Growth and reproduction in spiny dogfish Squalus acanthias L. (Elasmobranchii: Squalidae), from the west coast of Ireland

The age, growth characteristics, maturity, and reproductive cycle of commercially caught spiny dogfish Squalus acanthias were investigated over a 12 month period. The specimens ranged in age from 4 to 30 years, with asymptotic lengths of 79 and 112 cm estimated for males and females, respectively. The lower age range reported here when compared with previous North Atlantic studies is attributed to fishing pressure. Fifty per cent maturity was estimated at 57.5 cm in males and 78.2 cm in females, and fecundity was positively correlated with female size. Although recently formed candles and full-term embryos were observed throughout the year, parturition occurred mainly from August to January. The minimum fecundity recorded was four (determined from developing ova/candled embryos), while the maximum was 16 (determined from embryo counts), and fecundity was found to increase by up to four between pregnancies. The overall sex ratio of embryos was 1:1, although this balance was rarely observed in any one female. The results presented here indicate that neither growth rate, size at maturity, nor fecundity have significantly changed due to fishing pressure.