9'° ^«° !Z ^ .^ 



I ' ' ' -'_ _ _-» n.^o Qia Q3» * 



Figure 4.— Distribution of planktonic stages of species of Penaeus in the northwestern Gulf of Mexico, 



January to March 1963. 



extended from 15 fath. south of Cameron, La., 

 to the westernmost transect northeast of 

 Brownsville, Tex. To the east, a small con- 

 centration occurred just west of the Mississippi 

 Delta in 15 and 40 fath. 



In October to December, spawning continued 

 to increase as is shown by the greater num- 

 bers of early larval stages in plankton hauls. 

 Although planktonic stages were again widely 

 distributed, they occurred primarily in waters 

 outside the 7j-fath. contour. Highest concen- 

 trations were restricted generally to a zone 

 between the 15- and 25-fath. contours in the 

 west and to the 25-fath. zone in the east. 



Seasonal Trends in Abundance, 1962 and 1963 



Trends in the abundance of Penaeus larvae 

 (postlarvae excluded) at comparable depths 

 were similar in 1962 and 1963. In the 7|-fath. 

 depth zone, numbers of larvae increased in 

 the spring, nnaintained a relatively high level 

 through summer, and decreased in the fall. In 

 15 to 25 and 35 to 60 fath. of water, two peaks 

 of abundance were evident- -one in late spring 

 and early summer and the other in the fall. 

 Greatest numbers of larvae were taken during 

 the fall. In both years, about 22 percent of the 

 total, weighted larval catch occurred in 7| 

 fath., 58 percent in 15 to 25 fath., and 20 per- 

 cent in 35 to 60 fath. (fig. 5). 



Earlier data indicated that larval abundance 

 was closely related to water temperature, 

 particularly landward of 25 fath. In 1962, 



lOOi- 



< 



I 0,1 



\ I 



\ I 



> / 



\ / 



\ / 



T r — I 1 1 1 r 



15-25 FATHOMS 



m 10 



1 1 ; 1 1 1 1 r 



35-60 FATHOMS 



Figure 5. — Abundance of Penaeus larvae in depths of 

 7| fath., 15-25 fath., and 35-60 fath., 1962. 



11 



