436 U. S. BUREAU OF FISHERIES 



treatments, including that of copper oleate. They also show that 

 oleic acid has a marked deteriorating effect. This latter fact is of 

 great importance in its bearing on the possibility that commercial 

 grades of copper oleate may contain some free oleic acid. 



RESULTS OF PRACTICAL APPLICATION OF COPPER OLEATE BY 



FISHERMEN 



During the 1923 season between 60,000 and 100,000 pounds of 

 copper oleate were used by fishermen. In order to determine whether 

 these practical trials had produced satisfactory results, we visited 

 the fishermen along the New England and middle Atlantic coasts, 

 examined their nets, and obtained from them their observations and 

 opinions. 



Lobster and pound-net fishermen from Maine to Long Island 

 have, with few exceptions, had excellent results. At the time the 

 survey was made copper oleate had been tried on but a very few 

 gill nets in this region. 



Those fishermen who used copper oleate found that it was an 

 excellent antifouling agent and preservative as long as it remained 

 in the twine. The length of time during which it remained in the 

 twine varied from 14 days to 5 or 6 months. In those cases where 

 it washed out in 14 days the fishermen believe that the grade of 

 copper oleate used was very poor. 



Various combinations of copper oleate with other substances were 

 tried by the fishermen. One of the most successful of these was a 

 mixture of a small amount of copper paint with the kerosene solu- 

 tion of copper oleate. This is reported as being an excellent pre- 

 servative for use on pound nets. 



The fishermen were about equally divided in their opinions as to 

 whether gasoline or kerosene gave better results as a solvent. Gaso- 

 line seems to give a more uniform distribution of oleate through 

 twine, drys more rapidly, and leaves twine less oily than kerosene. 

 On the other hand, kerosene is cheaper than gasoline and also safer 

 because it is not so inflammable. It was also found that in most 

 cases better results were obtained when the net or webbing was 

 allowed to steep in the solution for several hours, preferably over 

 night, instead of 5 or 10 minutes, as was first recommended. 



The principal suggestions from users of copper oleate were as 

 follows : 



1. Steps should be taken to prevent copper oleate from washing 

 out of the webbing as rapidly as it now does. 



2. There is need for some substance which, when combined with 

 copper oleate, will give it more body, so that the webbing will be 

 better protected from mechanical wear. 



3. When copper oleate is used on seines, some substance should 

 be added to prevent the slipping of knots when the seine is hauled. 



With respect to the first of these suggestions, one must remember 

 that if copper oleate is to prevent growth successfully it is necessary 

 for it to be at least slightly soluble in water. An entirely insoluble 

 substance would not preserve at all. It is doubtful, therefore, if it 

 would be advisable to decrease the solubility of copper oleate to any 

 great extent. We have conducted experiments that have indicated 

 that if the solubility is appreciably decreased by such substances as 



