Reproductive cycle and human chorionic gonadotropin-induced ovulation
in hatchery reared Japanese catfish Silurus asotus
N.
Kumakura, K. Sakai, F. Takashima-2003
Fisheries
Science, 69(3):
495-504
Abstract :
The
annual reproductive cycle, including the first maturity of ovarian
development and plasma levels of testosterone (T) and estradiol-17 beta (E2), was examined in female Japanese catfish Silurus asotus reared
under natural conditions. In addition, the possible period that final oocyte
maturation and ovulation can be induced by human chorionic gonadotropin
(hCG) injection were investigated. Results showed that female Japanese
catfish matured 1 year after hatching under reared conditions. The beginning
of vitellogenesis was in March and ovarian development and plasma T and E2
levels peaked in June. Thereafter, the gonadosomatic index gradually
decreased to October and regression of oocytes at the tertiary yolk globule
stage was observed. Female Japanese catfish could be induced to final oocyte
maturation and ovulation by hCG treatment during the period from June to
September. In addition, the fertilization rates were relatively high and
stable during this period. These results suggest that yearling female
Japanese catfish can be used as brood stock for seed production. This is the
first study to investigate the annual reproductive cycle in Japanese
catfish. These data will provide useful information regarding brood stock
management and seed production.
(Department of Aquatic Bioscience, Tokyo University
of Fisheries, Minato, Tokyo 108-8477, Japan, Tel: 81-596-58-6411,
Fax: 81-596-58-6413, Email: naokik@fra.affrc.go.jp)