with similar distribution of shrimp sizes 

 were pooled. The diagrams were con- 

 structed from data presented in the appen- 

 dix. 



SEX RATIO 



The sex ratios in each sample which had 

 at least 30 of each sex showed no marked 

 difference with changes in the size of 

 female shrimp (fig. 5). The ranges of sex 

 ratios for each cruise are shown in 

 figure 6. The mean percentage of females 

 varied considerably for each cruise, sug- 

 gesting that either there is grouping by- 

 sexes on the grounds or our sampling 

 induced variation, or both. There was an 

 indication of fewer females in the catches 

 from September to December, while during 

 January there were more than 50 percent 

 females; there were close to 60 percent 

 females during July-September. 



IS 20 2S 30 is 40 4S SO 



AVERAGE FEMALE CARAPACE LENGTH (MM) 



Figure 5.--The percentage of females by size of female 

 shrimp. 



( ) 0) 



c 



WWBCR Of SWLES USeO T 



| ...Ne, | .o. | ...L.. | ,.. | ... | .,. | ...U|..,|.„.U | „, | .„. | 



1*57 I IH. 



Figure 6, 

 shrimp 

 1958. 



--The range and mean percentage of female pink 

 in the catches, by months, September 1957-November 



SIZE OF SHRIMP 



DISTRIBUTION OF SHRIMP BY SIZE 

 AND DEPTH 



The average size of shrimp on the fish- 

 ing grounds increases with depth. This 

 relationship is illustrated by plotting the 

 average sizes of all samples throughout 

 the year against depth, keeping the sexes 

 separate (figs. 7 and 8). 



45 



40 



z 

 s 



35 



< 30 



25 



20- 



15 



N°225 



• 1. 

 . I • 



1 L . 



. I 



I . : 



i.^ 



10 



15 20 



DEPTH (FM.) 



25 



Figure 7.--Relationship of depth of water and average size of 

 female shrimp. 



In addition to separate treatment of data 

 from males and females, the trend of the 

 combined sexes is shown (fig. 9). The 

 curve representing male data shows a 

 slope of 0.618 mm. (Sd yx = 0.752 mm.) 

 for each fathom change in depth. The 

 female shrimp show a more rapid in- 

 crease in length of carapace with increase 

 in depth, 0.868 mm. (Sd y-x = 1.16). The 

 combined data provide an intermediate 

 slope, 0.739 (Sd yx = 0.881). Despite this 

 relation between size of shrimp and depth, 



10 



