grouper tagged

WaterLine photo by Capt. Ralph Allen

The tag in this red grouper was mostly obscured by algal growth, but it’s pretty easy to scrape off.

There are a lot of fish in the waters of Southwest Florida. Hundreds of species live here. They come in countless shapes, sizes and colors, and they have different life cycles, growth rates, seasonal migrations, prey and habitat preferences, salinity requirements, water temperature preferences, oxygen level tolerances and so many other variables that this sentence would run on even longer if an attempt were made to include them all. (Apologies to the editor!)

Learning about all these different fish is a never-ending process, and there is much that we still don’t know. This means that the scientists who study our fishes must constantly scramble to uncover clues about them in any ways that they can. One tool that has been used for many years by fishery biologists is to put tags in fish. The act of tagging a fish doesn’t produce much immediate information — but a recapture can produce useful data that helps us learn about that species.

There several different types of tags that can be applied to fish. The most common type of tag we see in local fish is a spaghetti tag, or a dart tag. Spaghetti tags are used a lot because they are cheap and are quick and easy to apply with minimal stress to the fish.

Picture a strand of spaghetti about 4 inches long made of flexible plastic and with a barb similar to a fish hook barb on one end. The tag will be imprinted with tiny letters which provide contact information for the tagging agency and the serial number for that specific tag. These are applied by sticking the barbed end of the tag an inch or so under the skin of the fish, usually along the top of the back so that most of the tag remains outside the fish.

Spaghetti tags are usually bright yellow or orange in color to increase the odds that they’ll be noticed by an angler who later lands a tagged fish. That’s important, because this type of tag only provides usable data if the fish is later caught again and information about its recapture is reported back to the tagging agency. You might think that a bright yellow or orange tag sticking out of the back of a fish would be pretty obvious, but if the tag has been in the fish for any length of time, it will probably have accumulated a layer of algae growth which tends to camouflage it.

There are many other types of tags, some of which can be found in fish in Southwest Florida waters. Anchor tags are similar to dart tags but are usually larger. They’re anchored inside the fish by a stainless steel toggle that turns sideways inside the body of the fish. Anchor tags are often used in sharks and in pelagic fish such as billfish and tunas.

A PIT (passive integrated transponder) tag is a tiny thing about the size of a rice grain. It’s inserted inside a fish and requires an electronic reader to locate and read, much like when a pet dog is chipped. These are useful because they can be placed in very small fish. The fingerling snook Mote Marine released in the Harbor last year were all PIT tagged.

Sonic tags are battery-powered pingers that look about like a tube of lip balm, though they could be larger or smaller. When activated, they transmit a coded pattern of audible beeps which is specific to that tag. Sonic tags can be hung on the outside of the fish on the end of an anchor tag, or (more likely) surgically implanted inside the body cavity of the fish.

Sonic tags allow real-time tracking of a tagged fish, but only if they are in range of a listening device. Some tagging projects coordinate the tagging of a batch of fish and the installation of arrays of underwater recording devices in the area being studied. Scientists can download recorded data to figure out the movement patterns of the fish. Biologists can also use portable tracking devices which they can hang off the side of a boat in hopes of locating pinging fish. In Charlotte Harbor there have been sonic tags applied in redfish, sharks and sawfish.

When Hurricane Charley visited Charlotte Harbor in 2004, there was an array of listening devices in lower Pine Island Sound which was being used to track the movements of small sharks. Interestingly, many of the sharks left the area prior to the arrival of the storm. They knew something was coming.

There are also satellite tracking tags. These include a GPS tracking device, a radio transmitter, and other instruments which might record data such as the depth at which the fish is swimming and water temperature. The radio transmitter is capable of sending a signal to a satellite. But there’s a catch: Radio frequency signals can’t be transmitted very far underwater.

There are a couple of different strategies used to get around this problem. One is to install a time release attachment to the tag. This type of tag rides around with the fish for a predetermined length of time recording data, then disconnects, floats to the surface, and uploads its data.

Other tags are designed to stay with the host fish for a long time but only transmit data when that fish is near the surface. If you’ve looked at those popular tracking websites for the great white sharks which roam the Atlantic and the Gulf, you are seeing tracking data from this type of tag. Gaps in the track occur when the shark stays deep for a while.

You might catch a fish that’s been tagged. The fact that a fish is tagged doesn’t change your ability to keep or your requirement to release that fish. That decision still follows the regular size, bag and seasonal rules for that species.

But you should attempt to help our fish scientists gather their data by reporting your recapture. If your tagged fish is going to be released, the ideal scenario is for you to get the length of the fish, then record the serial number of the tag and the information about the tagging agency and release the fish with the tag still in place. That way it might be able to supply more data via future recaptures. If you can’t quickly read the data off a dart or anchor tag, clip it off near the skin of the fish and keep it, then release the fish.

If you’re harvesting the fish, remove the tag when you clean it. Whoever you report the tag to will want to know the species, length, date and location of the capture. When compared to the data that was recorded at the time of tagging, your information can provides data about fish movements and growth rates. To report a tagged fish, call the FWC’s Tag Return Hotline at 800-367-4461.

Capt. Ralph Allen runs the King Fisher Fleet of sightseeing and fishing charter boats located at Fishermen’s Village in Punta Gorda. He is an award-winning outdoor writer and photographer, and is a past president of the Florida Outdoor Writers Association. Contact him at 941-639-2628 or

Capt. Ralph Allen runs the King Fisher Fleet of sightseeing and fishing charter boats located at Fishermen’s Village in Punta Gorda. He is an award-winning outdoor writer and photographer, and is a past president of the Florida Outdoor Writers Association. Contact him at 941-639-2628 or


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