Since fishermen have extended their trawling grounds 

 into deeper Gulf waters, the brown shrimp has become more 

 important than the white. Brown shrimp are associated with 

 muddy substrates of peat and sandy mud. They bury them- 

 selves during the day and at night they feed in the Gulf's 

 surface waters. Trawlers bring in their greatest catches 

 during summer nights. Brown shrimp spawn in the open Gulf 

 waters during fall and early winter. Larvae reaching the 

 estuary nursery grounds remain until maturity when adults 

 return to the open water in June (Figure 3.1). Brown 

 shrimp are more tolerant of high salinities than white, 

 19 ppt (parts per thousand) being an optimum salinity 

 (Barrett and Gillespie, 1973). Growth of the brown shrimp 

 is dependent on moderate temperatures, 20 C or greater, 

 and salinity near 19 ppt (White, 1975). 



Estuarine nursery grounds provide shrimp with safety 

 until they reach maturity. Plants, animals, and inorganic 

 and organic detritus in the nurseries provide food for the 

 shrimp. The estuarine nursery grounds are affected in two 

 major ways by man's activities. First, changes in salinity 

 and chemical composition of water are the results of 

 channeling. Secondly, loss of vegetated marsh areas by 

 channeling and dredging reduces the shrimp supporting 

 capacity of the estuaries (McGinnis et al., 1972: 3-24). 



Another problem which may affect the shrimp catch is 

 the laying of pipelines. Pipelines laid in bays and offshore 



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