The catching of fish on a larger scale at sea involved the use of fishing nets and from evidence of finds at Birka and Ribe these too were made from nettle-hemp. It would also appear that the nets that were made were not exclusively for the use of fishermen; they would be used for trapping and be a convenient method as bags for storage and carriage.
The construction of fishing nets is similar to that of recent years and it is only necessary to master the use of only two knots: the clove-hitch and the sheet-bend. First of all a heavier duty line is positioned at a convenient working height and running the estimated length of the intended net.
A long quantity of nettle-hemp is then tied to the main line using the clove-hitch knot; these need to be equally spaced along the main line. After the length of the main line has been completed it is then that the hemp is tied together, using the sheet-bend, to form the mesh. The most difficult and important part of the operation is the ability to make sure that the mesh is kept to the same dimensions: fingers or a piece of scrap wood may be used as a rough guide. To help hold the nettle-hemp a netting needle may be used. The netting needle can be made out of wood, bone or antler.
Stone weights have been found that have been attributed as net sinkers. These weights have a hole or holes bored into them and help, with the aid of buoyant floats, keep the net vertical in the water and fished as a gill or seine net. An alternative style of net sinker has been found at Hedeby in Northern Germany. Rather than drill a hole through a stone, a hoop of willow or hazel is made around the stone which is fairly flat to start with, then across and either side of the stone, some bark crosses are sewn with fine bark strips to the hoop, pinning the stone in between. The hoop left sufficient room between the stone and the hoop itself.
Long-netting could also take place in similar locations to that of the on-shore long-liner. The net would be angled so that the incoming tide would wash over it and then, on its way out, fish would become entrapped. A variation upon this is to make a tide pool out of rocks, which allows the tide to flood it and bring in fish too, but as the tide runs back out to sea, the pool drains through the stones trapping the fish behind the rock wall.
Nets would have also been used to net off sections of rivers or even complete rivers to trap migratory fish such as salmon, trout and sea trout. They may also have been used to section off breeding areas as the Romans had done a few centuries earlier.
Haaf-netting (from the Norse 'haf', the open sea) was a form of net fishing practised in areas like the Solway Firth mudflats to catch salmon. The nets used are cumbersome affairs - 16 feet (5 meters) of meshed twine slung over a 14 foot pole. The fishermen would form a line and walk up to their chests against the tide in the channel. The haafer holds the net against the water with his left hand and grips the beam with his right. He pulls six meshes with his thumb to make a bag, and when a salmon enters he presses down on a special rung. The haaf floats to the top; the netsman turns his back to the tide, kills the fish with his 'mell', or mallet, and flings it into a special compartment - while concentrating on not being swept away by the strong tidal flow