unpublished data, the condusions of which were 

 included in the paper by Gimter et al., 1964). 

 Williams (1955a) pointed out that in North 

 Carolina young white shrimp are most abundant 

 in the areas of lowest salinity and that in general 

 they live in waters of lower salinity than do the 

 brown or pink shrimps. Gunter (1961a) suggested 

 that the low salinity of Louisiana nureery gromids 

 may be optimal for juvenile white shrimp. Joyce 

 (1965) reported that white shrimp made up by 

 far the largest percentage of shrimp in localities of 

 lower salinities and that no white shrimp were 

 caught in the high-salinity waters of tlie Edge- 

 water-Oak Hill (Fla.) area. The fact that white 

 shrimp move fartlier upriver and grow to a great- 

 er size in inshore waters seems to indicate that the 

 young have a higher tolerance to low salinity over 

 a longer period of their development than the sym- 

 patric Penaeus. 



Gunter and Hildebrand (1954) are of the opin- 

 ion that in Texas there is a direct corresjaondence 

 between rainfall of the State and production of 

 white shrimp. Gunter et al. (1964) jDointed out 

 that the drought from 1947 to 1957 was accom- 

 panied by a remarkable decline in production of 

 white shrimp, and when the long drought was over 

 the annual production increased 331 percent from 

 1957 to 1958. 



The lowest salinities at which the young of P. 

 setiferus have been recorded are 0.42 p.p.t. in the 

 northern Gulf of Mexico (Gunter and Shell, 1958) 

 and 0.26 p.p.t. in northeast Florida (Joyce, 1965). 



Although the field studies mentioned above in- 

 dicate that white shrimp prefer low-salinity 

 water, other studies show tliat they are not affected 

 adversely by higli salinity and are rather insensi- 

 tive to large fluctuations in salinity. Lindner and 

 Anderson (1956) , as a result of their investigation 

 in the waters of Louisiana, and Hoese (1960a, 

 1960b) who worked in various localities along the 

 coast of Texas, concluded that within certain areas 

 at least, young shrimp are indifferent to varying 

 salinity. In Laguna Madre small white shrimp 

 have been found at salinities of 47.96 p.p.t. (Hilde- 

 brand, 1958) and 41.3 p.p.t. (Gmiter, 1961a). 

 Lmiz (1956) reared juveniles at 17.6 to 33.2 p.p.t., 

 and Johnson and Fielding (1956) found that 

 white shrimp could be reared successfully in ponds 

 at salinities of 18.5 to 34 p.p.t. Laboratory experi- 

 ments by Zein-Eldin (1963a) showed that, under 

 constant temperature and rather restricted diet, 

 postlarval shrimp can survive and grow within a 



wide range of salmity. She stated that "it would 

 appear that salinity tolerance per se may not play 

 a direct role in the growth and survival of post- 

 larval and juvenile slirimp in the estuarine en- 

 vironment." Joyce (1965) observed a temperature- 

 salinity relation in the distribution of inshore 

 shrimp and stated that apparently these shrunp 

 remained away from areas of low salinity during 

 cold weather. This finding agrees with the labora- 

 tory findings of Zein-Eldin and Aldrich (1965), 

 who observed that postlarvae of P. a. aztecus, at 

 temperatures below 15° C, exhibited decreased 

 tolerance to low salinity. Burkenroad (1939) sug- 

 gested tliat the general geographic distribution 

 of the species possibly depends on a temperature- 

 salinity correlation and that temperature might 

 limit tlie occuiTence of white shrimp within an 

 extreme range of salinity. 



ENEMIES AND DISEASES 



P. setiferus, like Penaeus in general, constitute 

 part of tlie diet of many carnivorous teleost and 

 some elasmobranch fishes (Gunter, 1945; Darnell, 

 1958). Cannibalism, common among Penaeus as 

 soon as they reach the postlarval stage, makes their 

 maintenance in aquariums difficult for laboratory 

 experiments if they are not well fed. 



White shrimp appear to suffer from a number 

 of diseases, some of them caused by parasites. Telo- 

 sporidians, cnidosporidians, trematodes, cestodes, 

 and nematodes have been recorded from white 

 shrimp (Sprague, 1950, 1954; Kruse, 1959; Hut- 

 ton, Sogandares-Bernal, Eldred, Ingle, and Wood- 

 burn, 1959; Hutton et al., 1962; Hutton, 1964: 

 Aldrich, 1965). Dawson (1957) and Joyce (1965) 

 reported Balanus on white shrimp. 



HARDINESS 



According to De Sylva (1954), P. setiferus is 

 more delicate and short lived than P. d. duorarum 

 and P. a. aztecus. Apparently, it is also the most 

 susceptible to low temperatures. Broad (1965) too 

 considers P. setiferus less hardy than P. a. aztecus. 



Commercial Importance 



This species is fished in several areas along the 

 eastern coast of the United States, the most im- 

 portant of which are Georgia and the northeast 

 coast of Florida. The most northern fishery is in 

 the vicinity of Pamlico Sound, North Carolina. 



The largest production by far is in the Gulf of 

 Mexico, where the waters of Louisiana and eastern 



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U.S. FISH AND WILDLIFE SERVICE 



