune, Kampong Cham will be undertaken 
in March 2002 to further develop the fish culture 
technique and help scientists target the research to 
farmers’ requirements. The community-based project 
will be implemented with the arrival of an Australian 
Youth Ambassador (AYA), Morgan Edwards, and 
financial support from the AusAID funded 
Community Development Fund (CDF). To identify 
the appropriateness of this technology to the 
community, a preliminary survey of 105 people in the 
Som Rong Commune and 105 people in Lvea 
commune, both in Kampong Cham province, was 
conducted. 
RESULTS 
Fish production 
Hybrid catfish (average weight 1.38g ± 0.1; 
average length 5.58cm ± 0.1) were raised in a harpa 
for 7 weeks and reached an average weight of 10.93g 
± 0.5 and average total-length of 10.95cm ± 1.52 
before being released to the rice field. The average 
FCR for catfish during this holding period was 2.5. 
 Fish were on grown in the rice field for a total of 
86 days (22nd October - 15th January 2002). Fish were 
fed on a mixed diet of dried fish and rice bran (30% 
crude protein), as rodent capture was low due to 
extensive flooding at CARDI on 15th October. The 
total volume of fish harvested from the four study 
sites was 17.2kg. The two study sites (east and west) 
produced 7.2 and 2.6kg of fed fish respectively. 
Production of unfed fish from both study sites (east 
and west) was 1.4 and 2.9kg respectively. A further 
2.3kg of wild fish was harvested from both the east 
and west fed ponds and 0.9kg from the east and west 
unfed ponds. Wild fish were primarily made up of by 
Snakehead (Trey raws), Climbing Perch (Trey crang) 
and minor contributions from Trey chloin, Trey 
codjoh and Trey changwa. By the end of the culture 
period the fed fish were significantly larger (62.4g 
±3.1, 18.8cm ±0.3) than the unfed group (37.4g ±2.7, 
15.5cm ±0.3). The rate of survival was low in both 
treatments with 31% survival from the fed group and 
22% survival from the un-fed group.  
The fed treatment was fed at 10% biomass per 
day for the first 62 days however this was reduced to 
5% per day as water quality deteriorated while the 
other group was not fed for the culture period. Figure 
1 shows average weight increase and Figure 2 shows 
the average length increase of fish fed and unfed in 
the rice field. The fed fish consumed a total of 32.7kg 
of supplementary feed in the rice field resulting in an 
FCR of 1.9. 
Water quality deteriorated in the fed ponds over 
the culture period resulting in an average final pH of 
5.93 compared to the unfed ponds that had an 
average final pH of 6.62. 
Fed East
R2 = 0.7093
Un-fed East
R2 = 0.6638
Un-fed West
R2 = 0.4421
Fed West
R2 = 0.7604
0
10
20
30
40
50
60
70
80
90
10 12 14 16 18 20 22
Weeks
W
ei
gh
t (
g)
 
Figure 1: Average weight gain of fed and unfed 
walking catfish hybrids from two rice field culture 
sites (east and west).  
Fed East
R2 = 0.5701
Fed West
R2 = 0.7727
Un-fed East
R2 = 0.432
Un-fed West
R2 = 0.4296
10.0
12.0
14.0
16.0
18.0
20.0
22.0
24.0
10 12 14 16 18 20 22
Weeks
Le
ng
th
 (c
m
)
 
Figure 2: Average length gain of fed and unfed 
walking catfish hybrids from two rice field culture 
sites (east and west).  
 
Product taste and acceptability 
From a survey of 35 people, 31% selected C. 
macrocephalus as their first choice of fish for overall 
taste and fish characteristics, 24% of the survey 
group selected the fed CARDI hybrid as their first 
Cambodian Journal of Agriculture: Volume 6, 2002 Edition 
 12
choice for taste and fish characteristics, third was the 
unfed CARDI hybrid (21%), fourth was C. batrachus 
(14%) and the final choice was a hybrid from another 
farm (10%). 
From the survey, 59% of the test group identified 
that the most desired catfish are light in colour, 36% 
identified that medium sizes of 200g are preferred 
and 44% identified that fat fish are preferred (Figure 
3). 
0
10
20
30
40
50
60
70
80
90
100
sm
all
, d
ark
, s
kin
ny 2
me
diu
m 4
lar
ge
, li
gh
t, f
at
Sample characteristic
D
es
ire
d 
ch
ar
ac
te
ris
tic
 (%
)
Shape
Colour
Size
Figure 3: Desired characteristics of catfish identified 
through a survey of 35 CARDI staff members.  
 
Rat trapping 
Rat trapping was very low during the fish culture 
period due to floods driving rat populations out of the 
area in mid October. However at the end of 
December as the rice crop matured rat trapping was 
more frequent. During the period of fish culture, 22nd 
October - 15th January, 25 rats were caught. In this 
period traps also collected a number of snakes and 
frogs. Rodent capture was still being achieved at the 
end of the fish culture period and was maintained. 
Rice yield 
Rice yield was expected to be low due to 
extensive floods at CARDI 15 days post transplant. 
Rice did not recover from this early damage and as a 
result the average yield was 920 kg ha-1. Rice yield 
from the 200m2 treatment sites was significantly 
higher for both east and west fed treatments (26kg 
and 21.5kg respectively) compared to the east and 
west unfed treatments (14.5kg and 11.5kg 
respectively). 
 
