Bottom Trawling (Single Boat)
Shellfish trawls for species such as nephrops or shrimps differ very little from whitefish gear apart from being generally more lightly rigged and subject to a smaller regulation minimum mesh size. Trawls for queen scallops, on the other hand, use much heavier twines than are found in whitefish nets, with bellies and cod-ends heavily protected by cow-hide chafers or similar due to the abrasion which occurs between catch and sea bottom.
The advent of twin-trawling i.e. one vessel towing two bottom trawls side-by-side using one pair of otterboards to spread both nets, is a comparatively recent and somewhat controversial development in the nephrops fishery. The objective is to increase the effective swept area of the gear, and hence the catch.
Each dredge consists of a ruggedly constructed triangular steel frame and tooth-bearing bar, behind which a mat of linked steel rings is secured. A heavy netting cover joins the sides and back of this mat to form the bag in which the catch is retained. Scallops, which usually lie recessed in sand or fine gravel, are raked out by the teeth and swept into the bag. Several dredges are towed together from a tow bar and the larger vessels generally tow two bars, one from each quarter.
Scottish scallopers or 'clammers' range from the small inshore vessel (less than 10 metres) towing perhaps three or four two foot dredges up to the large beam trawler types equipped with outrigger booms which can handle up to 24 dredges, 12 on each bar.
Potting and Creeling
Pots and creels are small traps baited with fresh or salted bait and set on the sea bed in coastal waters to catch lobsters, crabs and nephrops. The frames, constructed from wood, metal or plastic, are netting covered with an entrance through one or both sides, or through the ends. A laced slit in the netting facilitates baiting and removal of catch.
Scottish creeling is mostly prosecuted by inshore vessels less than 18 metres.