spawning seasons of the brown shrimp by 

 ovarian examination, reported that ripe brown 

 shrimp rarely occur in water less than 27 m. 

 deep along the Texas and Louisiana coasts. 



SPAWNING IN RELATION TO 

 BOTTOM TEMPERATURES 



Because penaeids are poikilothermic and 

 larval abundance is apparently related directly 

 to seasonal warming of bottom waters, we con- 

 sidered the possibility that spawning, indicated 

 by the presence of naupliar stages in plankton 

 hauls, might occur over a rather narrow tem- 

 perature range. The yearly range in bottom 

 temperatures decreased with an increase in 

 depth. At the shallowest stations, tempera- 



tures ranged from 5.9" to 30.4- C, and at the 

 deepest stations, from 16.8 to 26.2° C. In gen- 

 eral, naupliar stages occurred over a tempera- 

 ture range of 17.0 to 28.5° C, but the magni- 

 tude of the range varied between depths (table 

 5) . At 14-, 27-, 46-, and 82-m. stations the mag- 

 nitude of the range where nauplii were taken 

 was 3.8°, 11.5 , 8.5°. and 5.6° C, respectively. 



DISTRIBUTION OF PLANKTONIC-STAGE 

 SHRIMP 



Ai'eal distribution charts for each planktonic 

 stage were made for January to March, April 

 to August, and September to December. Values 

 plotted at each station were obtained by averag- 

 ing catches per 100 cm.^ of water filtered for 



95 W 



Figure 5. — Relative abundance and distribution of planktonic-stage Penaens spp., January to March 1961. 

 U.S. FISH AND WILDLIFE SERVICE 329 



