Growth and reproduction of Loxechinus albus (Echinodermata: Echinoidea) at the southerly peripheries of their species range, Falkland Islands (South Atlantic)

Sea urchins Loxechinus albus were collected from an unfished population inhabiting inshore areas of the eastern part of the Falkland Islands (Southwest Atlantic) at bimonthly intervals between January 2005 and March 2006. The gonads of 491 specimens were sampled to ascertain GSI, and a subsample was examined microscopically in order to determine sex and maturity stage. Age was determined by ring counts on genital plates of 349 specimens with the annual periodicity of ring deposition validated by marginal increment analysis. This investigation suggests that the study population spawns at the warmest time of the year thus allowing for greater growth in their pelagic larvae and newly settled juveniles. Size at age data were found to be asymptotic and out of three growth functions tested the von Beralanffy growth model best described the data. The relatively short period of optimal water temperatures around the Falkland Islands does not enable L. albus to grow as fast as in other regions with higher seasonal temperatures (central Chilean coasts) resulting in relatively small adult sizes.