Growth and reproductive biology of the sea star Astropecten aranciacus (Echinodermata, Asteroidea) on the continental shelf of the Catalan Sea (northwestern Mediterranean)

The growth and reproductive biology of the sea star Astropecten aranciacus was investigated on the continental shelf of the northwestern Mediterranean Sea. Sea stars were captured monthly in two bathymetric ranges (5-30 and 50-150 m) between November 2009 and October 2012. Bathymetric segregation by size in A. aranciacus was detected: small individuals inhabit shallow areas (5-30 m), while large individuals inhabit deeper areas of the continental shelf (50-150 m). Recruitment was recorded twice nearshore but no recruitment was detected offshore during the whole study period. Three cohorts were identified in each bathymetric range and growth rates were estimated. A. aranciacus population exhibited a seasonal growth pattern, being higher from June to October in the nearshore cohorts and from February to October in the offshore ones. Histology and organ indices revealed that spawning likely started in March, coinciding with the spring phytoplankton bloom and the increase in sea water temperature, and extended until June-July. Ratio between males and females was approximately 1:1 throughout the year and in both bathymetrical ranges. The size at first maturity (R50 %) was estimated to be R = 112 mm. A. aranciacus did not show an inverse relationship between gonad index and pyloric caeca index.