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

Northern qoahogs. 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 co llected at the two sites near the mouth of the creek were significantly lar ger than those collected in the upper reaches of the tidal creek. The backc alculated mean SL, however, were similar among sites within most age classe s. Mean ages of individuals near the mouth were significantly older than th ose from the upper reaches. Differences in the population age structure wer e also observed among sires. Several factors are explored to explain the up stream pattern of decreasing SL and ages of quahogs in Two Sisters Creek.