The southern shrimp fishery at Rio Grsiide is decidedly seasonal 

 (see table 8), the season generally extending froin December through May. 

 At this time the young of P. brf-si l iens is are leaving Lagoa dos Patos for 

 the sea. The intraseasonal pattern is quite consistent in that the 

 heaviest runs almost always occur in March, but the fluctuations in annual 

 catch can be considerable. The 19Sh landings, for example, were about 3.i; 

 million pounds, whereas the 1955 landings were over I|..9 million pounds, 

 and the 1956 landings were not expected to exceed 2 million pounds. These 

 fluctuations in landings appear to be the result of biological rather than 

 economic factors. They may be associated with rainfall, since it was re- 

 ported that excessively rainy years were poor shrimp years, which suggests 

 that excessive quantities of fresh water in Lagoa dos Patos might restrict 

 the area of the shrimp nursery gro'unds. 



TABLE 8.— FRESH SHRIMP, RECEIVED AT PLAINS IN RIO GRAITOE, BRAZIL, 



BY MONl'HS, 1953 TO 1955 

 (Converted to pounds, heads-on weight) 



1/ Less than 100 pounds. 



15 



