Gametogenic Cycle Of Ensis Siliqua (Linnaeus, 1758) In The Ría De Corcubión, Northwestern Spain

Abstract

The reproductive cycle of Ensis siliqua in the Ría de Corcubión (northwest Spain) was studied using condition indices and histological methods. The gametogenic cycle was annual, with a long sexual rest period during summer and autumn, when the gonadal condition index (GCI) was at minimum levels and sexes were differentiated. Gametogenesis started during November–December and the only period of spawning occurred in April–May. The gonadal condition index (GCI) used showed a clear relationship with the gametogenic stage, rising from zero in stages 0 (sexual rest) and I (start of gametogenesis), to its highest values in stages IIIA (ripe) and IIIB (start of spawning), before decreasing significantly in stage IV (exhaustion). In contrast, the meat condition index (MCI) did not show statistical differences between gametogenic stages. We suggest that the analysis of GCI (based on gonadal weight) may prove a valuable technique in fishery management to recognize the reproductive stage of E. siliqua populations, particularly as it is less expensive and time consuming than histological techniques.