FISH FARMING TECHNOLOGY
Shogun twisted knotless machine
When SUPRA® meets Muketsu netting by Elihai Radzinski, Fibras Industriales SA, Peru
“Each product can
adapt to different
customer’s needs”
Nylon raschel netting Braided knotted netting
In past articles we have discussed alternative products that FISA produces for the aquaculture industry and how each product can better adapt to different customer’s needs depending on the species of fish farmed, the oceanographic conditions, potential predator risks and never to forget the working conditions and maintenance system each specific farm utilises for its cages. We have already discussed the various ropes that can be used for the structure of the cages and mentioned such options as Polysteel, PE, PP, Nylon, Polyester and FISA’s trademark products such as Polymax® and Polytar® ropes. Additionally, we have discussed the various raw materials that can be used for netting. We mentioned some advantages and disadvantages of nylon netting versus polyester netting, the lightweight advantages of UHMWPE and some potential disadvantages of that product and we finished off mentioning FISA’s Supra® Advanced Fibers which is a third generation HDPE netting. In the following paragraphs we will outline some basic characteristics of the knotted netting, braided netting, raschel netting and Shogun® netting, otherwise known as twisted knotless Muketsu netting. Raschel “knotless” netting is probably the most common type of netting used in aquaculture. This knotless netting is a low cost knitting manufactured on Raschel-type machines, thus the origin of the name, and is characterised by the relatively fast production process. Raschel netting is normally manufactured using nylon, polyester, polyethylene or multifilament PP. A big advantage of Raschel netting is the fact that the nature of the knitting leads to lineal ruptures thus making it much easier to repair. Also, some farmers claim that knotted (twisted or braided) netting can damage the fish skin when it rubs with the knots. We are not sure how to dimension this potential risk in knotted netting, but it must be mentioned. The biggest advantage of Raschel netting is its price. Because of the fast production process, it is possible to sell each kilogram of netting at much more competitive pricing. Additionally, as the Raschel machines allow for production of wider sections (large numbers of mesh deep) this can lead to less joints requires in the assembling/rigging of the cages thus further reducing costs. Having mentioned all the advantages of the most common netting, we feel obliged to also mention some potential disadvantages, the biggest one being that this netting is knitted meaning that once there is a small tear it will rapidly extend and increase escape probability. An additional disadvantage for nylon and polyester Raschel netting, which are by far more resistant than the polyethylene or pp versions of this netting, is the fact that these are multifilament products and the looseness of the filaments means there will be higher probability of fouling attaching to the netting at a faster pace. As always, the specific natural conditions and working habits of each farm will determine whether Raschel netting, and what raw material, would be most adequate for that farm. FISA’s vast experience with producing Raschel netting for over 50 years in all its variations can be critical to defining the most effective and cost-efficient version to be used. A second type of netting FISA has been manufacturing for over 70 years is the twisted knotted 32 | November 2019 - International Aquafeed