Table 1. — Recommended solutions and quantities of three vital dyes used to mark pink shrimp. 



(Total lengths are midpoints of 20-mm, classes.) 



RECOVERING MARKED SHRIMP 



The importance of planning each marking 

 experiment so that it provides adequate means 

 for recovery of the marked animals should 

 be stressed. Many workers will agree that a 

 common failing in mark-recapture experi- 

 ments is that too much attention is given the 

 marking phase and not enough the recovery 

 phase. 



Marked shrimp can be readily detected by 

 any perceptive observer and will be returned 

 by fishermen if they know what to look for. 

 In some experiments carried out in Florida, 

 pink shrimp marked with Trypan blue were 

 still recognizable as having been marked more 

 than 10 months after being released. Shrimp 

 marked with fast green FCF have been re- 

 captured, recognized, and returned after more 

 than 6 months since release. 



The most practical way to Inform fishermen 

 what a marked shrimp looks like is to show 

 them one preserved in a vial of formalin or 

 brine. Samples in vials attached to posters 

 displayed in shrimp processing plants serve 

 almost as well. By providing actual specimens 

 for examination, the likelihood of later re- 

 ceiving discolored but unstained shTlmp is 

 greatly reduced. Other means of publicizing 

 experiments as well as descriptions of marked 

 shrimp should also be considered. There is, 

 however, no good substitute for personal con- 

 tact with individual fishermen. 



Rewards should be sufficiently large to in- 

 duce fishermen and processors to examine 

 catches closely and to return quickly any 

 marked shrimp they may discover. Whenever 

 possible, rewards should be paid promptly 

 and in cash. 



SUMMARY 



Field observations coupled with the results 

 of laboratory experimentation illustrate the 

 important considerations in successful use of 

 biological dyes for marking shrimp. The 

 staining method is simple, rapid, and is 

 proving useful in studying movement patterns 

 as well as determining growth and mortality 

 rates of commercially important species. 



Experience demonstrates that shrimp 

 marked with dyes will be recognized by 

 fishermen, although perhaps not as readily 

 as those marked with tags. Thus, more atten- 

 tion must be given the recovery phase of a 

 staining experiment than that of an experiment 

 in which tags are used. 



Important points to consider in the initial 

 phase of a shrimp-staining experiment include 

 condition of water in the area of staining 

 operation, availability of shrimp, and tiie 

 likelihood of recovering marked specimens. 

 It is also well to check the general condition 

 of the shrimp available for marking, because 

 using many shrimp in soft-shelled condition 



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