Spent ovaries were found to revert to the yellow 

 stage in a period of a few days and then to develop 

 toward a ripened stage again in 2 or 3 months. 

 A large female is estimated to produce a half 

 million to a million eggs at a single spawning 

 (Anderson, King, and Lindner, 1949). 



It was thought that studies of the ovary would 

 lead not only to discovery of spawning grounds 

 but also to knowledge of how many times a female 

 shrimp might spawn, and to the approximate age 

 and length of life of the shrimp. Such hopes were 

 incompletely realized. The likelihood of multiple 

 spawning and absence of permanent scars or 

 walled-off areas in the ovary precluded aging by 

 this method. It is possible, but not proved, that 

 a shrimp can spawn more than once in a season. 

 Occurrence of ripe females suggests that spawn- 

 ing in Louisiana takes place offshore in depths 

 greater than 4.5 fathoms, probably between 5 and 

 17 fathoms. Heegaard (1953) reported occurrence 

 of spawning 6 or more miles from shore in from 

 10- to 15-fathom water in Texas. The exact loca- 

 tion of spawning grounds off the Carolinas re- 

 mains unknown. 



Developmental stages of the white shrimp were 

 elaborated in detail by Pearson (1939), based on 

 plankton tows off the Mississippi River Delta and 

 the coasts of South Carolina, Georgia, and 

 Florida, and on rearing experiments with material 

 taken from plankton catches at St. Augustine 

 Inlet, Fla. (The eggs of penaeids are not carried 

 on the pleopods of the females as in other de- 

 capods, but are broadcast.) In this study, few 

 eggs were found, but this circumstance was at- 

 tributed to the fact that the eggs are demersal, 

 hence, hard to capture, and perhaps deposited 

 chiefly beyond the area sampled. Of the material 

 available for rearing, 5 of 15 eggs hatched within 

 24 hours after capture. Developmental stages 

 prior to hatching were described, and, following 

 hatching, five naupliar, three protozoeal, two 

 mysis, and a series of postlarval stages were de- 

 scribed. Pearson thought it likely that though 

 the larvae are more or less at the mercy of cur- 

 rents in the environment, they still are capable 

 of considerable independent movement. From the 

 spawning place at sea, a great number of the 

 larvae move inshore and enter estuaries at about 

 the second postlarval stage (7 mm. total length), 

 and it is at this stage that they abandon planktonic 



20 



for a benthonic existence. The length of larval 

 existence from time of hatching to entrance into 

 estuaries was judged to be about 2 or 3 weeks. 



Heegaard (1953), studying wild populations of 

 larval white shrimp, and Johnson and Fielding 

 (1956), studying populations reared in captivity, 

 gave somewhat different interpretations of this 

 portion of development. Heegaard suggested that 

 the number of molts in certain portions of the 

 larval history may vary individually; Johnson 

 and Fielding, while agreeing with Pearson's 

 descriptions of stages, gave evidence for shorter 

 time of development from hatching to first post- 

 larva (about 2 weeks). They also gave evidence 

 for very rapid growth of the young, 2.1 mm. and 

 1.7 mm. per day in different experiments under 

 conditions of full feed. The same authors secured 

 good growth in both high and medium salinities. 



Bearden (1961) demonstrated that postlarval 

 P. setiferus enter South Carolina sounds from 

 June through September, a period similar to the 

 supposed recruitment period in North Carolina 

 (Williams, 1959). 



Once in estuaries on so-called "nursery grounds" 

 the young grow rapidly. Williams (1955a) esti- 

 mated an average increase in length of 36 mm. 

 per month (1.2 mm. per day), and other estimates 

 of similar nature have been made (Gunter, 1956; 

 Loesch, 1957). The young, which in the early 

 part of their benthonic existence tend to seek the 

 fresher, shallower portions of estuaries, move 

 gradually into deeper, saltier water as they grow, 

 and with approaching maturity they return to 

 sea. Hoese (1960) suggested that migration to 

 estuarine nursery grounds may not be essential 

 to development in this species, but Gunter (1961) 

 gave much evidence to the contrary. Most of the 

 individuals that grow to maturity appear to live 

 a year or a little longer. Some exceptional in- 

 dividuals in the deeper portion of the range may 

 live to be about 2 years old. Mature females at- 

 tain a larger size than mature males. Lindner 

 and Anderson (1956) estimated that mature P. 

 setiferus grow at a rate of about 20 mm. per month 

 during the period March to October. 



In addition to annual cyclic movements of 

 larvae into estuaries, and subsequent movement 

 of subadults back to sea, tagging experiments have 

 indicated that P. setiferus may make coastwise 

 migrations of considerable length. In their ana- 



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