Scallop Dredging uses steel dredges with a leading bar fitted with a set of spring loaded, downward pointing teeth. Behind this toothed bar (sword), a mat of steel rings is fitted.
A heavy net cover (back) is laced to the frame, sides and after end of the mat to form a bag. Sets of dredges are shackled to a hollow steel tow bar, which is connected to the main towing warp by a series of chain bridles. Larger vessels generally tow two bars, one on each quarter. Dredge gear is often rigged in a very similar way to beam trawls.
Scallops, which are usually found in sand and light gravel, are raked out by the teeth and swept into the bag.
|Potential Impacts (Biological/Environmental)||Gear Selectivity||Regulation|
• Capture and removal of small sized marine organisms and non-target species
• Non-catch mortality
• Capture of undersized target species
• Increased vulnerability to predation
• Displacement and removal of stones
• Damage to seabed strata and reefs
• Hard contact fishing method means damage can be related to weight of gear.
• Diameter of rings and size of back netting.
• Thickness of teeth on bar
• Width of dredge
• Spacing of teeth on the bar
• Sediment type
• Weight of dredge
• Maximum number of dredges per side of vessel
• Minimum size of ring on the bag and minimum mesh size
• Minimum distance between teeth
• Minimum fish sizes
• Maximum weight limit per dredge
• Fishing for scallops in the Scottish zone using the “French dredge” is prohibited. (a dredge with a rigid fixed digging plate).
• Seasonal closures
Improvement measures and initiatives taken by Scottish Fishermen
• Vessels using the new toothless gear have found that drag has been significantly reduced as it is lighter and there is no hard impact damage to the seabed. Environmental damage and displacement is much reduced, and fuel consumption greatly improved, thus reducing carbon and environmental footprints.