What Is Longline Fishing and How It Works

Table of Contents

1. Introduction
2. Defining Longline Fishing
3. Pelagic vs. Demersal Longlining
4. The Mechanics: How a Longline is Deployed
5. Comparison of Longlining Methods
6. Environmental Impact and Bycatch
7. The Survival Connection: Trotlines and Set Lines
8. Gear Considerations for Longlining Principles
9. The Human Element of Longlining
10. Conclusion
11. FAQ

Introduction

If you have ever spent time on the coast or watched a professional fishing fleet head out to sea, you have likely seen the massive reels and coiled lines that define one of the most efficient fishing methods in the world. Longline fishing is a technique that allows a single vessel to cover miles of ocean and target specific depths with surgical precision. At BattlBox, we focus on the tools and skills that provide an edge in the wild, and if you want that curation delivered month after month, you can subscribe to BattlBox to build your kit over time.

This article explores the mechanics of longlining, the different types of sets used in the open ocean and on the seafloor, and the environmental considerations surrounding this practice. We will also look at how these industrial concepts translate into small-scale survival techniques like trotlining. If you are looking to stock up on practical fishing tools, the Fishing collection is a useful place to start.

Defining Longline Fishing

Longline fishing is a commercial fishing technique that uses a long central line, called the mainline, with many smaller baited lines branching off at regular intervals. These smaller lines are known as snoods or gangions. At the end of each snood is a single hook.

Unlike trawling, which drags a massive net through the water, longlining is a passive method. The gear is set in the water and left to "soak" for a period of time. Fish are attracted to the bait and hook themselves. This method is used to catch high-value species like tuna, swordfish, and halibut.

Quick Answer: Longline fishing is a commercial method using a long mainline with hundreds or thousands of baited hooks on shorter branching lines called snoods. It can be set near the surface (pelagic) or on the ocean floor (demersal) to target specific species.

The length of these lines can be staggering. In large-scale industrial operations, a single mainline can stretch for over 25 miles and hold several thousand hooks. However, the same principle is used by artisanal and recreational fishermen on a much smaller scale.

The Anatomy of a Longline

To understand how this system works, you have to break down the components. Every part of the rig serves a specific purpose, from maintaining depth to ensuring the hook stays set.

• Mainline: The primary cord that supports the entire rig. In commercial settings, this is often a heavy-gauge monofilament or braided nylon.
• Snoods (Gangions): Short lengths of line attached to the mainline. They are spaced far enough apart to prevent the hooks from tangling with one another.
• Hooks: Usually circle hooks or J-hooks, depending on the target species and local regulations.
• Floats and Weights: These are attached to the mainline to control the depth of the hooks.
• Anchors: Used in bottom-set longlining to keep the gear in a specific location on the seafloor.
• Radio Buoys: These help the crew locate the line for retrieval, especially when it has drifted over miles of open water.

Pelagic vs. Demersal Longlining

Longline fishing is generally categorized by where the line sits in the water column. This depends entirely on the behavior of the fish the crew is trying to catch.

Pelagic Longlining

Pelagic longlining occurs in the open ocean, away from the seafloor. The line is suspended near the surface or at mid-water depths using a series of floats. This method is primarily used for migratory species that swim in the upper layers of the ocean.

Common target species for pelagic lines include:

1. Tuna (Yellowfin, Bigeye, and Albacore)
2. Swordfish
3. Marlin
4. Mahi-mahi

Because these lines drift with the current, they are often referred to as "drift lines." They are not anchored to the bottom, allowing the vessel to cover vast areas of the sea as the bait moves naturally through the water.

Demersal Longlining

Demersal longlining is used to catch fish that live on or near the ocean floor. The mainline is weighted down with anchors or heavy sinkers to keep it stationary. This is a very common method for catching high-quality whitefish.

Common target species for demersal lines include:

1. Halibut
2. Pacific Cod
3. Sablefish (Black Cod)
4. Grouper

This method is highly effective because it places the bait exactly where bottom-dwelling predators are feeding. It also tends to be more localized than pelagic fishing, as the lines are anchored to specific underwater features like reefs or continental shelves.

The Mechanics: How a Longline is Deployed

Setting a longline is a highly coordinated process that requires specialized machinery and a skilled crew. Even a small error can result in a massive "bird’s nest" of line that can take hours to untangle.

Step 1: The Set

The vessel moves at a steady speed while the mainline is fed out from a large hydraulic drum. As the line goes over the stern, crew members quickly attach the baited snoods using high-strength clips. This must be done with precision to ensure even spacing.

