Download length weight relationship of hippocampus kuda

LENGTH WEIGHT RELATIONSHIP OF
HIPPOCAMPUS KUDA (BLEEKER, 1852) (FAMILY:
SYNGNATHIDAE), OFF THOOTHUKUDI WATERS,
SOUTHEAST COAST OF INDIA
T. Vaitheeswaran1 and V.K. Venkataramani2
Directorate of Fisheries Extension and Research (Fisheries),
Fisheries College and Research Institute Campus,
Thoothukudi - 628 008
ABSTRACT
Length-Weight relationship was studied in Hippocampus kuda collected from
the reef islands of Gulf of Mannar by SCUBA diving for a period of six months from January
2004 to June 2004. The slope value (b) estimated for H. kuda male was found to be 2.4259
and for females 1.7260. The regression equations calculated for female was Log W = 2.7044 + 1.7260 Log L and for male was Log W = -4.1805 + 2.4795 Log L. The correlations
coefficient was found to be significant (P<0.01). The significant difference between sexes of
the species 'F' value was at 1% level. The b value differed from the ideal cube law of '3' as is
with the case of length-weight relationship studied in this species else where. The slope
value was compared here could be very useful for comparison with the marine ornamental
species in other geographical locations.
Keywords: Hippocampus kuda - length-weight relationship - regression analysis- Population dynamics Gulf of Mannar - Southeast coast of India.
INTRODUCTION
The Gulf of Mannar biosphere Reserve
there are 21 reef islands extending between 08 47'N
78 12'E and 09 15'N 79 14'E from Tuticorin to
Pamban, Southeast coast of India. Among finfishes,
this marine province harbours 115 marine ornamental
species which finds a good place in domestic
aquarium and also for export (Venkataramani et.al.,
2004 a). The study of length-weight relationship of
H. kuda is having vital importance to fisheries
biologists as it serves three purposes. First, it
establishes the mathematical relationship between
the two variables, length and weight so that the
unknown variable can be readily calculated from
the known variables in practical fisheries problem.
Secondly, the relative condition can be estimated to
assess the general well being of the animals. Finally,
it is used in the estimation of potential yield per
recruit in the study of their population dynamics.
The actual relationship between length and weight
may part from the cubic value 3 and this may be due
Corresponding author1: E.mail: [email protected]
Senior Research Fellow, Directorate of Fisheries Extension and Research (Fisheries),
Fisheries College and Research Institute Campus, Thoothukudi-628 008.
2. Dean, Fisheries College and Research Institute Campus, Thoothukudi-628 008.
Tamilnadu J. Veterinary & Animal Sciences 8 (3) 119-125, May - June, 2012
119
Vaitheeswaran and Venkataramani
to environmental condition in which the animal lives
and also due to the physiological condition of the
animal.
Global trade in marine ornamental fish was
estimated to include more than 1,200 species from
54 countries (Bruckner, 2001). Estimates value the
global trade at US$ 28 to US$ 44 million annually
(Wood, 2001). Hippocampus kuda commonly called
as spotted seahorse coral fishes occur in good
numbers in the reef islands of Gulf of Mannar.
Seahorses (Genus: Hippocampus) are members of
the family Syngnathidae, which also includes pipe
fishes, pipe horses and seadragons. They are found
in-shallow, coastal, tropical and temperate waters
from about 450 S to 450 N (Louire et.al., 1999). Heather
and Keith (2009) have reported 46 species of
Hippocampus species (seahorse) from different
geographical areas and world oceans. Of the 46
species, H. kuda occurs in large numbers in the reef
islands of Gulf of Mannar, Southeast coast of India.
The precious of ornamental fishes such as clown
fish, butterfly fish, wrasse, damsel fish, rabbit fish,
scorpion fish and leather jackets were recorded in
large quantities in coral reef islands of Gulf of
Mannar. In 1995, it was conservatively estimated
that at least 20 million seahorses (more than 56 metric
tonnes) were caught for the traditional medicine
market. In response to a significant increase in
international demand, a target fishery for seahorses
along the southeast coast of India in the Gulf of
Mannar was started in 1992 (Lipton, 1998). Along
Ramnadu coast in TamilNadu, dried sea horse is used
as a medicine to arrest whooping cough in children
(Marichamy et.al., 1993).
Seahorses are exploited both as an
incidental catch (by-catch in trawl nets) and target
catch, for export. It is estimated that the global trade
in dried seahorses exceeded 70 tonnes in 2000. This
would amount to at least 24.5 million seahorses, using
an average of 350 seahorses per kilogram. The large
importers are Philippines, Thailand, China and Hong
Kong, while largest exporters are India. (Annual sales
120
at least 1.3 million seahorses or 3000 kg). India is
one of the largest exporters of dried seahorses
globally, exporting at least 3.6 tonnes (1.3 million
seahorses) annually (Vincent, 1996), and
contributes to about 30% of the global seahorse
trade. The global trade involves at least 20 million
seahorses a year. Presently, the commercial
exploitation of seahorses is being carried out from
TamilNadu and Kerala coasts (Anil et.al., 1999). The
value of the seahorses is quite high; the price of
dried seahorses in Hong Kong markets ranges from
Rs.11,500 to 45,000 (US $ 275 to 1200) per kg
depending on the species, quality and size.
