Reproductive biology and histological features of female thread fin bream Nemipterus japonicus in Gulf of Suez, Egypt

Reproductive biology and histological features of female thread
fin bream Nemipterus japonicus in Gulf of Suez, Egypt
Amal M. Ramadan
National Institute of Oceanography and Fisheries,
Red Sea and Suez & Aqaba Gulfs Branchs
P. O. Box 182, Suez, Egypt
E-mail: [email protected]
Received 23th May 2010, Accepted 27th July 2010
Abstract
In the present study the value of the exponent in the length-weight relationship for females was 2.975 which
indicate that this species has isometric growth. The length at which 50% females were mature was 11.1 cm. The GSI
increased gradually with ovarian development where recorded maximum value 4.3 in May and minimum value 0.5
in February. Fecundity increased at the rate of 2.8971, 1.0199 and 0.8135 times of the total length, weight of fish
and weight of ovary, respectively. Positive correlation was observed between fecundity and total length, weight of
fish and weight of ovary. The stages of ovarian development and reproductive season of female thread fin bream
Nemiptrus japonicus in Suez Gulf was investigated by using the gonado somatic index (GSI) and ovarian histology.
The stages of oocyte development were classified into eight developmental stages (Perinuleolus, cortical alveolus,
oil droplet, yolk globule, migratory nucleolus, prematuration, and maturation) based on histological characteristics.
Oocytes development appears to be apparently spawned more than one time during the prolonged spawning season
(summer). Therefore N. japonicus belong to synchronus groups. The stage of the most developed oocyte was used to
classify the stage of ovarian maturation. Oocytes in the perinucleolus, cortical alveolar and oil droplets stages were
present in ovaries throughout the fishing season in the Gulf of Suez. So, the spawning season of Nemiptrus
japonicus is prolonged one which extends from May to September in Suez Gulf.
Keywords: Nemiptrus japonicus, length-weight relationship, length at first sexual maturity, fecundity, ovarian
histology, reproductive biology, spawning season.