Spatial distribution, biomass and size structure of Ctenodiscus australis (Echinodermata: Asteroidea) in shelf- break areas, Argentine

Ctenodiscus australis is a common sea star in the Argentine Continental Shelf. Nevertheless, information about its population parameters is lacking. We investigated the spatial distribution, biomass and size structure of this sea star through a spatial and temporal scale in Patagonian scallop (Zygochlamys patagonica) fishing grounds associated with the shelf-break front in the Argentine Sea. The sea star C. australis was very common in the Patagonian scallop management units (MUs) analysed and reached 100% presence in most of them. The species biomass showed latitudinal differences with the highest values in northern MUs during the period 2002-2005, probably related to the organic content in sediments. The comparative study in two areas subjected to different fishing efforts in the same MU showed the highest biomass of this sea star in the area with low fishing effort. The size-frequency distribution of C. australis suggests a low or sporadic recruitment and slow growth. Differences in the median size were found between MUs but these cannot be attributed to fishing effort.