Cost savings and positive environmental benefits from using more durable materials in scallop dredges –

Cost savings and positive environmental benefits from using more durable materials in scallop dredges Published:  03 March, 2009

Sea trials to test the use of more cost effective materials and components in Queen Scallop (Aequipecten opercularis) dredges have shown cost savings and also very positive environmental benefits in reducing seabed impact, leaving less sand in the dredge, much cleaner queens and a reduction in the King Scallop bycatch.

West Coast Sea Products (WCSP) Ltd, of Kirkcudbright, Dumfries and Galloway, successfully applied for funding under the Seafish Industry Project Fund to test a range of different materials suitable for dredge construction, which have the potential to reduce the weight and cost of these dredges. Sea trials are ongoing aboard King Challenger BA 87 skippered by Dougie White.

“Tom Abram, Consultant Engineer with the Product Development Unit at Lancaster University, along with his team, went right back to basics looking firstly at the current design and materials used in the construction of Queen Scallop dredges. The steel type and quality, carbon content, and the hardening of the steel were also investigated along with various other material options such as polymers and ceramics,” said Mike Humphrey Seafish project manager.

“As a result of this preliminary research WCSP have been trailing new materials to replace those used in dredges that are at present subject to the most excessive wear. Because of this they are constantly being replaced or repaired at ever increasing costs to vessel owners. The chain bellies or mats, which are probably the most expensive and time consuming to produce, cost around £1000 each to replace, and other parts such as skids and teeth require constant upkeep,” he said.

Changes already made to the dredges in the form of flappers and modified bellies have shown very positive results in reducing seabed impact and King Scallop bycatch. The flexible rubber flappers have been found to be very effective in reducing stones in the dredges and perform as well as the conventional teeth dredges.

An earlier version of an altered dredge has also been tested, with a grid section replacing approximately half of the conventional ring belly and has achieved very positive results. This has now been taken a stage further with the size of the grid section increased to leave only a few rows of steel rings remaining. This has resulted in less sand in the dredge and much cleaner queens.

“I estimate that the introduction of grids has reduced the costs of the bellies by 50%. There are also environmental benefits of this development work. The use of rubber belting to replace teeth and the possible use of lighter materials such as polymers has the potential to greatly reduce the impact of the gear on the seabed, benefiting both the sustainability and viability of the industry. We are still keen to look at the possible use of polymers, nylons and plastics as replacement materials,” said John King, MD of West Coast Sea Products Ltd.

“These dredges are subject to severe wear from abrasion with the seabed, and since the price of these components is a significant proportion of the cost of the gear, it is important to obtain suitable materials at the right price whilst keeping manufacturing costs down. These savings could help to secure a business that is vital to the local economy in terms of the employment it sustains, both onshore and off,” said Mike

“This is an important area of research which we hope can also be extended to develop King Scallop dredge gear in the future. The information provided in the material report from Lancaster University will transfer readily to that fishery. The Lancaster report on this project will be available in April,” he said.

For further information on this project contact Mike Humphrey at Seafish.