International Journal of Aquaculture 2013, Vol.3, No.3, 8
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10
http://ija.sophiapublisher.com
9
many authors among which are Ude et al. (2011) from
Echara River, Southeastern Nigeria and Ogbuagu and
Ayoade (2012) from Imo River, Etche.
Table 1 Number of species in each taxonomic group of
zooplankton sampled (December, 2011 – June, 2012)
Taxonomic group
Total number of species Percentage (%)
Cladocera
5
31.25
Rotifera
4
25.00
Protozoa
4
25.00
Copepoda
2
12.50
Ostracoda
1
6.25
Total
16
100.00
Figure 1 Taxonomic group abundance of zooplankton in River
Ogun
Table 2 Abundance of zooplankton in River Ogun (December 2011 – June 2012)
Zooplankton groups
Genus/ Species
Genus/Species
Abundance (N)
Zooplankton group
abundance
Percentage zooplankton group
abundance (%)
Cladocera
Polyphemus
Ceriodaphnia
Scapholeberis
Bosmina
Eurycerus
33
10
35
38
30
146
48.18
Rotifera
Platyias
Cupelopagus
Keratella
Testudinella
11
33
23
12
79
26.07
Protozoa
Amoeba
Oikomonas
Paramecium
Blepharisma
12
7
15
8
42
13.86
Copepoda
Diaptomus
Canthocamptus
21
3
24
7.92
Ostracoda
Cypridiopsis
12
12
3.96
Total
303
303
100.00
The low zooplankton abundance and diversity
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. There is
therefore need to regulate the amount of pollutants
discharged into the river so as to avoid total ecological
collapse and extinction of the populace.
3
Materials and Methods
3.1
Geography of the River
Ogun State is a state in South-western region of
Nigeria. It borders Oyo and Osun states to the North,
Lagos State to the South, the republic of Benin to the
west and Ondo State to the east. Abeokuta is the
largest city and capital of the state (NBS, 2012). River
Ogun (Figure 1) is one of the main rivers in the
southwestern part of Nigeria with a total area of 22.4 km
2
and a fairly large flow of about 393 m
3
secG
1
during
the wet season (Oketola et al., 2006). It has
coordinates of 3°28′E and 8°41′N from its source in
Oyo state to 3°25′E and 6°35′N in Lagos where it
enters the Lagos lagoon (Ayoade et al., 2004). There
are two seasons in Ogun river basin, a wet season
between April and October and a dry season from
November to March. Mean annual rainfall ranges
from 900 mm in the north to 2 000 mm towards the
south. The estimates of total annual potential
evapo-transpiration have been put between 1 600 mm
and 1 900 mm (Bhattacharya and Bolaji, 2010). The
water is used for agriculture, transportation, human
consumption, various industrial activities and domestic
purposes. Along its course, it constantly receives
effluents from breweries, slaughterhouses, dyeing
industries, tanneries and domestic wastewater before
finally discharging to Lagos lagoon (Ayoade et al.,