| dc.description.abstract | Scylla serrata (Forskal) was sampled at
Kiwambale using madema traps while Thalamita crenata
(H. Milne Edwards) was sampled at Gazi using a scoop
net. The objectives of the study in both crabs were:
i) To determine the maturity stages of ovaries.
i i ) To determine the developmental stages of the
eggs.
iii)To find out the mlnimum slze at sexual
maturlty.
iv) To estimate fecundity.
v) To find the sex ratio of the crabs.
vi) To determine the breeding cycle.
The ovarian maturity stages were described as
stage o \/irgin / Resting, stage 1- Developing,
stage 2- well developed , stage 3- Ripe. In S.
serrata, maturity stage 0 was only obtained once
during the study - period, while stages 1-3 were
obtained in low numbers in some months. The most
abundant was maturity stage 2 which occurred in large
numbers in each sample. The devefopmental stages
of eggs were grquped into 10. Only five ovigerous S.
serrata were obtained which had their eggs in stages
1-3. The smallest ovigerous crab had a carapace
width (CW) of 139.75 mm and a crab of 77.1 mm (CW)
had an actlvated ovary in stage 1 of development. A
positive relationship exists between fecundity and
carapace width (t= 3.546; d. f. = 3; p
< 0.05) and egg mass weight (t = 3.251; d.f. = 3; P ~
(>.0::::,) respectively •. Jhile there lS no significant
relationship fecundity and egg size (t =
o . 029; d. f. = 3; P > 0 . .1). A test of homogeneity of
the blnomial of the sex ratio showed homoscedacity
(X2 = 14.615; d.f. = 13; P > 0.(5) and the
sex ratio did not differ from a 1:1 (""X2 = 0.776; d. f.
= 1; P > O. (2) . The variance test of homogeneity of
the binomial distribution in relation to Slze shows a
very significant difference (X2 = 32.83; d.f. 9', P
< 0.(5) . There was no significant difference when
the overall mean sizes for males and females were
compared using the t-test (t = 0.178; d.f. = 18; P >
0.(5) . The spawning season of S. serrata in Kenya
..
is from August to De2ember when ovigerous crabs were
obtained. ~ Inspite. of tflis, these crabs had active
,
ovarles (stages 1-3) throughout the sampllng period.
In Trie l ami ta c r erie t:e , ovarian maturity stage 2
"'las' the mos t abundan t throughou t _the samp ling period
while maturii;y stages 0, 1 and' 3 occurred at low
~"P" "
frequency during the samp 1i'f'lg period. All
developmental stages 1-10 were observed in oVlgerous
females but later developmental stages predominated
during the two breeding peaks in September and
The minimum size at sexu~l maturity
28 .9 mm (CW) . A positive relationshlp eXlsts between
..•
fecundity and carapace width (t 4.95; d.f. = 205; p
< 0.0(1) and egg mass weight (t 7.687; d ..f. = 205;
-XlVp
~ 0.0(1) respectively while there lS no significant
relatlonship between fecundity and egg size (t
0.3695; d . f . 205; p > 0.1) . The test of
homogeneity of the binomial distributlon of the sex
ratio showed homoscedasticy (X2 = 16.83; d.f. = 11; P
> 0.(5) and the overall sex ratio did not differ
from a 1:1 ( X 2 = 19.577; d.f. 1; P < 0.(5) . The
varlance test of homogeneity of the binomial
distribution In relation to the size shows a very
significant difference (X2 = 112.2; d.t. = 12; p <
0.001). There was no signlficant difference when the
overall mean sizes for males and females were
compared using t-test (t = 0.83; d. f . 24; p >
0.05) . This crab species breeds throughout
the year. But femal...e, crabs with carapace width 40.5
and 45.5 mm are actively breeding throughout the the
sampling period. The females had activated ovaries
throughout therefora they are continuous
breeders. | en |
