Environmental Engineering Reference
In-Depth Information
have the speciic knowledge of the growth pattern
of a freshwater teleost ish,
Channa punctatus
(Bloch), inhabiting the polluted waters of
Hussainsagar lake, which is situated in between
the twin cities of Hyderabad and Secunderabad
in Andhra Pradesh, India.
Results and Discussion
The parabolic and logarithmic relationship
between length and weight of
Channa punctatus
from Hussainsagar lake is shown in Figs.
16.1
and
16.2
. When the observed length (cm) was
plotted against the observed weight (gm), an
exponentialcurvewasobtainedasseeninFig.
16.1
,
but when both the variables were plotted against
each other in their logarithmic forms, a straight
line was obtained. The value of the correlation
coeficient (
r
) was calculated to be 0.991 indicating
a high degree of correlation between the length
and the weight. The regression equation derived
using the recorded data is represented by log
W
= −1.485 + 2.621 log
L
, and its arithmetic trans-
formation is
W
= −0.03273
L
.
2.621.
Since the value of regression coeficient
(
b
= 2.621) is less than “3” and not equal to 3, this
indicates that the ish from the Hussainsagar
water body shows deviations from the cube law.
Spencer (
1871
) and Allen (
1938
) have suggested
that for an ideal ish following the cube law, the
value of “
b
” remains constant at “3,” but Hile
(
1936
) and Martin (
1949
) advocated that the
value of “
b
” usually ranges between 2.5 and 4.0,
and in a majority of cases, “
b
” is not equal to 3 as
the ish normally do not retain the same shape or
body pattern throughout their life span (Lecren
1951
; Rounsefell and Everhart
1953
; Ali et al.
2000
). The value of
b
< 3 represents that the ish
Methods
The present study was conducted on nearly 200
specimens of
Channa punctatus
(Bloch) ranging
from15to30cminlength.Forconveniencethe
ishes were divided into eight groups according
to their length. The ishes were collected from
ive different stations of Hussainsagar lake using
a cast net. The ishes were then brought to the
laboratory where they were weighed after
soaking water with the help of a blotting paper.
Then the statistical relationship between length
and weight of ishes was established using the
following formula:
(
)
WaL
b
=
Lecren1951
where
W
= weight of the ish,
L
= length of the
ish,
a
= constant, and
b
= regression coeficient.
The length-weight relationship is usually
expressed in its logarithmic form as
(
)
Log
Wa bL
=
log
+
log
Lecren
1951
.
The correlation coeficient (
r
) was calculated by
using the following formula:
∑
∑
XY
XY
r
=
2
⋅
2
where
X
= log length and
Y
= log weight.
The condition factor (
K
) was determined by
using the following formula:
W
×
100
3
K
=
L
where
L
= length in cm and
W
= weight in gm.
Fig. 16.1
Parabolic relationship between the length and
weight of
Channa punctatus
from Hussainsagar lake
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