International Journal of Aquaculture 2013, Vol.3, No.3, 8
-
10
http://ija.sophiapublisher.com
8
Research Report Open Access
The Zooplankton Species Composition and Abundance in Ogun
River,
Abeokuta, Ogun State, Southwestern Nigeria
Benjamin Onozeyi Dimowo
Department of Aquaculture and Fisheries Management, College of Environmental Resources Management, Federal University of Agriculture, Abeokuta, Ogun
state, Nigeria
Corresponding author email:
benjamindimowo@yahoo.com
International Journal of Aquaculture, 2013, Vol.3, No.3 doi: 10.5376/ija.2013.03.0003
Received: 9 Jan., 2013
Accepted: 29 Jan., 2013
Published: 17 Feb., 2013
Copyright © 2013
Benjamin. This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use,
distribution, and reproduction in any medium, provided the original work is properly cited.
Preferred citation for this article
:
Benjamin, 2013, The Zooplankton Species Composition and Abundance in Ogun River, Abeokuta, Ogun State, Southwestern Nigeria, Vol.3, No.3 8-10 (doi:
10.5376/
ija.2013.03.0003)
Abstract
Investigation on the species composition and abundance of zooplankton in Ogun River, Abeokuta, Ogun state,
Southwestern Nigeria was carried out for a period of seven months (December, 2011-June, 2012), Using hand trawling method, 55 µm
mesh size plankton net was trawled horizontally ten times to capture zooplankton. The zooplankton samples were put into properly
labeled plastic containers and preserved in 4% formalin solution. A total of sixteen genera from five taxonomic groups were recorded
from Ogun River.
Cladocera
predominated both in terms of species composition and abundance. Five species of
Cladocera
was
recorded consisting of 31.25%.
Protozoa
and
Rotifera
recorded four species each consisting of 25%.
Copepoda
recorded two species
consisting of 12.5%, and
Ostracoda
with one species consisting of 6.25%. The low nature of zooplankton abundance and species
composition observed in this study must have been caused by the polluted nature of the water due to the anthropogenic activities
carried out around its shores The dominance of
Cladocera
in this river is similar to findings from River Echara and River Imo,
Southeastern Nigeria.
Keywords
Abundance; Composition; Southwestern Nigeria; Ogun River; Zooplankton species
Introduction
Zooplankton (singular zooplankter) is weakly swim-
ming microscopic animals that drift with water
currents (Microsoft Corporation, 2008; Encyclopaedia
Britannica, 2012). The zooplankton can be divided
into two categories which includes meroplankton and
holoplankton. Meroplankton (also known as temporary
zooplankton) is plankton that spend only part of their
lifecycle as plankton. Examples include: fish larvae,
insect larvae etc. Holoplankton (also known as
permanent zooplankton) is plankton that stays all their
life as plankton. Examples include:
crustacea
,
Protozoa
and
Rotifera
.
Zooplankton in association with
phytoplankton makes up the planktonic food supply
(
Encyclopaedia Britannica, 2012). In aquaculture,
small sized zooplankton e.g. rotifers etc. are often
used as food stock for fish larvae. In nature,
phytoplankton is fed on by zooplankton which is in
turn fed on by other higher animals such as larger
zooplankton, fin fish and shell fish etc. Almost all
aquatic life depends on the zooplankton at least at an
early stage of life. As a result of this dependence, any
abrupt change in the species composition and
abundance of zooplankton will affect all consumer
aquatic life with problems emanating from food
shortages which then lead to competition for available
food, cannibalism, stress and death. The importance of
the study of zooplankton hence cannot be undermined.
This study is therefore aimed at investigating the
species composition and abundance of Ogun River.
1
Results
Sixteen species belonging to five taxonomic groups
were recorded from Ogun River (Table 1). Five
species of
Cladocera
consisting of 31.25 by
composition, four species each of
Rotifera
and
Protozoa
consisting of 25% by composition, two
species of
Copepoda
consisting of 12.5% and one
species of
Ostracoda
consisting 12.5% by
composition were recorded. The abundance by group
taxonomy is presented in Figure 1 and Table 2.
Cladocera
was the highest with 48.18% followed by
Rotifera
(26.07%),
Protozoa
(13.86%),
Copepoda
(7.92%)
and
Ostracoda
(3.96%).
2
Discussions
The dominance of
Cladocera
has been observed by