Wear and Tear I : How Microplastics Come To Be

So we’ve looked into the matter of fishing nets and gears, and the whole shebang on ghost fishing. These are obviously the more common and most visible pollutive issues with regards to the fishing industry. But what about the micro ones? The issues that are so small you wouldn’t think to worry about them at first glance. With microplastics, it’s possible that they may have been too small to see at all.

Microplastics are most commonly defined as plastics that are <5mm and can come from various sources – one of which would be the fishing industry [1]. Fishing nets don’t have to be discarded into the ocean as a whole for them to wreak havoc on the environment. Even while they are in usable condition and in active operation, fishing gear can still manage to pollute the ocean through the gradual release of microplastics into the ecosystem [2].

When fishing equipment are cast out to sea from the vessels, they encounter harsh natural elements such as strong water currents, rough sea surface features, and aggressive wave formations that apply friction on the fishing gear [2]. Despite their long-hailed durability, plastic nets and lines are not immune to wear and tear, hence are susceptible to these natural elements that slowly chip away at their forms, producing microplastics that escape into the marine environment.

Of course, it goes without saying that Abandoned, Lost and otherwise Discarded Fishing Gear (ALDFG) are also sources of such microplastics as they spend their remaining lifetime floating through the oceans [2].

Microplastics from Danish seine fishing

Previous studies had already reported that Norwegian fisheries as a whole emit around 200,00 kilograms of microplastics annually [3]. A recent study by Syverson et al [3] had attempted to assess the contribution of specifically Danish seine fishing in Norway towards this mass of microplastic pollution in the ocean.

Figure 1: Illustration of Danish seine fishing method and stages [4]

Danish seine fishing, also known as anchor seining, involves the use of ropes and a conical net that sweeps through the water for fish before they are slowly hauled back up [3,4]. The report was able to pick out various reasons for the degradation of these plastic seine ropes, and cited exposure to UV radiation as the most common cause [3]. After being weakened by UV radiation, the ropes are more vulnerable to wear and tear due to friction when in contact with the water and seabed.

Figure 2: Worn Danish seine rope after 12 months of use [3]

In the end, it was found that Danish seine fishing gear suffered an annual total mass loss of up to 97,000 kilograms due to wear and tear, half of which was contributed by the larger fishing vessels. Although the results suggest significant contribution of microplastics from fishing gear, it is important to note that such studies come with significant amounts of uncertainty due to the difficulty in obtaining large and representative sample sizes, as well as trying to account for the myriad of factors that could affect wear and tear.

References:

[1] US Department of Commerce, N. O. and A. A. (2016, April 13). What are microplastics? NOAA’s National Ocean Service. Retrieved February 10, 2023, from https://oceanservice.noaa.gov/facts/microplastics.html

[2] Montarsolo, A., Mossotti, R., Patrucco, A., Caringella, R., Zoccola, M., Pozzo, P. D., & Tonin, C. (2018). Study on the microplastics release from fishing nets. The European Physical Journal Plus, 133(11). https://doi.org/10.1140/epjp/i2018-12415-1

[3] Syversen, T., Lilleng, G., Vollstad, J., Hanssen, B. J., & Sønvisen, S. A. (2022). Oceanic plastic pollution caused by Danish seine fishing in Norway. Marine Pollution Bulletin, 179, 113711. https://doi.org/10.1016/j.marpolbul.2022.113711

[4] Australian Fisheries Management Authority. (2014, March 22). Danish seine. Australian Fisheries Management Authority. Retrieved February 10, 2023, from https://www.afma.gov.au/fisheries-management/methods-and-gear/danish-seine

Wear and Tear I : How Microplastics Come To Be

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