Author: Bullbuster Team
Tagging and Monitoring Fish
"After you catch your breath, you notice your fish has some sort of tag... What should you do if you see one?"
The sun is out and the seas are rolling, you have your rig set up in 1800 feet of water in four knots, and the line is tight with a fish on. You sweat and strain while hand cranking the animal to the surface and somehow maintain the strength to wrestle him into the boat- and how magnificent he is! This is what it’s all about, right? After you catch your breath, you notice your fish has some sort of tag dangling from the base of his dorsal fin. What is this tag? What should you do if you see one?
These tags are a vital component of fisheries research and management. They are used to capture information and gain perspective, to create a more comprehensive assessment of fish populations. This includes the ability to learn more about their patterns of movement, mortality rates, and population dynamics. Those insights provide a better understanding of the species, which can then lead to more effective management decisions. If you are an avid fisherman, it is important to understand the purpose of tagging, and to be aware of the presence of tags and how you should report them.
Tagging Objectives
"[Tagging programs] are used to capture information and gain perspective, to create a more comprehensive assessment of fish populations"
(Find Out 10 Ways Fish Tagging Information Is Actually Used)
Using mark and recapture methods, tagging programs may have several main objectives. First and foremost, tagging is used to study movement. Having the location information at the release and recapture for a subset of fish provides a collection of tracking info that can be used to analyze patterns of movement for the entire population. In association with other environmental or biological factors, these patterns can be used to better monitor and manage the population. Also, sometimes fish species are managed in divided stocks (see Cooperate Yellowtail Flounder Tagging Project in New England). By following patterns of movement for fish within each stock, researchers and managers can get a better sense of how these populations may move and intermix, and how to resolve associated stakeholder conflict, if necessary.
Another objective tagging programs strive for is calculating the exploitation rate for the fishery, or determining how many fish are removed from the population over time. Tag reports collected from commercial and/or recreational fishermen provide information on the amount of individuals fished from the population, in a certain timeframe, which researchers can use to model the rate of exploitation. The rate of fishery exploitation is critical to managers who work to come up with a set of regulations balanced for sustainable catch; maximizing harvest while also protecting the health and viability of populations.
"Input from all involved entities is necessary to create the most efficient set of regulations"
Fishermen partnerships in cooperative tagging and management programs are essential to creating fully comprehensive regulation systems by including the expertise of the fishermen themselves. Tagging programs would not be as successful without the help of fishermen and mariners reporting tags; their input is critical because they are equally important stakeholders in the fishery. Input from all involved entities is necessary to create the most efficient set of regulations to protect our fisheries for future generations, for the integrity of the environment, but to also foster the continued success of the industry.
Types of Tags
"Fish may either be biologically or chemically tagged, or physically tagged internally or externally, depending on the objectives of the project and the target species."
When deciding what type of tag to use for a particular study, researchers must consider cost, the duration of the study, and perhaps most importantly, the species targeted and the potential impacts inflicted on the fish. Consider that an attached tag could cause injury or infection, or could increase drag and add stress. For these reasons, there are a variety of tags that exist, designed differently to serve the purposes of the study and to be as minimally invasive to the targeted species.
Fish may either be biologically or chemically tagged, or physically tagged internally or externally, depending on the objectives of the project and the target species.
Biological and Chemical Tags
One way to tag fish is by making some kind of mark on the body, such as fin clipping, branding, or marking scales. Chemical marks can also be made, for example, tattooing or injecting, or even feeding, dye. Advantages to making natural or chemical tags include lower cost, less handling time, large numbers of fish can be marked at once, as well as smaller species because there is no additional piece of equipment to amount to stress. However, it is important to consider that tagging fish in this way is used to identify fish stocks; individual animals cannot be recognized.
