The Use of Atkins -Type Tags on Shrimp 

 Donald M. Allen and Thomas J. Costello 



An ideal tag should be easily recognized by a casual observer, yet 

 have no abnormal effect upon movennent, growth, or survival of the tagged 

 aniinals. In the case of crustaceans, such as shrimp, the tag must be re- 

 tained through successive molts. Petersen disk tags have been used extens- 

 ively to mark shrimp since 1934. Such tags are easily recognized and are 

 retained through molting. The information derived from experiments in 

 which shrimp were marked with Petersen disks has contributed greatly to 

 our knowledge of certain aspects of shrimp biology. Observations reveal, 

 however, that shrimp tagged with Petersen disks undergo excessive mor- 

 tality, which apparently increases as the size of shrimp marked decreases. 

 An additional disadvantage is the fact that such tags restrict shrimp agility, 

 which could affect normal movement and survival. 



The deleterious effects of the Petersen disk tag may, in part, be 

 attributed to trauma, resulting fronn continued impalement on the rigid nickel 

 pin, the excessive weight of the plastic disk-nickel pin assembly, and the in- 

 creased Awater resistance to the disks which may "toe out" as the shrimp 

 moves forward. The latter deficiency is particularly apparent >vhere extra 

 pin length is allowed between the disks for growth. 



In recent years, shrimp have been marked with biological stains 

 which apparently have little, if any, effect upon movement, growth, and sur- 

 vival of marked individuals. The biological stain marks are retained through 

 ecdysis. Although stain marks are not recognized as readily as nnechanical 

 tags and their use requires an intensive recovery campaign, the stain-marking 

 technique has been used successfully to study growth, migrations, and mor- 

 tality rates of commercial shrimp populations. However, there is still a need 

 for a numbered tag which can be used to follow growth and migrations of indi- 

 vidual animals. 



It is probably not possible to design a mechanical tag ^vhich can 

 favorably compare with a biological stain mark in respect to the effect upon 

 shrimp survival and movement. However, a modified Atkins tag conrunonly 

 used on fish has several advantages over the Petersen disk tag when used 

 for marking shrimp. This tag is composed of a small oblong strip of cellu- 

 lose acetate (0. 8 mm. thick and inscribed with printed information) secured 

 to a short length of monofilament nylon line, which has a loop in the free end. 

 The tag is attached to the shrinap by means of a slender surgical needle (in- 

 testinal thin), which has had the eye cut open on one side. The nylon loop is 

 hooked by the needle eye, and the needle is inserted laterally through the 

 muscle tissue of the first abdominal somite of the shrimp, taking care to 

 avoid the nerve cord and gut. After the nylon line is drawn through, the 

 plastic strip is passed through the nylon loop twice, securing the tag in posi- 

 tion. 



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