•Minimum landing size is above maturity size.•A female of S. arctus can spawn up to three consecutive times a year.•S. arctus has a long, continued reproductive and breeding period in the NE Atlantic.•The prohibition to fish ovigerous females leads to a bias towards capturing males. This work addresses the study of a population of the slipper lobster S. arctus in the Galician coast (NE Atlantic), where a decrease in the exploited stock has been observed in the last decades, as has occurred in other populations of this species throughout its geographical distribution range. In spite of this fact and of its high commercial value, the management of its fishery relies on poor knowledge of relevant biological aspects such as its reproductive biology. For this purpose, monthly sampling has been carried out between February 2008 and June 2009 to characterize the reproductive cycle, breeding cycle, and sexual maturity size of S. arctus in the study area. The obtained results are particularly interesting to attempt to improve fishery management. On one hand, the current regional minimum landing size (90 mm total length; 30 mm cephalothorax length, CL) has been demonstrated to allow newly sexually mature individuals—regardless of which sexual maturity criterion is applied (females: 16.3–25.7 mm CL; males: 16.3–25.8 mm CL)—to reproduce at least once. On the other hand, the long breeding cycle observed in the area, with presence of ovigerous females throughout the whole year except for October and with values over 50% for 7 months a year (between February–August), along with the prohibition to catch ovigerous females, makes the fishery highly biased towards males, and the reproductive potential of the stock could therefore be affected.