lysis of these experiments, Lindner and Ander- 

 son (1956) showed that in fall and winter, shrimp 

 tend to move south along the Atlantic coast; in 

 late winter and early spring, there is a return 

 movement ; and during late spring and summer, 

 position of the population is relatively static. 

 Large individuals are prone to move longer dis- 

 tances than small shrimp. The longest recorded 

 southward movement was by a shrimp tagged at 

 Beaufort, N.C., in October, and recovered 95 days 

 later off Florida, 360 miles from the point of re- 

 lease. The greatest counter movement was from 

 Cape Canaveral, Fla., in January, to South Caro- 

 lina 168 days later, a distance of 260 miles. 



Distribution of P. setifems is not uniform, and 

 this may be conditioned by a number of factors. 

 These are usually thought to be salinity, tempera- 

 ture, and substrate. The young may utilize waters 

 of somewhat lower salinity than the young of 

 related penaeids (Burkenroad, 1934b; Williams, 

 1955a). Hildebrand and Gunter (1953) and 

 Gunter and Hildebrand (1954) demonstrated a 

 strong positive correlation between the white 

 shrimp catch for a given year and total rainfall 

 for that year and the 2 preceding years in Texas, 

 high rainfall being followed by good catches. In 

 colder portions of the year no young are found in 

 inside waters, at least in the Carolinas (Williams, 

 1955a). Penaeus setiferus is usually found on a 

 muddy substrate on trawling and nursery grounds 

 (Springer and Bullis, 1954; Hildebrand, 1954, 

 1955), and in experimental tanks it has been 

 shown to choose muddy substrates in preference 

 to sandy or rocky bottoms even though it burrows 



to a lesser extent than its near relatives (Williams, 

 1958). 



In recent years the subadult populations of 

 white and other penaeid shrimp in estuaries have 

 been exploited for fish bait. Studies of such fish- 

 eries have given more detail on migrations and 

 density of population (Loesch, 1957) and on 

 individual length-weight relationships (Chin, 

 1960). 



Penaeus duorarum Burkenroad. Pink, spotted, brown 

 spotted, or grooved shrimp 



Figures 10-11 



Penaeus brasiliensis: Hay and Shore [In part], 1918, p. 377, 

 pi. 25, fig. 6. 



Penaeus duorarum Burkenroad, 1939, p. 31, figs. 18, 19, 23, 

 25-27 (rev.). 



Recognition characters. — Integument thin, pol- 

 ished, translucent. Carapace with a median carina 

 continuous anteriorly with rostrum and extending 

 nearly to posterior border of carapace, flanked on 

 each side by a broad, rounded groove; posterior 

 half of carina with a median longitudinal groove ; 

 anterior half arcuate, highest above orbit and with 

 9 or 10 sharp teeth ; posterior tooth remote from 

 others, anterior 6 or 7 on rostrum proper. Lower 

 margin of rostrum wth two to three teeth (oc- 

 casionally one) ; tip slender, horizontal or directed 

 slightly downward, unarmed. Anterior margin of 

 carapace with strong antennal spine on carina 

 extending backward nearly to well-developed 

 hepatic spine. Cervical groove extending halfway 

 from hepatic spine to dorsal carina. A subhori- 

 zontal suture below hepatic spine, and a groove 

 extending from near hepatic spine to near base of 

 ocular peduncle. An orbital ridge behind eye. 



Figure 10. — Penaeus duorarum Burkenroad. Animal in lateral view with part of appendages removed, "Form A" 



from North Carolina ; natural size. 



MARINE DECAPOD CRUSTACEANS OF THE CAROLINAS 

 763-049 0-^65 3 



21 



