Biodiversity,Environment

and Functional Biology

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Department of Zoology

University of Lucknow, Lucknow

Our environment, our future

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© Department of Zoology, University of Lucknow, Lucknow

ISBN: 978-93-84935-15-3

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Studies on Length-weight relationship, Length-length relationship and Condition factor

of Sperata aor from river Ganga

Aafaq Nazir and M. Afzal Khan

Section of Fishery Science & Aquaculture, Department of Zoology,

Aligarh Muslim University, Aligarh – 202 002 (U.P), India

khanmafzal@yahoo.com

ABSTRACT

The present study was undertaken to assess length-weight relationship, length-length

relationship and condition factor of Sperata aor (Hamilton, 1822), a freshwater catfish

of the family Bagridae. The fish samples were collected from April 2013 to March 2014

from river Ganga. The length-weight relationships of S. aor showed negative allometric

(b=2.89) pattern of growth. The coefficient of determination (R2) suggested that length

and weight are highly correlated. The length-length relationships were highly

significant (R2 > 0.99, p < 0.001). The mean condition factor was 0.534, inferring that

fish are in poor condition.

Keywords: Length-weight relationship, length-length relationship, condition factor,

Sperata aor.

1. INTRODUCTION

The long whiskered catfish, Sperata aor (Hamilton, 1822) is a freshwater bagrid widely

distributed in India, Pakistan, Nepal, Bangladesh and Upper Myanmar. It is highly priced

delicious catfish and well preferred because its flesh contains only a few bones (Talwar and

Jhingran, 1991).The length-weight relationship is very important for proper exploitation and

management of the population of the fish species. The length-weight relationship is the most

significant biological parameter which is being extensively used to provide information on

growth (isometric or allometric) and give insight into the health of a fish and its community

(Okgerman, 2005 and Ritcher, 2007).

In fishery biology, length-weight relationships are useful for limited sample sizes to convert

the growth-in-length equations to growth-in-weight, for use in stock assessment models and

to estimate stock biomass (Binohlan and Pauly, 1998; and Ecoutin et al., 2005).The length-

length relationship

is of great importance for comparative growth studies, therefore the length-length relations of

species under various environmental conditions should be known to make the results more

reliable when making comparisons between populations (Moutopoulos and Stergiou, 2002).

In fishery science, the condition factor is used to compare the relative well being or

plumpness of fish. Condition factor may be used to detect variations in fish condition, which

may vary with food abundance and the reproductive stage of the stock (King, 1995). It has to

be regularly checked to assess the physiological characteristics of the fish (Bister et al., 2000;

Froese, 2006 and Rypel and Richter, 2008). Therefore, the objective of the present work was

to study the length-weight relationship, length-length relationship, and condition factor of S.

aor inhabiting river Ganga.

2. MATERIALS AND METHODS

Fish samples were collected monthly across river Ganga from April 2013 to March 2014.

Fishes were sampled using gill nets and cast nets of various mesh sizes. Fish samples were

transported to the laboratory and were identified according to Talwar and Jhingran (1991)

and Jayaram (1999). Total Length (TL), Fork Length (FL) and Standard Length (SL) of all

fish samples were measured to the nearest 0.1 cm with a digital calliper. Body weight was

recorded as Total Weight (TW) including gut and gonads to the nearest 0.1 g with a digital

balance.

The length-weight relationship is estimated by using the equation W= aLb, where W is the

total weight in grams, L is the total length in centimetres (Ricker, 1973). The statistical

relationship between TW and TL were calculated using the equation: Log W = Log a + b

Log L; Where, W is the total weight of fish in grams, a is the intercept (constant), b is the

regression coefficient (slope), and L is the total length of fish in centimetres.

TL vs SL; SL vs FL; and FL vs TL relationships were calculated by linear regression analysis

(Hossain et al., 2006).

The condition factor K (Fulton, 1904) was calculated from the equation: K= W/L3 × 100

Where, W is the total weight of fish in grams, and L is the total length of fish in centimetres.

All calculations and statistical analyses were performed using MS-Excel and SPSS (Version

16.0).

3. RESULTS

A total of 135 specimens ranging from 16.3 cm to 85.2 cm in total length and 25 g to 2950 g

in total weight were examined for this study. Length-weight relationship parameters are

shown in Table 1 and Figure 1. The value of b (2.89) indicated negative allometric growth

pattern for S. aor. The coefficient of determination (R2) was 0.997 suggesting that two

variables; length and weight are highly correlated.

