For minimizing cannibalism of African catfish (Clarias gariepinus) larvae two trials for a period of 14 and 15 days respectively in four aquaria of size 120x49x32 cm³ were conducted. Seven days old African catfish larvae with an initial total length and weight of 7.84 (±0.40) mm and 4.40 (±1.18) mg respectively in the first trial and similarly 7.52(±0.61) mm and 3.98 (±0.56) mg in the second trial at the rate of same stocking densities of 2500 larvae in each aquarium were stocked in both trials. Cannibalistic larvae were separated by using grader frame from each treatment at 7 days and 5 days interval during first and second trial respectively. Two mesh sizes i.e., 5 mm and 7 mm were used in the grader frame in both trials. Survival rate was significantly higher in T1 than that of T2 in each trial. Grading of larvae with 5 days interval resulted higher survival rate than that of 7 days interval

Faroque, M.A.A.

Islam, M.S.

Khan, M.H.K.

Mollah, M.F.A.

Aquatic Commons

Bangladesh J. Fish. Res., 3(2), 1999: 181-186 
Minimization of cannibalism of African catfish ( Clarias 
gariepinus Burchell) larvae in indoor culture system 
M.F.A. Mollah, M.S. Islam*, M.A.A. Faroque and M.H.K. Khan 
Dept. of Fisheries Biolog1} & Genetics, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh 
*Corresponding author 
Abstract 
For minimizing cannibalism of African catfish (Clarias gariepinus) larvae two trials 
for a period of 14 and 15 days respectively in four aquaria of size 120 x 49 x 32 cm3 
were conducted. Seven days old African catfish larvae with an initial total length and 
weight of 7.84 (±0.40) mm and 4.40 (±1.18) mg respectively in the first trial and 
similarly 7.52(±0.61) mm and 3.98 (±0.56) mg in the second trial at the rate of same 
stocking densities of 2500 larvae in each aquarium were stocked in both trials. 
Cannibalistic larvae were separated by using grader frame from each treatment at 7 
days and 5 days interval during first and second trial respectively. Two mesh sizes 
i.e., 5 mm and 7 mm were used in tl:te grader frame in both trials. Survival rate was 
significantly higher in T1 than that of T2 in each trial. Grading of larvae with 5 days 
interval resulted higher survival rate than that of 7 days interval. 
Key words : Clarias gariepinus, Cannibalism 
Introduction 
African catfish has been well adopted to the environment of Bangladesh and its 
growth rate is highly encouraging. There is an increasing demand of its larvae. 
Though different techniques of larvae rearing of the species have been established 
through research, cannibalism is considered as one of the serious impediments for 
large scale larvae and fry rearing of the catfish. 
Cannibalism is the process of both killing and eating an individual of the same 
species. As a biological phenomenon, sibling cannibalism can possibly be regarded as 
a specialized predation strategy developed as a mechanism to ensure survival of 'fit 
individuals', in the Darwinian sense, under 'harsh' or unstable environmental 
conditions reproductively to contribute successfully to future generation (Fox 1975). 
Cannibal phenotypes are morphologically similar to, but much larger than normal 
phenotypes. 
Though in nature cannibalistic populations are self-regulated below the capacity 
of the environment and more resilient, cannibalism is considered as the only problem 
under high density fish culture since the mid 1970s. Larval and juvenile sibling 
cannibalism occurs in important culture species such as yellowtail (Seriola 
quinqueradiata), turbot (Scophthalmus maximus), eels (Anguilla anguilla), koi-carp 
(Cyprinus carpio), sea-bass (Dicentrarchus labrax) and gilthead bream (Sparus aurata) 
M.F.A. Mollah et al. 
(Chaudhuri & Tripathi 1979, Smith 1979, Kentouri 1980, Degani & Levanon 1983). 
Cannibalism has been recorded in wild populations of Clarias gariepinus (Corbet 1961 
and Bruton 1979). Aboul-Ela et al. (1973) reported that heavy losses (up to 65%) have 