"This is typically done in hatcheries...and is reflected in otoliths"
Also, chemical tag retention can vary based on water chemistry, and temperature, and the growth of fish may cause the tag to migrate, disperse, or disappear. Finally, potential impacts from the chemical marker, such as levels of toxicity, must be considered to reduce negative effects. Another way to naturally tag fish is by thermally marking them. This is typically done in hatcheries: researchers can manipulate the water temperature during incubation, which is reflected in the way the series of rings on the otoliths form (like tree rings). In this way, researchers can make a unique 'bar code' on the otoliths that is identifiable under a microscope. A disadvantage to marking otoliths is that later identification is lethal.
Internal Tags
Internal tags are injected or inserted into the muscle, cartilage, or body cavity of the fish. Examples of internal tags include coded wire tags, passive integrated transponder tags, and body cavity tags. The biggest advantage using internal tags is that once placed, the tag has little to no effect on the growth, health, and survival of the fish. These tags are also appropriate for almost any size and species; indeed they are often used to tag smaller fish that could not support or would not cope well with a tag placed externally. Other advantages include high possible retention rates (tags do not get pulled, fall off, or have growth cover them), some types can be applied semi-automatically, meaning more fish can be tagged at a time, individual fish recognition is possible with associated identifying codes (batch or individual), and some are able to be repeatedly and non-lethally recovered. There are several disadvantages researchers must weigh when considering tag options, these include: the expensive equipment required for internal tag application and detection, training/expertise is required to insert tags safely (may not be suitable for citizen science), tag retrieval and identification can be labor intensive (cannot rely on the general public to report tags), the tag may become less visible with time or migrate within the body cavity, making it difficult to find, and the small size of the tag provides limited space for information.
Types of Internal Tags:
1. Passive Integrated Transponders (PIT): PIT tags are small, typically only a few millimeters in size, can be coded electronically from 35 billion unique codes, and powered by a magnetic field. PIT tags are similar to the internal tags often placed in pets. They are injected into the body cavity or thick tissue, have no impact on the behavior or health of the fish (once healed), and can be automatically detected and decoded in situ with a special receiver- avoiding sacrifice and minimizing handling. PIT tags are often used in smaller fish species, and for populations that require non-intrusive recovery.
2. Coded Wire Tags (CWT): CWT's are very small pieces of magnetized stainless steel wire, containing an etched in binary code for identification purposes (250,000 unique code combinations). The wire is injected into the snout or cheek of the fish, and is usually combined with some kind of outer marking (fin clips, etc.) to mark its presence. The magnetized wire is detected in close range with a handheld wand or receiver. CWT's, also sometimes to referred to as microtags, are useful for small fish, or large datasets. CWT retrieval often involves killing the fish and removing the tag to read the code under a microscope. One important application of CWTs is their use to track hatchery salmon in the Pacific Northwest, and compare them to unmarked wild caught salmon, for fisheries-management purposes.
3. Acoustic Telemetry Tagging: Telemetry is the process of recording data remotely and transmitting the readings to receiving equipment. There are many types of acoustic tags, that may emit radio, or sonar, or use GPS (Global Positioning System) on a Data Storage Tag (DST). Acoustic telemetry tags involve two parts: the "pingers" that are implanted in the body cavity, or secured externally, which emit an acoustic pulse that is picked up by nearby hydrophones. Acoustic tags are effective because they record continuous readings of fish movements and can therefore provide really fine-scale information. They have greatly increased the knowledge of fish migration and distribution, and behavior analysis, and are vital to sustainable management of fish resources. However, acoustic telemetry can be very expensive and labor intensive. It requires expertise is performing surgery while inserting the tag, and the fish need to be fairly large in size to support the tag. These tags are most often used for large pelagic fish such as billfish and sharks.
4. Subcutaneous/ Visible Implants: typically small strips of plastic with printed code that are placed subcutaneously under the skin where the strip is still visible on the surface. Visible Implant Elastomers (VIE) are tags that are injected as a liquid, beneath tissue that is transparent enough to see the VIE externally, typically behind the eye. Placing these types of tags requires a small incision or injection, and also usually requires another biological mark to identify that a subcutaneous tag is present. Also, individual identification is usually not possible; this method is mostly used for identifying fish stocks.
