Static bioassays were performed to observe the toxic effect of malathion to Barbodes gonionotus at 0.0 to 20.0 ppm concentrations. Malathion at 5.0 ppm was harmless to B. gonionotus and concentrations above 6.0 ppm were found to be lethal. Malathion at 2.06 ppm was safe for the B. gonionotus

Hoque, M.M.

Hossain, M.A.

Nahar, Z.

Aquatic Commons

Bangladesh]. Fish. Res., 4(1), 2000: 101-104 
Scientific Notes 
Toxicity of malathion to silver barb (Barbodes gonionotus 
Bleeker) fingerlings 
M.M. Hoque*, Z. Nahar and M.A. Hossain 
Freshwater Station, Bangladesh Fisheries Research Institute, Mymensingh-2201, Bangladesh 
*Corresponding author 
Abstract 
Static bioassays were performed to observe the toxic effect of malathion to Barbodes 
gonionotus at 0.0 to 20.0 ppm concentrations. Malathion at 5.0 ppm was harmless to B. 
gonionotus and concentration above 6.0 ppm were found to be lethal. Malathion at 2.06 
ppm was safe for the B. gonionotus. 
Key words: Toxicity, Malathion, B. gonionotus 
Thai silver barb or rajpunti (Bm·bodes gonionotus) was introduce to Bangladesh from 
Thailand has shown considerable promise as a culturable species in ponds, ditches and 
other seasonal water bodies with low cost inputs at low level of management. The fish is 
becoming popular in paddy-fish culture systems also. The main problem of widespread 
culture of B. gonionotus in rice field is the indiscriminate use of insecticides for control of 
insect pests. Pesticides may cause extensive damage to different vital organs of fishes 
(Gosh and Dutta 1985) and also cause degradation of aquatic ecosystem which gradually 
reach disastrous limits and thus become a potential killer of fish population (Mckim et al. 
1974). 
A good number of literature's has been reported on the toxicity of agrochemicals to 
varieties of cultivable fishes (Ghosh and Dutta 1985, Haque 1989 and Hoque et al. 1993), 
with little information is available on the toxic effects of malathion to fishes. Since 
malathion has become a regular part of pest management in rice field, therefore, it is 
essential to evaluate the toxic effect of malathion to B. gonionotus with a view to 
formulate recommendation for the safe use of this pesticide in rice-cum-fish culture 
practice in Bangladesh. 
The study was conducted at Freshwater Station, Bangladesh Fisheries Research 
Institute, Mymensingh, during the period during August'98. Twenty six aquaria each of 
90 litre capacity were used for this purpose. Two aquaria were kept as control. Healthy 
rajpunti of three months old were acclimatized to the laboratory condition by keeping in 
holding tank before bioassay experiment. Initially a few screening tests were performed 
to find out the mortality range of B. gonionotus. The fishes were supplied mixed 
plankton food collected with a plankton net (mesh size, 150 11m). 
M.M. Haque et al. 
Malathion chemically known as 0, 0-dimethyl phosphorodithioate of diethyl 
mercaptosuccinate with 57% active ingredient was collected from local BADC dealer 
and tested at 0.0, 2.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 12.0, 16.0 and 20.0 ppm 
concentrations with three replications. Ten fishes ofuniform size (7.6±1.0 em, 6.3±1.9g 
) were placed to each aquarium at least 24 hour prior to the addition of the pesticide to 
water. Relative toxicity of malathion to rajpunti was determined by means of standard 
96-h semi-static bioassay (APHA, 1975) method. Initially the observations were made at 
3 hourly intervals and after 24 hours, the interval time was 6 hours. The behaviours of 
the fish was observed regularly at 3 hours interval. Dead fishes were recorded and 
subjected to a binomial formula after Ward and Parrish (1982): 
LCso= (AB)I;z 
Where A = Highest toxin concentration in which none of the test organisms died. 
B = Lowest toxin concentration in which all organisms died. 
Safe level of concentrations were calculated using the following formula, 
C=48h LC50 x 0.3/S2 
Where C = Harmless concentration and S = 24h LC 5of48h LC50 
Toxicity to fish depends on a number of factors such as species, age and health of 
fish, concentration of chemicals, exposure period and physico-chemical characteristics of 
water. During the period of investigation temperature of water was 28.0 + 0.5 while 
dissolved oxygen content varied between 4.3 to 5.5 ppm. The total hardness of the water 
was in the range of f08 - 110 ppm and pH was fairly stable (8.0 + 0.3). The physico-
chemical parameters ofthe water were within the desirable range for fish (Boyd 1979). 
Per cent mortality of the test fish at different concentrations are shown in Table 1. 
It can be seen from table 1 that the mortality of fish increased gradually with 
concentrations of toxin. Malathion below 5.0 ppm was ineffective to kill any fish within 
96 hours. Malathion at 9.0 ppm killed all the B. gonionotus in 24 hours. Low rates of 
mortality were observed in B. gonionotus when exposed to 6'.0 ppm of malathion for more 
than 72 hours. Mortality was found to increase as the dose of the malathion was 
