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2009 Runner-Up ($10,000) HOVERCRAN

/ ©: ILVO-Fisheries
Components of the HOVERCRAN system include (l to r) the electric winch, the adapted beam trawl, and the control cabinet.
© ILVO-Fisheries

The HOVERCRAN

Institute for Agricultural and Fisheries Research, Belgium
The brown shrimp (Crangon crangon) fishery is widespread in the coastal zones of the North Sea. Inherent in the equipment used are two major problems: (1) the small meshed nets have poor selectivity, resulting in large amounts of bycatch, and (2) the heavy bobbin rope used to startle the shrimp into the net wreaks havoc on the seabed.

The winning team built the HOVERCRAN (HOVERing pulse trawl for selective CRANgon fishery) with these basic principles in mind: simplicity, robustness, durability and cheap design. The device is a modified 8-meter shrimp beam trawl, in which the heavy bobbin rope has been replaced with 12 lightweight electrodes.  A harmless, lowintensity electric field close to the seafloor selectively provokes a startle response in brown shrimp.

The elevated footrope lets nontarget species escape underneath the hovering trawl and collects the shrimp that jump up into the water column. This technique reduces bycatch volume by 35 percent and decreases seafloor contact by 75 percent. It has implications for a large number of shrimp fisheries around the world where bycatch is the biggest issue the industry faces.

The challenge of this research was to design and integrate specific equipment capable of creating an electro-pulse that induces a maximum response in the shrimp only. Equipment needed included a pulse generator, a winch for hauling and lowering the supply cable, and a control unit to check operation.

That the existing shrimp fishing gear can serve as the basis for the construction of the HOVERCRAN is an important advantage. The additional system components can be placed on the available gear without making radical changes to the existing infrastructure. This means that HOVERCRAN does not negatively influence the current way of fishing. The towing speed, tow duration and choice of location remain the same. But with HOVERCRAN’s automatic controls in place to prevent human errors, the crews are safer and work time between hauls is shorter due to less bycatch.

Current technical modifications for bycatch reduction in the Crangon fishery focus on catch separation or filtering after species have entered the trawl. Damage incurred by contact, or stress caused during the capture and escape process, may lead to higher mortality of bycatch. HOVERCRAN can play an essential role in reducing these discards through an alternative startling method that succeeds in catching bottom-dwelling shrimp without touching the seafloor.

Hans Polet, HOVERCRAN lead researcher, ILVO Fishing Gear Technology Section

The ILVO - Fishing Gear Technology Section: 2009 Runner-up

The Institute for Agricultural and Fisheries Research (ILVO) - Fishing Gear Technology Section is a dynamic group of 13 motivated people with different backgrounds and skills. The primary objective of the group is the development of sustainable fisheries from a technical perspective, and particularly via applied fishing methods.

The HOVERCRAN team consists of:
  • Hans Polet, engineer. Leader of the Fishing Gear Technology Section and initiation of the HOVERCRAN research, Polet launched the innovative idea to use electric pulses as a means to develop a species-selective electro-trawl for the brown shrimp fishery.
  • Bart Verschueren, biologist with technical experience. Coordinator of the HOVERCRAN research.
  • Fernand Delanghe, electrical engineer. More than 35 years of experience in fisheries research.
  • Norbert Van Craeynest, technician. Ex-fisherman with lifelong experience in all kinds of fisheries.
  • Eddy Buyvoets, technician. Expert knowledge of net construction.
  • Manfred Van Elslande, ex-shrimp fisherman. With his lifelong experience in the Belgian coast Crangon fishery, he was skipper on the HOVERCRAN testing vessel.

Building a future in which humans live in harmony with nature.

Photos and graphics © WWF or used with permission. Text available under a Creative Commons licence.