Effects of clam hand dredging on macrofauna: A field experimental approach in a sandy tidal flat at a Marine Extractive Reserve

The clam Anomalocardia flexuosa (Linnaeus, 1767) is commonly fished in southern Brazil using highly efficient fishing gear—a hand dredge known as “hook”. We tested the immediate impact of this dredge on macrofauna in a sandy tidal flat in a Marine Extractive Reserve based on a BACI (Before After Control Impact) model. The sample design for the test was defined in five random areas located in a sand tidal flat. Each area was divided into three treatments, namely Control (undredged), Dredge 1 (D1) and Dredge 3 (D3), and the samples were collected before and after none, 1 and 3 dredge tows, respectively. Dredging had a quantitative impact mostly on the mollusk assemblage. The distribution and dominance patterns of the polychaete assemblage revealed the homogenizing effect of the hook. After dredging, macrofauna diversity was significantly lower. However, this effect was also observed in areas of greater initial abundance and diversity.