NURSERY GROUND, AGE STRUCTURE AND ABUNDANCE OF JUVENILE SQUAT LOBSTERPLEURONCODES MONODON ON THE CONTINENTAL-SHELF OFF CENTRAL CHILE

Newly settled individuals and juveniles of several benthic decapod cru staceans spend their first months or years in nursery habitats differe nt from those of the adult population. It was unknown if this was the case for the squat lobster Pleuroncodes monodon, an exploited crustace an which inhabits the continental shelf off central Chile, and of whic h 2 adult populations exist, the larger Achira (35 degrees 10' S to 36 degrees 15' S) and the smaller Biobio (36 degrees 35' S to 36 degrees 50' S). We report here the presence of a large nursery area of the sp ecies, connecting both adult populations; the habitat is dominated by extensive sulphide microbial communities which fluorish at very low ox ygen concentrations. We inferred the existence of northerly and southe rly migration routes from the nursery ground to the adult populations, with juvenile year classes migrating as they advance through age clas ses. The juvenile population was composed of 2 year classes: 0 yr old (newly settled individuals) and 1 yr old juveniles; thus juveniles see med to spend their first year of life in the nursery area. Total abund ance was estimated as 3290 x 10(6) individuals (asymmetric 95 % confid ence interval: 2153 to 7039 x 10(6)), although the above figure is a l ower bound because the sampling did not cover the whole nursery area. We hypothesize that the Biobio adult population is not self-sustaining , but depends on a surplus production of juveniles from the Achira pop ulation.