Chapter 11: Design and Analysis of Tagging Studies
William E. Pine, Joseph E. Hightower, Lewis G. Coggins, Matthew V. Lauretta, and Kenneth H. Pollock
Tagging and marking studies of fish populations are used to examine movement patterns and estimate growth rates, demographic parameters, and abundances. The key steps in conducting an effective tagging study are (1) careful planning to ensure that study objectives are addressed, (2) selecting an appropriate tag or mark, (3) ensuring that sufficient numbers of animals are marked and recaptured to generate parameter estimates of sufficient precision to meet management needs, (4) meeting the sometimes rigorous assumptions required to provide accurate parameter estimates, (5) employing appropriate analytical methods, and (6) interpreting the results properly. This chapter provides guidance on designing simple tagging studies to calculate common fisheries estimates such as abundances, survival rates, components of mortality (fishing and natural), movement patterns, and growth rates.
Most tagging and marking studies are similar in that they create a subset of animals from the population that are “known” and identified by their tags or marks. This subset of animals is then followed through space or time (or both) by subsequent recaptures and used to provide information on the entire population. A strength of a well-planned tagging program is that multiple characteristics of interest to researchers and managers, such as movements, growth, and mortality rates, can often be addressed in the same study. Many essential questions must be considered for any tagging study, including the following.
1. What types of marks or tags are going to be used (fin clips, traditional passive tags, or telemetry tags)?
2. Who will tag the animals (biologists or cooperative recreational or commercial fishers)?
3. Are tagged fish representative of the population as a whole?
4. How will tagged animals be recaptured (collected from fishers or captured and released by biologists)?
5. Where and how often will relocations or recaptures be attempted?
6. What is the tag-shedding rate or how can it be estimated? Does tagging cause increased mortality of tagged fish?
7. Are tag-reporting rates relatively high and consistent across the study area and the duration of study?
Answers to all of these questions, and others, will affect the design of tagging studies; they are
considered in detail in this chapter.