PROGRESS IN BIOLOGICAL INQUIRIES, 1935 403 



sible explanations ; namely : ( 1 ) A southern migration into Florida 

 of the larger Georgia shrimp during the fall and winter. (2) Deple- 

 tion through fishing of the large Georgia shrimp, while the Florida 

 fishery was maintained by natural growth of native shrimp. (3) A 

 winter offshore movement in Georgia of the more developed shrimp. 

 (4) A combination of any two or all three of the above possibilities. 

 The regular and recurrent nature of these phenomena leads us to 

 believe that migration is probably the most important factor influ- 

 encing them. 



Measurements were made by Mr. Lindner in an attempt to deter- 

 mine whether or not differences in body proportion existed which 

 would make possible the identification of shrimp as to point of origin. 

 It was found that although racial differences do seem to occur in the 

 shrimp, possible intermingling and probable seasonal and environ- 

 mental changes in body proportion have made it impossible to inter- 

 pret these data without experimental studies. 



Tagging experiments w^ere conducted on confined shrimp at Aran- 

 sas Pass, Tex., by Mr. Mosher and Mr. Lindner in order to deter- 

 mine the feasibility and best means of marking. These experiments 

 showed that the celluloid disc type of tag affixed to the first abdomi- 

 nal somite of the shrimp was most probably the best method as it 

 apparently interfered less with movements and molting, and was 

 retained better than other devices. During September, October, and 

 November this method was placed in practice in the field by Mr. 

 Lindner and Mr. Anderson. A total of 3,800 shrimp were tagged 

 along the Georgia and Florida coasts. 



The success of this method of tagging is evidenced by the fact that 

 by the end of December almost one-fourth of the tagged shrimp had 

 been taken by the fishermen and returned to the investigators. Al- 

 though these experiments are by no means completed it is quite evi- 

 dent that there does occur a southward movement of shrimp from 

 Georgia into Florida during the fall and winter. Some of the tagged 

 shrimp had moved distances upwards of 200 miles. The success of 

 the Florida winter fishery probably thus depends to a large extent 

 upon the production of shrimp in Georgia, and upon these shrimp 

 escaping the Georgia fishermen. The numerous returns indicate that 

 the fishery is very intense. The importance of continuing these 

 studies is obvious. 



During the coming year tagging operations will be extended 

 throughout the entire area of the South Atlantic shrimp fishery in 

 order to determine whether there is a return movement of shrimp 

 from Florida to Georgia in the spring, and also to discover the direc- 

 tion and extent of the migrations along the North and South Carolina 

 coasts. Data have been collected which indicate that there may also 

 be a winter concentration of shrimp in the vicinity of Cape Hatteras. 

 In addition, arrangements have been made for securing a pond in 

 the vicinity of Brunswick, Ga., where experiments can be conducted 

 to determine the mortality owing to tagging. From these experi- 

 ments, and from the tagging returns it is hoped that some conclu- 

 sions can be derived as to the actual intensity of the fishery. 



It is evident from data gathered in Louisiana and Texas that the 

 Gulf shrimp also are migratory. Throughout the fall and winter 

 it is customary for the majority of large shrimp to disappear from 



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