100 U.S. BUREAU OF FISHERIES 



where the laboratories are located. The stations have been so chosen 

 that they represent a wide variety of ecological conditions that grade 

 from the brackish waters of Bayou St. Denis in upper Barataria Bay 

 to the saline waters of the Gulf 12 miles off Barataria Pass. 



The stations are visited twice every half month and at each an 

 otter trawl haul is made, the surface- and bottom-water temperatures, 

 salinity, pH and turbidity determined, and, if conditions are suitable, 

 a plankton tow is taken. When the trawl haul is completed the 

 catch is emptied on deck and separated into piles according to species. 

 Each species of fish is counted and recorded and a random sample of 

 200 Penneus setijerus (common shrimp) is taken. Each shrimp in 

 the sample is sexed, measured, and the gonad development noted. 

 The measurements are made from the tip of the rostrum or "spine" 

 to the end of the telson or "tailfin." They are taken to the nearest 

 millimeter on an especially devised measuring board and recorded as 

 total length. As the shrimp of lesser economic importance are found 

 in the random sample of 200 common shrimp, they are separated out 

 and later the same procedure of sexing, measuring, and gonad exam- 

 ination is carried out on them. In this way the ratio of the common 

 shrimp to other species in the catch is determined. 



Somewhat similar sampling procedures are followed in both North 

 Carolina and Georgia, but in Texas the method of sampling is altered 

 to fit the commercial fishery. Here the observer is located at a can- 

 nery from which he obtains random samples of shrimp from eight 

 commercial trawl boats each week. The length measurements and 

 other observations on the specimens are made in the same manner as 

 in Louisiana. 



There are three species of sea shrimp, all of which are members of 

 the family Penaeidae, that are of commercial importance in the South 

 Atlantic and Gulf States. The common shrimp or lake shrimp 

 (Penaeus setiferus) comprises over 95 percent of the total, while the 

 grooved shrimp (Penaeus brasiliensis) and the sea bob (Xiphopenaeus 

 kroyeri) together yield the remainder. Since the common shrimp 

 (Penaeus setiferus) is by far the most important commercial species, 

 the investigations have been centered chiefly on solving the life his- 

 tory of this species. These investigations have already yielded many 

 facts concerning the life history of the common shrimp (Penaeus 

 setiferus) , and a report is now in press covering some of the findings — 

 a brief summary of the more important ones will be given here. 



From an analysis of the length-frequency data gathered in North 

 Carolina, Georgia, Louisiana, and Texas, it is evident that the common 

 shrimp remains in the catch for only 1 year. In the Georgia area, 

 the shrimp spawn from about the latter part of March until about 

 the end of August. The young shrimp hatched in the spring, grow 

 rapidly and appear in the fishery during July, with a mode at about 

 90 millimeters. These small shrimp-of-the-year furnish the heavy 

 fall and early winter catch. The following spring they mature, spawn, 

 and pass from the fishery. By the first of October, there is none of 

 these year-old shrimp remaining in the Georgia waters; they disappear 

 rapidly during July, August, and September, following the appearance 

 of the young of the succeeding year class. 



From all indications, the spawning seems to be in the outside waters 

 or at least in waters of high salinity. The young post-larval stages, 

 from 8 or 9 to 100 millimeters, are found in abundance on the inside 



