Settlement and recruitment patterns of Mytilus galloprovincialis L. in the Ría de Ares-Betanzos (NW Spain) in the years 2004/2005

Abstract

The present study explores the settlement and recruitment capacity of Mytilus galloprovincialis L. on artificial collectors in the Ría de Ares-Betanzos (Galicia, NW Spain) in 2004 and 2005 following standard industrial techniques. Three locations in the ría (Arnela, Redes and Miranda) were selected to investigate larvae settlement after the main spawning event (July 2004/2005). Assessment of the recruitment capacity was performed in autumn (September 2004/2005) when mussel seed is usually gathered from the collector ropes and introduced into industrial cultivation at low densities. For both years, the highest settlement densities were recorded at the most seaward location, Miranda. Differences in settlement densities between locations are discussed in terms of the water circulation regime in the ría and the local hydrographic conditions. In 2004, statistical differences in post-settlement mortality resulted in similar recruitment densities at Arnela and Miranda, which were higher than at Redes. In 2005, recruitment densities in Redes and Arnela could not be assessed because predators (Spondyliosoma cantharus L.) eliminated the settled population at these locations. Site-specific differences in recruitment density may be attributed to the environmental limitations of each location as well as intra-specific competition