Seines, purse seines and lift nets

Fish that swim in schools can be efficiently caught with seines (long ropes). Seines are very long ropes, either with or without a net at both ends, which can be deployed from both boats and shores. The loose ends of the seine ropes are fixed to the boat or something ashore in order to herd and haul the fish.

Usually one end of the rope has a buoy attached to it, which is deployed first. The centred net and the second rope are deployed consecutively as the ship returns to the initially deployed buoy in a large circle. After the deployment, the buoy is brought back on board and the net is hauled while the ship sails.

Danish seines

Danish seining is a variant of the bottom seine fishery and is also called snurrevaad. Danish seining uses bag shaped nets attached to long ropes. Unlike the seining method described above, this method anchors the deployed buoy to the sea floor and then deploys the net and the second rope, again in a large circle. The ship does not sail while hauling in the net but positions itself near the anchored buoy. This traditional method of seining is therefore also called anchor seining. A potential negative impact is the by-catch of undersized fish and non-target species.

Purse seines

Purse seining is an active fishing method that targets pelagic species, such as herring and mackerel. Purse seines are deployed around schools of fish, trapping them between three netting walls, preventing the fish from escaping. Purse seines can vary in size with some being 150 metres tall and 500 metres wide. This fishing method uses relatively low amounts of fuel and has no impact on the sea floor. However, the amount of by-catch can form a problem, especially in the tuna fishery.

Purse seine with FAD

Fish Aggregating Devices (FADs) are floating objects like buoys which are used to attract fish species that like to school around floating objects, after which the nets are deployed. Advanced FADs have sonar and GPS, so the fishermen can see where the FADs are and how many fish have aggregated. As tuna school with other species (of tuna) the method has a lot of by-catch, including sea turtles, rays, sea birds, and sharks.

Purse seine without FAD

Because Fish Aggregating Devices (FADs) have a lot of bycatch of sea turtles, rays, sea birds, and sharks, the alternative of not using FADs is a more sustainable fishing method.

Lampara

The lampara net is a surrounding net, shaped like a dust pan or a spoon. When the two wings of the net are hauled simultaneously, it creates a pinching motion, causing the bottom part of the net to close up and retain all of the fish inside.

Scottish seines

Scottish seining uses very long nets which are bag shaped in the centre. The gear can be set from either a boat or shore. The fishing method is similar to the seining method that was described at the top of the page. After the ship has deployed the two ropes and the centred net, it returns to the initially deployed buoy and hauls it on board. The ship then sails forward while hauling the net. Dutch fishermen use this method to target tub gurnard, striped red mullet, squid, and plaice. This technique has a low fuel usage and less impact on the sea floor in comparison to bottom trawls.

Beach seines

A beach seine is a seine net that is operated from the shore which mainly targets demersal fish species. The gear is composed of a bunt (bag or lose netting) and long wings often lengthened with long ropes for towing the seine to the beach. The headrope floats on the surface, the footrope is in permanent contact with the bottom and the seine acts as a barrier which prevents the fish from escaping from the area enclosed by the net. A (potential) negative impact of beach seines is the amount of by-catch due to the use of large nets or small mesh sizes.

Boat-operated lift nets

The nets used for this fishing technique are often square and are attached to curved bars that cross each other (crossbar). A rope is attached to the intersection of the cross, which is pulled to move the net vertically through the water. The nets are placed on the sea floor and are quickly hauled up after a specific period of time, catching the fish that are situated directly above the net. Depending on the target species, lamps or bait can be used to attract fish.

Boat-operated lift nets can be hauled manually or mechanically. Large lift nets are held open by several long poles that can be placed on either side of the boat and a  number of pulleys and/or small winches are used to drop and haul up the net. The amount of unwanted by-catch is low, but the use of lamps attracts more unwanted species.

Shore-operated lift nets

Shore-operated lift nets are often stationary platforms that can be placed on the bank of a river or on suitable beaches. The more modern lift nets can be operated manually or mechanically. Fish is often attracted by the use of bait and light.