Fecundity and Egg Size of Grey-Eel Catfish Plotosus canius (Hamilton, 1822)
from the Coastal Waters of Kampong Telok, Negeri Sembilan Peninsular Malaysia
M. Aminur Rahman
Despite the vast researches on catfish species in Malaysia, Plotosus canius, the grey- eel catfish which is primarily found throughout the coastal seas of Malaysia has been neglected. No single published work on aspects of biology, especially its reproductive biology is available. In this study, fecundity and egg size of P. canius from coastal waters of Kampong Telok, Malaysia were studied. A total of 32 gravid females were used in the study. The mean fecundity of the female having a length of 50.28 cm and a wet body weight of 680 g was estimated to be 865 eggs. Fecundity was found to show positive relationship with total length (r = 0.379), body weight (r = 0.494) and gonad weight(r = 0.336) but the values were not statistically significant (p>0.05). Egg diameter (mm) among the various length groups showed a polymodal distribution but the differences were statistically significant (p>0.05). This study being the first attempt to gather information of P. canius in Malaysia would form a basis for future works of this catfish.
to cite this article:
B.I. Usman, S.M.N. Amin, A. Arshad and M. Aminur Rahman, 2013. Fecundity and Egg Size of Grey-Eel Catfish Plotosus canius (Hamilton, 1822)
from the Coastal Waters of Kampong Telok, Negeri Sembilan Peninsular Malaysia. Asian Journal of Animal and Veterinary Advances, 8: 348-354.
Received: July 02, 2012;
Accepted: July 23, 2012;
Published: February 11, 2013
Plotosus canius (Hamilton, 1822) commonly known as Grey- eel catfish
belonged to family Plotosidae. It is amphidromous and demersal (Riede,
2004) and dwells primarily in marine environment, mostly coastal seas; but
sometimes found in lower parts of rivers in freshwaters or brackish waters (Kuiter
and Tonozuka, 2001). P. Canius is native to Asia and Australia. It
can be found in countries such as Malaysia (Mohsin et
al., 1993), Bangladesh (Rahman, 1989), Australia
(Hoese et al., 2006), India (Talwar
and Jhingran, 1991), Fiji (Seeto and Baldwin, 2010),
Laos (Kottelat, 2001); Papua New Guinea (Kailola,
1987), Thailand; Vietnam (Nguyen and Nguyen, 1994),
Singapore, Indonesia, Brunei, Cambodia, Myanmar, Philippines and Sri Lanka (Fischer
and Bianchi, 1983). In Malaysia, the fish is commonly known as Sembilang
or Gemang. It is highly priced (RM 15-20 kg-1) and mostly
sold fresh in the markets (Mohsin and Ambak, 1996).
Fecundity is the term frequently used to express the capacity of fish in terms
of eggs production and has been defined by Gupta and Gupta
(2006) as the number of ripening eggs in the ovaries of female before
spawning. Knowledge of fish fecundity is very important because it has
much relevance to fish population studies. It has also been studied to establish
relationship with length, weight and ovary weight, to provide relative index
of density dependent factors affecting the population size and also to develop
numerical relationship between egg production and recruitment (Amin
et al., 2009; Sarker et al., 2002).
Information on fecundity is also very important in order to evaluate a fish
for its commercial potentialities (Lawson, 2011). Fecundity,
size/length at sexual maturity, size of egg, sex ratio and gonadosomatic index
are very important aspects of life history theory formulation (Mekkawy
and Hassan, 2011). To the best of our knowledge, information on fecundity
and egg size of P. canius in Malaysia has not yet been reported. Such
information is very crucial in conservation and management of the stock and
in assessing variations among populations of the fish in various locations.
This study therefore, provides the first information on fecundity and egg size
of the fish from Malaysian coastal waters. Therefore, the results from this
study would serve as an input parameter for further detail studies on this fish
species in Malaysia.
MATERIALS AND METHODS
Fish sampling and laboratory preparation: About 30-35 samples of fresh
fishes were collected during full moon from the fishermen of the coastal region
of Kampong Telok Negeri Sembilang for a period of four months (from February
to May, 2012). After collection, samples were immediately preserved in ice box
and transported to the Marine Biotechnology Laboratory, Institute of Bioscience,
Universiti Putra Malaysia. In total, 32 gravid female fishes were used for the
four months study period. Before dissecting, the body weight for each fish was
measured to the nearest gram (g) using digital electronic balance; and total
length was measured to the nearest millimeter (mm). The fish was then dissected
and the ovary was taken out and immediately preserved in 5% formalin in labelled
vials for subsequent analyses.
Fecundity: Fecundity studies were performed for both ovary lobes together
by washing the preserved ovaries and dried using blotting paper and finally
weighed to the nearest 0.001 g. For each ovary, sub-samples were collected from
three positions (fore, middle and rear), each sub-sample was then measured to
the nearest 0.001 g and the number of eggs in each individual was then counted.
Fecundity was estimated using the following formula described by Gupta
and Gupta (2006):
||Total weight of ovary
|W1, W2 and W3
||Weights of each sub-samples
|N1, N2 and N3
||Egg counts in each sub-samples
Egg size: Measurement of the egg size was done by measuring the egg
diameter in millimeter (mm) using KEYENCE digital microscope (VHX-500). For
each female fish, fifteen eggs were collected from each of the anterior, middle
and posterior region of the ovary and the diameter measured.
