Shell Bottom See the map below to explore the extent of North Carolina's shell bottom habitat. It was produced using data collected by the Estuarine Benthic Habitat Mapping Program. Note that mapping has not been completed in a portion of Brunswick and Hyde counties. If the map is not displaying properly, view it in a standalone browser window. Shell bottom habitat exists in areas of bottom composed of living or dead oysters, hard clams and other shellfish. These areas include oyster beds, oyster rocks, oyster bars and shell hash and can be intertidal (exposed at low tide) or subtidal (always underwater). In North Carolina, Shell Bottom habitat is restricted to inshore bodies of water like bays, estuaries and rivers. Function of Shell Bottom Habitat Shell bottom habitat provides structure, shelter and food for many fish and invertebrate species. Living shellfish on shell bottom filter algae and bacteria from the water column improving water quality. Water filtration by oysters, clams and other shellfish clears the water column for growth of submerged aquatic vegetation. Additionally, shell bottom protects shorelines from erosion by reducing wave energy. How Fish Use Shell Bottom Habitat Oysters and other shellfish attach to the hard surfaces of shells. Shell bottom is important nursery habitat for blue crabs, stone crab, sheepshead and many other non-fishery species. Larger fish such as drum, sea bass and flounder forage on and around shell bottom habitat. Shell bottom provides spawning and refuge habitat for crucial prey species like goby, anchovy and grass shrimp. Highly Associated Species Oysters Clams Blue crabs Stone crabs Sheepshead Drum Sea bass Flounder Threats to Hard Bottom Habitat Shell bottom habitat is damaged by fishing gear, boats and dredging. Excessive oyster or clam harvest even by hand harvest methods reduces total area and overall quality of shell bottom habitat. Pollution from chemicals and sediment can kill living oysters and excess nutrients and other inputs from land can impact shell bottom species and the species they support. Important Facts about Shell Bottom Habitat A single oyster can filter 25 to 30 gallons of water per day. Oyster rocks were once so numerous they were considered a hazard to navigation.