Distribution, length-weight relationships and reproductive characteristics of Sepia orbignyana, Férussac, 1826 in the Northern and Central Adriatic Sea

Abstract

Sepia orbignyana was studied in the eastern part of the Northern and Central Adriatic Sea at samples collected from 1996 to 2011. A total of 249 individuals was analysed. The species was widely distributed in the Central Adriatic Sea and in some areas of the Northern Adriatic Sea, at depths between 22 and 237 m, with greater density recorded from 50 to 200 m. The sex ratio (m/f) was 1.27:1. The mantle length ranged from 29 to 100 mm in females and between 22 and 92 mm in males. The negative allometric growth was observed in males and females. The smallest mature male and female had mantle lengths 42 mm and 60 mm, respectively. The length at first maturity was 58 mm in males and 66 mm in females. The potential fecundity of mature females varied between 77 and 806 oocytes, with a mean of 365±179. In the gonads of mature females oocytes at different stages of development (lengths from 0.21 to 9.33 mm) were found. The number of spermatophors in males ranged from 32 to 597 with lengths between 3.32 and 11.81 mm. The results indicated that S. orbignyana in the Adriatic Sea has group-synchronous ovulation and most probably is an intermittent terminal spawner.