PROCEDURE 



Design of Experiments 



The experimental plan was based on the assump- 

 tion that nursery grounds that furnish recruits to 

 Tortugas and Sanibel pink shrimp populations are 

 located in the estuaries and shallow marine waters 

 of south Florida. To delineate these nursery 

 areas and relate them to specific offshore shrimp- 

 ing grounds, young shrimp at selected coastal 

 sites were captured, marked, and released near 

 the point of original capture. Recovery of these 

 marked shrimp on the Tortugas or Sanibel grounds 

 established the affiliation of shrimp from a nursery 

 area to those on the offshore grounds. 



Inshore release sites were selected geographically 

 near centers of juvenile shrimp abundance. At 

 several of the selected locations, juvenile pink 

 shrimp are plentiful only seasonally. Therefore, 

 to obtain sufficient shrimp for marking, timing of 

 inshore releases necessarily coincided with these 

 estuarine peaks of abundance. Proceeding with 

 marked shrimp releases according to these criteria, 

 we established the affiliation of shrimp from 

 shallow water areas along an extensive expanse of 

 coastline to the offshore grounds. 



Three offshore mark-recovery experiments, de- 

 signed primarily to determine growth and mortal- 

 ity rates, also furnished information concerning 

 migration and distribution of the larger pink 

 shrimp. 



Marked shrimp, which form the basis of this 

 report, were stain-marked by injection of biological 

 stains (Menzel), 1955; Dawson, 1957; Costello, 

 1964). 



Recovery of Stained Shrimp 



Shrimp fishermen and packers were informed of 

 the purpose of mark-recovery experiments prior to 

 each release of stain-marked shrimp. Preserved 

 stain-marked shrimp in glass vials were displayed 

 and posters describing stain-marked shrimp were 

 placed in shrimp packing plants. For each 

 recovery, together with the position, date and 

 depth of recapture, rewards of from $1 to $5 were 

 offered at various stages of the program. 



Except for four recoveries made by Bureau of 

 Commercial Fisheries vessels, all 2,201 of the 

 marked shrimp recoveries which form the basis of 

 this report were made by commercial fishing 

 vessels. Inshore recoveries were made by bait 



shrimp fishermen in Biscayne Bay, Barnes Sound, 

 and Florida Bay, and near Indian Key. 



Stain-marked shrimp released offshore in or near 

 areas where shrimp trawlers were active were 

 caught and returned for reward payments in 

 surprising numbers. Two groups released on the 

 Tortugas grounds yielded 1,227 recoveries — 21.1 

 percent of the first group released and 33.3 percent 

 of the second group released. On Sanibel, 563 

 marked shrimp were recovered from a release of 

 2,496 — a 22.5 percent recovery. 



Inshore or estuarine releases were usually in 

 localities remote from commercial fishing opera- 

 tions. This is reflected in recovery rates which 

 averaged less than 1 percent of the numbers 

 released. 



Recovery rates are affected by factors such as 

 the effective number of marked animals released — 

 the number returned safely and in good condition 

 to the environment from which captured. Also 

 affecting recovery rates are direction of migration, 

 location and amount of fishing effort, and aware- 

 ness and interest of industry personnel in a position 

 to recover marked shrimp. Some or all of these 

 factors varied during the course of these experi- 

 ments, and they have been considered in evaluat- 

 ing the data. 



MIGRATIONS 



Release and Recovery Sites 



Table 1 summarizes pink shrimp mark-recovery 

 experiments in south Florida waters from 1958 to 

 1963. Release sites are numbered in chronological 

 order. 



Figure 2 depicts the numbered release sites and 

 general area of recovery of stain-marked shrimp. 

 Arrows joining release and recovery sites do not 

 necessarily indicate routes of migration. 



On the southwest coast of Florida, marked 

 juvenile pink shrimp released in large numbers in 

 Pine Island Sound (10) migrated to the south and 

 northwest portions of the Sanibel grounds but not 

 to the Tortugas grounds. A release southeast of 

 Sanibel, at Indian Key (14), resulted in recoveries 

 near Indian Key and on both the Sanibel and 

 Tortugas grounds. On the southwest coast of 

 Florida and in Florida Bay, marked juvenile pink 

 shrimp released near Shark River (6), Flamingo 

 (2), Bottle Key (9), and Peterson Keys (3) were 

 recovered in the Tortugas shrimp fishery. Several 

 shrimp from Bottle Key were also caught in 



MIGRATIONS OF FLORIDA PINK SHRIMP 



451 



