Observations on the feeding habits of Clarias liocephalus in wetlands of Western Uganda

Observations on the feeding
habits of Clarias liocephalus in
wetlands of Western Uganda

Sr. Jane Yatuha:
Jeremiah Kang’ombe, Justus
Rutaisire & Lauren Chapman

Presentation outline

• Background
• Study Methods
• Results & discussion
• Conclusion
• Acknowledgements
• References

2

BACKGROUND
What is C. liocephalus?

Smoked C.
liocephalus
on market
stalls

3

B/G
Fresh C. liocephalus
The type used in this
study

4

B/G
• Clarias liocephalus (C. carsonii )

• Small air-breathing catfish abundant in
wetlands and river systems in E/A
• An integral part of diets of many communities
in Uganda
• Source of income/protein for rural communities
who access it freely & easily 5

B/G
What about C. liocephalus?
• C. liocephalus has significant
economic, ecological and nutritional
attributes
– in part associated with its very high biomass in
dense papyrus-dominated wetlands distributed
in East Africa and the Nile Basin
• Its abundance in wetlands of Uganda
is an indication that it is well adapted to
colonize the niche successfully.
6

B/G
Why C. liocephalus?

Increase in demand

Loss of habitat

Malnutrition in rural communities
in the region
7

Increased demand for C.
liocephalus

Bait market

Indiscriminate
harvesting

8

Loss of habitat (strain the persistence of
C. liocephalus)

Forests replacing wetlands

9

Cattle grazing in what used to be a wetland

10

R. Rwizi threatened

Settlement
De
gra
de
ba d ri
nk ve
s r

11

Why C. liocephalus?

•Little information exists on the ecology
of the species to permit evaluation of
current threats
•General studies have been done in rivers and
lakes
No feeding ecological study has been done
specifically for this species &
in a wetland habitat where it appears to have a
very high biomass.

12

Background
Objectives
• The purpose of this study was to
quantitatively describe the diet of C.
liocephalus across ontogenic & spatial
gradients

Prey choice

Feeding strategy 13

Why study diet?
•It is important to understand ecological needs
of species & how changes in the habitat
conditions may affect their energy requirements
& acquisition

•Quantification of fish diets is important in
defining nutritional requirements of potential
aquaculture species

14

STUDY METHODS

Study Area

15

Rwizi-rufuha wetland system a chain of
wetlands along R. Rwizi a tributary of L.
Victoria in W/Uganda

Study area

sites from heavy and
lightly fished wetland

16

Methods
• Monthly collections (basket traps for 12 months)
• Euthanize with clove oil and transported on ice

• Stomachs excised following standard procedures

• Record: site, sex, TL & SL, Total weight &
eviscerated weight , stomach weight & stomach
fullness (using codes)
• Stomachs preserved in 10% formaldehyde

• Prey items sorted & identified to lowest possible
taxon under a stereo- microscope at 5xto28x mg 17

METHODS

Local basket
traps

Dissection and content
analysis in lab

Length measurement
18

Methods
Data analysis
A combination of Numeric, Occurrence and
Volumetric indices were used to describe the
diet of the species as expressed in terms of:
 abundance & importance

 Prey specific abundance Index P=(∑Si/∑Sti)100)
Feeding strategy

LWR between sites analysed with non-
parametric tests 19

Results and applications
•The size ranged between 5.3 – 29.6 cm
total length and 1.24 -138.6 g total weight.
There was a significant variation in TL
( p<0.01) between lightly and heavily fished
sites
•The largest fish were got from site
where fishing is regulated, while the
smallest sizes came from the open
access wetlands where fishing is
indiscriminate and uncontrolled
20

The outstanding disparity in fish size
distribution across the sites may be
attributed to fishing pressure 21

Evaluation Index OCCURRENCE NUMERIC VOLUMETRIC
Prey ID %Frequency % by No. %Vol.

Terrestrial Insects 5.03 1.58 1.83

Hemiptera 6.29 1.51 1.60

Mollusk 6.60 4.14 1.65

Odonata 6.92 2.41 2.10

Unidentified prey 8.49 0.00 4.71

Fish 9.43 4.22 16.74

Non-prey items 17.30 - 0.18

Other 18.24 13.33 6.04

Detritus 26.73 0.00 13.90

Coleoptera 28.30 10.54 9.19

Insect parts 30.50 - 8.50

Plant material 52.20 - 14.08
22

Diptera 52.52 62.27 19.48

The feeding strategy plot for C. liocephalus

23

Results & Appl
•C. liocephalus as a generalist feeder whose diet
was dominated by aquatic dipteran larvae and plant
material
The significant presence of plant material
shows that the species may utilize plant protein
and this is an important clue if the species was
selected for aquaculture
•High within phenotype component -wide niche
breadth since many individuals utilized most prey
items simultaneously:

Can effectively forage at different ecological levels
an optimal strategy especially in habitats that are 24

prone to change

•Major prey categories appeared across all
sizes
possible intra-specific competition in C.
liocephalus. Competition is likely when
prey occurrence is above 25% in two or
more size classes.
•Presence of C. liocephalus juveniles in some
stomach samples pointed to possible
cannibalistic feeding habit in this species
The low level of occurrence for C.
liocephalus prey (2.8%) suggests that
cannibalism & piscivory in C. liocephalus is
low compared to large & medium sized
clariids like C. gariepinus &C. ngamensis 25

CONCLUSION

C. liocephalus is a generalist feeder that draws prey
from several trophic levels depending on the
availability.
The major prey taxa in its diet are aquatic dipterans
and plant material.
The size distribution is strongly related to fishing
pressure and this may affect the life history of this fish
in the future.
26

Acknowledgements

Sponsoring
& Chance GOD
to present

Practical
& technical
Support
&
For Guiding
this study
Supervisory team 27

REFERENCES
•Amundsen, P. A., Gabler, H. M. & Staldvik, F. J. (1996). A new approach
to graphical analysis of feeding strategy from stomach contents data –
modiﬁcation of the Costello (1990) method. Journal of Fish Biology. 48,
607–614.

•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 Cichlid. Trans. Zool. Soc. Lond. 35, 47-114

•Chapman, L. J. (1995) Seasonal dynamics of habitat use by an air-
breathing catfish (Clarias liocephalus) in a papyrus swamp. Ecology of
freshwater fish. 4, 113-123

•Costello, M. J. (1990) Predator feeding strategy and prey importance: a
new graphical analysis. J. Fish Biology. 36, 261–263

•Hyslop, E. J. (1980) Stomach contents analysis: a review of methods and
their application. Journal of Fish Biology. 17, 411-429

•Lima-Junior, S. E & Goitein, R. (2001) A new method for the analysis of
fish stomach contents Acta Scientiarum Maringá. 23, 421-424. 28

Observations on the feeding habits of Clarias liocephalus in wetlands of Western Uganda

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