International Journal of Aquaculture, 2016, Vol.6, No.6, 1
-
10
8
curema
in northeastern
region in Brazil.
Liza carinata
spawning season in Khuzestan coastel waters was reported in
December to March by (Hashemi et al., 2013), while the spawning period of
Liza subviridis
in Indian was recorded into
two period from September to October and from February to March (Rahman et al., 2015). Variation in the spawning
season for
Liza carinata
may be a result of environmental or population related factors (Stoumbound et al., 1994) or
may vary from species to species, differing from one population to another population of the same species and may vary
year after year within the same population (Adams, 1980; Hashemi et al., 2013). Based on these results, all maturity
stages of
Liza carinata
observed for the population of Suez Bay, this reflects that Suez Bay is the spawning location for
this species.
Monthly changes in the concentrations of circulating sex hormones and their importance for reproduction have been
reported for several species of teleost. Studies have shown that annual fluctuations of hormones related to reproductive,
feeding and growth cycles in fishes. Annual rhythm of hormones closely related to factors such as temperature,
environment, species of fish, length of day and gonadal sex steroids (Pavlidis et al., 2000).
In a variety of species, the level of serum E2 begins to increase in accordance with the appearance of active vitellogenic
oocytes, and reaches the highest levels at tertiary yolk stage oocyte in the ovary, and sharply declines in fish with
postvitellogenic and atretic ovaries. (Smith and Haley, 1988; Silvers et al., 1993; Kumar et al., 2015) reported an
increase in plasma E2 levels once spawning commences and remains high throughout the period of oocyte growth.
(Sen et al., 2002) reported that concentration of plasma testosterone T in Indian major carp
Labeo labeo
rohita
is
expected to be high when it is no longer needed for aromatization, while T levels during postvitellogenic stage exhibited
a quick decline in this fish, coinciding with the fall of plasma E 2 concentration. A sudden drop in the plasma E 2 level
in
Labeo rohita
from vitellogenic to postvitellogenic stage may be explained in terms of switching off the aromatise
(CYP19) activity as the oocytes progressed to maturation. Almost a similar profile of E 2 has been reported during the
transition from vitellogenic to maturational stage in rainbow trout (Fostier et al., 1983). This drop in circulatory E 2
levels probably reduces the intensity of sex steroid feedback, allowing the occurrence of hypothalamus - mediated
gonadotropnes surge, which is required for the development of oocyte maturational competence. Increments in ovarian
gonadosomatic index and oocyte development are associated with changes in 17β - estradiol levels in circulation (Lee
and Yang, 2002).
The slight increase of testosterone T levels during oocyte development may be related to its role as precursor of E 2
synthesis. At high concentration, T might also be involved in hepatic vitellogenin synthesis (Rinchard et al., 1993). The
sudden peak was measured when most fish were in final maturation (stage V), an effect of the release of testosterone T
into the plasma when this was no longer needed for aromatization. This acute rise in testosterone indicates that oocytes
are fully mature and ready to ovulate (Kobayashi et al., 1989; Adebiyii et al., 2013).
This result clarifies that sexual hormone before maturity has fluctuation and affect by different seasonal and
environmental condition (Allen and Joseph, 2006).
It is known that the role of sex steroids in controlling the maturation cycle in teleost especially during spawning times is
altered by environmental or hormonal manipulation, and this has both theoretical and practical relevance (Flammarion
et al., 2000; Sehafii, 2014). Based on the results of this study seem, sex steroid hormones during spawning are changed,
and the change of seasons and the environment is very effective.
5 Conclusions
This study cared about studying the reproductive pattern of female of
Liza carinata
from Suez Bay which represented a
good spawning zone for this species, from the previous results spawning season considered as a long winter spawning
season so over - fishing in this period affected the population number, from this point management should regulate
fishing in this period to save fish-recruiting number and maintain the species abundance.
