8-25 Towing the Trawl.— When it is esti- 

 mated that enough cable has been payed out to 

 place the trawl at the desired trawling depth, 

 the ship's speed should be slowed to the in- 

 tended trawling speed simultaneously as the 

 winch is stopped. Reasonable maneuvering 

 can be accomplished by the ship dtiring trawling. 

 The length of the trawling period should be at 

 least several hours. At an early point in 

 operations, a trial series of tows should be run 

 so that a graph can be drawn showing the 

 necessary amount of cable to be payed out for 

 a certain depth when hauled at a certain speed. 



8-26 Retrieving the Trawl.— After the 

 trawling period is over, the ship should be 

 slowed to the desired trawling speed less the 

 speed of cable recovery by the winch. The 

 slowing of the ship as the winch begins to re- 

 trieve the wire must be a smooth operation, so 

 that the actual net speed always remains the 



same. Any time the retrieving action is stopped, 

 the ship's speed should be increased again to the 

 desired trawling speed. Caution should be 

 taken at all times to see that the actual trawling 

 speed of the net is kept constant, to avoid 

 excessive strain from an increase in speed, and 

 to avoid allowing entrapped animals to escape 

 with a decrease in speed. 



8-27 Additional Instructions. — Any increase 

 in trawling speed may cause the trawl to dive 

 more steeply. This additional deepening must 

 be taken into consideration if tows are being 

 made close to the bottom. 



Because of the additional strains due to the 

 surging of the towing ship during heave swells, 

 the trawl normally will be used in fair weather. 

 Special emphasis should be placed on trawling 

 when a pronounced deep scattering layer is 

 indicated on the echo sounder. 



The depth of towing is of prime importance, 



84 



H. O. 607 



