oo 



OO'OOO O ID o 00 



WHOLE SHRIMP 

 NUMBER PER POUND 



WHITE SHRIMP (P. SETIFERUS) 



40 50 60 



WHOLE SHRIMP 



WEIGHT IN GRAMS 

 (X) 



Y = 0.644X + 0.01 1 



X = I.534Y + 0.081 



(N= 1306) 



Figure 3. --Nomograph for conversion of weights and numbers of whole and headless white shrimp. 



(fig. 2) of a uniform size such that 20 weigh 

 1 pound will yield headless shrimp of a size 

 such that 32 will weigh the same. 



The relative precision inherent in the equa- 

 tions given in the second column of table 1 

 and in the lower right hand corner of each 

 graph can be exemplified by substituting some 

 hypothetical data in those for white and brown 

 shrimp. Appropriate calculations reveal that 

 in the white shrimp (fig. 3), the headless 

 weight of any individual whole shrimp may be 

 estimated to within I gram with a confidence 

 probability of 95 percent. Thus the esti- 

 mated "tail" weight of a white shrimp weigh- 

 ing 40 grams in the round would be 25.77 

 ± 0.85 grams. 



Due to an appreciably smaller sample size, 

 conversion estimates in the brown shrimp 

 (fig. 1) will be somewhat less precise than 

 those in the white shrimp. Thus the estimated 

 whole weight of a headless brown shrimp 

 weighing 45 grams is 72.61 t 1.95 grams, 

 indicating precision of an order of magnitude 

 still sufficiently small for all practical pur- 

 poses. In general, the precision of conver- 

 sion estimates for the first four species listed 



in table 1 will be such that estimates within 

 2 grams (most within 1 gram) will be the 

 rule. 



Obviously, the nomographs presented here 

 only enable weight conversion in the case of 

 individual shrimp, and would find greatest 

 use by the fishery biologist faced, for ex- 

 ample, with the problem of converting head- 

 less shrimp sampled for weight-frequency 

 analysis to whole-shrimp units. The statistical 

 agent, on the other hand, has a greater need 

 for a simpler function which would allow 

 him to convert large- volume landings in either 

 direction and with reasonable precision. 



In re-examining the prediction equations 

 given in the second column of table 1, note 

 the rather small values indicated for the 

 equation parameter. A, the expression for 

 either variable when the other is zero. Theo- 

 retically, A should always be zero since a 

 shrimp without a head (or conversely, without 

 a tail), regardless of stage in morphological 

 development, is a physical impossibility. 

 Parenthetically, "head" as used herein and 

 throughout the shrimp industry, refers to the 

 shrimp's cephalothorax, which does not be- 