Step 2: The Soak

Once the entire line is deployed, it is left to soak. The duration of the soak depends on the target species and the water temperature. If the line is left too long, predators like sharks may eat the hooked fish. If it isn't left long enough, the catch rate will be low.

Step 3: The Haul

Retrieval is the most labor-intensive part. A hydraulic hauler pulls the mainline back onto the vessel. As each snood comes up, a crew member unclips it. If a fish is on the hook, it is brought on board, processed, and immediately iced to preserve quality.

Key Takeaway: Longline fishing is a highly organized process that relies on mechanical haulers and precise timing to manage miles of line and thousands of hooks effectively.

Comparison of Longlining Methods

Environmental Impact and Bycatch

While longlining is more selective than some other industrial fishing methods, it is not without its problems. The most significant issue is bycatch. Bycatch refers to the accidental capture of non-target species.

Because thousands of hooks are left unattended in the water, other animals often take the bait. This can include:

• Sea Turtles: Turtles may get hooked or entangled in the lines as they swim to the surface to breathe.
• Seabirds: Albatrosses and other diving birds often dive for the bait as the line is being deployed. They can become hooked and drown.
• Sharks: Many shark species are attracted to the struggling fish on the line and end up hooked themselves.

Mitigation Techniques

To combat these issues, modern longline vessels use several clever strategies to reduce their impact on the environment. Many of these are now required by international law.

Circle Hooks are one of the most effective tools. Unlike traditional J-hooks, circle hooks are designed to hook fish in the corner of the mouth rather than the gut. This makes it much easier to release bycatch alive and increases the survival rate of the animal.

Bird Scaring Lines (also called Tori lines) are brightly colored streamers that fly behind the boat during deployment. They prevent seabirds from getting near the baited hooks until they have sunk deep enough to be out of reach.

Weighted Snoods help the baited hooks sink faster. The faster the bait leaves the surface, the less time it spends in the "danger zone" where seabirds and turtles are most likely to encounter it.

Myth: Longlining is the same as "ghost fishing." Fact: Ghost fishing refers to lost or abandoned gear that continues to catch fish. While longlines can be lost, most commercial crews use GPS buoys to ensure every mile of line is recovered, as the gear is extremely expensive.

The Survival Connection: Trotlines and Set Lines

While most people will never operate a 30-mile longline, the principles of this method are vital for emergency preparedness and long-term survival. In a survival situation, your energy is a finite resource. Sitting with a single rod and reel is an active process that consumes time.

A trotline is essentially a miniature version of a demersal longline. It is a stationary line set across a stream, river, or between two points in a lake. By using a trotline, you can "fish" 24 hours a day while you focus on building shelter, gathering firewood, or purifying water.

Why Trotlines Work for Survival

• Passive Procurement: You set it and forget it. You only need to check it once or twice a day.
• Multiple Hooks: Having 10 to 20 hooks in the water at once dramatically increases your chances of a catch compared to a single line.
• Resource Efficiency: You can use found cordage, handmade hooks, and natural bait like worms, crawfish, or insects.

If you are building a broader preparedness setup, the Emergency Disaster Preparedness collection pairs well with the mindset behind passive food procurement.

Step-by-Step: Setting a Survival Trotline

If you find yourself in a situation where you need to procure food efficiently, follow these steps to set a basic trotline.

Step 1: Choose Your Location Look for "bottlenecks" in a river or areas with submerged structure like fallen trees. Fish use these areas for cover and travel. Ensure the water is deep enough that your bait stays submerged but shallow enough that you can safely retrieve the line.

Step 2: Secure the Mainline Tie one end of your heavy cordage to a sturdy tree or stake on the bank. Stretch the line across the water to another anchor point. Ensure the line is taut but has enough give to handle the weight of a large fish. A compact cord system like Quikcord BattlBox Edition is built for tangle-free paracord storage when you need cordage organized fast.

Step 3: Attach Your Drops Every 3 to 4 feet, attach a shorter piece of line (12 to 18 inches) to the mainline. Use a knot that won't slide, such as a Prusik knot or a simple overhand loop. Attach a hook to the end of each drop.

Step 4: Bait and Weight Bait every hook with whatever local forage is available. If you are in moving water, you may need to add a small weight or a heavy stone to the mainline to keep it from floating to the surface. For quick handline work, a kit like the Exotac xREEL Roundabout Kit fits the same keep-it-simple approach.

