Da. Methven et al., SEASONAL REPRODUCTION AND PLASMA-LEVELS OF SEX STEROIDS AND VITELLOGENIN IN ATLANTIC HALIBUT (HIPPOGLOSSUS-HIPPOGLOSSUS), Canadian journal of fisheries and aquatic sciences, 49(4), 1992, pp. 754-759
Atlantic halibut (Hippoglossus hippoglossus) collected off Newfoundlan
d first mature at about 80 cm fork length (FL) for males and about 115
-120 cm FL for females. Captive Newfoundland halibut did not release m
ilt or eggs or have detectable levels of estradiol-17-beta or 11-ketot
estosterone until exceeding 80 cm (males) and 115-120 cm (females). Es
tradiol-17-beta and testosterone increased to highest levels in female
s during gonadal recrudescence before spawning. Lower levels were obse
rved in spawning fish. Vitellogenin (VTG) levels were highest in spawn
ing fish. A sudden drop in estradiol-17-beta and VTG preceded release
of the first batch of eggs. Estradiol-17-beta, testosterone, and VTG f
luctuated with release of successive batches of eggs. Male halibut sta
rted to mature during fall and early winter, as indicated by increased
testosterone and 11-ketotestosterone and abdominal swelling. Milt was
first released in january and February when testosterone and 11-ketot
estosterone were near maximum levels. Hence, rising levels of plasma s
ex steroids and VTG in fall indicate that reproductive activity is und
erway 1-2 mo before any noticeable swelling of the abdomen. Individual
maturing halibut can be sexed by rising levels of estradiol-17-beta a
nd VTG (females) and 11-ketotestosterone (males) in late fall and earl
y winter.