Reproductive biology of the velvet swimming crab, Necora puber (Brachyura: Portunidae), in the Orkney Islands, UK

This study focused on the reproductive biology of the velvet swimming crab, Necora puber (L.), and its implications for managing the fishery in the Orkney Islands, UK. According to gonadal observation, 50% of the population became sexually mature at 43.8 mm carapace width (CW) for females and 52.8 mm for males. Ovigerous females were observed from January to July, with peak occurrence in spring. Clutch size (N) ranged from 5000 to 278,000 eggs, and was related to CW by the equation: N × 10³ = 0.0026 × CW ^2.5169, displaying considerable variability, possibly due to the fringe location of the population related to its general species distribution. Reinstatement of the closed season, coinciding with the peak moulting period, is recommended. The minimum landing size is appropriate for the population in terms of sexual maturity. The common practice of discarding recently moulted and ovigerous individuals should be incorporated into the fishing regulations.