CIFT findings to help reduce diesel consumption by trawlers

Lower drag on fishing net brings down water resistance

The V-shaped otter boards for trawl nets developed by a team of researchers at the Central Institute of Fisheries Technology (CIFT) in Kochi has been found to help reduce diesel consumption by trawl boats considerably.

An otter board is a frame or a device that keeps the mouth of the trawl net open horizontally while the net is dragged through the waters. Principal scientist M. P. Ramesan at CIFT says the new accessory would help reduce the drag on the fishing net and, consequently, bring down water resistance and fuel consumption.

The traditional otter boards used to be made of wood, while the new device is of steel, says Dr. Ramesan. The innovation will aid in reducing fuel consumption, reduce carbon emissions and improve economic performance of the trawl boats.

In India, trawling constitutes about 50% of the marine fish landings and is also one of the most energy-intensive fishing activities compared to other forms of fishing. A study by CIFT in 2018 revealed that about 165 million litres of diesel is consumed annually by the 3,678 trawlers in Kerala. The hydrodynamic drag of the trawl net and accessories is the major factor responsible for high fuel consumption.

A pair of otter boards account for 20% of the trawl drag. CIFT introduced V-form steel otter boards now used for trawling in India. The newly developed V-form double-slotted otter boards are found to be effective in creating less drag as the slots (or the net mouth opening) permit water to flow through more freely, reducing the resistance significantly.

Field trials of the new V-form double-slotted otter boards fitted on-board CIFT research vessel RV Matsya Kumari–II revealed that on an average three litres of diesel can be saved per hour compared to conventional otter boards.

It is estimated that there are 35,228 trawl boats in India. Diesel consumption by trawlers varies from 15 to 45 litres per hour depending on the size of the vessel, power of the engine and other factors, including the skill of the navigator, ocean currents and so on.

The total diesel savings by using a V-form double-slotted otter board is approximately 21 to 24 litres per day. A multi-day trawler engaged in 20 days of fishing can save up to 480 litres of diesel in a month.