increased. Total mortality within 3 hours (3h LC100) was observed at 12.00 ppm. Nine 
ppm of malathion killed all the fishes in 24 hours whereas diazinon and sumithion 
caused total mortality (24h LC100) at 6.00 ppm and 5.00 ppm respectively on more or less 
same size B. gonionotus (Hoque et al. 1993). Lower than 5.0 ppm concentration did not 
cause any mortality. The safe level of this insecticides was found to be 2.06 ppm for B. 
gonionotus. In the same species the safe level is 1.63 and 1.42 ppm for diazinon and 
sumithion respectively (Hoque et al. 1993). Sharama et al. (1981) reported that malathion 
was safe for Clarias batrachus at 2.72 ppm concentration, whereas it was 1.12 ppm for 
Labeo rohita of 10.5 em size at temperature of 21.0°C (Rahman 1989). These variations 
appeared to be related with the differences in species of fish. 
Median lethal dose concentration (LC50) of malathion were estimated to be 13.85, 
9.16, 8.36, 7.07, 7.07, 6.70 and 6.52 ppm for 1, 3, 6, 12, 18, 24 and 48 hours of exposure 
respectively (Table 2). The LC50 value of malathion for 96h exposure was found to be 56 
102 
Toxicity of malathion to silver barb 
ppm for Heteropneustes fossilis (Ghosh and Dutta 1985), 4 ppm for Chana punctatus 
(Dubale and Shah 1979) and 0.35 ppm for C. striatus (Choudheri et al. 1984), which are air 
breathing fishes. LC50 value of malathion for some non-airbreathing fishes like fatheads, 
blue gills, gold fish and guppies was 23.0, 0.09, 0.045 and 0.84 ppm (Pickering et al. 1962). 
LC50 does for 48h in Tilapia mossambica was reported to be 5.54 ppm (Sailatha et al. 1981). 
The 24h LC50 for B. ticto was 4.0 ppm and B. daniconius was 6.0 ppm (Singh and Sahai 
1984). 
Tablel. Cumulative percentage mortality of rajpunti to malathion at different concentrations 
Doses 
(ppm) 
0.0- 5.0 
6.0 
7.0 
8.0 
8.5 
9.0 
10.0 
12.0 
16.0-20.0 
1h 3h 6h 12h 18h 24h 48h 72h 96h 
0 0 0 0 0 0 0 0 
0 0 0 10 10 10 10 10 
0 0 0 10 30 30 30 30 
0 10 20 50 70 70 70 70 
0 10 30 60 80 90 100 100 
0 40 60 70 90 100 100 100 
0 100 100 100 100 100 100 100 
0 100 100 100 100 100 100 100 
100 100 100 100 100 100 100 100 
Table 2. Values of LC50 of malathion at varying time intervals 
H A B LCso 
1 12.0 16.0 13.85 
3 7.0 12.0 9.16 
6 7.0 10.0 8.36 
12 5.0 10.0 7.07 
18 5.0 10.0 7.07 
24 5.0 9.0 6.70 
48 5.0 8.5 6.52 
H== Time passed during the experiment (in hour) 
A= Highest toxin concentration (ppm) in which none of test organisms died 
B== Lowest toxin concentration (ppm) in which all test organisms died 
LC50= Calculated median lethal concentration (ppm) of malathion against 
rajpunti calculated from Binomial test LC50 == (AB)I12 of Ward and Parrish (1982) 
0 
10 
30 
70 
100 
100 
100 
100 
100 
After application of malathion in the aquarium the fish exhibited various signs of 
distress. At high concentrations an initial period of excitation was noted. Fish swam 
rapidly and opercular rate increased. A severe reaction involved in fin extension and 
temporary body curvature. Similar reaction was observed by Hoque et al. (1993). Most 
of the fish came to the surface water showing sign of suffocation with in 10 to 15 
103 
M.M. Haque et al. 
minutes. Gradually they lost equilibrium, became paralyzed and finally settle down to 
the bottom of the aquarium and remained to §arne position till death. Similar reactions 
were also observed in tilapia, Oreochromis nilotica (Haque 1989) and in B. gonionotus 
(Hoque et aZ: 1993). 
In aquatic medium the organophosphorus insecticides enter into the blood stream of 
fishes cause rupture of the gill epithelium, hemolyse the red blood corpuscle and destroys 
the nerve impulses by inhibiting the cholinesterase (O'Biren 1967). This inhibition 
results in the apparent death of the organisms. The rate of inhibition is related to the 
degree and duration of exposure. 
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American Public Health Association (APHA), 1975. Standard methods for the examination of water and 
wastewater. 14rh edition, Washington, D.C., USA, 1193 pp. 
Boyd, C.E., 1979. Water quality in warm water fish ponds. Alabama Agricultural Experiment Station, Alabama. 
379 pp. 
Choudheri, D.K., A.K. Sadhu and P.K. Mukhopadhyay, 1984. Toxicity of two organo-phosphosphorue 
insecticides malathion and phosphomidon to the fish Channa sttiatus. Environ. Ecol., 2(2): 143-147. 
Dubale, M.S. and P. Shah, 1979. Histopathological lesions induced by malathion in the liver of Channa punctatus. 
Ind.]. Exp. Bioi., 17: 693-697. 
Ghosh, R. and J. Dutta, 1985. Malathion toxicity in air breathing catfish, shingi, Heteropneustes fossil is (Bloch). 
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(Linn.). Geobios, 8(5): 237-239. 
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(Manuscript received 12 December 1998) 
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Toxicity of malathion to silver barb (Barbodes gonionotus Bleeker) fingerlings

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Toxicity of malathion to silver barb (Barbodes gonionotus Bleeker) fingerlings

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