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Purse seines
Purse seines
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Characteristics
OverviewA purse seine is made of a long wall of netting framed with floatline and leadline (usually, of equal or longer length than the former) and having purse rings hanging from the lower edge of the gear, through which runs a purse line made from steel wire or rope which allow the pursing of the net. For most of the situation, it is the most efficient gear for catching large and small pelagic species that is shoaling.Plan
The principal net sections and ropes for a purse-seine
The principal net sections and ropes for a purse-seine
Handling EquipmentSmall purse seines can be operated entirely by hand in small scale fisheries. In artisanal or semi-industrial fisheries, the purse seine handling equipment may include: a purse seine winch or a capstan, a purse line reel, a brailer and a power block and in some fisheries, a net drum. In industrial purse seine fishery, the basic equipment include, in general: a hydraulic power block, a powerful purse seine winch, a number of derricks, including a brailer or a fish pump, and small winches, an auxiliary boat "skiff" and sometimes, an helicopter.Vessel OverviewThe purse seine can be used by a large range of vessel sizes, ranging from open boats and canoes up to large ocean going vessels. The purse seines can be operated by one or two boats. Most usual is a purse seine operated by a single boat, purse seiner, with or without an auxiliary skiff. Fish OperationSearching for fish aggregation, then checking (when possible) the fish species and evaluating school sizes and its catchability, prior to surrounding it is the major part of a purse seine operation. The purse seine is set around a detected school of fish. After that, the net is closed underneath the school by hauling the purse line running through the rings (pursing). Hydroacoustic instruments, like sonars are important tools to locate fish aggregations. Also common is the use of "natural" signs of fish aggregations (often observed with binoculars) to start with the fishing operation, like concentration of sea birds, ruffling of the water surface and presence of groups of dolphins. Artificial "Fish Aggregating Devices" (FAD's) and light attractions are used in some fisheries to concentrate the fish.Target SpeciesAggregated pelagic species (schools) of all sizes from small sardines to the large tunas ( Skipjack tuna , Yellowfin tuna ).Water Area OverviewAll over the world.Gear EnvironmentIn general the purse seines are surface gears used in the marine coastal and high-sea waters. Aggregated resources in the upper levels are most common, but fish at depths up to 300 m can be targeted. The purse seines are also used in inland areas when there is enough room for the operation of a large net).ImpactsEnvironmental Because of its characteristics there is no impact on the bottom habitat (except when the water depth is less than the height of the seine during the fishing operations and that the lower edge of the gear wipes the sea bottom).Species The main negative impact is the incidental capture of dolphins in certain fishing areas. Special techniques have been developed to reduce bycatch of dolphins; the Medina panel and "back down" operation, which allow encircled dolphins to escape alive. When small pelagic purse seines are used with light attraction, there may be incidental catch/bycatch (including too small fish, juveniles or endangered species). The increasingly used practice of encircling floating objects, including man-made FADs increases the capture of small sized and immature aggregating around such devices.
 
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