Current Research Journal of Biological Sciences 3(2): 175-179, 2011
ISSN: 2041-0778
© Maxwell Scientific Organization, 2011
Received: June 24, 2010
Accepted: August 10, 2010
Published: March 05, 2011
The Fecundity, Gonadosomatic and Hepatosomatic Indicies of Pellonula
Leonensis in the Lower Nun River, Niger Delta, Nigeria
T. Kingdom and M.E. Allison
Department of Fisheries Technology, Niger Delta University, Wilberforce Island,
PMB 071, Yenagoa, Bayelsa State, Nigeria
Abstract: The Fecundity, Gonadosomatic (GSI) and Hepatosomatic (HIS) Indicies of Pellonula leonensis were
studied from May 2001 to April 2002 in the Lower Nun River, Niger Delta. The absolute fecundity (F) ranged
from 348 eggs (Total length, TL = 5.70 cm) to 4075 eggs (TL = 6.30 cm) (with a mean of 2080.20±92.82 eggs).
However, there was no significant seasonal variation in the fecundity. Relative fecundity ranged from 61 to 655
eggs/cm or 834 to 2828 eggs/g with overall means (±S.E) of 343±14 eggs/cm or 1410±51 eggs/g. Body weight
was the best predictor for fecundity with a correlation value of 0.57. There was absence of significant variability
in the mean monthly and seasonal GSI and HSI values indicating that P. leonensis had an all year round
reproductive pulse in the Nun River.
Key words: Fecundity, gonadosomatic, hepatosomatic, Nun, Niger Delta, Pellonula
net with stretched mesh sizes of 8, 12 and 15 mm
classified as (small, medium and large gill net)
respectively each measuring 35m in length and 3 m in
depth with a surface area of 105 m2.
INTRODUCTION
Descriptions of reproductive strategies and the
assessment of fecundity are fundamental topics in the
study of the biology and population dynamics of fish
species (Hunter et al., 1992). Within a given species,
fecundity may vary as a result of different adaptations to
environmental habitats (Witthames et al., 1995). Reports
show that P. leonensis spawned throughout the year in
Volta Lake (Reynolds, 1974), Kainji Lake (Otobo, 1978),
Anambra River Ezenwaji and Offiah, (2003) and Lower
Nun River (Kingdom and Allison, 2009). LoweMcConnell (1987) also reported that this species matures
in one year. This paper therefore aims at providing
additional information on the reproductive P. leonensis in
the lower Nun River, Niger Delta; covering areas such as
Fecundity, Gonadosomatic and Hepatosomatic indicies.
Information provided will serve as a basis for rational
exploitation of P. leonensis in the Nun River.
Laboratory procedures: The total length of each
specimen was measured in centimeters on a transparent
plastic ruler. The fish was then placed on a top loading
balance, to measure its weight to the nearest 0.01 g and
the sexes separated by internal examination of the gonads
after dissection of the fish.
Fecundity: Fecundity (absolute fecundity), which is the
total number of eggs in the ovaries of a fish prior to
spawning (Bagenal, 1978) was estimated by direct
counting of spawnable eggs in the female ovaries
(Ezenwaji and Offiah, 2003). Counting was done under
the stereo microscope.
Relative Fecundity (RF) was obtained as the number
of eggs per unit length (cm) or the number of eggs per
unit weight (g) of fish. Scatter diagrams of fecundity
against total length, body weight, gonad weight and liver
weight were plotted using linear regression technique and
the best predictive equation for fecundity was computed
as logarithm transformation of the equation:
MATERIALS AND METHODS
This study was carried out in the fresh water reaches
of the Lower Nun River around Anyama Ijaw in Southern
Ijaw Local Government Area of Bayelsa State, Nigeria.
The Nun River is one of the numerous low land rivers in
the Niger Delta. The Niger Delta basin covers all the land
between latitude 4º15! N and 50º36! N and longitude 5º25!
E and 7º37! E.
Sampling was carried out for twelve calendar months
biweekly (May 2001 - April 2002) using three sets of gill
F = aXb (Bagenal, 1978)
i.e., Log F = Log a + b Log X
a = constant, b = exponent, X = Total length, Body
weight, Gonad weight, Liver weight.
Corresponding Author: T. Kingdom, Department of Fisheries Technology, Niger Delta University, Wilberforce Island, PMB 071,
Yenagoa, Bayelsa State, Nigeria
175
Curr. Res. J. Biol. Sci., 3(2): 175-179, 2011
Table 1: Monthly variation of mean fecundity and relative fecundity of P. leonensis in the Lower Nun River
Relative fecundity
--------------------------------------------------------------Mean egg
Mean
Month/Year
Range
Mean±S.E.