External Tags
The original tagging programs used external tags, which are still used most often today. External tags are important because they are easily detected, and can carry information about individual animals as well as reporting instructions, which is useful for recapture and recovery. Anglers and mariners are able to report fish that are tagged externally, adding to the dataset, which is not done with internal or biological tags. External tags are popular because they can be very cheap, and easy to make, making them cost effective. Also, they can be easy to apply (no incisions required) and may only require a simple application tool. There are many types of external tags to accommodate fish of all sizes, they can be applied to many different species and large numbers of fish, individual fish identification is possible because there is room to print information, and they may have a long retention time. External tags are used in many tagging programs that engage the public because of their easy application and identification. The information from these tagging programs can be given back to anglers who help in reporting, which in turn can encourage more tag-returns to perpetuate the monitoring. Unlike acoustic telemetry or other advanced internal tags, external tags do not typically provide information about the time between mark and recapture. Several other disadvantages to consider for external tags are that tag return rates can be highly variable, the protruding tag may have an effect on the fish's growth, health, and survival, and the tags can become fouled or overgrown, or entangled. Also, it is often difficult to tag very small fish, and may have an effect on the fish's behavior or swimming performance.
Types of External Tags:
1. T-Bar Anchor Tags: also known as spaghetti tags, are simple external tags made of vinyl or monofilament tubing. T-bar tags are common because they are relatively cheap, they can be coded to have unique animal ID numbers and reporting information printed on the tubing, they can be applied to the fish quickly, and are appropriate for most species of fish large enough to support the 2inch tag. These tags are inserted at the base of the dorsal fin. Downsides to using T-bar tags include the requirement of a tagging gun, some training, and that these tags can be shed from the animal fairly easily.
2. Petersen Discs: two discs that are easily applied under the dorsal fin of the fish with a pin and pliers. Petersen discs can also be used on mollusks by gluing them to their shells. They are very low cost, can be printed to have unique animal identification, and are permanent. There may be minor injury inflicted during application, and some training is necessary. Petersen discs were invented in the late nineteenth century and were widely used during the first half of the twentieth century. Similar to Petersen discs are Anchor tags and Batchelor Buttons.
3. Carlin/Atkins Tags: these are dangling tags, and consist of a plastic disc that is attached the fish by threading a wire or thread through the tissue and looping the disc in. These tags come in a variety of materials and shapes and can be applied to several different parts of the body, depending on the size and species. Carlin and Atkins tags are most often applied to the operculum, or gill cover.
4. Other Dangling Tags: unlike other tags that are firmly fixed to the skin, dangling tags are usually attached at the end of some thread or wire. These include Flag tags, made of PVC plates shaped as long rectangles, Alcathene tags, which is a boat shaped tag that often includes a slip of paper embedded with reporting information, Hydrostatic tags, which are neutrally buoyant plastic tubes, Arrow tags, that a barb to prevent shedding, and other types of T-bar tags such a Floy and Dart tags. Dangling tags are easy to apply and to recognize, but their downside is that they can be shed off relatively easy.
5. Strap Tags & Jaw Tags: are lightweight, noncorrosive metal tags that attach to the operculum, fins, caudle peduncle, or jaw of the fish with a locking mechanism secured with a pair of pliers. These tags are easy to apply and are most popularly used on fish with extra bony or tough opercles (gill covers), such as Sturgeoun, Flounder, and Halibut.
6. Pop-up Satellite Tags: Pop-Up Satellite Archival Tags (PSATs) are, by far, the most expensive external tag. However, they are incredibly valuable because they collect real time data: location and movement of the animal, as well as environmental measurements for temperature, salinity, depth, light levels, etc., and can transmit the recorded information to orbiting satellites, which relay to the researchers’ computers. PSATs are battery powered, and at a preset time, the battery can activate the dissolution of the anchor attachment to completely detach from the fish and float at the surface of the water to 1) broadcast the data and 2) allow for possible recovery. This makes PSATs effective for studying large pelagic fish such as billfish, tuna, and sharks.
