1956 ' 1957 ' 1958 ' 1959 ' I960 ' 1961 ' 1962 ' 1963 ' 1964 

 Figure 20. — Monthly landings of white shrimp from Louisiana waters'and brown shrimp from Texas waters, 1956-64. 



Gulf coast from Mobile Bay to the United 

 States-Mexican border indicate that the rela- 

 tive abundance of brown shrimp during a given 

 period is about the same throughout this area. 

 In years of high abundance, brown shrimp 

 are plentiful over the entire area, and during 

 years of low abundance, brown shrimp are 

 scarce over the area. The factors respon- 

 sible for such widespread fluctuations in abun- 

 dance are unknown, but are assumed to be linked 

 to oceanographic conditions. Taking this type 

 of comparison one step further, figure 21 

 illustrates a relation during 1958-64 between 

 the abundance of brown shrimp along the 

 Texas coast and pink shrimp on the Tortugas 

 grounds. If the levels of abundance of shrimp 

 in these two widely separated areas follow 

 similar trends in the future, we will have 

 stronger evidence that widespread oceanog- 

 raphic conditions are responsible for much 

 of the difference between years of good and 

 poor harvests. 



Fluctuations in abundance of white shrimp 

 do not correspond to those of pink or brown 

 shrimp, possibly because the former are 

 spawned in near- shore Gulf waters where the 

 effects of oceanographic factors are confounded 

 by influences of land origin. Like the brown 

 shrimp stocks, however, population levels of 



60r 



TORTUGAS PINK SHRIMP 



1958 



I960 



1962 



1964 



Figure 21. --Comparative abundance of 

 Tortugas pink and Texas brown 

 shrimp, 1958-64. 



25 