Sample Size
number/cm
egg number/g
13
373
1435
May 2001
1158-3152
2255.69±156.03abc
16
294
1227
Jun.
898-3126
1781.86±141.02c
Jul.
Aug.
2
390
1688
Sept.
1626-2824
2225±599abc
4
252
1142
Oct.
1106-1994
1464.25±204.63C
4
275
1436
Nov.
1176-2022
1472±193.39C
10
347
1437
Dec.
1411-3276
2089.4±194.95bC
5
258
1321
Jan. 2002
1192-1898
1439.6±121.78C
11
496
1952
Feb.
1960-4075
3087.36±227.15a
11
272
1044
Mar.
348-3864
1671.64±330.18C
5
436
1460
Apr.
2294-3916
2804.8±288.7ab
Season
Dry season
348-4075
2048.62±142.72
45
317
1389
Wet season
899-3916
2119.67±110.53
36
373
1453
Overall
348-4075
2080.20±92.82
81
343±14
1410±51
Different letters (a,b,c,d) in the same column indicate significance (p<0.0001)
eggs/g with overall means (±S.E) of 343±14 eggs/cm or
1410±51 eggs/g (Table 1).
Fecundity - total length, fecundity - body weight,
fecundity - gonad weight and fecundity - liver weight
relationships of P. leonensis in the Lower Nun River are
shown in Fig. 1, 2, 3 and 4, respectively. The relationships
of this population expressed in linear regression equation
are as follows:
Gonadosomatic Index (GSI): The Gonadosomatic Index
(GSI) was determined (King, 1995) as:
GSI = 100 (Gm/Tm)
where;
Gm = Mass of Gonad
Tm = Total mass of fish
Hepatosomatic Index (HSI):
The HSI was determined (Htun-hun, 1978) as:
F = -10.44 TL 2.90 (p<0.001; r = 0.54)
F = 1333.40 BW 0.95 (p<0.001; r = 0.57)
F = 2103.25 GW 0.05 (p<0.05; r = 0.09)
F = 4113.49 LW 0.17 (p<0.001; r = 0.23)
HSI = liver weight x 100
Body weight
The correlations were positive but low; body weight
had a better predictive value of 0.57 than total length
(0.54) gonad weight (0.06) and liver weight (0.23)
Mean monthly values were computed and plotted to
ascertain monthly variations. Means were also computed
for size classes and test of significant differences between
males and females tested.
Gonadosomatic Index (GSI): GSI values are shown in
Fig. 5. There was no significant variation (p>0.05) in the
mean GSI values between male (3.82±1.62) and female
(7.33±0.70) of P. leonensis. The highest GSI values were
attained in February for combined sex while the lowest
values were recorded in July. However, there was no
significant variation (p>0.05) in monthly and seasonal
GSI means. Also, there was no significant difference
(p>0.05) in the mean GSI value of different class sizes
(Table 2).
RESULTS
The range, mean monthly and seasonal fecundity are
given in Table 1. The mean monthly fecundity showed
four seasonal peaks. The highest mean absolute fecundity
of 3087.36±227.15 eggs was recorded in February. The
other peaks were observed in April (2804.8±288.87 eggs),
May (2255.69±156.03 eggs), September (2225±599 eggs)
and December (2089.4±194.95 eggs). But the overall
fecundity of P. leonensis ranged from 348 eggs (Total
length, TL = 5.70 cm) to 4075 eggs (TL = 6.30 cm) (with
a mean of 2080.20±92.82 eggs). However, there was no
significant seasonal variation in the fecundity. Relative
fecundity ranged from 61 to 655 eggs/cm or 834 to 2828
Heptosomatic Index (HSI): HSI values are shown in
Figure 6. There was no significant difference (p>0.05) in
the mean HSI values between male (1.14±0.78) and
female (0.87±0.04). The highest HSI values were obtained
176
Curr. Res. J. Biol. Sci., 3(2): 175-179, 2011
Fecundity
3.7
3.4
3.1
F=10.44TL2.90
r=0.54
2.8
2.5
0.62 0.64 0.66 0.68 0.7 0.72 0.74 0.76 0.78 0.8 0.82 0.84 0.86 0.88 0.9 0.92
Total length
Fig. 1: Relationship between fecundity total length of P.leonensis in the lower Nun River
3.7
F=1333.40BW 0.95
r=0.57
Fecundity
3.4
3.1
2.8
2.5
-2
-1
0
1
Body weight
Fig. 2: Relationship between fecundity and body weight of P. leonensis in the lower Nun water
3.7
F=2103.25GW 0.05
R=0.06
Fecundity
3.4
3.1
2.8
2.5
-3
-2
-1
Gonad weight
0
1
Fig. 3: Relationship between fecundity and gonad weight of P. leonensis in the lower Nun water
1978) for P. leonensis (140 to 4,900 eggs) in Kainji Lake
but different from the range given by Balogun (1987)
(6,322-30,623 eggs) in Lagos lagoon and Ikomi (1993)
(9,567-16,235 eggs) in Warri River. However, the mean
absolute fecundity obtained here is close to the 2,000
relatively large eggs reported by Reynolds (1969) but
different from the 896±477 eggs estimated by Ezenwaji
and Offiah (2003) and 13,635 eggs by Balogun (1987)
in Anambra River and Lagos Lagoon, respectively.