The estimation of yield per recruit in
prediction models, and in the estimation of biomass
from length observations. Though the biodiversity
of ornamental finfishes are high in reef islands of
Gulf of Mannar, limited studies have been made on
population dynamics. The species is non-migratory
and has been recorded at a depth 10-15 meters in
the reef islands. As no work has been done on this
species thereafter from Thoothukudi coast, in the
present study, an attempt has been made to study
the length-weight relationship in H. kuda from the
reef islands of Gulf of Mannar, Southeast coast of
India.
Distribution and Habitat
Seahorses are exclusively marine generally
living in coastal habitats in shallow temperate and
tropical waters. They are distributed from C 500 north
to 500 south, while the highest diversity of species
occurs in the Indo-Pacific region (Lourie et.al.,
1999). While individuals of most seahorse species
were found in shallow waters (<30 m depth), many
have been found between depths of 40 and 100 m;
Hippocampus kelloggi were reported to depths of
90 m in Malaysian waters (Choo & Liew, 2003), and
Hippocampus minotaur and H. histrix were reported
from trawls at 100 m in Australia (Gomon, 1997).
Overall, the most commonly reported seahorse
habitat was seagrass, and mangroves were the least
reported (Lourie et.al, 1999). Temperate species
Tamilnadu J. Veterinary & Animal Sciences 8 (3) 119-125, May - June, 2012
Length weight.....
predominantly inhabited algae, while tropical
species were primarily found among coral reefs.
Some estuarine species, such as H. abdominalis,
H. capensis, H. kuda and H. reidi (Rosa et.al., 2002),
appear to tolerate fluctuating salinities, although
they could experience high rates of mortality during
freshwater flooding (Russell, 1994; Bell et.al., 2003).
employed to find out whether the regression
coefficients differed significantly between males
and females. The significance of difference in the
estimate of 'b' in pooled data of sexes from the
expected value of 3 (isometric growth) was tested
by the't' test as given by the formula.
t
= b-3/ Sb
MATERIALAND METHODS
b = regression coefficient of log transformed data.
Length-weight relationship study was
carried out in 173 specimens of Hippocampus kuda
(Fig 1) ranging from 86 to 135 mm in total length. A
total of 173 specimens were measured for the lengthweight relationship studies, which include 86
females and 87 males. The length of females ranged
from 93 to 135 mm and weight 4 - 10g. The males
were recorded in the length range of 86- 130 mm and
the weight ranged from 4 - 10g. The specimens were
collected from Van island and Kaswari islands 08º
50'N 78º 15'E and 08º 52'N 78º 15'E of Thoothukudi
coast by undertaking SCUBA diving. The diving
was made for six months (thrice in a month - once in
10 days) from January 2004 to June 2004.
Seahorse measurements were most
commonly given as height (ht) or standard length
(SL). Height was measured from the top of the
coronet to the tip of the straightened tail, while SL
was measured as head, trunk and tail length (Lourie
et.al., 1999). The total-length (TL) cannot be
measured in seahorses because they lack a caudal
fin; researchers who claimed to have measured TL
had probably recorded height. For the purposes of
this study, all SL measurements were converted to
Ht using metric conversions provided by
researchers and weight was recorded to the nearest
0.1 gm. Specimen where the tails are broken are
rejected. The length-weight relationship was
calculated by the method of least squares using the
equation of LeCren (1951): W= a. Lb , where W=
weight in fish, L total length of fish and 'a' and 'b' are
the exponents. The same in the logarithmic form
can be written as log W = log a + b log L. Analysis
of covariance (Snedecor and Cochran, 1967) was
RESULTS AND DISCUSSION
The maximum length recorded for this
species in the Kaswari islands of Gulf of Mannar
was 13.0 cm. The reported maximum length for this
species is 30 cm (Myers, 1991). The linear equation
was also fitted separately for males and females.
The correlation coefficient derived for the lengthweight relationship for males and females are given
in Table.1. The regression equations derived for both
the sexes are presented below Table.2.
Female Log W
= -2.7044 + 1.7260 Log L
Male Log W
= -4.1805 + 2.4259 Log L
The results showed significant between
sexes of the species and the 'F' values were found
to be significant at 1% level (Table.3). The observed
total length plotted against total weight males and
females are presented in Figure 2 & 3.
