Oyster reefs provide habitat for fish and invertebrates that require structural complexity for foraging, nesting and refuge from predators. Fish associated with oyster reefs range from residents that use the reef as a primary habitat to transient species that are wide ranging and may forage on or near the reef. Some fish species, such as oyster toad fish, gobies, and blennies, attach eggs to the undersides of oyster shells, relying on reef architecture or microhabitat for reproductive success. Crabs commonly are found in greater densities on oyster reefs than on surrounding open-bottom habitat where vulnerability to predation is greater and prey resources are less abundant. Bivalves including clams and mussels also may utilize reefs as a refuge from predators enabling populations within reefs to act as a source for mudflat and marsh populations that may be depleted more easily by predators.