Table 2. --Trade names and manufacturers of 

 secondary marking materials 



ventral sinuses or in the gills (table 4). In no 

 instance, however, did these secondary pig- 

 ments obsucre the primary marks. Both the 

 primary and secondary marks could easily be 

 identified up to 276 days after marking. The 

 marks did not appear to fade, nor were they 

 lost during nnolting. 



A laboratory experiment was conducted to 

 determine whether it would be possible to 

 localize the secondary pigments in nnore than 



one area of the shrimp's body in order to in- 

 crease the number of different marks that 

 could be used simultaneously in a mark- 

 recapture experinnent. It was found that the 

 secondary pigments could be confined to the 

 middorsal surface at the joint of the sixth 

 abdominal segment and to the ventral surface 

 between the second and third abdominal seg- 

 ment, thereby effectively doubling the number 

 of distinguishable secondary marks. 



The possibility that the fluorescent material 

 may be lethal to shrimp was also investigated. 

 The first few experiments provided only pre- 

 liminary information because mortality was 

 confounded by cannibalism or escapement of 

 shrimp. However, the results from these ex- 

 periments suggested that there was no dif- 

 ference in survival between groups of shrimp 

 injected with fast green and any of the five 

 fluorescent marks. 



In later experiments, it was therefore 

 deenned necessary to determine the effect on 

 survival of only one of the fluorescent marks 

 used with fast green or Trypan blue. The sur- 

 vival of shrimp in this series of experiments 

 (table 5) was not affected by escapement or 

 cannibalism, because each experimental ani- 

 nnal was held in a separate compartnnent. 

 Each experiment included three groups of 

 shrimp, of which one was unmarked, another 

 was injected with distilled water, and a third 

 was injected with a combination mark. The 

 first group served as a control and was conn- 

 pared to the second group to determine the 

 effect on survival of the treatnnent associated 

 with marking. The second group, in turn, acted 

 as a control for the third group to ascertain 

 the influence of the combination mark on sur- 

 vival. Mortality was generally most variable 

 during the first few days after marking and 

 thereafter remained relatively constant. Fewer 

 shrimp died in the marked groups than in the 

 control groups; therefore, neither the marking 

 materials nor the method of marking has any 

 lasting effect on survival. The five fluorescent 



PRIMARY MARK 

 (Biological Stain) 



SECONDARY MARK 

 (Fluorescent Pigment) 



Figure 1. — Location of marking materials in double-marked shrimp. 



5 



