Distribution of common octopus and common squid paralarvae in a wind-driven upwelling area (Ria of Vigo, northwestern Spain)

The variation of paralarval abundance in a region subjected to wind-driven upwelling (Ria of Vigo, northwestern Spain) was studied. Research cruises were undertaken during the favourable upwelling season (May to October) in 2000 and 2001. Each cruise included biological and hydrographic sampling and consisted of five stations in waters located to the east and west of the Cies Islands. A total of 221 paralarvae of Octopodidae and Loliginidae were collected over the 12-month study period. During 2000, higher abundance of paralarvae was observed in July, September and October for Loligo vulgaris and Octopus vulgaris. In 2001, abundance of both species was higher in May and also in September for O. vulgaris. The mantle length of the paralarvae varied from 1.25 to 2.25 mm and from 1.00 to 4.90 mm within the O. vulgaris and L. vulgaris individuals, respectively. The presence/absence of upwelling modulates the abundance and spatial distribution of loliginid and octopod paralarvae. The relationship between the distribution and movement of these paralarvae in the Ria of Vigo seems to follow the circulation system defined for this area; when the upwelling extends its influence inside the Ria, the paralarvae are transported to the inner part in a west–east direction.