Abundance of Strombus Gigas Zero-Year Class Juveniles at Banco Chinchorro Biosphere Reserve, Quintana Roo, Mexico

Distribution and density of zero-year class juveniles were determined at six sites of Banco Chinchorro from December 1997 to July 1998. Conchs were sampled bimonthly during the three main climatic seasons of the region —cold, dry, and rainy. Replicate tows were made in each site with a bottom sledge 1-m² mouth and 1-cm mesh; juveniles caught were measured using calipers and separated into five size classes. Plant biomass collected by the sledge was measured. To analyze the organic content and sediment type additional samples were taken. Highest juvenile density was recorded in the dry season (0.145 juveniles m⁻²), with juveniles of 50–60 mm and 30–40-mm size classes as the most abundant (0.06 juveniles m⁻²and 0.035 juveniles m⁻², respectively). Penélope (0.075 juveniles m⁻²) and Cayo Centro (0.055 juveniles m⁻²) were the most important sites of conch juvenile distribution. There was no significant difference in density by site; however, juveniles were more common at the central and northern parts of Banco Chinchorro. Organic matter varied from 2.27 ± 0.41 at Isla Ché to 4.72 ± 3.87% at Cayo Norte. Sediment type varied from coarse sand at the south end (0.58 ) and medium sand (1.34 f) at the central and north ends of Banco Chinchorro. Juvenile abundance exhibited a direct correlation with water temperature and larval abundance, and an inverse correlation with plant biomass. Zero-year class juveniles were most abundant in medium sand and coral rubble areas, mainly unconsolidated sediments with high organic contents reinforcing the notion that they inhabit a different environment than of year-class juveniles.