60 U. S. BUREAU OF FISHERIES. 



comparison with that in lines treated with copper paint, yet in pre- 

 serving effect it occupied second place when it did not occupy first. 

 In the Key West and Beaufort series, where different concentrations 

 (7, 7|, 11, and 12^ per cent) were tried, solutions of copper oleate in 

 gasoline, the higher concentrations, gave in every case better results. 

 The additit)n of a small quantity of cresol effected no improvement, 

 but the small quantity of oil seemed to increase the preserving effect. 

 It is probable, therefore, that still higher concentrations than we used 

 or repeated applications of copper oleate will give even better results 

 and should equal any other preservative tried. 



Copper oleate does not stiffen lines to which it is applied to an 

 objectionable degree. In fact, it appears to be quite suitable for 

 gill nets and other soft gear, where flexibility is essential. Lines 

 treated with it made about three times as many swings, acting as 

 pendulums, as lines treated with tar. The weight imparted to lines 

 by the application of copper oleate is insignificant, being only about 

 1§ per cent of the original twine. In these two particulars — that is, 

 flexibility and weight — copper oleate greatly excels tar and copper 

 paint. In ability to withstand mechanical wear, lines treated with 

 copper oleate are better than any other treated lines tested. In 

 this particular, also, it is far ahead of copper paint, which causes 

 excessive wear. 



Copper oleate prevented the attachment of marine growths to the 

 lines exposed at all places, in this particular being equaled only 

 by copper paint. Copper oleate when used alone, dissolved in gaso- 

 line and with or without oil, imparts to the lines a color that varies 

 between azure and green as concentration varies. This color is said 

 by some to be desirable. Japanese fishermen have introduced in 

 the northwest the practice of dying green their gill nets used for 

 salmon. The acceptability to different fishermen of the color im- 

 parted by copper oleate will be greatly influenced by their customs 

 and their notions of fish behavior. 



In ease of application and time required to dry copper oleate is 

 equal to any other preservative tested. When dissolved in gasoline 

 or benzol in the proportion of 1 to 2 pounds of copper oleate to 1 

 gallon of solvent, the lines or nets need only be dipped in it and 

 spread out to dry. Drying requires about one-half hour for cotton 

 lines and two or three liours for linen or hemp. Applied in gasoline 

 with a little mineral oil, then, copper oleate answers well all the 

 principal requirements of a good net preservative. When copper 

 oleate alone dissolved in benzol is applied to cotton twine, the copper 

 oleate seems to creep to the surface of the twine as the solvent 

 evaporates. The addition of about 1 pound of mineral oil or creosote 

 to each 10 pounds of copper oleate prevents this creeping. Creosote 

 seems preferable to oil as being cheaper and in possessing a toxicity 

 of its own. 



The combination of copper oleate and tar preserves the nets better 

 than either copper oleate or tar alone. After six months' exposure 

 in both fresh and salt water the samples of cotton line preserved 

 with these combinations were equal in strength to the original unex- 

 posed samples. It made little difference whether the copper and tar 

 were applied separately, or mixed. Tliis being so, the choice would 

 be the mixture that would require less labor in being applied. This 

 combination is similar to copper paint in preserving effect and to 



