PROGRESS IN BIOLOGICAL INQUIRIES, 193 3 339 



allows for the operation of subsurface and bottom fine mesh nets. 

 Consequently, it is expected that during the coming spawning season 

 the young stages of /-*. scfifervs will be found in considerable abun- 

 dance in the oil'shore waters. 



Body proportional measurements of Penaeus setifemus in Louisi- 

 ana indicate the possibility of two groups or races of common 

 shrimp. This work is still in a formulative stage and must be con- 

 tinued over a longer period of time and in more localities before 

 definite conclusions can be drawn. 



In Louisiana and Texas a disappearance of large Penaeus setif- 

 £rus^ similar to that in Georgia, takes place during the winter. In 

 these two States there is no winter fishery for large shrimp, such 

 as occurs in Florida, to indicate where the winter habitat may be. 

 At the onset of colder weather in the fall the shallow coastal waters 

 of Louisiana cool rapidly to a distance of about 10 miles offshore. 

 Further offshore, beyond this variable zone, bottom temperatures 

 are higher. As greater depths are reached, however, bottom tem- 

 peratures of the Gulf again decline. Consequently, there is a zone of 

 warm bottom water off the Louisiana coast throughout the winter 

 bounded on one side by colder inshore waters and on the other by the 

 cold waters of the depths of the Gulf. The recent addition of a 

 winch to the Blach Mallard has allowed collecting cruises in this 

 warm water zone as weather permitted. Both large P. setiferus and 

 P. hrasiliensis were found in this area during the winter of 1933. 

 Collecting trips are made throughout this warm water zone off 

 Louisiana whenever possible in an effort to determine whether or 

 not shrimp concentrate in dense schools in certain offshore localities 

 as it is customary for them to do inshore. With the present type of 

 vessel it is exceedingly difficult to make any intensive survey of 

 offshore waters because rough seas are prevalent throughout most of 

 the winter. 



The grooved shrimp, Penaeus hrasilienms, evidently spawns most 

 prolifically in the Gulf throughout the winter for during December, 

 January, February, March, and April an abundance of postlarval 

 young are taken in the surface plankton tows. From March until 

 June the young grooved shrimp which were spawned in the Gulf 

 are found in large quantities in the inside waters along the entire 

 Louisiana coast. As they develop, the grooved shrimp disappear 

 from the inside and adjacent offshore waters and few remain by 

 July or August. These shrimp, with few exceptions, cannot be found 

 until the following winter when a newly hatched group of young 

 appears. During the winter of 1933 large, mature grooved shrimp 

 were obtained in nearly every haul in the offshore warm water zone. 

 This fact indicates that the inside waters serve not only as nursery 

 grounds for the common shrimp but for the grooved shrimp as well. 

 The grooved shrimp, however, move offshore at an earlier stage than 

 the common shrimp. With the present geographic limitations of the 

 fishery, the young grooved shrimp leave the fishing areas before 

 they have reached sufficient size to be of much commercial value. 



Except for the detailed accounts of one cannery, it has been im- 

 possible to secure adequate catch records to determine the relative 

 abundance of the shrimp. The data which have been obtained do 

 not indicate serious depletion of the supply, but this fact does not 



