|A beam trawl consists of a cone-shaped body ending in a bag or codend, which retains the catch.|
|These trawlers use strong outrigger booms to tow their fishing gear. |
Shrimp beam trawling using big sized vessels
|Species EnvironmentShrimp belonging to the Penaeid family are targeted in the tropical countries while Pandalid and Crangonid shrimps are mainly caught in the Northern regions. In general, shrimps have similar life histories. Spawning occurs offshore and the fertilized egg develops rapidly into larvae. Juveniles are carried shoreward by currents in shallower waters or for same species into the estuaries, where they rapidly grow. As they reach maturity, they move offshore to complete the life cycle.Fishing GearIn these Bottom trawls, the horizontal opening of the net is provided by a beam on the upper side, made of wood or metal, which may be 10 m long or more. Beam trawls are used mainly for shrimp and flatfish fishing. Beam trawls can be used either with single rig, i.e., operated generally from the stern or more rarely from the side of the vessel, or with a double rig, i.e., two gears towed simultaneously. Several variations of the basic beam trawl have evolved in different locations. These may include beam trawls fitted with two or more wheels to ease the passage of the gear over the seabed. A few are fitted with a full width roller or steel shoes for the same purpose. The shrimp fishery in the Netherlands uses double beam trawling exclusively. Each vessel has two booms rigged at the foremast. While fishing, the booms are lowered into a horizontal position.Small scale Beam trawls This type consists of a funnel-shaped net and bag, the 2 to 4 m opening of which is held horizontally and vertically open by a wooden pole or metal frame fitted with two lateral metal sledges. In Florida in the USA and the Gulf of Mexico, the traditional beam trawl has developed into a more sophisticated gear where the sledges have been replaced by rollers.Vessel OverviewIndustrial beam trawlers use strong outrigger booms to tow their fishing gear. The vessel might be of different size from small to large beam trawlers. In general, the vessels range from 15 to 40 m with engine power varying between 150 and 500 HP, with a 3 men crew. On the Dutch flat-bottomed boats of 15-20 m length have been preferred as long as the vessel fished mainly in the shallows. The beam trawlers in Alaska are small, all less than 60 feet overall, with very basic rigging and equipment. |Handling ModeIf the vessel is not equipped with refrigeration facilities, the shrimps have at least to be stored in ice. However, they must not come into contact with the melting ice. For this reason the shrimps are put into polyethylene bags which are closed and stored in crushed ice.Fishery Production SystemsBeam trawling is a fishing method for industrial and small-scale shrimp fisheries, very often, two beam trawls are towed simultaneously.Fishing EnvironmentBeam trawls are towed with very close bottom contact in sand-mud or sand fishing grounds normally in shallower depth than 100 meters.Fishing OperationsClose bottom contact is necessary for successful operation. To avoid bycatch of juvenile fishes selectivity devices are assembled (sieve nets, sorting grids, escape holes). The towing speed for shrimp is between 2.5 and 3 knots. When the beam trawl is used for shrimping, the foot rope is held off the seabed by setting a string of wooden rollers ahaed of the foot rope. This allows unwanted species, such as starfish and crabs, to escape under the belly of the net. The shrimp, stimulated by the approaching rollers, jump vertically and are caught in the net (this means less sorting on board and there is less damage to shrimp through contact with unwanted bycatch). Another advantage of beam trawling, particularly in countries with high labour costs, is that a small crew is required as only the cod ends are brought on board.Fishery AreaThis gear is very popular in South-East Asia fisheries, in the live-bait shrimp fisheries in Florida in the USA, Japan, North America and the Gulf of Mexico. But also in the North Sea.SeasonalityThe trawling season may change zone by zone according to the target species and its migration patterns. According to the national fisheries regulations, in many countries, fishing with beam trawls may be closed in the coastal waters for certain periods of the year according to the time difference in spawning and feeding of the target species in the waters concerned.IssuesEnvironmental The major impact of beam trawl on species is capture and removal from the ecosystem of small sized organisms (juveniles) and non-target species, which frequently are discarded at sea.
Example of a big sized beam trawler (Norway)