JONES and DRAGOVICH: UNITED STATES SHRIMP FISHERY 



46 60 



41 4S 



36 40 



26 30 



16 20 





• 



77 



\ O 



GUIANA 



78 



EFFORT: HOURS X 100 



>200 ^A 150-2O0 



79\ 



O x O x • • • 



\ " \ 



HAZH 



80 



\ o \ o \ • 







81 



\ o \ o \ • • • • ''., • \ • • 



& 



DEPTH IN FATHOMS 



FIGURE 10. — Distribution by fishing zone and water depth of the fishing effort reported on logbooks by U.S. vessels in the Guianas- 



Brazil fishery, July 1972 to December 1974. 



that the maximum sustainable yield was 28.7 

 million pounds, which could be taken by 692 ves- 

 sels. This estimate was made from the relation- 

 ship between the logarithm of the annual catch 

 per vessel and average number of vessels (r = 

 0.80) for the years 1965-74. A linear surplus yield 

 model applied to the data for the same years 

 suggested that the maximum yield was 27.1 mil- 

 lion pounds, which could be taken by 531 vessels 

 (r = 0.82) (Figure 14). 



The average number of vessels is the only index 

 of total effort available for the fishery before 1972. 

 The double-rigged Florida-type shrimp trawler 

 has been, almost without exception, the only type 

 vessel used in the fishery. Increases in fishing ef- 



ficiency probably occurred as the length and 

 horsepower of the vessels increased (Jones and 

 Dragovich 1973), and as the addition of refrigera- 

 tion equipment permitted longer and farther 

 ranging fishing trips; but these changes were 

 minor in the 1965-74 period. 



Before 1965 the increase in average annual 

 catch per vessel paralleled the increase in fleet size 

 (Table 5). The catch per vessel rose sharply be- 

 tween 1961 and 1962; from 1962 to 1965 the in- 

 crease continued but was less pronounced. Pre- 

 sumably, during these early years of the fishery, 

 the efficiency of the fleet increased as familiarity 

 was gained with the fishing grounds. The earlier 

 data, therefore, were not used in the model. After 



711 