Gross margin 
Total costs and potential sales for rice and fish 
are recorded in Table 1. 
Table 1: Cost and profit statement related to rice 
field fish culture. 
Item Unit Unit price 
(Riel) 
Gross 
Margin 
(Riel) 
Fingerling 1,000 
head 
50 -50,000 
Fish Food 32.7 kg 1,000 -32,700 
Fish  17.2 kg 4,000 +68,800 
Rice 73.5 kg 500 +36,750 
 
Preliminary survey 
 From the 210 people surveyed in Kampong 
Cham, it was found that 17.6% are growing fish in 
ponds with an average production of 185kg year-1. 
The main species being cultured is the shark catfish, 
Pangasianodon hypophthalmus, local name Trey Pra. 
Farmers that were not growing fish clearly indicated 
that they would like to be able to but are primarily 
restricted by lack of technology and capital (Table 2). 
 
Table 2: Main problems facing farmers that are not 
growing fish but would like to be able to. Data 
presented as a mean percentage of farmers. 
Restriction Som Rong Lvea 
Low protein diet 5.2 0.5 
Lack of technology 17.7 15.2 
Lack of capital 18.2 23.8 
Water restrictions 4.8 4.2 
Disease 5.2 1.4 
Low market price 3.5 0.0 
Other 21.6 27.1 
DISCUSSION 
1. Fish production 
FCR of 1.9 is comparable to figures presented by 
Pillay (1990) of 2.  
Water quality was poor in one of the fed ponds 
therefore the feeding rate was reduced from 10% 
biomass per day to 5% biomass per day. Water pH 
was lower in the fed ponds. Fed ponds showed high 
amount of algal growth while unfed contained little. 
Future projects will integrate herbivorous species to 
utilize primary production. 
2. Product taste and acceptability 
The taste test suggests that consumers have a 
dislike for farmed fish due to inconsistent products 
reaching the market place as the farmed fish from 
CARDI were selected as the consumers second 
preference. The data also identified that consumers 
are after catfish of a medium size (200g), of light 
colour and that are fat. 
 
Cambodian Journal of Agriculture: Volume 6, 2002 Edition 
 13
3. Rat trapping 
Rodent capture did not begin until late stages of 
the rice maturity. It is postulated that surrounding 
crops provided food for the rats but as they were 
harvested the rats moved into the TBS crop. 
4. Rice yield 
Floods at CARDI on the 15th October caused 
considerable damage to newly transplanted rice as 
well as driving out the rodent population. It is 
estimated that rice yield was affected by 50%. In one 
case dogs also attacked trap with rats, flattened 2m2 
of rice. 
The agronomic crop benefited from fish culture 
due to the increased nutrient load to the soil from 
accumulation of excrement and unconsumed feeds 
during the fish culture period. 
5. Gross margin 
This pilot project has identified a new technology 
that will not only increase the farmer's income and 
nutritional diversity but will improve rice yield 
through rodent pest management and nutrient influx 
from fish culture.  
6. Preliminary survey 
Farmers identified that lack of capital and 
technology were the major constraints for them to 
adapt fish culture.  
 
ACKNOWLEDGEMENTS 
Special thanks must go to Parrah, for his 
technical assistance in this project. We would also 
like to thank all of the students from the Royal 
University of Agriculture who came to CARDI and 
offered their assistance during this project Orn Por 
Soeun, Ou Rorthmony, Thov So Thorn and Bun Rim 
Than. 
 
REFERENCES 
Bunra, S., Gregory, R. 1995. Trap pond mapping as a 
survey tool for aquaculture development 
planning. Seminar on Aquaculture in South and 
Southeastern Cambodia, Bati Fish Seed 
  Station, Prey Veng, December 13th – 14th 1995. 
Dunham, R.A., Brummett, R.E., Ella, M.O., Smitherman, 
R.O. 1990. Genotype – environment interactions 
for growth of blue, channel and hybrid catfishes 
in ponds and cages at varying densities. 
Aquaculture. 85, 143-151. 
Gregory, R. 1997. Ricefield fisheries handbook. Cambodia 
– IRRI – Australia Project, Phnom Penh. 
Pillay, T.V.R. 1990. Aquaculture Principals and Practices. 
Nutrition and feeds, 92-156. Fishing news book. 
Blackwell Science. 
Sihapitakgial, P. 2000. Breeding of freshwater indigenous 
fishes of Thailand. National Inland Fisheries 
Institute. Department of Fisheries. Jatujak, 
Bangkok.  
Subasinghe, R., Phillips, M.J., Tacon, A.G.J. 1998. FAO 
Fisheries department review of the state of world 
aquaculture Southeast Asia. 
Tarnchalanukit, W. 1986. Experimental hybridisation 
between catfishes of the families Clariidae and 
Pangasiidae in Thailand. Environmental Biology 
and Fisheries. 16, 317-320. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Cambodian Journal of Agriculture: Volume 6, 2002 Edition 
 14
  
Appendix 1 
Integrated rice / fish farming with rodent pest management  
System layout 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
20 m 
20 m 
Rodent barrier 
0.3 m 
Drain 
Fish 
pond 
Dyke 
Rice field 
1.5 m 
Rat trap 
4 m 
Rat trap 
Fed pond  @ 5 
- 10% biomass 
day-1 
Un-fed 
pond 
250 walking catfish 
= 1.25 m-2 
4 m 
Drain 
250 walking catfish 
= 1.25 m-2 
Division 


Rice Field Fish Farming Integrated with Rodent Pest Management in Cambodia

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Rice Field Fish Farming Integrated with Rodent Pest Management in Cambodia

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