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Published on: Mar. 23, 2011

Lake Sturgeon

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Fin Cutting

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Scanning a Coded Wire Tag

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As kids, we enjoyed chasing friends in a game of tag. Now that we are a little older, and work as fisheries biologists, we are involved in a different version of tag. No, we aren’t chasing each other around one of the conservation areas. Rather, we’re tagging a variety of fish species to learn about the critters that swim in our big rivers, lakes and streams. And you, as anglers of Missouri, can help us.

Marks and Tags

There are a variety of ways that fisheries biologists can identify individual or groups of fish. In some cases, the easiest thing to do is to mark the fish. For instance, the Missouri Department of Conservation began stocking fingerling lake sturgeon into our big rivers in the 1980s. The first two batches of fish were marked by clipping off one of their pelvic fins. This permanent mark affects the fish for only a short time, but allows biologists to identify those fish for the rest of their lives. Several of the fish have been recaptured in the Missouri, Mississippi and Illinois rivers.

Occasionally, biologists will cut off a small piece of a fish’s fin to mark it temporarily. This short-term mark helps us estimate the number of fish in a population and has very little impact on the fish. Often, the piece of fin grows back.

The more common method of marking fish today is to use a variety of tags. Some of them are very simple, while others incorporate modern technology. A simple tag commonly used is called a coded wire tag, or CWT. This tag is a 2- to 3-millimeter-long piece of wire that is embedded somewhere in the fish’s flesh or fins. The only way to detect it is to use a very sensitive metal detector. Because biologists can’t see the tag, the tag’s location on the fish is the key to telling us which batch of fish it belongs with. This type of tag is frequently used to mark an entire batch of fish stocked in a given year.

A more advanced type of tag is the passive integrated transponder tag, or PIT tag. PIT tags used in Missouri are rarely more than 5 or 6 millimeters long. Each tag has a unique series of letters and numbers that help us identify each individual fish. A special reader sends a signal to the PIT tag. The signal charges the tag, which sends the unique code back to the reader, allowing biologists to identify the individual fish.

The most advanced type of tag in use is a radio or sonic transmitter. Transmitters vary in size, depending on the size of fish they will be used with and the length of time biologists need the tag to transmit the signal. In most cases, the transmitter is surgically implanted into the fish’s body cavity. Each transmitter emits a signal that allows biologists to find and follow an individual fish to determine movement, habitat use and behavior.

Many fisheries projects incorporate the use of visible tags. In these studies, biologists rely on anglers to provide information about the tagged fish when they catch them.

The most commonly used visible tag is the T-bar, or spaghetti tag. This tag is similar to tags used to mark clothing in many stores. A special tagging gun is used to attach the tag near the fish’s dorsal fin. The “T” part of the tag serves as an anchor to hold the tag in place. The visible part of the tag can be a variety of colors and includes a unique number that identifies the fish and contact information for reporting the tag.

Another commonly used visible tag is the dangler tag. Dangler tags are the size of a large medicine capsule and are attached near the fish’s dorsal fin by a pair of thin wires. This type of tag also includes an individual fish number and contact information.

What Do We Learn?

When anglers report catching tagged fish, biologists gain information about those individual fish and the information can be applied to the rest of the population. We learn how fast fish grow, how far they move and how long they live after tagging. Visible tags returned by anglers help us estimate the number of fish that are caught and harvested, allowing us to better manage these populations.

When you report catching tagged fish, we also learn a little about you! We learn what species of fish you like to fish for, where you like to fish and what size of fish you like to keep. The information you report helps us better manage the fish population for the species and size of fish you like to catch.

While we are never surprised to hear that a tagged river or stream fish is no longer in Missouri, we are frequently surprised by how far some fish go and where they are later caught. During a recent paddlefish study, a fish was tagged at the mouth of the Osage River near Jefferson City. Nearly two years later, that fish was recaptured in a floodplain lake in Arkansas. The fish had traveled more than 700 miles down the Missouri and Mississippi rivers! We would have never known that if the fish hadn’t been tagged, and subsequently reported.

What to Do if You Catch a Tagged Fish

The most important thing that you, as an angler, can do to help us is to report the tag in a timely manner. The information that you provide will be used to help us better manage both local and statewide fisheries. If too many people fail to report tags, we may come to the wrong conclusions on the best way to manage these fisheries.

Another reason to report tagged fish is that some tags include a reward. Tag rewards vary by project and may expire over time. So don’t delay, report today! While it would be great if no one needed a reward for reporting a tagged fish, history has proven that rewards increase tag reporting. Even now, you may be thinking about a tag or two that may be lying in your tackle box. It’s time to dig it out and send it in. Even old information can be useful.

To report a tagged fish, look for a phone number or address on the tag. The print may be small, so a magnifying glass may be needed. Write down any information you see on the tag. There are a lot of biologists, both within and outside of Missouri, who are tagging fish. The information on the tag will help us identify who tagged the fish.

Call or write to the contact on the tag. In order to claim a reward, we MUST have the tag. In many cases, once we have processed the tag, we can send it back to you with information about that particular fish. If the tag does not say “reward” it likely does not include one. However, it is still useful to have the information. In those cases, leave the tag attached to the fish but write down the number and the contact information, then report the tag as soon as you can. By leaving the tag on the fish when you catch-and release it, you make it possible for us to gain additional information from it in the future.

When you submit a tag for a reward, include your mailing address, when and where you caught the fish, the length and whether or not you kept the fish. It is okay if you don’t remember all of the details. Provide as much information as you can.

If you can’t read the information on the tag, contact your local Missouri Department of Conservation office. Based on the information you provide, we may be able to identify who used the tag and a reward may still be available.

While not everyone will catch a tagged fish, many of you will. It is a special experience when you get to learn how you have contributed to the study of fish populations in Missouri.

And with that, there is just one more thing to say … Tag! You’re it! We’ll see you on the water!

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