Age and size of Mercenaria mercenaria in Two Sisters Creek, South Carolina

Northern quahogs, Mercenaria mercenaria (L.), were sampled from four sites in Two Sisters Creek, South Carolina. Shell lengths (SL) were measured and ages estimated from increments in shell sections. Mean SL of individuals collected at the two sites near the mouth of the creek were significantly larger than those collected in the upper reaches of the tidal creek. The back-calculated mean SL, however, were similar among sites within most age classes. Mean ages of individuals near the mouth were significantly older than those from the upper reaches. Differences in the population age structure were also observed among sites. Several factors are explored to explain the upstream pattern of decreasing SL and ages of quahogs in Two Sisters Creek.