search for the fish where local hydrographic conditions are favorable for 

 its presence. 



The gear used by the trawlers is the Michelet trawl, derived from the 

 Vigneron-Dahl gear. 



The functioning of the trawl with doors, which first appeared in the last 

 years of the 19th century, is based on holding open the net not, as in the old 

 beam trawl, by a massive transverse timber but by the dynamic action of 

 two vertical boards held in an oblique position and tending thus to be pushed 

 apart by the stream of water just as a kite rises under the force of a stream 

 of air. 



These boards are in the form of two wooden rectangular panels, about 

 3. 5 meters long and 1. 4 meters high, protected, on the bottom, by a heavy 

 iron shoe allowing them to slide along the bottom and causing them to weigh 

 more than a ton. 



The two doors are attached at their rear to the two extremities of the 

 trawl opening and to the trawler by two separate cables attached to two tri- 

 angular brackets, on the internal face of the door, of different height which 

 pivot on their parallel bases. The point of pivoting on the larger bracket is 

 placed on the vertical mid-line of the door, that of the smaller forward 

 bracket on a parallel line one quarter of the length of the board. The apexes 

 of the two brackets are brought together as the attachment point for the tow- 

 ing cable. This arrangement caused the door to take an oblique position as 

 towed, thus assuring a maximum width of opening of the trawl. 



On the first doored trawls, the otter trawl type, the doors were attach- 

 ed directly to the wings of the net. The innovation characterizing the 

 Vigneron-Dahl gear was the attachment of the doors at a distance of 50 to 

 100 meters from the ends of the wings by a length of cable. The cable is 

 about 75 meters in the Michelet trawl. In this trawl, the cable coming from 

 each of the doors is attached to a spreader of hardwood 1. 5 meters long, in 

 a vertical position, which itself is attached to the wing of the net by three 

 parallel steel cables nine meters long. 



The great advantage of trawls of the Vigneron-Dahl type is an important 

 increase in the area swept, by fact of the action of the doors at the end of 

 the cables which prolong the sides of the net, effecting a greatly superior 

 opening. These arms of the net frighten the fish and concentrate them be- 

 fore the opening of the trawl. 



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