Capture and
handling stress affects the endocrine and ovulatory response to exogenous
hormone treatment in snapper, Pagrus auratus (Bloch & Schneider)
J.J. Cleary, S.C. Battaglene, W. Pankhurst-2002
Aquaculture
Research, 33(11): 829-838
Abstract:
Sexually mature female hatchery-reared
snapper, Pagrus auratus (Bloch & Schneider) were captured from
sea cages by handline and injected at first capture (control) or 24h after
capture, transport and subsequent confinement (delayed injection) with
either saline, luteinizing hormone releasing hormone analogue, human
chorionic gonadotropin, or 17α-hydroxyprogesterone. Blood was sampled
before hormone treatment and again after 168h, and fish were checked daily
for ovulation. Plasma levels of 17β-estradiol (E2), testosterone (T),
17 α, 20 β dihydroxy-4-pregnen-3-one (17,20 β P) and cortisol
were determined by radioimmunoassay. The ovulatory response was assessed
from the proportion of fish ovulating, ovulation volume, egg quality and
fertility. A delay in injection resulted in significantly lower plasma
E2 and T levels in response to hormone treatment, smaller ovulation
volumes, and poorer egg quality than in control fish. The results are
consistent with the generally inhibitory effects of stress on reproduction
in fish, and confirm the requirement to treat fish with hormones designed to
induce ovulation, as soon as possible after capture and disturbance.