Types of Fish Tagging Systems Explained: PIT, Acoustic, Satellite & More

From monitoring salmon migration in rivers to tracking sharks across entire oceans, fish tagging has become one of the most essential tools in modern marine and freshwater science. But not all fish tagging methods are the same. Depending on the species, location, study goal, and budget, researchers choose from a variety of tagging technologies—each with its own pros, cons, and use cases.

We’ll break down the most commonly used fish tagging systems including PIT, acoustic, satellite, and archival tags—to help you understand how they work, when to use them, and what kind of data they can generate.

Whether you’re a fisheries biologist, conservationist, or curious angler, here’s everything you need to know about today’s fish tracking technologies.

Why Fish Tagging System Matters

Before diving into the different types, let’s revisit why fish tagging is important.

Tagging allows scientists to:

• Monitor migration routes and timing

• Estimate population size and survival

• Study habitat preferences

• Evaluate the success of hatchery releases

• Inform policy for sustainable fishing

Without a robust fish tagging system, much of a fish’s life would remain a mystery, especially in open water where direct observation is nearly impossible.

1. PIT Tags (Passive Integrated Transponder)

Overview:
PIT tags are small, battery-free devices that emit a unique code when scanned by a tag reader. They’re implanted into the body cavity or under the skin of a fish.

How It Works:
A stationary or handheld reader sends out a magnetic signal. When a tagged fish passes nearby—usually within 30–60 cm—the tag is activated and its ID is recorded.

Best Used For:

• Freshwater species (e.g., salmonids, sturgeon, eels)

• Long-term monitoring in rivers, streams, and hatcheries

• High-volume tracking at fish ladders or weirs

Pros:

• Low cost

• Long lifespan (no battery)

• Accurate, individual-level data

Cons:

• Requires fish to pass close to the reader

• Limited use in open marine environments

2. Acoustic Tags

Overview:
Acoustic tags are battery-powered transmitters that send out sound pulses with unique codes. Underwater receivers (hydrophones) detect these signals and log the data.

How It Works:
Each tag emits an ultrasonic ping at regular intervals. These signals can be picked up by an array of hydrophones placed throughout a waterbody. Depending on tag power and environment, detection ranges can reach up to 1 km.

Best Used For:

• Coastal and estuarine species

• Tracking fish movement in bays, rivers, and offshore structures

• Studying predator-prey interactions

Pros:

• Can cover large areas

• Real-time detection with high spatial resolution

• Suitable for complex movement studies

Cons:

• Higher cost than PIT tags

• Requires periodic retrieval or maintenance of receivers

• Shorter lifespan (usually 3 months to 2 years)

3. Satellite Tags

Overview:
Satellite tags are used for large, migratory marine species that roam vast distances. These tags communicate directly with satellites when they break the surface.

Types of Satellite Tags:

• SPOT (Smart Position or Temperature): Sends location and environmental data when the tag is at the surface.

• PAT (Pop-up Archival Tag): Stores data for a set period, then detaches and floats to the surface to transmit via satellite.

How It Works:
Tags are externally attached to the fish. Once the fish surfaces or the tag detaches, it connects with satellites to send location and sensor data.

Best Used For:

• Large pelagic fish (e.g., tuna, sharks, swordfish)

• Long-distance migrations in the open ocean

• Global movement and depth tracking

Pros:

• Tracks fish across oceans

• Provides rich data on depth, temperature, and movement

• Useful where no receiver network exists

Cons:

• Expensive (often $2,000–$5,000 per tag)

• Short lifespan (weeks to months)

• Requires fish to surface or tag to pop off

4. Archival Tags

Overview:
Archival tags are data loggers that store environmental data over time. These tags must be physically recovered to access the data.

How It Works:
Implanted or attached to the fish, archival tags record temperature, depth, light levels, and sometimes salinity. They do not transmit data until retrieved.

Best Used For:

• Deep-diving or bottom-dwelling species

• Long-term behavioral studies

• Commercial fisheries (tags often recovered during harvest)

Pros:

• High-resolution data

• Long recording periods (up to several years)

• Detailed behavior insights

Cons:

• Data only accessible upon recapture

• Limited use for small or hard-to-recapture species

5. External (Conventional) Tags

Overview:
These are basic tags like spaghetti or dart tags, often used in large-scale mark-recapture studies.

How It Works:
A visible tag is attached externally, usually to the fish’s dorsal area. Fishers or researchers report the tag number upon recapture.

Best Used For:

• Population estimation

• Simple migration tracking

• Recreational tag-and-release programs

Pros:

• Very inexpensive

• Easy to apply

• Good for broad population-level studies

Cons:

• Relies on recapture and reporting

• No movement or environmental data

• Tags can be lost or damaged

Choosing the Right Fish Tagging System

The ideal fish tagging system depends on several factors:

If you’re tagging thousands of salmon smolts in a river, a PIT-based fish tagging system offers scalability and cost-efficiency. If you’re tracking a handful of bluefin tuna, satellite or acoustic tags provide the spatial reach and behavioral data needed.

Real-World Applications

• NOAA Fisheries uses PIT and acoustic tags to track salmon survival through hydropower systems in the Columbia River.

• The Tagging of Pacific Predators (TOPP) program used satellite tags to track over 20 marine species across the Pacific Ocean.

• The Atlantic Salmon Federation uses acoustic arrays to monitor migration and mortality rates along the eastern seaboard.

These programs have generated transformative data that guides species recovery, ocean zoning, and fishery management worldwide.

Final Thoughts

Understanding the different types of fish tagging systems is critical for designing effective ecological research and conservation programs. Each tag type offers a unique window into fish behavior—whether it’s a battery-free PIT tag recording a salmon’s journey through a river, or a satellite tag tracing a shark’s oceanic expedition.

By aligning your goals, species, and budget with the right technology, you can gather data that drives better decisions—for fisheries, for ecosystems, and for the future of aquatic life.