In fishes, generally the growth pattern
follows the cube law (Lagler Karl, 1952). Beverton
and Holt (1957) stated that major deviations from
isometric growth are rare. Such cubic relationship
for fishes will be valid when fish grows isometrically.
But in reality, the actual relationship between the
variables, length and weight, may depart from this,
either due to environmental conditions or condition
of fish (Le Cren, 1951). According to Martin (1949)
the value of the exponent 'b' in the parabolic
equations usually lies between 2.5 and 4. Depending
upon the deviation of 'b' values from '3' fishes can
be classified into three groups (i) b= 3 where the
Tamilnadu J. Veterinary & Animal Sciences 8 (3) 60-67, 119-125, 2012
121
Vaitheeswaran and Venkataramani
body form of fish remains constant at different
lengths (isometric) (Allen, 1938), (ii) b<3 when fish
becomes more slender as the length increases and
(iii) b>3 (allometric) when fish grows more stouter
with increase of length (Growner et.al., 1976). In
majority of the fishes the shape and density change
with increasing age, which often causes the
regression coefficient of weight of length, depart
from 3. The present observation is also in agreement
with the above view and it can be concluded that
the cube formula W = al3 will not be a proper
representation of the length-weight relationship for
H. kuda as the't' value is significantly different and
the growth is not isometric. Recently, the Ministry
of Environment and Forests, Government of India
through a Gazette Notification has included all
Syngnathids in Schedule I of the Wild Life
(Protection) Act, 1972. The Statistical analysis
revealed that the length weight relationship of the
fish when compared between the two stations
differed significantly.
species, it could be concluded that the slope value
is less than 3 for the both sexes of H. kuda.
Beverton and Holt (1975) suggest that the
value of 'n' is almost always near to 3. Several theories
have been advanced by a number of workers as to
what governs or influences the value of 'n' is
dependent and governed by the feeding behavior
of fish. Also the size of type of food consumed by
the fish seems to have influence on the value of 'n'.
for example, planktonivores, herbivores and
predators have different ranges for the value of 'n'
H. kuda are undergoing progressive changes in
shape and condition as they grow and consequently
affecting the regression of the log of weight and log
of length.
Choo, C.K., and Liew, H. C. (2003). Spatial
distribution, substate assemblages and size
composition of seahorses (Family
Syngnathidae) in the coastal waters of
Penninsular Malaysia. Journal of Marine
Biology Association., U.K. 83, 271-27
In fishes 'b' value is usually '3' in the lengthweight relationship, but during growth change in
specific gravity of body contour, morphological
changes due to age may also cause the coefficient
of regression of logarithm on logarithm of length, to
depart substantially from 3.0 (Rounsefell and
Everhart, 1953). Thus, comparing the slope of
Hippocampus kuda with other Syngnathidae
Growner, H. John., Rogelio, O., and Juliano (1976).
Length-weight relationship of pond raised
milk fish in the Philippines. Aquaculture., 7,
339-346
122
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Table 1
Statistics in the length-weight relationship of males and females of Hippocampus kuda
Sex
Male
Female
N
SX2, SY2, SXY
SX, SY
N
87
86
=
=
=
SX
178.7741
174.7733
SY
69.9825
69.0776
SX2
354.6052
355.3338
SY2
57.4341
56.6111
SXY
174.7434
140.6156
Number of fish
Sum of squares and product
Sum of logarithmic values of length and weight respectively.
Tamilnadu J. Veterinary & Animal Sciences 8 (3) 119-125, May - June, 2012
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Vaitheeswaran and Venkataramani
Table 2
Regression data for the length-weight relationship of males and females of Hippocampus kuda
Sum of Squares and Products
Sex
Male
Female
DF
B
SS
2
DF
87
86
X
354.6052
355.3338
XY
174.7434
140.6156
Y2
57.4341
56.6111
DF
b
2.4259
1.7260
86
85
: Regression freedom
: Regression Co-efficient
: Sum of Squares
Table 3
Test of Significance
Source of Variation
Deviation from individual
with in sexes
Difference between
Regression
Deviation from Total
Regression
DF
1
Sum of Square
412.0393
Mean Square
412.0393
171
411.9449
2.5437
172
823.9842
Observed F
161.9842
Significant at 1% level
Figure 1
Hippocampus kuda
124
Tamilnadu J. Veterinary & Animal Sciences 8 (3) 119-125, May - June, 2012
LOG WEIGHT IN G
Length weight.....
LOG LENGTH IN CENTIMETER
LOG WEIGHT IN G
Figure 2
Logarithmic relationship between length and weight of male Hippocampus kuda (BLEEKER, 1852)
LOG LENGTH IN CENTIMETER
Figure 3
Logarithmic relationship between length and weight of female Hippocampus kuda (BLEEKER, 1852)
Tamilnadu J. Veterinary & Animal Sciences 8 (3) 119-125, May - June, 2012
125