Figure 2.— Double-rigged, Florida-type trawlers predominate in the Gulf of Mexico shrimp fleet. 



to rely to an increasing extent on small shrimp to 

 keep production at a profitable level (Kutkuhn, 

 1962). 



Believing that utilization might be improved by 

 inhibiting the harvest of small shrimp, the Florida 

 State Board of Conservation established in 1957 

 what is called a "control" area (Ingle, Eldred, 

 Jones, and Hutton, 1959, figs. 1-3). This area 

 was so situated that the preponderance of shrimp 

 entering the open fishing grounds ostensibly 

 migrated through it. Fishing was not to be per- 

 mitted in the control area whenever periodic 

 surveys disclosed that the shrimp therein were 

 smaller than the size at which 50 headless and 

 uniformly sized individuals weigh 1 pound. This 

 regulatory concept was revised in mid- 1961 when 

 the Board delineated a permanently closed con- 



servation area which incorporated part of the 

 earlier control area and extended the latter's 

 boundaries to enclose all of Florida Bay (fig. 1). 

 Also circumscribed was a less extensive manage- 

 ment (control) area from which only shrimp of 60 

 "headless-count" or larger may be taken. 



MARKING PHASE 



The Tortugas mark-recapture experiment was 

 designed to take complete advantage of the 

 physical and regulatory features of the fishery. 

 Shrimp destined to make up the experimental 

 population were to be captured, marked, and 

 released just prior to the onset of heaviest expected 

 fishing intensity. Concentrations of precom- 

 mercial-size shrimp moving through the State 

 management area offered the opportunity to 



316 



U.S. FISH AND WILDLIFE SERVICE 