Tagging Programs
If you are an avid angler, chances are you have already come across a tagged fish. There are several programs, at federal, state, and university levels, that you should be aware of. It is important to understand why the tagging program exists and how the resulting information can improve fishery management and may affect you.
The NOAA Fisheries Service Apex Predators Program
The Apex Predators Program (APP) is based out of the National Marine Fisheries Service Laboratory in Narragansett, Rhode Island. Their focus is on commercially and recreationally important shark species in national waters along the US east coast. APP manages several tagging programs for shark life history studies; these tagging programs are designed to collect data for research on shark distribution and migration patterns (including rates and routes), reproduction, feeding ecology, age and growth analysis, and mortality.
The Cooperative Shark Tagging Program (CSTP) was launched in 1962 with just 100 volunteers and has since expanded to include thousands of volunteers from all over North America and Europe. Their goal is to study Atlantic sharks through a collaborative effort of recreational and commercial fishermen, and the National Marine Fisheries Service scientists. The two main tags they use are fin tags (also known as Rototags, similar to Petersen discs) and dart tags (also known as M tags).
As of 2013, CSTP has tagged over 230,000 sharks from 52 species and has recaptured 14,000 sharks from 33 species. Some of their recaptured individuals did not migrate significantly while other, such as a particular shorten mako shark, traveled over 4000 nautical miles between mark and recapture. The individual shark with the longest "time at liberty", or time between mark and recapture, was recaptured after nearly 28 years!
Many shark species have wide ranging distributions, across national boundaries and within multinational fisheries. Therefore, it is critical to maintain a cooperative effort when completing research in hopes for successful fishery management and conservation.
Other studies from APP include a new Spiny Dogfish tagging study and a Double Tagging experiment. Spiny Dogfish is an important commercial fishery that is considered sustainably managed and responsibly harvested under US regulations, making it a smart seafood choice for consumers. Secondary experiments are also often conducted to increase understanding of fish behavior, how the presence of a tag may have an impact of a fish' chances of survival, and how effective tags are in terms of tag retention. Double tagging is placing two tags on one fish, and recording the status of the tags (Are both still present? Did one fall off?) at recapture to calculate tag shedding (as a result of improper application or biological rejection) and ultimately make adjustments to the tagging program, if necessary.
To learn more about Federal tagging programs, check out NOAA Fisheries.
The Large Pelagic Research Center (LPRC)
The LPRC is located in Gloucester, Massachusetts, and is part of the Massachusetts Marine Fisheries Institute. Founded in 2003, the Center aims to work with fishing communities to research the life histories and ecology of large pelagic fish such as tuna, billfish, and sharks, and turtle species, and to provide strong science for policy makers and fishery managers using ecosystem-based management strategies.
For example, LRPC was of the first to use satellite pop-up tags for research on Atlantic Bluefin Tuna. With the onset of these electronic tags came several important discoveries about the bluefin tuna, including the intermixing of eastern and western Atlantic stocks and new spawning grounds, both of which have implications for improved protection. Another major ongoing tagging program focuses on sailfish in the Atlantic. Although the recreational fishery for sailfish is thriving, many researchers believe sailfish populations are fully exploited, especially in the Western Atlantic. Since the 1950's, over 90,000 sailfish have been tagged by cooperative agencies. However, there is still much to learn about their distribution and population centers, as well as their spawning and migration habits. Although sailfish have been legally banned from commercial fishing in the United States since 1988, they are still unintentionally caught as by catch in pelagic longline fisheries (in fact, bycatch is believed to account for one third of the entire Atlantic sailfish fishery mortality).
Tuna Research and Conservation Center
The Tuna Research and Conservation Center (TRCC), a joint program between Stanford University's Hopkins Marine Station and the Monterey Bay Aquarium, aims to advance the research and education of tuna and other highly migratory species. The TRCC 14-year tagging program has revealed new information about separate tuna stocks in the Atlantic, as well as critical spawning and foraging habitat. By comparing the data collected from tagging to oceanographic data (physical conditions: currents, temperature, etc.), TRCC scientists have created a comprehensive modeling program able to predict future spawning habitat, which can lead to more dynamic and effective protective regulations. Other species TRCC has devoted research to include makos, great whites, salmon sharks, sailfish, swordfish, and marlin.
