Issue 13, Spring 2019

Fish Tagging 101

Fish have been tagged (or marked) since anglers first started catching them. The 1653 edition of the fishing classic The Compleat Angler noted how anglers tied ribbons to the tails of juvenile salmon to verify that these fish return from the sea to the same rivers where they were born. While the concept of tagging a fish to monitor its movement is intuitive, there are several aspects of a tagging program that can be customized based on the question at hand. But before you can begin a tagging study, you must first ask three important questions.

What are the objectives? In other words, what do you hope to learn from tagging fish? For example, fish tagging can be used to measure movement, abundance, growth, exploitation, and/or demographics (survival, mortality, longevity). In fact, a carefully designed tagging study can be used to measure several of the metrics above. The specific objectives of the tagging study will determine the answer to the next question.

Who will tag (and recapture) the fish? Deciding who will tag and recapture the fish will determine the types of questions that can be addressed and how the resulting data can be interpreted. Three general tagging programs are described below.

Angler-based tagging programs: Angler-based tagging programs are a cost-effective way to encourage citizen science and are best suited to provide information on fish movement. Successful angler-based tagging programs target specific species, have defined objectives, and offer training to angler-taggers (either in person or through print/digital means). An excellent example of this is the Sport Fish Tag and Release Program at the University of Southern Mississippi's Gulf Coast Research Lab (GCRL). The tagging program at GCRL began in 1989 and started with cobia. It has since expanded to include speckled trout and tripletail. Angler-based tagging programs are examples of "tag-return" programs.

Biologist-based tagging programs: Given the amount of data that must be collected (precise lengths, weights, and locations) and the strict assumptions that must be met (100% tag reporting), most tagging studies designed to estimate abundance, mortality, or growth are conducted completely by biologists who capture, tag, release, and later recapture the fish of interest. An example of this is the tagging program conducted by the International Pacific Halibut ommission, which used a biologist-based program to estimate fishing mortality, natural mortality, and migration rates for Pacific Halibut. These types of programs are often known as "capture-recapture" programs.

Fishery-dependent tag-return programs can be a mixture of the two types mentioned above. In this case, biologists tag the species of interest, but they rely on recreational and commercial fishers to return the tags. An example of this is a "high-reward tagging program," where anglers receive a monetary reward for reporting recaptured fish.

What type of tag will be used? Now that you've defined the tagging study objectives, and decided who will capture, tag, release, and recapture the fish, it's time to select a tag type. There are several tag types, ranging from inexpensive conventional tags to complicated electronic tags. Below are three broad categories of tags commonly used in fisheries settings.

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