FIELD TECHNIQUES FOR STAINING- 



RECAPTURE EXPERIMENTS WITH 



COMMERCIAL SHRIMP 



by 



T. J. Costello 



Fishery Research Biologist 



Bureau of Commercial Fisheries 



U.S. Fish and Wildlife Service 



Miami, Florida 



ABSTRACT 



Field application of the staining method for marking commercial shrimp is 

 treated in detail. The method is shown to be simple, rapid, and applicable over a 

 wide range of shrimp sizes. It is proving useful for studies of shrimp migration, 

 growth, and mortality. Two disadvantages are: (1) the requirement that, for purposes 

 of measuring growth, stained shrimp be of uniform size when released and (2) the 

 need for developing a high degree of interest among fisherman so that maximum 

 numbers of stained shrimp will be noticed and recovered from commercial catches. 



An outline of practical procedures for planning and conducting staining-recapture 

 experiments with shrimp takes into account (1) the scope of the individual experiment 

 relative to the availability andconditionof shrimp, (2) field facilities and equipment, 

 (3) kinds of staining agents, manner of application, and precautions to be exercised 

 in their use, and (4) the importance of an intensive recovery program. 



INTRODUCTION 



Tagging and other marking methods have 

 long been used to identify experimental ani- 

 mals in population and behavior studies. Con- 

 siderable knowledge about fishes, particularly, 

 has accumulated through application of a wide 

 variety of fish-marking techniques. When 

 properly designed and executed, mark-recap- 

 ture experiments provide information on fish 

 population movements and measures of popu- 

 lation growth and mortality. 



Since their exoskeleton is shed when molting 

 occurs, crustaceans are less suited than 

 fishes for the attachment of tags. Despite 

 this shortcoming, several experiments em- 

 ploying tags have yielded valuable information 

 about shrimp populations (Lindner and Ander- 

 son, 1956; Iversen and Idyll, 1960). Due to 

 the shrimp's fragility, however, effective 

 application of tags is restricted to those 



portions of a population comprising the largest 

 and most robust individuals. 



Seeking an alternative marking method, 

 Menzel (1955) reported that white shrimp 

 (Penaeus seti ferns) carefully injected with non- 

 toxic solutions of biological stain, suffered 

 relatively little mortality, and after periods 

 of up to 60 days still retained sufficient stain 

 to permit identification. Moreover, the method 

 appeared feasible for marking the smallest 

 juveniles as well as the largest adults. Dawson 

 (1957) elaborated on Menzel's technique and, 

 experimenting in the laboratory with a wide 

 variety of stains, found four that promised 

 to be suitable for large-scale, mark-recapture 

 experiments. Feeding and Immersion were 

 also tested as means for marking shrimp, but 

 the injection technique gave best results. In 

 all methods the primary retention site of the 

 stain proved to be in the branchial region. 