US Fish and Wildlife Research Institute, Florida
There are several on-going tagging programs designed by biologists with the Fish and Wildlife Research Institute to target important recreational and commercial fisheries in the state of Florida. Some of the targeted species include Cobia (migration of Gulf and Atlantic stocks), Goliath Grouper (which are federally protected, do not remove!), Largemouth Bass (associated fishing activity), Snook (life history studies), and Sturgeon (also federally protected, do not remove! Studies include differences between native and hatchery fish).
Anglers are encouraged to report any tagged fish they come across, which you can do here, on the myFWC website.
Gulf Coast Research Laboratory
The Gulf Coast Research Laboratory (GCRL), through the University of Southern Mississippi, have been a leader in the Gulf of Mexico marine sport fish tag and release realm for nearly thirty years. Their angler-cooperative program aims to monitor important fisheries in the area: Cobia, Tripletail, and Spotted Seatrout, and learn more about the relationships between coastal marine habitat and fish sustainability. GCRL provides anglers with free tagging kits that use dart tags. Check out their online brochure with more information about each specific tagging program and how you can participate.
Tag Louisiana
The Louisiana Cooperative Marine Fish Tagging Program, or 'Tag Louisiana', is a collaboration between the Louisiana Department of Wildlife and Fisheries, the Coastal Conservation Association (LA), and other in-state universities and non-profit organizations. The program was initiated to collect valuable mark and recapture information on important fisheries species, such as redfish, trout, and snapper. The data collected contributes to the state's Department of Fish and Wildlife management decisions process. Two main goals Tag Louisiana strives for include establishing an extensive tagging network that employs and educates local anglers, and improving the overall understanding of these important sport fish movements, patterns of habitat use, and population dynamics.
Grey Fishtag Research
A non-profit international organization dedicated to creating an international network or professional fishermen and scientists to promote the sustainability of marine game fish.
The Billfish Foundation was founded in the 1980’s by a group of scientists and avid fishermen to advance research and education for improved species conservation. Their largest project, the billfish tag and release program (link: http://www.billfish.org/research/tag-and-release/), is the most extensive of its kind. Since 1990, TBF has recorded over 220,000 tag and release reports.
There are several different institutions and agencies that use the data collected from the tags, it depends on the region and species targeted. For example, specific projects in the past have contributed to University of Southern Mississippi, University of Miami, the National Oceanic and Atmospheric Administration, University of Queensland (Australia), to name a few. Socio-economic studies have also been completed to analyze the fishing tourism industry in parts of Central America, South America, and the Caribbean.
If you find a TBF tag (which is not necessarily easy), do not try to pull it out of the muscle, as that may cause damage. Cut the monofilament leader below the tag, separating it from the head inside the muscle. Take a measurement of the fish from the base of the jaw to the fork in the tail, and estimate weight. Also record your GPS position of the capture. You can email TBF at tag@billfish.org or call them (954)938-0150.
Get Involved
The most effective resource management must include input and expertise from all stakeholders involved in the fishery: research scientists, resource managers, politicians, recreational and commercial fishermen, etc. Often times fishermen have a greater understanding for, and are more in tune of, the fishery their livelihoods depend on. Therefore, as a fishermen with stakes involved, you should consider getting involved with a tagging program that interests pr pertains to you. If you see a tagged fish, you should absolutely follow the instructions provided and do your part to report it. Many of these mark and recapture programs do not have a high return rate (studies with a 1-2% return rate are considered successful), so every individual fish recaptured and reported can make a difference. Also, many of these programs provide training and tagging kits for fishermen to get directly involved with the whole process. Check out the program descriptions and associated links above, as well as other articles provided on our site, for more information about how you can get involved!
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