Nurseries, spawning grounds and recruitment of Octopus vulgaris in the Strait of Sicily, central Mediterranean Sea

Abstract

The presence of nursery and spawning grounds and the relationship between sea surface temperature (SST) and the abundance of juvenile O. vulgaris in the Strait of Sicily, central Mediterranean, are investigated using fishery-independent data (trawl surveys, 1994–2008). Annual distributions were generated for mature animals and juveniles for spring/summer (the peak spawning season) and autumn (peak recruitment) using an inverse distance weighted deterministic interpolation. Based on the persistence of abundant recruits and mature animals, respectively, nursery and spawning grounds were identified. The correlation between annual recruitment and SST during hatching and recruitment was also investigated. Concentrations of juveniles (nurseries) were located off the southwest coast of Sicily and in the central Strait of Sicily, including south of Lampedusa on the African shelf, but just one consistent concentration of mature animals (spawning grounds) was found in the northwestern part of the Strait. There was a significant positive correlation between recruitment and SST. Results are discussed in the light of environmental parameters, and a hypothesis on possible stock units in the area was developed. The direct and indirect effects of SST variation on the recruitment process were also examined.