Evaluation of a fluorescent elastomer internal tag in juvenile and adult shrimp Penaeus vannamei

An elastomer tag was injected into 1830 juvenile (mean weight 1.63 g) and 260 adult (mean weight 38.22 g) shrimp (Penaeus vannamei) during trials for identification of individual family crosses. The tag was injected intramuscularly into the ventral side of the sixth tail segment using a compressed air pump set at 100 psi and a 3 ml syringe with either a 27 gauge needle (juveniles) or a 21 gauge needle(adults). Five fluorescent colors (red, orange, blue, green, and lime) were tested for tag retention and readability during growout in outdoor fiberglass tanks, The use of ultraviolet light in reduced natural light greatly increased the ability to read the color of those tags which were not easily visible with the naked eye. Tag retention was 99.9% in the juveniles and 100% in the adults after a 10-14 week period. Juvenile shrimp molted an estimated 17-23 times and adult shrimp molted an estimated 5-7 times. Among the five tag colors there were varying degrees of visibility, with red being the easiest to identify and lime being the most difficult to identify, Histological examination showed mild inflammation and scarring at the site of tag injection. These results indicate that Penaeus vannamei can be internally tagged with an elastomer that is externally visible for identification of individual populations.