IV-96 



SECTION 1. SUSTENANCE: USE AS A FISH AND WILDLIFE HABITAT 



FISH 



Estuarine dependence is a convenient term for describing a nor- 

 mally complex biological interrelationship between the estuarine 

 environment and an aquatic organism. This dependence includes a 

 vast spectrum of biological relationships. Practically all of 

 the sports fish species are dependent upon the estuarine zone for 

 one or more phases of their life development, and approximately 

 65 per cent of all commercial fish species are estuarine-dependent. 

 The discussion in Chapter 1 concerning life in the estuarine zone 

 described the nature of estuarine dependence and gave examples of 

 several estuarine-dependent species important to human society. 



Many fish species live their entire lives in the estuarine zone 

 and are well -adapted to this type of environment. The oyster, 

 for example, has lived in the estuary for millions of years, as 

 evidenced by the huge denosits of shell on the bottoms of bays. 

 The shallow water, salty substrate, and intermediate salinities 

 are ideal for oyster culture. 



Other species may use the estuary only as a passage zone on 

 their way to freshwater streams or to the open ocean. However, 

 in doing so, they also utilize the high production of fond that is 



