ranged from about 0.23 to 0.33 nun. in diameter. 



5. Spent. Ovaries are flaccid and their color 

 fades, becoming milky as the regi'ession proceeds. 



Eggs of pink shrimp, like those of other Penaetis, 

 are demersal. According to Dobkin (1961), "'eggs 

 are yellow brown in color and opaque, although 

 when light is reflected in a certain way, the cho- 

 rion sliows the blue hue reported by Pearson 

 (1939) for the eggs of P. setiferus.'^ 



SPAWNING 



Spawning takes place in oceanic waters at 2 to 

 26 fm. and probably at greater depths also. In 

 laboratory experiments by Ewald (1965b) spawn- 

 ing occurred "in the early morning. 



Field work by Cununings (1961), Tabb, Du- 

 brow, and Jones (1962), and Jones et al. (1964) 

 gave some indications that on the Tortugas 

 grounds spawning continues throughout the year. 

 Evidence is also strong that spawning is more 

 intense during spring, summer, and fall (Ingle et 

 al., 1959; Cummings, 1961; Jones et al., 1964). On 

 the basis of analysis of fishery statistics Kutkhun 

 (1962) indicated two peaks of spawning, one in 

 the spring and the other in the sununer. Farther 

 north spawning is thought to be restricted to cer- 

 tain months; Joyce and Eldred (1966) stated that 

 at the St. Petersburg and St. Augustine latitudes 

 in Florida, spawning does not begin until early 

 spring, and Williams (1955a, 1965) reported that 

 in North Carolina postlarvae enter inshore water 

 only from May to November. 



The northernmost breeding population of P. d. 

 duorarum seems to be that ofl' North Carolina 

 where Burkenroad (1949), Broad (1950), and 

 Williams (1955a) reported mature females. 



In regard to the relation of spawning to water 

 temperature in P. d. duorarum, Eldred et al. 

 (1965) stated that rising temperatures seem to 

 be the most important factor inducmg spawning, 

 whereas Idyll and Jones (1965) indicated that 

 spawning intensity is afi'ected mostly liy absolute 

 temperature and clianges in temperature. The min- 

 imum temperature at which Jones et al. (1964) 

 found hours-old larvae was 19.6° C. vSpawning 

 has been recorded up to 30.1° C. (Eldred et al., 

 1965) and 30.6° C. (Jones et al., 1964). 



P. d. duorarum probably spawns more than once 

 as is believed to be true for various other Penaeus. 

 This assumption is based on the evidence that large 

 females about 180 mm. t.l. and longer are found 

 with their ovaries in a developing stage, which 

 suggests that preparation for a second spawning 



was taking place. Cummings (1961) found one 

 ripe female with large ova in addition to a group 

 of undeveloped ova, which also suggests the de- 

 velopment of two successive batches of eggs by an 

 individual. 



SEX RATIO 



The general ratio of males to females is about 

 1:1 in inshore jjopulations (Tabb, Dubrow, and 

 Jones, 1962; Eldred et al., 1961; Saloman, 1965). 

 The sex ratio in off'shore populations has not been 

 definitely established. Studies by Iversen et al. 

 (1960) on the Tortugas grounds showed that the 

 percentage of females does not increase with size. 

 Kutkuhn (personal communication), however, 

 found that the percentage does increase, and Ingle 

 etal. (1959) and Eldred et al. (1961), on the basis 

 of their sampling in a restricted area on the same 

 grounds, also found a predominance of females at 

 greater lengths. Sexes appear to segregate because 

 many samples contain but one sex. 



Postembryonic Development 



LARVAE, POSTLARVAE, AND JUVENILES 



By maintaining eggs that had been sjjawned in 

 the laboratory, Dobkin (1961) ascertained that 

 P. d. duorarum goes tlirovigh five nauplial stages 

 preceding the first protozoea. He also tried to work 

 out the rest of the larval development by assem- 

 bling stages obtained in jDlankton tows. This inves- 

 tigation produced a second and a third protozoea 

 and three mysis stages before the postlarvae de- 

 veloped. The studies by Jones et al. (1964) and 

 tlie rearing experiment by Ewald (1965b) seem to 

 corroborate that pink shrimp pass through 11 

 larval stages. The larval cycle in the laboratory 

 occurred in a minimum of 15 days, during which 

 time the animal grew from a first nauplius to first 

 postlarva. 



Dobkin (1961) described the larval stages of 

 P. d. duoranim and found them slightly larger 

 than, and different from, those of P. setiferus. 

 Some lar\-al specialists question the A"alidity of the 

 diagiiostic characters given, maintaining that ob- 

 ser\able distinguishing feature.s between the cor- 

 responding larvae of the two shrimps have not 

 been found. First and second postlarvae were 

 closely similar to those of P. .^cfiferus and had 

 about the same size range. In P. d. duorarum first 

 postlarvae ranged from 3.8 to 4.8 mm. t.l. (Ewald, 

 1965b, obtained somewhat smaller first postlarvae, 

 2.9 to 4.6 mm. t.l.) , the second 4.7 to 6.6 mm. In the 



514 



U.S. FISH AND WILDLIFE SERVICE 



