IV-84 



to higher salinity waters of the estuary of the adjacent 

 sea to spawn. The American eel and the Blue crab are 

 examples of this type. 



(3) Migratory Estuarine Species 



The great majority of estuarine dependent species fall under 

 this classification. Some use the brackish and freshwater 

 areas of the estuarine zone for reproduction; some as a 

 source of food; some for shelter, either as adults or young; 

 and some for all these reasons. They all have 1n common 

 the basic need for both estuarine and ocean environments at 

 some point 1n their life cycle. This group Includes the great 

 majority of fish and shellfish of direct importance to man, 

 such as shrimp, menhaden, flounders, and red drum. 



Various types of dependency are Illustrated by several examples. 



SHRIMP 



The commercially Important shrimp are of three kinds: brown, white, 

 and pink. These species are concentrated along the South Atlantic and 

 Gulf coasts of the United States. The pink shrimp spawns in offshore 

 waters at depths of 100 to 150 feet, salinity between 3.61 and 3.77 per- 

 cent, and temperatures between 64 and 77°F. After 13 or 14 hours, the 

 eggs hatch and the larval shrimp begin to pass through a series of 

 developmental stages, at the same time beginning to move or drift 

 towards the Florida mainland about 100 miles distant (Figure IV. 7. 38). 



