PROGRESS IN BIOLOGICAL INQUIRIES, 1935 401 



the present inadequate records, to secure an estimation of the fluctua- 

 tions. Since the shrimp fishery extends over practically the entire 

 coastal area of eight Southern States, it is impossible for the present 

 staff to gather these statistics in the detail in which they should be 

 secured. 



Sexual maturity. — ^At Beaufort, N. C, Dr. J. S. Gutsell completed 

 his studies of the structiu*e and development of ovaries and ovarian 

 eggs of the commercial species of shrimp and is finishing a report on 

 his findings. This investigation has shown that in the Beaufort 

 region the common shrimps in many instances probably spawn at least 

 twice during the spawning season. Spawning at Beaufort is most 

 active in May, but continues throughout the summer and a large part 

 of the autumn. It seems probable that some of the shrimp in this 

 vicinity may survive through two winters and spawn during the 

 second year. In any event, the numbers which spawn in their second 

 year appear to be exceedingly few. Definite criteria have been found 

 for mature and spent ovaries. 



Food. — Since the completion of the ovarian studies Dr. Gutsell 

 has been engaged in determining the food of the shrimp and has 

 examined the contents of hundreds of stomachs of the common 

 shrimp, P. set! ferns., and the grooved shrimp, P. hrasfliensls, includ- 

 ing a considerable number from young of 1 to 3 inches in length. In 

 addition, shrimp have been kept in aquaria and fed various foods. 

 Fish, shrimp, and oysters were readily eaten, but an apparent prefer, 

 ence seemed to be shown for small barnacles. The stomach contents 

 indicate that the principal natural diet appears to be small Crustacea 

 (such as Cumacea) and polychaete worms. Both these forms are 

 generally found burrowing in mud or sand, where they are apparently 

 readily found by the shrimp. Mollusks, barnacles, fish, plants, and 

 plant material, including diatoms, small filamentous algae, pieces of 

 tissue from higher plants, and sand are also found in the stomachs 

 of the shrimp. 



Since the variation in food supply may vitally affect the abundance 

 and distribution of shrimp, it is a subject which cannot be neglected 

 in the present study, and which may give an important clew to the 

 causes of fluctuation in the shrimp fishery. 



Weight-length. — In Texas, Kenneth H. Mosher has continued the 

 sampling of the commercial catches during 1935. A total of 9,773 

 slirimp were measured and examined for stage of sexual maturity. Of 

 this number, 5,435 were from Aransas Pass, 4,038 were from Galveston, 

 and 300 were from Port O'Connor. The relative importance of P. 

 setiferus is indicated by the fact that of all the shrimp examined 

 throughout tlie entire year over 98 percent were of this species. In 

 addition to the length measurements, Mr, Mosher weighed 4,200 

 shrimp in order to obtain an extensive list of data from which to 

 compute the weight-length relationship. These data show that sea- 

 sonal differences occur in the weight-length relationship, and may, 

 therefore, throw light on various questions concerning shrimp biol- 

 ogy ; for example, on whether or not overcrowding of the population 

 exists. This study will therefore be continued. 



Larvae. — Our understanding of the life histories of the two com- 

 mercial shrimp, P. setiferus and P. hrasiliensis and other peneids has 

 become more clarified during the past year by the recognition of the 

 early growth stages of both species by John C. Pearson who has been 



