Reproductive biology of the longnose spiny dogfish from the South Adriatic Sea

Lacking information on the life history for the longnose spurdog, Squalus blainville (Risso, 1827), represents one impediment to obtaining reliable estimates of its reproductive parameters to be used to assess a fish stock status analysis. Data collected, in a scientific trawl survey (Mediterranean International Trawl Survey, MEDITS) as well as commercial landing/discard monitoring program in Southern Adriatic Sea (GSA 18), were used to provide information on population structure, size at maturity (L50), fecundity, embryonic development and reproductive cycle. The overall sex-ratio estimated was significantly skewed toward females. The analysis of maturity stage frequencies highlighted a clear seasonal pattern for females, while the males in active spawning were predominant in all the seasons. The L50 are 47.1 and 57.5 cm respectively for male and female. The ovarian fecundity (OF) increased significantly with maternal Total Length (TL) according to a linear relationship (OF=0.107xTL-2.648) as well as the uterine fecundity (UF) (UF=0.192 x TL – 8.818). The overall mean embryos sizes showed an increase from summer (11.7 cm) to autumn (13.0 cm) until reaching a highest significant size in winter (15.9 cm).