The observed low correlations of the fecundity - total
length and fecundity - gonad weight correspond well with
in February (5.07±4.18) for combined sex while the
lowest values were recorded in September (0.19±0.10).
However, there was no significant variation (p>0.05) in
the monthly and seasonal HSI values as well as the mean
HSI values of different class sizes (Table 3).
DISCUSSION
In this study, the range of absolute fecundity of 348
eggs (Total length, TL = 5.70 cm) to 4, 075 eggs (TL =
6.30 cm) agrees with the range reported by Otobo (1977,
177
Curr. Res. J. Biol. Sci., 3(2): 175-179, 2011
3.7
Fecundity
3.4
3.1
2.8
2.5
-3
-2.8
-2.6
-2.4
-2.2
-2
-1.8
-1.6
-1.4
-1.2
Fig. 4: Relationship between fecundity and liver weight of P. leonensis in the lower Nun water
GSI
15
10
5
0
May-01 Jun
Jul
Aug Sept Oct Nov Dec Jan-02 Feb Mar Apr
Months
HIS
Fig. 5: Mean monthly gonadosomatic index (GSI) of P.leonensis in the lower Nun River
6
5
4
3
2
1
0
May-01 Jun
Jul
Aug Sept Oct Nov Dec Jan-02 Feb Mar Apr
Months
Fig. 6: Mean monthly hepatosomatic index (HSI) of P.leonensis in the lower Nun River
Table 2: Mean GSI values of different size classes of P. leonensis in
the lower Nun River
Size class
Range
GSI Mean+S.E.
Sample Size (n)
3.5-4.5
0.18-1.63
0.89±0.17
9
4.5-5.5
0.04-384.62
5.47±2.65
145
5.5-6.5
0.17-83.68
5.30±0.58
203
6.5-7.5
0.15-38.17
6.15±1.17
35
7.5-8.5
0.17-3.41
1.70±0.40
9
8.5-9.5*
1
*: Sample with < 2 specimens were not included in analysis
weight relationship is the only one available on this
species.
In the exponential formula linking fecundity to total
length, the exponent ‘b’, with the numerical value 2.90
obtained for the lower Nun River population of
P. leonensis, is within the range 2.3-5.3 calculated for a
variety of species by Bagenal (1978). However, the value
is higher than the 1.82 calculated for the P. leonensis
population of Anambra River (Ezenwaji and
Offiah, 2003)
Table 3: Mean HSI values of different size classes of P. leonensis in
the lower Nun River
Size class
HSI Mean ± S. E. Sample Size (n)
Range
3.5-4.5
0.43±0.11
9
0.17-1.06
4.5-5.5
1.74±1.27
145
0-184.62
5.5-6.5
0.62±0.04
203
0.58-2.56
6.5-7.5
0.69±0.08
35
0.11-1.85
7.5- 8.5
0.69±0.10
9
0.34-1.18
8.5- 9.5*
1
*: Sample with < 2 specimens were not included in analysis.
GSI and HIS: The absence of significant variability in
the mean monthly and seasonal GSI and HSI values
confirm the fact that P. leonensis has an all year round
reproductive pulse. This was also the observation of
Ezenwaji and Offiah (2003) in their study of Anambra
River.
CONCLUSION
the earlier findings of Ezenwaji and Offiah (2003) for this
species in Anambra River but the best predictor of
fecundity observed in this study is contrary to the total
length they reported. The result on fecundity - liver
P. leonensis has an all year round reproductive pulse
with a mean fecundity of 2080±92.82 eggs while body
weight was the best predictor of fecundity in the Lower
Nun river populations.
178
Curr. Res. J. Biol. Sci., 3(2): 175-179, 2011
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ACKNOWLEDGMENT
We sincerely thank Mr. Hanson Uyi for his assistance
in identifying specimens and providing keys.
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