Statistical analysis: A scatter diagram was used to determine the relationship
between fecundity and total length, fecundity and body weight as well as fecundity
and gonad weight. All statistical analyses were considered significant at 5%
(p<0.05) and were done using SPSS computer software version 20. Mean values
were compared using one way analysis of variance (ANOVA) followed by Duncans
multiple range test.
Fecundity: A total of 32 gravid female specimens of P. canius measuring
from 41.23 to 60.00 cm and weighing from 439 to 906 g were used for the study
(Table 1). Fish with a mean total length of 50.28 cm and total
weight of 680 g produced an average of 865 eggs and has 9 eggs per unit of ovary
weight. Maximum fecundity of 1276 was observed in fish with a total length and
body weight of 60.00 cm and 777.00 g, respectively.
The relationships between fecundity and total length, fecundity and body weight
and fecundity and ovary weight were analyzed using models of linear and exponential
regression. The results showed that no significant relationship (p>0.05).
These results are summarised in Fig. 1. Figure
1 shows the relationship between fecundity and total length. A linear regression
provided the best fit curve with a positive result. The relationship is not
significant at 5% (p>0.05). A linear regression was also obtained for the
relationship between fecundity and body weight (Fig. 2). Analysis
of the relationship between fecundity and ovary weight also revealed a positive
linear relationship (Fig. 3). The relationship also found
not significant at 5% (p>0.05).
Egg size: Measurement of egg growth was done by measuring Egg Size (ES).
In this study, ES was ranged from 3.71 to 5.94 mm. The highest ES was found
in fish between 52- 55 cm total length, while the lowest was recorded in fish
between 58- 61 cm (Fig. 4).
|| Average counts of fecundity and egg size at various length
ranges of P. canius
|Values are Mean±SD
|| Linear relationships between fecundity and total length of
|| Linear relationships between fecundity and body weight of
|| Linear relationships between fecundity and ovary weight of
|| Variations in egg diameter among various lengths of P.
The pattern in the ES frequency distribution of P. canius showed polymodal
distribution (Fig. 5). The difference between the means at
various ranges of length was found to be statistically significant (p<0.05).
The present study represents the first attempt to examine the fecundity and
egg size of P. canius from the coastal waters of peninsular Malaysia.
These parameters are very important to understand the life history traits, breeding
biology and ontogenic development which will ultimately facilitate for the development
of aquaculture management and conservation of this important catfish species.
The mean fecundity of 32 females of P. canius was 865 eggs. The maximum
number of ova is estimated to be 1276 in females that ranged from 58- 61 cm.
While the minimum numbers of eggs were 476 in females of 55-58 cm in length.
However, Khan et al. (2002) reported higher fecundity
values from 1228 to 1867 in this fish having the size ranges from 36.5-40.5
to 65.2-69.2 cm, respectively. From their findings, older fishes were found
to produce fewer ova per unit weight of ovary than younger fish. It is somewhat
surprising that in this study, the opposite trend is found.
|| Egg diameter-frequency distribution of P. canius female
with length (a) 40-43 mm, (b) 43-46 mm, (c) 46-49 mm, (d) 49-52 mm, (e)
52-55 mm, (f) 55-58 mm and (g) 58-61 mm
However, this result may be explained by the fact that differences in the environmental
factors such as availability of food, ambient water temperature and population
densities could contribute to this. More research in this direction is suggested.
Increase in fecundity with increase in total length and body weights were observed.
Similar reports were shown by Khan et al. (2002)
in P. canius, Rahman et al. (2002) in
Liza parsia and Sarker et al. (2002) in
Mystus gulio. However these findings can not be extrapolated to all P.
canius population in Malaysian waters, because this research is the preliminary
in such direction, as such further work needed to be conducted to establish
A characteristic of life history of species is that is diverse is the size
of egg in that species and this could determine the reproductive patterns and
life history traits by mode of energy allocation to either single embryos or
brood output (Clarke et al., 1985). The polymodal
nature of egg size frequency distribution in almost all the length ranges predicted
that the species may spawn once or more over a long period of season. These
findings could be supported by the works of Ahmed and Haque
(2007) which reported a long period of spawning in this fish; between April-July.
Khan et al. (2002) mentioned P. canius also
have a long spawning period between April-August. However, in Malaysia future
work is suggested for this to be investigated.
In conclusion, the present study provides some basic information on fecundity
and egg size of the fish from waters of Peninsular Malaysia. A number of possible
future studies using the same fish from different coastal waters of Malaysia
are apparent and believed to be a good fishery management measures for P.
The present study is part of a Ph.D research work. Funded by the Universiti
Putra Malaysia under Research Universiti Grant Scheme (RUGS) with the Grant
No. 01-01-11-1120RU, Vot. No. 9199729. The help of Mohammad Hazmadi Bin Zakariya
of the Department of Aquaculture, Universiti Putra Malaysia for the fish sampling
and laboratory preparation is gratefully acknowledged. Also, we would like to
extend our appreciations to all the staff and students of Marine Biotechnology
Laboratory, Institute of Bioscience, Universiti Putra Malaysia who are too numerous
to mention for their help and support during the laboratory work.
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