the mouth of tne net open in a somewhat rectangular shape when in oper- 

 ation, and two lines attached to the trawl doors are made fast to the 

 vessel. A lead or ground line extends froim door to door on the bottom 

 of tne wings and moutn of tne net; and a float or cork line is similarly 

 extended at the top of the wings and mouth of the net. The size of the 

 net is measured by the width of the mouth, ij 



The steel trawling or towing cable extending from the vessel 

 to tne trawl door varies in size from a quarter to a half inch, depend- 

 ing upon tne size of tne vessel, the size of the trawl, and tne depths 

 fished. The ratio commonly used for determining the required lengtn 

 of caole is 5 or 6 fathoms of line to 1 fatnom of t^ater, although occa- 

 sionally in deeper water the ratio may be reduced to 3 to 1 or less. 

 In tne earlier days or the trawl fishery the towing cable consisted of 

 1/2- to 1-inch manila rope, and the line was seldom extended more tnan 

 UO fatnoms, which was sufficient for the depths then being fished. 



The tow lines are secured to the two trawl doors by means of 

 bridles (consisting of four chains) fastened to the doors somewhat like 

 tne bridle of a kite. The chains fastened to the net end of the trawl 

 door are somewhat longer than the front chains and the top chains are 

 somewhat longer than the bottow chains. Set thus, the doors have an 

 outward, downward thrust while being tewed through the water. 



The wings are the sides of the net and are tapered along the 

 top seam but straight along the bottom seam. They are attached directly 

 to tne trawl doors and extend to the mouth of the net, which varies in 

 width. Most trawls are shaped so that the lead line of the mouth rides 

 behind the float or cork line. This is referred to as the overhang, 

 setback, undercut, or cutback. A good many trawls use a tickler chain 

 of adequate length between the trawl doors to drag behind the float 

 line and scare the shrimp off the bottom in advance of the lead line. 



The net is tapered from the moutn to the throat, which is 

 about 6 feet in diameter. Attached to the throat is the tail, bag, 

 or cod end, an untapered cylinder of heavy webbing "Hhich holds the 

 catch. The end of the tail is closed with a slip-knotted tie rope. 

 To prevent chafing while being dragged on rough bottoms, various types 

 of gear are used, the most common being unraveled manila strands. In 

 addition to the chafing gear, and when fishing in shark and porpoise 

 infested waters, some trawls use covers of heavier, large-stretched 

 mesh that completely encircle the tail to protect the net from sharks 

 and porpoises which bite at fish gilled by the net. The shark covers 

 are also used for attaching the chafing gear to the bottom of the tail. 



7/ For a detailed description see Fishery Leaflet 39U, entitled Gulf 

 of Mexico Shrimp Trawl Design , and Fishery Leaflet li70, entitled 

 Double-Rig Shrjjip Trawling In the Gulf of Mexico . copies of which may 

 be obtained on request to the Fish and Wildlife Service, United States 

 Department of the Interior, Washington 2^, D. C. 



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