Population structure of the piked dogfish Squalus acanthias (Elasmobranchii: Squalidae), with preliminary reproductive observations

Squalus acanthias has been poorly studied in Uruguay, though reproductive studies have been carried out in Argentina in the decades of 1970–1980. The aim of this work was to analyze the population structure and the reproductive biology of S. acanthias along the Uruguayan continental shelf (south-western Atlantic Ocean) between 1995 and 2010. Total length (TL) ranged from 30–95 cm for females (n = 1,323) and 25–81 cm for males (n = 999). Significant differences in the TL frequency distributions between sexes and among seasons were detected, with abundances in the magnitude of up to 5,000 individuals/nm². Length at first maturity (TL₅₀) was 58.3 cm in males and 70.4 cm in females. Ovarian and uterine fecundity were 2–14 and 1–14, respectively, and both were positively correlated with maternal TL. Females with candled embryos were recorded in autumn. Embryo TL was significantly greater in winter, which is when parturition is likely occurring. Full-term embryos had a TL of 22–25 cm. Sex ratio of embryos was close to parity. Ovarian vitellogenesis was observed to be occurring concomitantly with gestation.