Studies on fecundity and Gonadosomatic index
of Schizothorax plagiostomus (Cypriniformes: Cyprinidae)
Muneera Jan 1, Ulfat Jan 2& G. Mustafa Shah 3
1,2,3 P.G. Department of Zoology, University of
Kashmir, Hazratbal, Srinagar, Jammu & Kashmir 190006,
India
1 janmuneera@ymail.com (corresponding author), 2 ulfatjan@yahoo.com,3 gmustafashah@yahoo.com
Abstract: The present investigation deals with the
assessment of fecundity and gonadosomatic index (GSI)
of Schizothorax plagiostomuscollected from the river Jhelum, Kashmir. The mean value of fecundity was estimated as 14599 (SD 9219.7) eggs with
a mean total length of 34.340 (SD 6.86) and a mean total body weight of 440.60
(SD267.62). The relationship of fecundity with other parameters such as total
length, total weight, ovary length and ovary weight were found to be linear and
the value of correlation coefficient (r) was 0.965, 0.961, 0.933 and 0.972
respectively. The highest value of GSI was recorded in the month of May 12.56
(SD1.81).
Keywords: Allometricrelationship, fecundity, spawning season, Schizothorax plagiostomus.
doi: http://dx.doi.org/10.11609/JoTT.o3269.5375-9 | ZooBank: urn:lsid:zoobank.org:pub:F21EC3E7-EB48-4204-88AE-6484DF9298FC
Editor: Neelesh Dahanukar, IISER, Pune, India. Date of publication:26 January 2014 (online & print)
Manuscript details: Ms #
o3269 | Received 26 July 2012 | Final received 18 November 2013 | Finally accepted
07 December 2013
Citation: Jan, M., U. Jan & G.M. Shah (2014).Studies on
fecundity and Gonadosomatic index of Schizothorax plagiostomus(Cypriniformes: Cyprinidae). Journal of Threatened Taxa6(1): 5375–5379; http://dx.doi.org/10.11609/JoTT.o3269.5375-9
Copyright: © Jan et al. 2014. Creative
Commons Attribution 3.0 Unported License. JoTT allows unrestricted use of this article in any medium,
reproduction and distribution by providing adequate credit to the authors and
the source of publication.
Funding: The first author is a PhD
research scholar registered in P.G. Department of Zoology, University of
Kashmir. This study was supported only by departmental research grant.
Competing Interest:The authors declare no competing interests.
For figures,
tables -- click here
Understanding reproductive behaviour of
fishes is not only important for elucidating the basic biology of the fishes but
it can also help in their management and conservation. The term ‘fecundity’ denotes the egg
laying capacity of a fish or the number of ripe eggs produced by a fish in one
spawning season. Knowledge of
fecundity is also an important aspect in stock size assessment, stock
discrimination (Holden & Raitt 1974) and rational
utilization of stock (Morales 1991) and in explaining the variation of
population as well as to make efforts for increasing the amount of fish
yield. Thus, studies on
reproduction behavior (fecundity) of fish are
important and a basic requirement for improvement of and effective fishery
resources management and conservation (Marshall et al. 2003; Grandcourt et al. 2009).
Schizothorax plagiostomus Heckel,is one of the most important commercial food fishes of Kashmir. But the decline of Schizothorax population in the water bodies of Kashmir is taking place due to many
factors especially habitat destruction, over fishing, competition for food and
breeding grounds from exotic carps, water pollution, etc. These complex factors have altered the
landscape and water flow which in turn have reduced
the fish stock in water bodies by affecting fish migration, spawning and
nursing grounds. The present study is aimed to determine the fecundity and its
relation with total body length, total body weight, ovary length & ovary
weight) which are useful in increasing the yield of fish species, stock
management and assessment in any water body. Hence, the present study will be useful
in understanding the relationship of fecundity with above mentioned body
parameters and thus serve as a tool for better management of this resource.
Materials and Methods
Fishes for the present study were procured
from three different sites of the river Jhelum (74–750E &
33.5-–34.50N)—Zero bridge, Chattabal and Kadalbal pampore—using cast net, every month. For fecundity estimation 30 specimens
were collected and analysed and for GSI estimation 5 fish specimens were
collected 3 times in a month. The study was carried from November 2010 to
October 2011. After noting down
morphometric parameters (body length and body weight) of the fishes in fresh
conditions, mature gravid fishes were dissected. The ovaries were removed and wiped with
blotting paper to remove moisture and then preserved in 5% formalin solution
for 24 hours so that the eggs would swell up for easy calculations. The fecundity of the fish was calculated
using the gravimetric method (Simpson 1959) as well as the volumetric method (Kandler & Pirwitz 1957). The total number of eggs per gonad was
obtained, i.e., absolute fecundity of fish. Relative fecundity was determined by the
ratio of total number of eggs per unit weight or length of fish. Its relation with various body
parameters such as body length, body weight, ovarylength and ovary weight was determined by using log transformation of power
law,
Y = aXb
i.e., Log Y = log a + b
log x
Gonadosomatic index (GSI) expressed according to de Vlaming(1982) method for assessing the development of gonads and was calculated as:
GSI = Gonad weight/body
weight *100.
Results
Ovary
structure: The ovaries of Schizothorax plagiostomus was a bilobedfleshy structure occupying a large part of the abdominal cavity. The two lobes of the ovary were almost
uniform in size. The middle portion
of the ovary was broader than the anterior and posterior region. The eggs were fully ripe and yellowish
in color in the mature ovary. It has been found that the shape, size,
and color change in different stages of maturity.
