50 r 



-1 1 1 i 1 1 — r~ 



5 6 7 8 9 10 II 12 13 14 5 6 7 8 9 10 II 12 13 14 



TOTAL LENGTH (MM. 



BROWN SHRIMP 

 ■WHITE SHRIMP 



Figure 3. — Seasonal size distribution of postlarval brown and white shrimp at Galveston Entrance, 1960-63. (N indicates 



sample size.) 



period and twice each month at four stations along 

 Galveston Island's Gulf beach for 1 year. 



Postlarval brown shrimp were collected at Gal- 

 veston Entrance from February until mid-December 

 of each year. At Galveston beach stations, they 

 were found throughout the year but in smaller num- 

 bers during the winter. Numbers of brown shrimp 

 postlarvae reached an annual peak between mid- 

 March and mid-April. 



Postlarval white shrimp were first caught at Gal- 

 veston Entrance and along the beach in May and 

 were most abundant through the summer. 



Postlarvae of browii and white shrimp were sep- 

 arated by morphometric characters and by the sea- 

 sonal occurrence of each species in the adjacent 

 estuary. The brown shrimp was the only Penaeus 

 species at the postlarval stage present along the Gal- 

 veston Island beach and at the entrance of Galveston 

 Bay from December through April. All individuals 

 were relatively large (11 mm. or longer) during this 

 period. After April, their average size decreased. 



remained relatively small throughout the summer, 

 and then increased again in the fall. White shrimp 

 postlarvae first appeared in May at lengths much 

 shorter than those of brown postlarvae in the same 

 collections; the total lengths of the majority ranged 

 from 6.0 to 8.0 mm. During the summer, the length 

 distributions of postlarvae of brown and white 

 shrimp overlap in the 8- to 10-mm. length range. 

 The two species at this stage of development may, 

 however, be separated by the morphological char- 

 acteristics described by Pearson (1939) and Williams 

 (1959). At times, the largest white shrimp post- 

 larvae in a sample were longer than the smallest 

 postlarvae of brown shrimp, but the mean lengths of 

 the white postlarvae were always less than those of 

 the brown postlarvae. 



The similarity of mean lengths of postlarvae col- 

 lected along the beach and at Galveston Entrance 

 suggests that significant growth does not occur along 

 the beaches and that the surf zone is not an impor- 

 tant nursery area for small slirimp. 



DISTRIBUTION OF SHRIMP NEAR GALVESTON 



153 



