Mechanised cleaning offers several benefits

In October this year, at the Cromaris adriatic fish farms, a new cage cleaning robot was presented. The device offers several benefits.

Takitarou Osaka, maker of the robot, and Marino Košta, Cromaris' robot operator

For two days at the beginning of October, there was plenty of activity at the Cromaris plants and fish farms, where seabass, dentex, meagre and gilthead seabream are bred in Gaženica, and off Zadar. Apart from the catamarans and fishing boats used to feed, monitor, maintain and catch the caged fish, a luxury motor vessel, the Nada, moored alongside with forty guests on board from all shores of the Mediterranean. They were managers and others responsible for technology at the largest Croatian fish farms, and their colleagues from Italy, Greece, Portugal, France and Tunisia. They were invited to a presentation of Yanmar’s new NCL-LX robot cage cleaner, organised by Navela, distributors for Yanmar, and Cromaris, the hosts. The robot is a powerful, high efficiency machine intended for use in large cages used to breed tuna or salmon, and also smaller fish such as sea bass. Takitarou Osaka, its creator, came in person to demonstrate how it worked.


Exclusive presentation of automated cleaning

Before coming to Croatia, the robot had spent several months being tested in Norway, and the Adriatic Sea was chosen as the location for this demonstration and monitoring for the entire Mediterranean, due to the high technological level of fish farming here, the fact that four Yanmar robots have been operational for several years in the area, and the experience acquired by Navela in Pula. Thanks to this, Navela has been awarded the status of sole distributor in the Mediterranean, where there is the greatest concentration of fish farms in this part of the world, outside Scandinavia. There are almost 21,000 cages for breeding white fish and 250 for tuna in the area.

Breeding technology and innovations are critical for the development of mariculture, and cage cleaning is an extremely important aspect. The condition of the nets from which cages are made has a direct effect on the success and quality of breeding. Nets which are submerged in sea water begin to acquire a coating, composed of algae, various invertebrates, the remains of fish food and fish secretions. This leads to a reduction in the free flow of fresh seawater and oxygen, which increases the risk of disease for the fish. The net is also more likely to be damaged, allowing fish to escape, while the added weight becomes a burden on the anchoring system. These problems also affect their feeding habits. The old technology used for cleaning cages was based on replacing them, which was a huge task with a high risk of damage to equipment. Of course, the notion of cleaning the cages in situ, during breeding, offers a completely different approach. Today, nets are changed, while the whitefish, such as seabass, are under a year old, and housed in smaller cages. When the fish are transferred to larger cages, mechanical cleaning is required, once or up to three times during the cycle until the fish reach maturity. Tuna cages are cleaned regularly throughout the cycle. Small cages are also cleaned mechanically if the mesh becomes severely overgrown and coated.


The robot in action along the net.


Sea robots

So, many people were interested in coming to see first hand an example of the second generation of Yanmar robots. Yanmar went into the cage-cleaning business nine years ago, after years of development and research on model NCL-SE3, better known as Sensui-Kun. In the late 1980s, Yanmar Marine Farms was established with the aim of researching mariculture and developing their own products to improve bio-resources and maintain the environment. Yanmar Marine Systems deal with the production of mariculture equipment. In Croatia, the Sensui-Kun robot was demonstrated five years ago in tuna farming. It is an underwater cleaning device with its own power supply, consisting of several components. The guidance mechanism with a monitoring system and independent power supply, including a high-pressure pump, is located on the service vessel, while the robot itself, which is the underwater component, is of course placed in the sea. It is equipped with jets for the intake of water under high pressure. This affects its propeller rotation, and the thrust enables the robot to maintain a neutral, floating position in relation to the cage. Cleaning is carried out by high-pressure jets. The entire operation can be managed by one person using a joystick, and the work process can be seen in real time on a screen. The tasks and benefits available through the use of this cleaning system are multiple. Clean nets mean parasites cannot develop, and other treatments to tackle growths or diseases are rendered less necessary. Water flow through the mesh is increased, and with it, the level of oxygen in the water, while the danger of injury to the fish is reduced, the cages do not become heavy due to growths and marine organisms, the use of cleaning products is reduced, and cleaning can be carried out whenever necessary.


The larger robot in the control position. Although an older model, it was the first time for many of the visitors to view it.

Multiple benefits

The economic benefits from the use of cleaning robots are also significant. Cleaning is four times as efficient as classic methods, and the effects last longer and reduce the need for new mesh. Damage to the mesh, which occurs when it is changed is also eliminated, reducing costs, particularly when one takes into consideration that changing the mesh requires a boat, five staff on board, and two divers in the water.

The technology used by both Yanmar robots is essentially the same. The difference is in the quantity and speed of cleaning they achieve. The smaller robot can clean 372 square metres of mesh per hour, while the larger one is four times more efficient, cleaning 1,600 square metres per hour. It is of course much bigger, with three cleaning discs and three propellers, rather than the single ones of the smaller model. It can tackle an area 191 cm wide, compared to the 57 cm reach of the smaller model. Its high pressure pump is capable of producing almost twice the cleaning water pressure.

The presentation at the Cromaris fish farms was the first opportunity for many of the visitors to see how these machines operated, while others were introduced to the larger model for the first time. They were particularly impressed by the fact that the system is fully integrated, providing fully functional equipment, and the opportunity to network with
others who are already using it.

Navela d.o.o.

Castropola 54, Pula
Tel. +385 52 214 542, fax. +385 52 213 558
This email address is being protected from spambots. You need JavaScript enabled to view it.

This article is reproduced with permission from More Magazine, Croatia

NCL-LX specifications

Outer dimensions:     1358 x 2287 x 874 mm

Weight:           500 kg

Max. treveling speed:            14 m/min

Max. reachable depth:           50 m

Max. cleaning surface:          1600 m2 /h

Propeller:       450 mm x 3

Water pressure:        20,5 MPa


NCL-SE3 specifications

Outer dimensions:     810 x 1003 x 760 mm

Weight:           150 kg

Max. treveling speed:            6,2 m/min

Max. reachable depth:           30 m

Propeller:       450 mm

Water pressure:        11,3 MPa

TV monitor:   15 inch, color

Control:          joystick x 2