CRS-46 



Most productivity studies have been undertaken in coastal areas, espe- 

 cially along the Southeast and Gulf Coasts. Few freshwater systems have been 

 investigated for productivity. Scientists are still debating a number of 

 basic questions, including total system productivity relationships between 

 primary production and individual species of commercial Importance — oysters 

 and finfish species for example, and relationships between changing wetland 

 plant communities (successional stages) and productivity. 18 / 



Habitat 



Wetlands may provide a wide variety of animals with food, breeding sites, 

 resting areas, nesting materials or sites, moulting grounds, or protection 

 from weather or predators. Some animals depend on wetlands for all these 

 functions while others may use them for just one or two, or only during a 

 portion of their life cycle. The pattern of use, including time and spe- 

 cific site needs within a wetland, makes it difficult to calculate the com- 

 posite value of wetland habitat. Habitat function is also affected by sur- 

 rounding land uses, natural changes in wetlands over time and the species 

 diversity and carrying capacity of each wetland type. 



Habitat for fish has been most extensively studied along the East and 

 Gulf Coasts. In 1980, an estimated 62.7 percent of the 6.7 billion pounds 

 of commercial fish caught by American fishermen was dependent on estuarine 

 areas, and wetlands are a key source of nutrients in most estuaries. 19 / 

 Some regional catches, such as those from the South Atlantic and Gulf Coast 



18 / Clark and Clark, Scientists' Report, p. 8-9. 



19 / U.S. Department of Commerce. National Oceanic and Atmospheric 

 Administration. National Marine Fisheries Service. Fisheries of the United 

 States, 1980. Current Fishing Statistics, No. 8100. Washington, U.S. Govt. 

 Print. Off., 1.981. p. 11. 



