PROGRESS IN BIOLOGICAL INQUIRIES, 1934 357 



does not appear until the e«j:<]:s are fully •2;ro'vvn. liy luciins of it a 

 substantially nuitured o<zix nuiy he ]iositively identificHl. This is of 

 importance, for if examination of an ovary shows that this structure 

 is present in the crop of laro^e e^gs it may be stated without any doubt 

 that the shrimp is ready to spawn; thus, with proper sampling, the 

 spawn inir season can be determined with precision. 



In addition, Dr. Guisell has examined a number of shrimp which 

 appear to have recently s])awne(l. From those studios he has 

 secured ovarian characteristics which ap])arontly are dia<rnostic of 

 spent shrimp. This is a ])articularly im]iortant and vfduable con- 

 tribution. Dr. Outsell is preparing a detailed report of these investi- 

 gations which he expects to have completed before the end of the 

 1935 spawning season. The completion of the report is expected to 

 terminate the study of this particular problem. 



Mr. Anderson, (hiring 1934, continued the sampling of the shrimp 

 population along the South Atlantic coast aboard Launch 5S. The 

 territory sampled re])iesents about 95 percent of the shrimp fishery 

 on the Atlantic coast. For the purposes of this investigation, 9 out- 

 side and 2 inside stations were visited once each month and from 

 2 to 4 trawl hauls were taken at each station. The outside stations 

 are from 35 to 50 miles apart and extend from Cape Romain, S. C, 

 to Cape CanaA'eral, Fla. The stations were so chosen as to give a 

 representative sample of the shrimp population at the more impor- 

 tant fishing centers along this coast. At each station otter trawl 

 hauls and plankton tows were made, surface and bottom temperatures 

 recorded, and salinities determined. A representative sample of the 

 shrimp obtained was measured, the development of gonads noted, 

 and the numbers of each species of fish secured were recorded. 



Confirmation of last year's data was obtained which indicated that 

 the large shrimp disappear from the usual fishing grounds during 

 the fall and winter along the Georgia and northern Florida coast. 

 Similarly, confirmation was also secured for last yeai''s data which 

 indicated a })rogressive increase in size of the common shrimp from 

 north to south along the Florida coast during the fall and winter. 

 Four possible interpretations may be placed upon these phenomena : 



1. There is a southward movement of the larger shrimp along the 

 Florida coast during the fall and winter. 



2. The larger Georgia and northern Florida shrimp move off- 

 shore during this period. 



3. Due to heavy fishing in the summer and early fall, the larger 

 shrimp are depleted along the Georgia and Florida coasts. 



4. Combination of any two or all three of the above factors may 

 be occurring. 



As a possible means of interpreting these changes in the population 

 of the shrimp on the South Atlantic coast, Mr. Lindner has been con- 

 ducting racial studies at frequent intervals in four widely separated 

 localities. Altliough those studies have not been completed, it has 

 been found that there are differences in body proportions in the 

 shrimp in different localities. A complicating factor arises in that 

 these differences appear to be associated not only with locality but 

 also with .season of the year and age of the shrimp. An important 

 discovery resulting from this study has furni.shed a means of distin- 

 guishing between group and I group shrimp during the late summer 

 and early fall. 



