Induction of spawning of
cultured greater amberjack (Seriola dumerili) using GnRHa implants
C.C. Mylonas, N. Papandroulakis, A. Smboukis, M.
Papadaki, P. Divanach-2004
Aquaculture, 237(1-4): 141-154
Abstract:
The objective of the current study was to examine the
possibility of maturing Mediterranean greater amberjack (Seriola dumerili)
in culture at two different facilities in Greece and inducing spawning using
gonadotropin releasing-hormone agonist (GnRHa) implants. Males in both
stocks (n=8) were in spermiating condition in mid June, though sperm
motility was low ranging between 5% and 30%, while motility duration ranged
between 2.1 and 2.5 min. Females of the first stock (n=4) at the same
time had ovaries with either primary oocytes or early vitellogenic oocytes
at advanced stages of atresia, indicating a failure in oogenesis. On the
contrary, the only female of the second stock contained oocytes at all
stages of oogenesis, including early final oocyte maturation (FOM; oocyte
diameter 650 µm). Implantation with a GnRHa implant induced the first spawn
about 36 h later. In the absence of another spawn, a gonadal biopsy was
taken 15 days later, indicating the existence of more oocytes at post
vitellogenesis and some with almost complete lipid droplet coalescence. A
second GnRHa implantation at this time resulted in consecutive egg releases
after 36 h, 4 and 5 days, with fertilized eggs only at 36 h and 5 days. The
study underlines the existence of important reproductive dysfunctions of
greater amberjack in captivity, and demonstrates that GnRHa implants can be
used for the induction of multiple spawns of viable eggs.
(Hellenic Center for Marine Research, Institute of
Aquaculture, P.O. Box 2214, Iraklion, Crete 71003, Greece, e-mail: mylonas@imbc.gr)