256 MARINE PRODUCTS OF COMMERCE 



vessel is set. A buoy is often used to mark an area where fishing is good, so that 

 the trawl may be set in the same spot. 



As much as 25,000 pounds have been taken on a single tow and trips of 

 350,000 pounds or more have been made during a period of 8 or 10 fishing days. 



Shrimp Trawls. Prior to the introduction of the shrimp trawl about 1912 al- 

 most the entire catch of shrimp had been taken by means of haul seines. By 1930 

 this gear accounted for less than 1 per cent of the total catch. The shrimp trawl 

 was first used experimentally for the collection of marine forms at the Bureau 

 of Fisheries Laboratory in Beaufort, North Carohna. Local fishermen, observing 

 the large quantities of shrimp taken during these experimental hauls, devised large 

 trawls for use specifically in shrimp fishing. By 1917 the use of the trawl had 

 spread throughout the South Atlantic and Gulf States. 



Shrimp trawls consist of a bag in which the fish are accumulated, a wing at 

 either side of the bag for directing the shrimp into the bag, an otter board, or 

 door, at the extreme end of each wing to keep the wings apart, and tow lines 

 attached to the doors and secured to the vessel. They are essentially like a regu- 

 lar otter trawl, but are smaller in size and lighter in construction. Headropes, 

 determining the spread of the net, vary from 20 to 140 feet and are usually se- 

 lected to conform to the horsepower of the vessel on which it is to be used (i.e., 

 90 foot spread for a 60 horsepower vessel). The wings and body of the net are 

 usually of 2/2-inch mesh, constructed of 24- to 30-thread medium cotton twine, 

 while the cod end is 2-inch mesh, of 54-thread medium cotton twine. 



Paranzella Nets. The paranzella net is of Mediterranean origin and was first 

 introduced into the fisheries of California in 1877 by an Italian fisherman. A 

 somewhat primitive type of trawl net consisting of a flat triangular bag of webbing, 

 it was developed from a beach seine or bag net, with a wide but low mouth. The 

 net narrows rapidly from the wide mouth to the bag or cod-end, which is so 

 arranged that it can be easily unlaced to discharge the fish when it is hoisted 

 aboard the boat. 



The net is made of cotton twine, having 4 to 8 different mesh sizes and rang- 

 ing from 5 inches at the mouth to 1/2 inches at the cod-end, the latter being made 

 of much heavier twine. The mouth has a spread of about 50 feet and the net is 

 about 150 feet or more in length. The towing warps are 1/4-inch diameter Manila 

 attached to each side of the mouth of the paranzella, and these warps average 

 between 400 and 500 fathoms in length. 



Although there are no floats on the headrope (top rim of the mouth), the 

 resistance of the webbing to the water produces all the lifting effect necessary. 

 Metal weights or chains attached to the footrope result in an elliptical opening 

 of the mouth as the net is towed. 



The net is operated with two vessels, each towing one warp and following 

 parallel courses about 125 fathoms apart. One of the vessels is usually larger 

 than the other and is the one onto which the net is lifted. Tows or drags are of 

 1/2- to 2-hours duration at 3 to 4 miles per hour, in depths of from 25 to 100 

 fathoms. 



The principal advantage of this type of operation is the greater control of the 

 net at practically any depth by the simple expedient of increasing or decreasing 

 the spread between the boats and the speed at which they are towing. However, 

 despite this net-controlling factor it is evident that the operation of two vessels 



