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European Journal of Applied Sciences – Vol. 11, No. 2
Publication Date: April 25, 2023
DOI:10.14738/aivp.112.13840. Nana, T. A., Kengne, T. J. E., Songmo, B.-L., Tendonkeng, F., & Efole, E. T. (2023). Dietary Ethology and Adaptability of Parachanna
Obscura (Gunther, 1861) Post-larvae Co-cultured with Zooplankton. European Journal of Applied Sciences, Vol - 11(2). 563-578.
Services for Science and Education – United Kingdom
Dietary Ethology and Adaptability of Parachanna Obscura
(Gunther, 1861) Post-larvae Co-cultured with Zooplankton
Nana, Towa Algrient
Department of Forestry,
Faculty of Agronomy and Agricultural Sciences,
University of Dschang, BP: 222 Dschang Cameroon
Kengne, Tonssi Joseph Emmanuel
Department of Animals Productions,
Faculty of Agronomy and Agricultural Sciences,
University of Dschang, BP: 222 Dschang Cameroon
Songmo, Berlin-Léclair
Department of Animals Productions,
Faculty of Agronomy and Agricultural Sciences,
University of Dschang, BP: 222 Dschang Cameroon
Tendonkeng, Fernand
Department of Animals Productions,
Faculty of Agronomy and Agricultural Sciences,
University of Dschang, BP: 222 Dschang Cameroon
Efole, Ewoukem Thomas
Department of Forestry,
Faculty of Agronomy and Agricultural Sciences,
University of Dschang, BP: 222 Dschang Cameroon
ABSTRACT
Controlling the food preferences of fish post-larvae after resorption of the yolk sac
as well as their stocking density are the determining factors for the success of fry
production. In order to contribute to the production of African snakehead fish,
Parachanna obscura fry, a study was carried out from May 8 to June 17, 2022 at the
Applied and Research Farm and at the Ichthyology and Applied Hydrobiology
Laboratory of the University of Dschang-Cameroon. To this end, 180 post-larvae of
P. obscura with an average weight of 1.05±0.18 g and an average total length of
4.97±0.46 cm were introduced into a zooplankton culture medium. The post-larvae
were divided into three (3) treatments D1, D2 and D3 corresponding respectively
to stocking densities 0.25; 0.75 and 1.25 ind/l. Each treatment was repeated four
times. Zooplankton data were collected every 7 days and fish samples for gut
content analysis every 10 days. At the end of the trial, the results related to the
survival and cannibalism rates did not show any significant difference between the
treatments. Nevertheless, the lowest rate of cannibalism (5.33%) was recorded in
D3 (density of 1.25 ind/l). Analysis of the contents of the digestive tract indicates
that food preferences decrease when fish stocking density is high. Thus, the post-
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European Journal of Applied Sciences (EJAS) Vol. 11, Issue 2, April-2023
larvae of P. obscura at low stocking density feed preferentially on copepods and
ostracods (Io = 100%), although the presence of rotifers and cladocerans is noted.
P. obscura post-larvae are selective in their choice of prey and size. This choice
depends on the environmental conditions (number of prey and predators present).
Keywords: diet, stocking density, post-larvae, Parachanna. obscura, zooplankton.
INTRODUCTION
In Africa, despite a freshwater fish species biodiversity and geo-climatic diversity, the
development of sustainable aquaculture is struggling to take shape (Mbéga, 2013). However,
several species remain very little known to be valued and sometimes are threatened with
extinction due to overexploitation, environmental degradation and disruption of the
community balance by introduced species (Beverton, 1992). Faced with this situation, the
production and conservation of these species through domestication are a better prospect for
ensuring their sustainability. Moreover, research institutes and international organizations are
now advising the domestication of endogenous species for the future development of
aquaculture.