Step 5: Check Regularly Check your line at dawn and dusk. Leaving fish on the line for too long can attract predators like snapping turtles or raccoons that will steal your catch and damage your gear. If you are carrying a small rig in your pack or go-bag, the EDC collection is where you can build around that everyday-ready setup.

Bottom line: A trotline is a force multiplier for food procurement that applies the industrial logic of longlining to a survival context.

Gear Considerations for Longlining Principles

Whether you are interested in the industrial side of fishing or the survival applications, the gear you choose makes the difference between success and failure. Longlining is hard on equipment. The salt water, the tension of the line, and the struggle of the fish will expose any weakness in your kit.

Cordage

For commercial use, monofilament is the standard because it is nearly invisible underwater. For survival use, we recommend braided nylon bank line. It is treated with a tar coating that protects it from UV rays and rot, making it much more durable for long-term sets than standard paracord. A good example of compact cordage utility is Quikcord BattlBox Edition, which keeps line organized and ready.

Hooks

The size of the hook should match your target. In a survival scenario, smaller hooks are generally better. You can catch a large fish on a small hook, but it is very difficult to catch a small fish on a large hook. Always carry a variety of sizes in your EDC (Everyday Carry) or go-bag.

Storage

Managing multiple hooks and lines is a recipe for a tangled mess. Use a "line winder" or a simple piece of notched wood to keep your mainline organized. For the snoods, a piece of foam or a dedicated hook organizer will prevent the hooks from dulling or catching on your other gear. If you want more ready-to-carry gear ideas, browse the Fishing collection alongside your core tackle.

The Human Element of Longlining

Longline fishing is more than just hooks and cordage; it is a testament to human ingenuity in harvesting resources from one of the most hostile environments on earth. From the massive vessels in the North Pacific to the survivalist setting a line in a backcountry creek, the goal is the same: efficiency.

At BattlBox, we believe that understanding these large-scale systems provides a deeper appreciation for the skills required to thrive outdoors. Whether you are building an emergency kit or just curious about how your seafood reaches the table, the mechanics of longline fishing offer valuable lessons in patience, strategy, and gear maintenance. For more on staying ready, the What to Buy for Prepping guide is a strong next read.

Key Takeaway: Success in longlining, regardless of scale, depends on understanding the environment and using the right tool for the specific depth and species you are targeting.

Conclusion

Longline fishing remains one of the most effective ways to harvest fish from the sea. By using a single mainline to deploy thousands of baited hooks, crews can target specific depths and species with incredible efficiency. While the environmental challenges of bycatch are real, modern technology and smarter gear choices like circle hooks are making the practice more sustainable for the future.

For the outdoor enthusiast, the principles of longlining provide a blueprint for passive food procurement. Learning to set a trotline or a stationary set line is a foundational skill that can save your life in a long-term survival scenario. It allows you to work smarter, not harder, by letting your gear do the heavy lifting while you manage other priorities.

"The best survival strategy is the one that works while you sleep."

If you are looking to build a kit that includes the high-quality cordage, hooks, and tools mentioned in this guide, subscribe to BattlBox and let the right gear show up at your door each month.

FAQ

Is longline fishing better for the environment than trawling?

Generally, yes, because it does not destroy the seafloor habitat like heavy trawl nets do. However, it does have a higher risk of bycatch for certain species like seabirds and turtles if mitigation measures aren't used. Because the gear is passive, it also consumes significantly less fuel than dragging a net through the water. If you are building an emergency-minded kit, the Emergency Disaster Preparedness collection is a practical complement to this kind of planning.

What is the difference between a longline and a trotline?

A longline is the commercial term for the large-scale method used in the ocean, often stretching for miles with thousands of hooks. A trotline is a smaller version used in freshwater rivers or lakes, typically anchored between two points. Both use the same basic anatomy of a mainline and branching snoods. For more everyday-ready carry options, the EDC collection is a natural fit.

How do fishermen keep birds from eating the bait?

Crews use several methods, the most common being "Tori lines" or bird-scaring lines. These are colorful streamers that scare birds away as the hooks are being deployed. They also use weighted lines to make the bait sink rapidly and may even dye the bait blue to make it less visible to birds from the air. If you want compact gear that helps keep your setup organized, Quikcord BattlBox Edition is worth a look.

Why are circle hooks used in longline fishing?

Circle hooks are designed to slide out of a fish's throat and hook into the corner of the jaw. This significantly reduces "gut hooking," which is often fatal. By using circle hooks, fishermen can release bycatch or undersized fish with a much higher chance of the animal surviving. For broader fishing-ready gear, browse the Fishing collection and choose the tools that fit your own setup.