Plasma steroid hormone profiles and reproductive biology of the epaulette shark, Hemiscyllium ocellatum

Examination of the reproductive biology of the oviparous epaulette shark, H emiscyllium ocellatum, was conducted on a wild population. Male sharks were found to reach maturity at between 55-60 cm total length (TL) and female s harks mature around 55 cm TL. Blood samples collected from mature male and female sharks were analyzed for sex steroid hormones to examine seasonal ho rmone patter ns. Plasma samples were analyzed via radioimmunoassay techniqu es with female samples measured for estradiol, progesterone, and androgen c oncentrations, and male samples measured for androgen concentrations. Male androgen concentrations showed a single broad peak from July to October wit h maximum hormone concentrations (60 ng/ml) occurring in August. Male andro gen concentrations were lowest in December-February (<20 ng/ml), and appear ed to correlate with reproductive activity and water temperature. Female an drogen concentrations were an order of magnitude lower than those for males and showed peaks in June (6 ng/ml) and December (8 ng/ml). Estradiol conce ntrations in females peaked during the months of September-November (0.5 ng /ml) coinciding with the egg laying period. Progesterone concentrations ran ged up to 0.5 ng/ml prior to the mating season. Observations of ova size an d egg production showed eggs develop in pairs and ova are ovulated at a siz e of 25-27 mm. Females lay eggs from August to January. Males were observed with swollen claspers from July through December, with the highest amount of sperm storage in the epididymis occurring between August through Novembe r. Our observations indicate that epaulette sharks in the waters near Heron Island mate from July through December. (C) 1999 Wiley-Liss, Inc.