of sexes could not be eliminated, however, 

 due to the fact that sex was not determined 

 for all specimens entering the samples. 



There is the question whether single whole- 

 to-headless (or vice versa) conversion factors 

 computed from datacombinedover all seasons, 

 etc., have maximum utility. Certainly they 

 have a high degree of usefulness in the routine 

 task of converting landing data, whereas too 

 many factors, a set for every situation, would 

 result in a loss of efficiency in data com- 

 pilation without an appreciable gain in accu- 

 racy. Shrimp processors, on the other hand, 

 recognize the fact that these factors are not 

 stable and, particularly, that they do vary 

 from season to season in a more or less 

 predictable manner. Taking every advantage 

 of this seasonal variation, the Louisiana shrimp 

 canning industry, for example, employs in nor- 

 mal business transactions four whole-to-head- 

 less conversion factors (0,595 to 0.667), each 

 being used in accordance with whatever appears 

 to be the prevailing whole-headless relation- 

 ship. Their use must assume, however, that 

 the size of whole shrimp landed is uniform 

 throughout each landing (since the conversion 

 is on a number-per-pound basis) and that 

 sexes are always equally represented. In the 

 present study, lack of sufficiently refined 

 data precluded an analysis that would assess 

 the combined influence of season and sex on 

 the relationship of interest. To make such an 

 analysis would have necessitated a greatly 

 expanded study, a need not clearly justified. 

 For instance, the whole-to-headless factor, 

 0.646, obtained for the season September- 

 February when inshore and offshore white 

 shrimp landings in Louisiana reach a maximum, 

 closely approximates that calculated from data 



combined overall seasons (table 1). The latter 

 factor, 0.648, is equivalent to that resulting 

 when conditions are such that a 210-pound 

 barrel of whole shrimp yields 136 pounds of 

 headless shrimp. Use of this factor at other 

 seasons, despite the possibility of lower yields- 

 per-barrel, would not, because of significantly 

 smaller catches during these periods, create 

 any appreciable difficulty from an economic 

 standpoint — unless, of course, the seasonal 

 price of shrimp fluctuated adversely, 



SUMMARY 



Estimation of factors relating whole to head- 

 less weights in commercial Gulf of Mexico 

 shrimps yielded values of 0.620 and 1.610 for 

 brown shrimp; 0,625 and 1.599 for pink shrimp; 

 0.648 and 1.543 for white shrimp; 0.652 and 

 1.533 for seabobs; and 0.601 and 1.659 for 

 rock shrimp. Subsequent analyses disclosed 

 that their statistical reliability was such that 

 in all cases, the coefficient of variation was 

 less than 1 percent. It was revealed further 

 (1) that the values for all species deviated 

 significantly from those traditionally used 

 heretofore, namely, 0.595 and 1.680; and (2) that 

 although the factors of interest varied sig- 

 nificantly from a statistical standpoint between 

 sexes, areas, and seasons, departures from 

 those values listed above were of little im- 

 portance. The new values are recommended 

 for use in procedures involving weight 

 conversion of commercial shrimp landings. 

 Nomographs which facilitate the conversion of 

 individual whole or headless shrimp on a simple 

 weight or number-per-pound basis are pro- 

 vided for the three most common species. 



MS #1165 



GPO 9 26 47 9 



