How long does lost fishing gear keep catching – and can materials make a difference?

This is the question researchers from UiT The Arctic University of Norway, SINTEF research institutes, and the French research institute IFREMER set out to answer in a study published earlier this year. They examined how biodegradable materials behave in water over time, and whether these could be realistic alternatives to nylon, the dominant material in today’s fishing industry. 

What did the researchers do? 

The study compared monofilaments made from three materials: nylon (PA/polyamide) and two biodegradable alternatives, PBSAT (polybutylene-succinate-co-adipate-co-terepthalate) and PBSA (Poly-butylene succinate-co-butylene adipate). Samples were placed in water at temperatures ranging from 40 °C to 80 °C to test how quickly the materials lost their strength. By using a method known as accelerated aging, the researchers simulated decades of wear and tear in just a few weeks. The aim was to predict, using a model based on the data obtained from accelerated aging, how long each material would remain functional if lost at sea. 

What did they find? 

The differences between the materials were striking. Nylon proved to be extremely durable. 

At 2 °C, it would take more than 1000 years for a nylon filament to lose half of its original strength. By comparison, PBSAT and PBSA would only last 10 and 20 years, respectively, under the same conditions.

At 15 °C, which corresponds to typical coastal waters in Norway during the summer, PBSAT would almost completely degrade after around 10 years, while PBSA would last about 50 years. At higher temperatures, the process was even faster: at 60 °C, the biodegradable materials became brittle and unusable within just a few days.  

These findings clearly show that the choice of material makes a significant difference. While nylon can remain a threat to marine life for centuries, gears made from PBSAT and PBSA would likely stop fishing after only a few decades – or sooner, depending on temperature and environmental conditions. 

Why does this matter, and what’s next? 

Since many fishing gears are used for only a few months each season, there is little need for a material as long-lasting as nylon. This study demonstrates that alternatives exist. Biodegradable fishing gear can be strong enough for commercial use – yet still able to gradually break down in nature at a relatively faster rate, causing less overall harm if it is not successfully retrieved. 

The results are promising for future use of biodegradable materials in fishing gear. But the researchers emphasize that this is just the beginning. The study focused only on one type of degradation – hydrolysis, the effect of pure water alone. In sea water and under real ocean environments, sunlight, waves, and microorganisms would also contribute to material breakdown.  

While the study used laboratory conditions and modelled results for colder waters, the researchers stress that even though the exact degradation time in the ocean will vary, the vast differences observed between nylon and the biodegradable materials in water still provide a clear indication of how much faster the alternatives are likely to break down in real marine environments. 

They also highlight that the results apply to monofilaments without knots or additional processing. Because knots weaken the material, real fishing nets would likely degrade faster than the models in this study suggest. For this reason, further field studies with actual nets – including knotted ones – are needed under real sea conditions. Only then could we know whether these materials can truly replace today’s fishing nets. 

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📌 The summary is based on the article "Biodegradable fishing gears: A potential solution to ghost fishing and marine plastic pollution", published in Marine Pollution Bulletin, written by Waranya Wataniyakun, Maelenn Le Gall, Maria El Rakwe, Christian W. Karl, and Roger B. Larsen. 

Numerous of studies on gillnets and longlines comparing PA to PSAT and PBSA have been done within SFI Dsolve. Find more articles here: https://dsolve-sfi.no/en/publications