In Cameroon, the hydrographic network is well populated with a great diversity of species (613
species of fresh and brackish water) (Vivien, 2012), however only a few species of fish
Labeobarbus batesii, Clarias jaensis, Campylomormyrus phantasticus, Mormyrops anguilloides,
Mormyrus macrophtalamus, Mormyrus tapirus etc have been the subject of a domestication
study (Zango et al. 2016; Tchouante et al. 2020; Tiogue et al. 2010, 2022). Despite these
advances, other species that can contribute to an increase in productivity are very little valued.
This is the case of the African snakehead fish Parachanna obscura, one of the 3 endogenous
species present in the five agro-ecological zones of Cameroon. It grows rapidly (2g/day), the
fry can reach a weight of 1kg after 4 to 5 months in ponds (De Graaf et al. 1996; Bolaji et al.
2011).
A resistant species that can live in stressful conditions, Parachanna obscura is highly valued due
to its tasty flesh and few bones, with high nutritional value and economic potential (Kpogue et
al. 2013). According to Bonou and Teugels (1985), strict carnivorous Parachanna obscura
requires a high protein intake for its growth and its breeding in captivity requires the use of
live prey since its diet in captivity is not yet mastered. In aquatic ecosystems, there is a diversity
of living prey serving as food for this species, including zooplankton. The latter plays a key role
in the trophic chain. It is also used as a basic food and without equivalent in a semi-intensive
system during the pre-fattening or fattening of fish (Lubzens et al. 2001; Piasecki et al. 2004;
Arimoro, 2006). Several works have been the subject of the introduction of zooplankton in fish
farming in order to increase the rate of growth and survival according to the density of larvae
at 4 weeks (Guerrin, 1988; Jha et al. 2006). This work has shown that the larvae initially mainly
consume rotifers and the Nauplian stages of copepods; older fish (from three to four weeks old)
prey on adult forms of Copepoda and Cladocera (Boyd, 1982). Despite this apparent potential,
very few studies have been conducted not only on the stocking density of Parachanna obscura
but also on their feeding behavior on zooplankton species in a semi-controlled environment.
To this end, a better knowledge of the live prey (rotifers, water fleas, copepods and ostracods)
solicited by post-larvae of Parachanna obscura in a rearing environment is essential to consider
the production of fry of this species. The general objective of this work is to contribute to the
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Nana, T. A., Kengne, T. J. E., Songmo, B.-L., Tendonkeng, F., & Efole, E. T. (2023). Dietary Ethology and Adaptability of Parachanna Obscura (Gunther,
1861) Post-larvae Co-cultured with Zooplankton. European Journal of Applied Sciences, Vol - 11(2). 563-578.
URL: http://dx.doi.org/10.14738/aivp.112.13840.
improvement of the production of Parachanna obscura fry through the study of the load density
and the preference of live prey in post-larvae. Specifically, to assess the effects of loading
density on:
- Survival and cannibalism;
- The dynamics of zooplankton groups (Rotifers, Cladocerans, Copepods and ostracods) present
in the culture medium;
- The contents of the digestive tract of Parachanna obscura.
MATERIALS AND METHODS
Period and Presentation of the Study Area
The study was conducted from May 08 to June 17, 2022 at the Application and Research Farm
and at the Ichthyology and Applied Hydrobiology laboratory of the Faculty of Agronomy and
Agricultural Sciences of the University from Dschang. Located in the agro-ecological zone of the
high plateaus of Western Cameroon, Department of Menoua and district of Dschang (5°17'0''
to 5°44' LN and 10°04' to 10°11' LE (Fig. 1) The city of Dschang is subject to a tropical type
climate characterized by 2 alternating seasons (monomodal climate). Precipitation varies
between 1800 mm/year with an average temperature of 20°C.
Fig. 1: Location of the study area
Animal Material
One hundred and eighty (180) post-larvae of Parachanna obscura with an average weight of
1.05±0.18 g and an average total length of 4.97±0.46 cm was used (Fig. 2). They came from the
natural environment where they were captured and calibrated by fish farmers. These post- larvae were packaged and transported in 20-litre cans (perforated above) to the study site
where they were acclimatized for 14 days in a concrete tank.