been attributed to larval and juvenile sibling cohort cannibalism of Clarias gariepinus. 
So, the present study was designed to establish a technique of minimizing 
cannibalism of its larvae. 
Materials and methods 
The experiments were conducted at the Department of Fisheries Biology and 
Genetics under the Faculty of Fisheries, Bangladesh Agricultural University, 
Mymensingh during July to September'97. Two trials were conducted during the 
period. Larvae of Clarias gariepinus for each trial were obtained by induced spawning 
of broods collected from the culture ponds of the department by using carp pituitary 
gland and 'Sumaach (HCG, India)'. The larvae were first fed after two days of 
hatching. They were provided with Tubificid worms in a paste form. Food particle 
size was gradually increased corresponding with the average mouth size of the 
larvae. The experiment was conducted in four aquaria of size 120 x 49 x 32 cm3 which 
were marked as treatment-1 (T1) and treatment-2 (T2) each having two replications. 
Grading was done in the two aquaria under T1 (experimental) while the aquaria 
under T2 were considered as control and no grading was done. 2500 larvae of 7 days 
old were stocked in each aquarium containing 156 litres of water i.e., 16 larvae per 
litre of water in both trials. In the aquaria the larvae were fed with Tubificid worms 
twice a day to their satiation level. Continuous water flow was maintained in each 
aquarium. About two-third of water of each aquarium was changed everyday. The 
aquaria were cleaned by siphoning after half an hour of feeding. 
For grading, a grader was developed which was a net tied to a rectangular frame 
of PVC (Polyvinyl Chloride) pipe. The first trial continued for 14 days while the 
second trial continued for 15 days. In the first trial grading was done two times - at 
the 7th and 14th day of starting the trial with the grader box of 5 mm and 7 mm mesh 
size respectively. In the second trial grading was done three times - at the 5th, 10th 
and 15th day of starting the trial with the grader box of 5 mm, 7 mm and 7 mm mesh 
size respectively. During grading, the grader was placed at one end of the aquarium 
carefully removing the larvae from that end. The grader was then drawn slowly from 
one end to the other. Feed was not provided to the larvae in the morning on the day 
of grading. After grading, the separated larvae from two aquaria under T1 (in which 
grading was done) were counted and total length and weight of each was recorded. 
The separated larvae were replaced in another aquarium. After grading total length 
and weight of twenty larvae from each aquarium (both experimental and control) 
were recorded on the day of grading and released in the respective aquarium. Dead 
bodies of larvae were collected daily from each aquarium every six hourly interval 
during each trial. Usually whole dead bodies and in some instances only the head 
portion of larvae were collected from the bottom of the aquaria. The whole dead 
bodies of larvae were considered as the natural mortality while the availability of 
182 
Cannibalism of C. gariepinus larvae 
heads and the complete disappearance of the larvae were considered as the mortality 
due to cannibalism. After final grading total number of remaining larvae in each 
aquarium was counted. 
Results 
Growth (total length and weight) of Clarias gariepinus larvae under different 
treatments (i.e. 1 T1 and T2) as recorded during the two trials (i.e.1 first and second 
trial) are presented in Table 1 and Table 2. The initial average total length and 
weight of the larvae stocked in the first trial were (7.84 ± 0.40) mm and (4.4 ± 1.18) 
mg. The final average length and weight of the larvae were 14.33 (± 0.13) mm and 
25.26 (± 1.60) mg; 31.01 (± 4.15) mm and 509.90 (± 24.84) mg in T1 and T2 respectively. 
At the end of the first trial the average number of larvae survived in T1 and T2 were 
715 and 26 respectively. The maximum and minimum length and weight of the 
cannibalistic larvae at that time in T2 were 66 mm and 2574 mg and 14mm and 23 mg 
