FISHERY BULLETIN: VOL, 87, NO. 1 



(South Atlantic Fishery Management Council 

 1981). 



Penaeus setiferus was the most abundant penaeid 

 collected in this survey, and it constituted 9% of the 

 total catch of decapod crustaceans (Table 1). This 

 species accounted for 10% of the total biomass of 

 stomatopods and decapods and occurred in 63% of 

 the 303 collections made. The stratified mean catch 

 per tow differed among seasons, with abundance 

 greatest in fall (30 individuals/tow) and lowest in 

 spring (2 individuals/tow) (Table 5). This seasonal 

 difference in abundance of P. setiferus in the near- 

 shore coastal zone is explained by movement of 

 white shrimp from estuaries to offshore waters in 

 fall. This emigration is associated with declining 

 water temperatures (Lindner and Anderson 1956; 



Pullen and Trent 1970). White shrimp enter the 

 estuaries as postlarvae in May, grow rapidly in the 

 estuarine nursery grounds, and move seaward 

 through late summer and fall (Weymouth et al. 

 1933). 



Within the three areas sampled, white shrimp 

 were most abundant in strata off Georgia during 

 every season except spring (Fig. 4). This may result 

 from a predominantly southward movement of 

 white shrimp during fall, winter, and summer as 

 discussed by Shipman (1980). 



The mean total length of white shrimp differed 

 by season with largest individuals occurring in 

 spring (x = 162 mm, n = 93). The larger average 

 size at this time was probably influenced by occur- 

 rence of female roe shrimp that move to nearshore 

 coastal waters from estuaries during the spring 

 (Lindner and Anderson 1956; Joyce and Eldred 

 1966; Harris 1974; Music 1979; Farmer et al. 1978). 

 The mean size of shrimp collected was largest in 

 strata off North Carolina/South Carolina (x = 152 

 mm, n = 1,439), while those from strata off Georgia 

 and Florida averaged 145 mm (w = 2,269) and 142 

 mm (n = 1,121), respectively. 



Penaeus aztecus 



Brown shrimp occur from Martha's Vineyard, MA 

 to the Florida Keys and into the Gulf of Mexico 

 where they occur on the Sanibel grounds, in Appa- 

 lachicola Bay, and to northwestern Yucatan (Wil- 

 liams 1984). Along the Atlantic coast of the United 

 States, P. aztecus is most abundant off North and 

 South Carolina (Cook and Lindner 1970). 



Brown shrimp were collected in 51% of the trawl 

 tows made during the study and were the second 

 most abundant Penaeus collected (Table 1). The 

 stratified mean catch per tow was much greater in 

 summer (44 individuals/tow) than during the other 

 seasons when <2 individuals/tow were collected 

 (Table 5). Brown shrimp usually occupy the estua- 

 rine nursery grounds from March through July 

 before emigrating to coastal waters in August. Emi- 

 gration, however, may be delayed if cooler than nor- 

 mal temperatures occur in spring (South Atlantic 

 Fishery Management Council 1981). The summer 

 cruise occurred from mid-July into September, 

 which overlapped the period when brown shrimp 

 emigrated from the estuary. During the summer 

 sampling period, brown shrimp abundance was 

 greatest in strata sampled off North Carolina/ 

 South Carolina (Fig. 4). Abundance during other 

 seasons was too low to assess any difference be- 

 tween areas. 



170 



