PROGRESS IN BIOLOGICAL INQUIRIES, 193 2 101 



in the bays, creeks, and lakes associated with high temperatures, low 

 salinities, and shallow niuddy-hottom waters. As these young indi- 

 viduals grow, they move to more saline waters. 



There is a differential growth rate between the males and females 

 with the latter outstripping the former. In the young under 100 

 millimeters there is no significant difference in size between the sexes. 

 In the spring, however, during the development of sexual maturity a 

 differential growth is evident, in which the males are outstripped, so 

 that in the spawning population the females are longer by nearly a 

 tenth. There are also other morphological differences between the 

 sexes; the males are characterized by having the inner ramus of the 

 first pair of swimmerettes elongated and modified to form a structure 

 termed the petasma which is apparently used in the transference of 

 the spernuitophores. This structure is lacking in the female. 



That temperature influences the shrimp is evidenced by the fact 

 that in Barataria Bay, La., during the fall of 1931, there was found 

 a high positive correlation between the weekly average length of the 

 shrimp and the average weekly air temperature. At the same time, 

 there was a high negative correlation between the proportion of 

 females in the catch and the temperature. In other words, an increase 

 in air temperature was associated with an increase in the average 

 length of the shrimp and a decrease in the proportion of females. 

 Similarly a decrease in temperature was associated with a decrease 

 in the average length of the shrimp and an increase in the proportion 

 of females. 



During the spawning season, there is evident a wide divergence in 

 the proportion of sexes in the inside and outside waters of Georgia. 

 From September 1931 to March 1932 the females were slightly more 

 abundant than the males in both the inside and outside waters. Begin- 

 ning about April (for both 1931 and 1932) the percentage of females 

 on the inside rose rapidly until by June over 80 percent of the pop- 

 ulation in the inside waters was composed of this sex. After the 

 June peak, the percentage dropped until the disappearance of the 

 large year-old shrimp from the catch made it impossible to follow the 

 sex ratio of this group. During the period of rapid rise in the pro- 

 portion of females on the inside, there was also a change in the propor- 

 tion on the outside. At first there was a rise in the percentage of 

 females then a rapid drop to about 30 percent, where it remained 

 until the large group disappeared. 



For the first two months following the appearance of the young 

 shrimp-of-the-year in the commercial catch, the males outnumbered 

 the females in this group in both the outside and inside waters. That 

 the rapid rise of the proportion of females on the inside and the 

 decline on the outside was closely associated with spawning can 

 hardly be doubted, as these changes in the population appeared dur- 

 ing the height of the spawning season. 



The shrimp is apparently omnivorous in its feeding habits as a 

 wide variety of both plant and animal remains have been found in 

 the stomachs. 



In an attempt to determine the effect of trawling on species other 

 than shrimp, an extensive survey was carried on for 2 years in Georgia. 

 From October 1, 1930, to September 30, 1932, 386 hauls were made 

 by launch No. 58 in the inside tidal waters of Georgia suitable for 

 commercial trawling operations. (Similar studies are now in progress 



