Several kinds of shellfish aquaculture are recognized as environmentally responsible, including the farming of bivalves like clams, oysters, mussels and scallops. Most environmental concern about aquaculture focuses on the farming of marine finfish and shrimp, which are often intensively cultivated carnivores. In contrast, farming shellfish has few negative impacts overall. Most shellfish feed on naturally occurring particulates; because supplemental feeds are not used, shellfish farming does not increase nutrient inputs to coastal waters. In fact, increased abundance of shellfish in an area is often considered to have a positive effect on water quality.