Standard fishing line is not biodegradable. Monofilament nylon, the most common type, takes an estimated 600 years to break down in the environment, and even then it doesn’t truly disappear. It fragments into microplastics that persist in oceans, soil, and waterways indefinitely. Fluorocarbon and braided lines fare no better.
How Long Fishing Line Actually Lasts
Research conducted in collaboration with the NOAA Marine Debris Program puts the decomposition timeline for plastic fishing line at roughly 600 years. That number is often cited as a worst-case figure, but it understates the real problem: the line never fully degrades into harmless substances. Instead, it breaks into smaller and smaller plastic fragments over centuries.
The primary force breaking down fishing line in the ocean is UV light from the sun. Sunlight triggers chemical and physical changes in the plastic, causing it to become brittle, crack, and shed tiny particles. These micro and nanoplastics leach chemical additives as they fragment, becoming increasingly toxic over time. So while a piece of discarded line may no longer look like fishing line after a few decades of sun exposure, it hasn’t gone away. It has just become harder to see and harder to clean up.
Why Discarded Line Is So Damaging
Fishing gear, including line, nets, and traps, makes up 50 to 100 percent of the plastic debris found in certain parts of the ocean. That range sounds extreme, but it reflects how concentrated fishing waste is in areas with heavy commercial or recreational activity.
Before fishing line breaks down into microplastics, it spends years as a nearly invisible hazard. Monofilament is thin, strong, and almost transparent in water, which makes it especially dangerous to wildlife. Birds, sea turtles, dolphins, and fish become entangled in discarded line, often losing limbs or dying from constriction, strangulation, or starvation. A single tangled mass of old line on a reef or shoreline can trap animals for years.
The microplastic stage brings a different kind of harm. Marine animals ingest tiny plastic fragments, which accumulate in their tissues and pass through the food chain. The chemical compounds that leach from weathered plastic add another layer of toxicity to an already serious problem.
Do Biodegradable Fishing Lines Exist?
They do, but your options are extremely limited. The most well-known biodegradable fishing line was Eagle Claw’s Bioline, which used a patented polymer designed to break down over time. Eagle Claw discontinued the product and has stated it has no plans to restart production. No other manufacturer has picked up the patent.
The Japanese company Toray produces a biodegradable line called FieldMate, made from a polymer that naturally occurring microorganisms can break down into water and carbon dioxide. It’s the closest thing to a truly biodegradable fishing line on the market. The catch: FieldMate is only sold in Japan, directly through Toray, and cannot currently be purchased elsewhere.
For most anglers around the world, there is no biodegradable fishing line available on store shelves today.
Performance Trade-offs With Biodegradable Materials
Even in research settings, biodegradable fishing materials come with real compromises. A study testing braided twine made from biodegradable polymers (PBS/PBAT) found it was about half as strong as conventional high-density polyethylene braid. That’s a significant drop in breaking strength, which matters when you’re fighting a fish or hauling a net.
Durability is another concern. After three years submerged in seawater, biodegradable monofilaments lost 20 percent of their strength in cooler water (around 59°F) and a full 80 percent in warmer water (around 77°F). That degradation is exactly the point for reducing ghost fishing, where lost gear keeps catching and killing animals. But it also means biodegradable line has a limited shelf life and may not hold up through a full fishing season in warm climates. The same research did show that trawl net performance was only slightly affected by switching materials, suggesting biodegradable gear could work in commercial applications if strength ratings improve.
What You Can Do With Old Fishing Line
Since the line you’re using almost certainly isn’t biodegradable, disposal matters. The worst thing you can do is leave it on the ground, in the water, or in a regular trash can where it can escape into the environment.
Many boat ramps, fishing piers, and tackle shops have monofilament recycling bins. Collected line is sent to recyclers who melt it down and repurpose it, often into underwater habitat structures that benefit fish populations. If you don’t see a recycling bin at your local fishing spot, you can cut used line into short pieces (under six inches) before throwing it away. Short segments are far less likely to entangle wildlife than long, looping strands.
Storing old line in a sealed container until you can recycle it is a simple habit that makes a measurable difference, especially given that a single spool of monofilament could otherwise persist in the environment for centuries.