566 FISHEKIES OF THE UNITED STATES. [54] 



Towing Nets for collecting free-swimming marine invertebrates at the 

 surface, or at intermediate depths between the surface and the bot- 

 tom. 



United States Fish Commission. 

 The towing nets employed by the United States Fish Commission are 

 essentially alike in size and construction, whether for use at the sur- 

 face, bottom, or intermediate depths. The ring is of one-fourth-inch 

 round brass, 12 inches in diameter, and is arranged for the attachment 

 of three leaders at equal distances apart, at each of which places two 

 little copper wires are soldered around the ring, with a narrow space 

 between them, just wide enough to permit of tying the leaders. This 

 method of fastening the leaders permits of the net being inverted and 

 used either side oat, an advantage of considerable importance when 

 working in a dirty sea. Two kinds of cloth are preferred for the nets — 

 silk bolting cloth and linen cheese cloth or scrim, the former, although 

 much more expensive than the latter, serving best and being more* 

 durable. Other kinds of material sometimes employed are fine em- 

 broidery canvas, bobbinnet lace, and crinoline. The nets are made from 

 18 inches to 2 feet deep, of two pieces of cloth cut in the shape of an 

 elongate semi-ellipse, and, therefore, taper gradually and terminate in a 

 full rounded end. A small stout cord is welded around the mouth, and 

 serves for its attachment to the ring, which is made by means of a con- 

 tinuous piece of sail twine winding around the ring and through the net 

 inside of the welded cord. Larger nets, with the ring 15 to 18 inches in 

 diameter, are occasionally employed, and also for surface work an elong- 

 ate, rectangular brass frame, measuring 30 inches in length by 6 inches 

 in width. In using the circular towing nets from the steamer for col- 

 lecting at the surface or at slight depths, a long spar is run out amidships 

 on the starboard side, thus permitting of the handling of four or five nets 

 at a time. For intermediate depths the nets have been attached to the 

 dredge-rope at the proper places as the rope was being paid out. 



Trawl Wings used in connection with the beam-trawls, for collecting free- 

 swimming marine invertebrates at the bottom of the sea. 



United States Fish Commission. 



Since 1880, it has been customary to use the towing nets at the bot- 

 tom, in connection with the beam-trawls of either pattern. This prac- 

 tice has been productive of most excellent results, and the towing-net 

 attachments to the trawls have come to be considered of nearly as great 

 importance as the trawls themselves. The ordinary form of towing 

 net is used, and, while it is impossible to tell with certainty from what 

 depth of water its contents were derived, whether at the bottom or on 

 the passage up, it is certain that they are far richer in quantity and 

 quality than when the nets are simply lowered to an intermediate 

 depth. The method of using the towing nets at the bottom, which was 

 devised by Capt. H. C. Chester, in 1880, is as follows : A rectangular 



