Seasonal trends of the reproductive cycle of Octopus vulgaris in two environmentally distinct coastal areas

Abstract

Octopus vulgaris is an important fisheries resource, particularly in Iberian waters. Species life cycle is short with capacity to adapt to different environmental conditions and, considered a simultaneous terminal spawner. Data on maturation and other biological parameters collected from January 2007 to November 2010 are used to define spawning seasons for octopus landed by the small-scale trap fisheries in two oceanographically distinct Portuguese coastal areas: the northwest coast (western Iberia upwelling system) and the south coast (Gulf of Cadiz system). On a monthly basis, we followed the proportion of mature individuals, and the Gonad-Somatic and Hayashi Indices. Length–weight relationship, weight-at-maturity, body condition and energy allocation were other biological parameters studied. Spawning season was markedly different in both areas. The northwest population spawns from March to July, in synchrony with the northwest coast upwelling season, and the south coast population spawns mainly in summer, between August and September. A less intense spawning peak in early spring is present occasionally in the south coast. Weight-at-maturity is geographically indistinct, but in both areas males mature at smaller sizes than females. Body condition increases significantly during maturation and mass allocation for reproduction results indicate that males and females channel energy to reproduction from several sources.