First observations on the reproduction of Alepocephalus rostratus Risso, 1820 (Osteichthyes, Alepocephalidae) from the Sardinian Channel (Central-Western Mediterranean)

Data are provided on the reproductive biology of a bathypelagic species Alepocephalus rostratus Risso, 1820 caught in the Sardinian Channel between 800 and 1200 m depth. The macroscopic and microscopic description of the gonads was based on 223 females and 95 males. Unlike most other teleosts, the testis is generally formed of two distinct subcylindrical lobes along the mid-line of the body cavity. A five-stage scale of development for both females and males was established based on the macroscopic and microscopic observation of the gonads. Biometric and histological analyses revealed synchronous development in the bilobed testis and 'group-synchrony' in the ovary. The temporal evolution of the gonadosomatic index and the monthly variations in the percentage distribution in the stages of ovarian development revealed an extended spawning period in this species.