International Journal of Marine Science 2016, Vol.6, No.22, 1-14
4
The sample was also identified for sexes into male and female (ovigerous and non ovigerous). Sex ratio was
determined by the criteria of shape and size of the abdominal flaps (Litulo, 2005). The male has cylindrical
abdominal flap with first pair of pleopods modified into gonopods and female has semicircular to circular
abdominal flap depending on maturation period to which eggs are attached (Qureshi and Saher, 2012).
Comparative abundance of ovigerous females was worked out to establish the reproductive period of these crabs.
3 Data Analysis
3.1 Measurement of allometric growth, population structure, abundance and size class
Samples were sorted on the basis of both sexes (male and female). For allometric growth measurements only 100
samples were taken randomLy in each month from the sample collected in ten quadrates from each sites. Carapace
length (C.L), Carapace width (C.W), abdominal width (Ab.W), abdominal length (Ab.L) and chelae length (Ch.L)
were measured, starting from 0.1mm with the help of centimeter scale under the Nikon binocular microscope. The
abdominal width (Ab.W) and abdominal length (Ab.L) were started to measure from 5
th
and 6
th
abdominal
somites. Allometric growth pattern was studied by plotting the C.L, C.W, and Ab.L, Ab.W, and CH.L relationship
using the regression method of MINITAB 11.0 software.
After measurements the sample was divided into the separate size class from smallest to largest size and the result
was depicted in the form of histogram plotted for showing trend of population structure and size class of each
sample.
3.2 Measurement of Sex Ratio
The Chi- squire (X
2
) test was employed to study of sex ratio of studied crab, where O is the observed value, and E
is the expected (1:1) value.
(X
2
) =
∑
(O-E)
2
/ E
3.3 Fecundity
For the determination of fecundities of
D. blanfordi
crab, eggs were counted of different size ovigerous females of
the same species. The methodology included the careful removal of eggs from the pleopods of ovigerous females
in 150 mL of water contained in a beaker with the help of fine brush. The eggs were carefully separated by tensing
out with the help of forceps and needle and then shake well in a beaker in order to obtain their uniform
distribution in water column. A counting tray was used for counting eggs. The procedure involved the placing on
the counting tray and a 1 mL sample of water placed for the counting eggs. An ordinary 3 mL disposable plastic
syringe was used for transferring the aliquots of egg samples to the tray Siddiqui and Ahmed, 1992). The egg size
(µm) of each female sample was measured by the ocular micrometer under the microscope. The relationship
between size of ovigerous female (C.W) and their number of eggs was also studied.
4 Results and Discussion
Dotilla blanfordi
was recorded throughout the year. Total 3868 individuals of
D. blanfordi
were recorded from two
sites (Clifton and Korangi Creek). There were 2151 individuals of
D. blanfordi
(1357 male and 794 female
individuals) sampled from Clifton whereas 1717 individuals of
D. blanfordi
were sampled from Korangi Creek (957
male and 766 female individuals). At Clifton the highest number of
D. blanfordi
were recorded in August (464 m
-2
),
332 male individuals m
-2
and 132 female individuals m
-2
whereas at Korangi Creek the highest number of
individuals were recorded in February (202 m
-2
), 95 m
-2
male individuals and 106 m
-2
female individuals (Figs. 1 and
2 respectively). At Clifton C.W of male individuals ranged from 1.5 to 10 mm (5.67 + 1.71 SD) and female
individuals ranged from 2.3 to 8.5 mm (5.46 + 1.06 SD) whereas at Korangi Creek the C.W of male individuals
ranged from 2.1 mm to 12.6 mm (6.48 + 2.00 SD) and of female individuals from 2.3 mm to 10.9 mm (5.7160 +
1.0772 SD) (Tables 1 and 2; Figs. 3 - 6).
