METHODS OF HANDLING PLANKTON NETS 203 



found that large horizontal nets can be closed with a reasonable degree of certainty. 

 But though almost all difficulties in the actual operation were overcome, the results fell 

 much below expectation. Frequently the catch was disappointingly small and on a 

 number of occasions the condition of the material left much to be desired. Throughout 

 these hauls with large nets a speed of about 2 knots was maintained, and it is possible 

 that the smallness of the catch when a net is closed indicates that an unexpectedly 

 large proportion of the material obtained in an open net is caught on the way up, when 

 the speed through the water is augmented by hauling. The poor condition of the 

 material in some hauls is probably to be attributed to the surging movement of the net 

 while being drawn to the surface. When a large horizontal net is hauled from deep water 

 after having been closed on the Nansen principle, it appears sometimes to behave like 

 an ill-constructed kite, the bucket lashing from side to side and causing serious damage 

 to the contents. If the fair-lead on the edge of the frame is omitted the trouble is 

 aggravated. On one occasion it was found, when the net had been hauled, that this fair- 

 lead had carried away, and the condition of the material was far worse than anything 

 previously seen. Except for the most heavily constructed organisms practically every- 

 thing was destroyed : even the limbs of the larger Crustacea were broken up into their 

 component segments. 



In spite of these disadvantages a large amount of material has been obtained in good 

 condition and with accurate data of the horizon at which it was caught, and this, though 

 less in quantity than that obtained in large open nets, should prove of considerable 

 biological interest. It is hoped in the future to conduct further experiments, with a 

 view to finding some method of closing large midwater nets which obviates the dis- 

 advantages referred to above. 



The N 450 was usually carried with the frame outboard, just abaft the mizen rigging. 

 When shooting, the bucket and net were put overboard and the lashings were cast off, 

 leaving the net suspended only from a slip-hook on the masthead tackle. When the 

 frame had been lowered sufficiently the slip-hook was tripped. In hauling, the net was 

 brought directly to its proper position on the port quarter, where it remained until it 

 was next required. The N 200 and TYF could of course be handled very easily and 

 no description of the procedure in shooting and hauling is necessary. 



When these large tow-nets were fished open, the net was shackled to a ball-bearing 

 swivel at the end of the wire rope, and a length of stray line, attached behind this swivel, 

 was used to carry the weight. The swivel is an important part of the equipment. When 

 any considerable length of rope is paid out, it is continually twisting and untwisting, and 

 unless a swivel is used, the stray line and weight will become foul of the net and prevent 

 it from fishing. Other nets can be employed at any desired point by fixing a stop on 

 the wire and attaching the net above this point by a shackle in the manner recommended 

 by Hjort {Depths of the Ocean, p. 49). 



When the net was to be closed, the weight was attached directly to a swivel at the end 

 of the wire rope and 20 or 30 m. paid out. The stop and large mechanism were 

 now attached to the rope just inside the fair-lead on the after rail, and when a final 