Relationship
between fecundity (F) and total length (Tl): Table 1 provides data for the two
variables i.e, fecundity and total length..According to it the number
of ova varied from 3437 for a fish of length 26.2cm to 34800 for a fish of
length 45.3cm. The relationship between fecundity and the total length can be
expressed as:
Log F = -0.976 + 3.30 log TL
Where F= fecundity and TL= total length in
cm.
The number of eggs contained was more or
less directly proportional to the total length of the fish body. The regression
equation was found to be linear (Fig. 1). The correlation coefficient (r) was 0.96 (p<0.001)
which corresponds to a very strong positive correlation and is highly
significant.
Relationship
between fecundity (f) and total body weight (bw): Table 1 provide data for fecundity and
total body weight. The number of ova varied from 3437 for a fish of weight
176.5g to 34800 in the fish weighing 1150g.The relationship between fecundity
and the total body weight can be expressed as:
logF =
1.26 + 1.09 logBW
Where F= fecundity and BW =body weight.
The relationship between fecundity and
total body weight was found to be linear and highly significant with the
correlation coefficient (r) equal to 0.961 (Fig. 2).
Relationship
between fecundity (f) and ovary weight (ow): Table 1 provide data for the two variablesi.e, fecundity and ovary weight. The weight of ovary
ranged from 10.11g to 120g in fish weighing 176.5g to 1150g. Fecundity varied
from 3437 in an ovary of weight 176.5g to 34800 in the ovary weighing
1150g.The relationship between fecundity and the ovary weight (Fig. 3) can be
expressed as:
logF =
2.69 + 0.917 logOW.
Where F= fecundity and OW = ovary weight.
Regression analysis showed that there is a
significant relationship (p<0.01) between the numberof eggs in the ovary i.e., fecundity and the weight of ovary. The number of eggs per female increased
with increasing ovary weight. The correlation coefficient was found to be
0.972.
Relationship
between fecundity (f) and ovary length (ol): Table 1 provides data for fecundity and
ovary length. The ovary length
ranged from 9.4–22.8 cm in fish ranging from 25.2–45.3 cm. The
number of ova varied from 3437 to 34800 in fish ranging in length from
26.2–45.3 cm. The
relationship between fecundity and ovary length (Fig. 4) can be expressed as:
logF =
1.45 + 2.37 logOV.
Where F= fecundity and OL = ovary length.
A significant linear relationship was
observed between fecundity and the ovary length, i.e., fecundity increased with
the ovary length. The correlation
coefficient(r) was found to be 0.933.
Length
weight relationship: Table 1 provide data for two variables,
i.e., total length and total weight of fish. The data showed a positive
correlation between the two variables. Fig. 5 shows relationship between these two variables. The correlation
coefficient was found to be 0.992. The relationship between total fish length
and total body weight can be expressed as:
Log BW = 2.9781 TL - 1.9819 (SE=0.0315; P<0.05).
Where BW = body weight, TL = total length and SE =
standard error.
Gonadosomatic Index (GSI): The
GSI value ranged from 1.87 to 12.66. The maximum GSI value 12.56 was found in
the month of May while minimum value 1.87 was obtained in the month of July.GSI exhibited variation in different months of the
year (Fig. 6). The GSI value
decreased during may to July which suggests that the
fish has completely spawned.
Discussion
Fecundity has been defined as the number
of ripening eggs prior to spawning (Bagenal 1978) and
is a main factor governing the size of a year class of a population. Nikolskii(1965) stated that “fecundity is a specific feature
that arises during the evolution of a new species adapted to a certain
environment and is directed towards the continuance of the species”.
In the present study, the number of eggs
was found to increase linearly with the increase in total length, body weight, ovary length and ovary weight. These findings are supported by the findings of previous
workers, Jhingran (1968), Raina(1977), Pathani (1981), Sunder (1984), Islam & Hossain (1990), Hussain et al.
(2003), Mohan (2005), Offem et al. (2008), Bahuguna & Khatri(2009). All the relationships
between fecundity and total length, body weight, ovarylength and ovary weight found to be highly significant (p< 0.005). Significant relationships between
fecundity and these variables were also reported by Das & Singh (1969), Hussain et al. (2003), Bahuguna& Khatri (2009), Alam & Pathak(2010).
The value of correlation coefficient ‘r’
in the present study indicate that among the above four parameters studied,
closest correlation of fecundity was observed with the ovary weight (r=0.972)
followed by total body length (r=0.966), body weight(r=0.961) and total ovary
length (r=0.933). Similar results were reported by Bahuguna& Khatri (2009).
Length weight relationship of this fish species is in
accordance with the model of LeCren (1951). It was observed that fish shows allometric pattern of growth (b<3). Similar results were
reported by Goel et al (2011) for schizothorax richardsonii and by Sundar (1985) for schizothorax curvifrons. It
was also observed that fecundity varies with fish size and it generally increase with increase in body weight and body length.
The gonadosomaticindex (GSI) was found in range from 1.87 to 12.56 in this study. The maximum GSI value was found in the
month of May (12.56) which indicated the maximum
gonadal growth. A sharp drop in the
GSI value had taken place in July (1.87) which might
have been caused by spawning. The
fish thus spawn during spring season although the gonads were fully mature in
the winter season but in a dormant phase because of severe winter and spawned
only on return of favorable exteroceptivefactors in spring season (Malhotra 1970; Jyoti et al 1972; Sunder 1984).
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