Size Structure, Abundance and Preliminary Information on the Reproductive Parameters of the Shortspine Spurdog (Squalus mitsukurii) in the Argentinean-Uruguayan Common Fishing Zone from the mid–1990s

Abstract

A total of 1 893 males and 1 124 females of Squalus mitsukurii were collected from latitudes 34º 30' S and 37º 00' S, in the south-western Atlantic Ocean, during early autumn, late autumn and spring 1995, early autumn 1996 and early autumn 1998. Length-frequency distributions signifi cantly varied between sexes for all seasons (P<0.05). Mature males predominated in all seasons throughout the analyzed area, according to their presence in the catches. In all periods sampled, immature females predominated except for late autumn 1995 where mature females were dominant. Signifi cant differences in density among seasons were recorded for immature and mature females and mature males (P<0.05). Density of immature females and mature males were signifi cantly different (P<0.05) for late autumn 1995 and early autumn 1996. Size-at-maturity was 43.1 cm and 55.9 cm total length for males (n = 1 181) and females (n = 862) receptively. The percentage of pregnant females ranged from 21.4% in spring 1995 to 49.8% in late autumn 1995. Ovarian fecundity varied significantly between early autumn 1995 and late autumn 1995 from 1–15 and uterine fecundity from 1–10, respectively. Embryo total length varied from 0.5–22.0 cm, attaining the highest values in autumn months. Size-at-birth was estimated to be 22–24 cm total length.