Knotless, strength and stability

Nichimo's Marine Business Group is home to knowledge and experience in a range of fields, and its advanced Ultra Cross (UC) knotless netting continues to draw attention.

Sustainable practices are becoming increasingly important in commercial fishing as the industry moves towards better efficiency, while by-catch, remains a significant issue, making sustainable options ever more important.

Japanese marine firm Nichimo, with a century of experience behind it, has been focusing on this area through R&D and the production of fishing nets and gear.

The four-strand braiding process used to produce UltraCross was developed by Nichimo

‘In the beginning, we had to produce innovative products to meet fishery regulations in the run up to the establishment of the 200-mile EEZ,’ said Takahiro Morioka of General Affairs at Nichimo.

‘Nichimo was already in a position to do this, having acquired the necessary technology and analytical ability. At the same time, fishing gear was getting bigger due to an increased demand for surimi – minced fish – in Japan. More raw material was required for production and you need a lot to produce 100 tonnes of surimi, 400-500 tonnes. To catch this, net material needed to be strong and resistant to high tensions. To meet this requirement using polyethylene, we had to develop special braided knotless netting. Our UC netting is one example of this.’

A model purse seine in Nichimo’s testing tank

UC’s netting’s manufacturing process maximises the use of the material’s strength. Standard knotless netting is made with two strands, where each strand is twisted through each other to form meshes without knots, but because it weakens the more the net is used, a four-strand braiding process was developed. This continuous monofilament and knotless netting is used for demanding applications.

Nichimo’s UC netting is supplied to trawlers and purse seiners in Japan and worldwide, while the company’s R&D team conducts experiments through a combination of flume tank testing and practical fishing. With its own purse seine and set net test tanks, as well as a 100-metre-long towing tank for trawls, Nichimo tests new and improved nets with up to three different current configurations at various depths. It also analyses the nets’ physical properties, impact on the sea floor and validates performance.

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‘Commercial fishing nets have to meet various conditions such as being lightweight or resistant to strong currents,’ Takahiro Morioka said.

‘Our facilities enable us to test these and more.’

He said that the advantages of UC netting are that it utilises various synthetic fibres to best advantage without damaging or weakening the material. A standard knotless net can run when there is a break but with UC netting a parted mesh will not spread.

Examining netting in one of Nichimo’s net lofts

This means that repairs can be carried out quickly and easily. The weight of UC netting is also less, as with no knots there is less bulk to the netting and there is a better flow of water, plus the greater resistance to abrasion means it lasts.

‘Knots can tighten or distort, which changes mesh size but UC netting maintains almost 100% of its original mesh size throughout its life and doesn’t hold any sediment thanks to the four-strand braiding. There is also very little impact on fish with less bruising and damage,’ Takahiro Morioka said.

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