During the last year, Western Seafood Company, Inc., through its subsidiary Marine & Industrial Specialities (MIS), has been trialling fishing gear with the aim of reducing fuel consumption and increasing operational efficiency, and Polar Fishing Gear was involved in the trawl doors project where several types of trawl doors were tested.

It found that drag resistance from the traditional wooden trawl door and small mesh shrimp trawls (45-50mm) is relatively high compared with most other fishing methods. On average, resistance from the trawl represents 80% of the total drag, with the trawl doors representing 20% to more that 40% of this.

In light of this, the company tested several types of modern trawl doors and different netting on its Gulf shrimp trawlers to see where operating costs could be reduced and how catch production could be improved.

The most common rigging on the Gulf based trawlers are doors sized 10'x40'' (3.1m²) or 9'x40'' (2.8m²) manufactured from wood or aluminium coupled to trawls in the 45' to 55' head rope range. A pair of doors are twin rigged and pulled from outriggers from each side of the vessel. Boats operating in this 'Quad' configuration average 550hp and operate at a 3 knot trawling speed. There are larger boats that have 800+ hp and even a few with 1500+ hp. These trawlers can be found towing four nets 80' and larger with doors as large as 14'x44'' (4.8m²).

The trials saw Neptune doors from Polar Fishing Gear give the best steel door results, achieving the best spread with minimum resistance. Subsequently, the final decision was to replace the 10' doors with Neptune 1.4m² doors and the 9' doors with Neptune 1.1m² doors.

The average fuel consumption of the larger boat is 20,000 gallons on a 30 day trip and 10,000 gallons for the same length of trip on the smaller boat.

Patrick Riley from MIS said that during production testing where Neptune doors towed from one side of the boat and traditional wooden doors on the other side, production was increased by 2.2%.

“In these times of high fuel costs and depressed shrimp prices, we have to find any increase in efficiency there is, and Atli's [Atli Mar Josafatsson from Polar Fishing Gear] doors certainly help in this regard. We were able to see our investment recovered in less that two 20 day trips typical of our fleet boats by reduced fuel costs alone”, said Riley. “We are now looking at trying the 1.1m² door with the same trawl configuration to see if we can come up with more savings.”

Atli Mar Josafatsson estimates that the resistance has reduced by 30% by replacing the doors only.

In a few months, more than 20 vessels from the states of Texas, Louisiana, Alabama, Mississippi, Florida, South Carolina, and Georgia will be modified and equipped with Neptune doors due to the fuel saving results.

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