Table 1: Parameters of length-weight relationship of S. aor collected from river Ganga

N Total length(cm) a b 95% CI of b R2

Min Max

135 16.3 85.2 -2.091 2.890 2.804-2.976 0.997

N, total number of samples; a, intercept; b, slope; CI, confidence interval; R2, coefficient of

determination

Figure1. Length-weight relationship of S.aor

Relationships between TL vs SL; SL vs FL; and FL vs TL are shown in Table 2 and Figures

2, 3 and 4.

y = 2.890x - 2.091R² = 0.997

0

0.5

1

1.5

2

2.5

3

3.5

4

0 0.5 1 1.5 2 2.5

Table 2: Parameters of length-length relationships of S. aor collected from river Ganga

Equation N a b R2

SL=a+bTL 135 0.140 0.762 0.994

FL= a+bSL 135 -0.279 1.098 0.993

TL= a+bFL 135 0.441 1.183 0.995

TL, total length; SL, standard length; FL, fork length; N, total number of samples; a, intercept; b,

slope; R2, coefficient of determination

Figure 2. Relationship between total length and standard length of S.aor

Figure 3. Relationship between standard length and fork length of S.aor

y = 0.762x + 0.140R² = 0.994

0

10

20

30

40

50

60

70

0 20 40 60 80 100

Sta

ndar

d l

ength

(cm

)

Total length (cm)

y = 1.098x - 0.279R² = 0.993

0

10

20

30

40

50

60

70

80

0 20 40 60 80

Standard length (cm)

Fork

len

gth

(cm

)

Figure 4. Relationship between fork length and total length of S.aor

The value of condition factor (K) for all fish samples were determined from the average lengths and

weights. The size-wise variation in condition factor is shown in Figure 5.

Figure 5. The size-wise variation in condition factor of S. aor

The condition factor (K) was plotted against the mean total length of the fish and it was observed that

the highest ‘K’ was at 32.9 cm and lowest at 85.2 cm. The mean condition factor of S. aor was found

to be 0.534 suggesting that fish are in poor condition.

4. DISCUSSION

In fish, the variable weight is considered to be the function of the variable length. If the fish retains

the constant shape and specific gravity throughout life then the value of ‘b’ would be exactly 3 and

fish will exhibit isometric pattern of growth (Weatherely and Gill, 1987; and Wootton, 1990). In the

present study value of ‘b’ for S. aor was 2.89 indicating negative allometric growth pattern and that

y = 1.183x + 0.441R² = 0.995

0

10

20

30

40

50

60

70

80

90

0 20 40 60 80

Fork length (cm)

To

tal

len

gth

(cm

)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 10 20 30 40 50 60 70 80 90

Mean total length (cm)

Condit

ion

fact

or

(K)

the fish exhibit increment in weight at much smaller rate than length increment of the fish. Thus, it

may be suggested that the condition of the target population of S. aor may not be good (Froese,

2006). Khan et al. (2011) studied length-weight relationships of 9 fish species and reported positive

allometric (b=3.24) growth pattern for S. aor (N=184) from the same river. Sani et al. (2010) studied

length-weight relationship of 14 Indian freshwater fish species from Betwa and Gomti rivers and

reported the value of ‘b’ 2.98 (N=30) and 3.02 (N=28) respectively. The observed differences in the

values in above mentioned studies may be due to the environmental differences, less number of

samples examined, or may be due to large number of smaller samples. Analysis of the length-length

relationship suggested that S.aor shows non-isometric growth pattern. The length-length relationship

values were highly significant (p< 0.001) with coefficient of determination (R2) for all the length-

length relationships being > 0.99. The proportion of total, fork and standard length of fish may be

affected by a number of factors like growth stage, food availability, health, condition and

preservation techniques (Gaygusuz et al., 2006). However, these factors were not taken into account

in the present study. The condition factor may vary when average weight of the fish is not increasing

in direct proportion to the cube of its length (Wootton, 1990). The mean condition factor in present

study was 0.534, inferring that fish are in poor condition which may be due to overpopulation,

disease, lack of food supply or spent condition. The findings of this study could be useful for the

formulation and implementation of scientifically sound fishery management policies.

5. ACKNOWLEDGEMENTS

The authors are thankful to the Chairman, Department of Zoology, Aligarh Muslim University,

Aligarh, India for providing necessary facilities for the study. We are also grateful to the

Science and Engineering Research Board, Department of Science and Technology, New Delhi for

funding the study and providing financial assistance to the first author (SR/SO/AS-40/2012).

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