274 MARINE PRODUCTS OF COMMERCE 



still proven successful, particularly in smooth seas, since it allows the man who 

 would otherwise have to be at the wheel to work on deck. 



Although the use of suction pumps requires that the fish in the hold be floated, 

 the success of this method of unloading, particularly in the sardine-herring fishery, 

 has recently led to its adoption for use at sea for unloading seines directly into the 

 vessel. 



Furthermore, a method for weighing the fish in conjunction with this equip- 

 ment has been reported, which eliminates any handling and considerable loss of 

 time. A few are already in use in the industry. 



Electrical Fishing Device. In connection with the developments of the suction 

 pump and its recent adaption at sea to remove fish from purse seines, there were 

 numerous speculative theories as to the possibility of simply sucking the fish 

 directly into a boat from the open sea without the aid of a net. Such an idea, 

 fantastic as it might appear, seems probable since the recent invention of a 

 German electrical fishing device, which has been developed to such a stage that 

 actual tests at sea have been planned. It has been pointed out that by placing 

 two electrodes into a body of water and varying the positive voltage on the 

 "anode" between 0.5 and 1.5 volts the fish within the field of the cathode and 

 anode are made to point toward the anode. The action of the varying electrical 

 field along the spine causes the tail muscles to alternately contract and relax, 

 moving the fish toward the anode. The usual commercial species of fish seem to 

 react within this voltage range without harmful effects. Since small fish are not 

 affected, it shows promise of being one of the most conservative ways of fishing 

 yet developed. 



During these same trial tests arrangements have been made for an American 

 firm to set up a large size fish-suction pump. As the fish move in toward the anode, 

 they are drawn directly into the hold of the vessel, eliminating the use of con- 

 ventional fishing gear of any sort. 



Economically, the advantages seem equally important as the rest of the in- 

 vention because the electrical method provides a greater certainty of successful 

 catch by covering a larger fishing field in a shorter fishing time. New areas, 

 heretofore inaccessible, can be exploited with fewer crew members and the trips 

 shortened by several days. It is further estimated that the cost of the electrical 

 equipment and its installation amounts to only 3 to 5 per cent of the value of 

 a medium-sized vessel. This invention, if successful, will revolutionize commercial 

 fishing. 



Preservation and Care of Fish Netting 



Although the life of a net may be extended by frequent mending, which is 

 diligently practiced, mending does not entirely overcome the impaired efficiency 

 and dependability of an old net. For this reason, and also because the additional 

 disintegrating factors caused by exposure to sunlight, air, and water further 

 weaken the net, the use of preservatives is necessary. 



The period of time in which a single net may be used, discounting the pos- 

 sibility of total loss by storms, etc., varies in the different fisheries from a few 

 weeks to a few years. With the application of net preservatives the average life of 

 any net is one year more or less. Because fishermen spend nearly 25 million dollars 

 annually for the replacement of nets, a figure representing about 8 per cent of 