respectively. 
Table 1. Growth (length and weight) of both cannibalistic and non-cannibalistic 
C. gariepinus larvae in the first trial 
Treatment Stocking Average Average 
s density length (mm) weight 
(per (mg) 
aquarium) 
Initial 1" grading 2"" Initial 1'' grading 2"" 
grading grading 
T* I 2500 7.84 11.66 14.33 4.40 13.96 25.26 
(±0.40) (±1.35) (±0.13) (±1.18) (±0.30) (±1.60) 
T,© 2500 7.84 13.66 31.01 4.40 35.23 509.90 
(+0.40) (±0.46) (±4.15) (±1.10) (±1.50) (+24.84) 
*Average growth of non-cannibalistic larvae after grading. 
©Average growth of both cannibalistic and non-cannibalistic larvae. 
Table 2. Growth (length and weight) of both cannibalistic and non-cannibalistic 
C.gariepinus larvae in the second trial 
Treatments Stocking Average length (mm) 
density 
Initial 1" 2"" 3"' 
grading .grading grading 
T* I 2500 7.52 9.46 11.30 14.90 
(±0.61) (±0.46) (±0.20) (±0.20) 
T,© 2500 7.52 10.69 15.81 32.41 
(±0.61) (±0.03) (±0.48) (±1.50) 
*Average growth of non-cannibalistic larvae after grading. 
©Average growth of both cannibalistic and non-cannibalistic larvae. 
Average weight (mg) 
Initial 1'' 2nd 
grading grading 
3.98 11.10 14.35 
(±0.56) (±0.30) (±0.75) 
3.98 16.36 62.91 
(±56) (±0.43) (±1.33) 
3"' 
grading 
27.20 
(±1.10) 
540.10 
(±7.19) 
183 
M.F.A. Mollah et al. 
In the second trial, the initial average length and weight of the larvae were 7.52 
(± 0.61) mm and 3.98 (± 0.56) mg. The final average length and weight of the larvae 
in T1 and T2 were 14.90 (± 0.20) mm and 27.20 (± 1.10) mg and 32.41 (± 1.50) mm and 
540.10 (± 7.19) mg respectively. At the end of the second trial the average number of 
larvae survived in T1 and T2 were 1258 and 21 respectively. The maximum and 
minimum length and weight of the cannibalistic larvae at that time in T2 were 61 mm 
and 2456 mg and 17 mm and 56 mg respectively. 
Table 3 presents the mean (± SE) of final number, total survival (%), natural 
mortality (%) and cannibalism-induced mortality (%) during the first and second 
trial. The average (± SE) of final number and total survival of C. gariepinus larvae 
were significantly higher (P < 0.01) in T1 than T2 in both trials, but the final number 
and total survival were higher in T1 of second trial than that of first trial. There was 
no significant difference between the natural mortality of T1 and T2 in any of the 
trials. The average (± SE) cannibalism-induced mortality was significantly higher (P 
< 0.01) in T2 than T1 in both trials. 
Table 3. Survival rate, natural mortality and cannibalism-induced mortality of C. gariepinus 
larvae during first and second trial after 14 days and 15 days respectively of rearing 
at the same stocking densities 
Group First trial Second trial 
Mean±SE t-values and Mean±SE t-values and 
T, T, significance T, T, significance 
level level 
Final number 715.00±33.00 25.50±4.50 20.70* 1258.00±69.00 20.50±3.50 17.91* 
Total survival 28.60±1.32 1.02±0.18 20.70* 1258.00±69.00 20.50±3.50 17.91* 
(%) 
Natural 10.80±0.68 9.80±2.60 0.37IS 7.64±0.72 7.98±2.62 -0.13 IS 
mortality(%) 
Cannibalism- 60.60±0.64 89.60±2.00 -13.81* 42.04±2.04 91.68±2.28 -16.23* 
induced 
mortality(%) 
* p < 0.01 
IS, Insignificant (P < 0.05) 
Discussion 
In the present experiment it was observed that the larger larvae of Clarias 
gariepinus first turned into cannibals. Giles et al. (1986) working on pike larvae also 
observed that the largest fish in each tank first turned cannibalistic. Both types of 
cannibalism i.e., 'tail-first' and 'head-first' as described by Hecht and Appelbaum 
(1988) in case of Clarias gariepinus larvae occurred in the present experiment. Growth 
and cannibalism of African catfish (Clarias gariepinus) larvae in all the treatments 
were investigated during the experiment. The results indicated that the growth rate 
184 
Cannibalism of C. gariepinus larvae 
of larvae varied among two treatments of both trials. Growth rate was higher in T2 
than that of T1 in both trials. As grading was not done in treatment T2 in both trials, 
