18. Reproduction of Spiny Dogfish in San Matias Gulf, Patagonia (Argentina)
Edgardo E. Di Giacomo, M. Raquel Perier, and Marina Coller
Abstract.—Spiny dogfish Squalus acanthias is distributed in the Southwest Atlantic Ocean between 34°S and 55°S. Information on size, sex, stomach contents, presence of gravid females, oocyte size, embryo size, and sex ratio were collected from bottom trawl surveys in eight of the years between 1986 and 2004. The species was recorded from a depth range of 66 to 165 m, with maximum densities found between 86 and 105 m. Female length was in the range of 46 to 101 cm and male length from 48 to 94 cm. Gravid females had lengths between 69 and 98 cm, and contained 4 to 11 embryos each (mean = 7.8, SD = 1.7). In 1996 intrauterine embryo growth was observed between August (females: 19.9 cm; males: 19.9 cm) and November (females: 22.3 cm; males: 22.6 cm). The sex ratio of embryos was 1:1. Litter size and near-term embryo length increased with the size of the pregnant female. Embryo sizes were not significantly different with respect to sex. A 2-year gestation cycle appears consistent with the data. Dogfish is a top predator in the San Matías Gulf ecosystem, feeding on fish species important to local fisheries.