\* 



■*■•', * 



.*^; 



'■y 



jS^ 



Figure 8. — Inclinometer used to measure the angle of stray, wire angle, of towing cable during plankton net 

 tow (also see Figure 3 where pendulum indicator is more clear; see Table 1 for source of specifications). 



begin. The data sheet used here for the plankton 

 tow (Fig. 10, specifications in figure legend) is 

 preprinted to record data for tows up to 300 m of 

 wire out. Twenty items are numbered for auto- 

 matic data processing. 



The tow. — Before the net-tow station is occu- 

 pied, the following numbered items should have 

 been recorded on the data sheet. 



1-Cruise, 3-Date, 4-Order occupied, 5-Station, 

 11-Net number (regular and/or fine) this is 

 usually the mesh-size number (see Fig. 10), 

 12-Meter number (regular and/or fine), 14- 

 Carry-over, initial meter reading (regular 

 and /or fine). 

 The net tow is made oflF either side of the ship 

 as follows: (Tows off the stern are not rec- 



ommended because of turbulence from ships' 

 screws.) 



1. The ship is stopped; the station depth is 

 requested from the bridge and recorded in 

 the lower left hand section of the data 

 sheet. 



Note: With 300-m wire out, and the wire angle 

 at 45°, the net is approximately 210 m deep. (Wire 

 out X cosine of 45°— 0.707— = net depth.) If 

 station depth is less than 130 fathoms (238 m), 

 a "Depth-of-Tow" graph (Fig. 11) is referred to 

 in order to determine the proper amount of wire 

 to pay out so that the net and gear will not hit 

 the bottom. Shallow and deep tows are payed 

 out and retrieved at the same rate as routine 

 standard tows. 



For shallow and deep tows, other than routine 

 (items 20-22), the section 20'-22' should be used, 

 recording lengths of wire out in decrements of 10, 

 as called by the winch man, and wire angles (see 

 below, procedure for tow, item 7a) at such calls. 



10 