there occurred a great size variation among the survivors due to cannibalism. As 
cannibalistic larvae were separated periodically from each aquarium under T1 in both 
trials, the remaining larvae were more or less of same size. Because of the same 
grader used in both trials there was no remarkable difference in growth rate in T1 in 
each trial. 
Survival rate was significantly higher in T1 than that of T2 where a severe loss 
occurred during the rearing period of Clarias gariepinus larvae into culture system 
because of cannibalism. Van Dame et al. (1989) reported severe losses (upto 40%) of 
Koi-carp (Cyprinus carpio) larvae and juveniles during the rearing with artificial diets 
at high densities. As grading was not done in T2 cannibalism-induced mortality was 
the highest in this case in both trials. So, it can be said that cannibalism of Clarias 
gariepinus larvae can be reduced by regular grading in larval rearing system. 
Final number of larvae survived, at the end of the trials, was higher in second 
trial compared to the first. In the first trial, grading was done at 7 days interval while 
in the second trial, grading was done at 5 days interval with same grader box. 
Cannibalism-induced mortality was apparently lower in T1 of second trial than that 
in T1 of first trial due to grading variation. So, it can be concluded that regular 
grading of fish by size with short intervals during culture period can minimize 
cannibalism of Clarias gariepinus larvae. 
References 
Aboul-Ela, I., F.I. Amer, and A.R. EI Bolock, 1973. Studies on spawning and spawning 
behaviour of Clarias lazera Cuv.et Val. in fish farms of the A.R. Egypt. Bull Zool. Soc. 
Egt;pt., 25: 25-33. 
Bruton, M.N., 1979. The food and feeding behaviour of Clarias gariepinus (Pisces: Clariidae) in 
Lake Sibaya, South Africa, with emphasis on its role as a predator of cichlids. Trans. Zool. 
Soc. Land., 35:47-114. 
Chaudhuri, H. and S.D. Tripathi, 1979. Problems of fish seed production. In: Advances in 
aquaculture (eds. T.V.R. Pillay and Wm. A. Dill). Fishing News books. pp. 127-134 
Corbet, P.S., 1961. The food on non-cichlid fishes in the Lake Victoria Basin, with remarks on 
their evolution and adaptation to lacustrine conditions. Proc. zool. Soc. Land., 136: 1-101. 
Degani, G. and D. Levanon, 1983. The influence of low density· on food adaptation, 
cannibalism and growth of eels (Anguilla anguilla L.). Bamidgeh, 35: 53-60. 
Fox, L. R., 1975. Cannibalism in natural populations. Ann. Rev. Ecol. Syst., 6: 87-106. 
Giles, N., R. M. Wright and M.E. Nord, 1986. Cannibalism in pike larvae, Esox lucius L.: some 
experiments with larvae densities. J. Fish Biol., 29: 107-113. 
Hecht, T. and S. Appelbaum, 1988. Observations on intra-specific aggression and coeval 
sibling cannibalism by larva and juvenile C. gariepinus (Clariidae: Pisces) under controlled 
conditions. J. Zool., 214: 21-44. 
l85 
M.F.A. Mollah et al. 
Kentouri, M., 1980. Rearing of larvae of sea -bass (Dicentrarclllls labrax) using frozen 
zooplankton organisms: preliminary results. Aquaculture, 21: 171-180. 
Smith, P.L., 1979. The development of a nursery technique for rearing turbot Scophthalmus 
maximus, from the metamorphosis to on growing size progress since 1970 by the British 
White Fish authority. In: Advances in aquaculture (eds. T.V.R. Pillay and Wm. A. 
Dill).Fishing News Books. pp. 143-149 
VanDamme, P., S. Appelbaum and T. Hecht, 1989. Sibling cannibalism in koi-carp, Cyprinus 
carpio L. larvae and juveniles reared under controlled conditions. J. Fish Bioi., 34: 855-863. 
(Manuscript received 5 August 1998) 
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Minimization of cannibalism of African catfish (Clarias gariepinus Burchell) larvae in indoor culture system

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Minimization of cannibalism of African catfish (Clarias gariepinus Burchell) larvae in indoor culture system

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