44 tr* s. BUEEAU or fisheeies 



A preservative treatment for pound and trap nets which produces 

 an extremely lightweight and flexible webbing consists of the fol- 

 lowing ingredients : 



Pounds 



Copper oleate 30 



Gasoline or kerosene (about Oy^ gallons) 70 



After the copper oleate has been dissolved in the gasoline or 

 kerosene the clean, dry webbing should be soaked for at. least five 

 minutes in the mixture, then drained and dried, when it is ready for 

 use. The treatment is reasonably' satisfactory for six weeks in salt 

 water and for a shorter period in fresh water. Somewhat better 

 results may be obtained b}' using the above mixture diluted with an 

 equal quantity of gasoline or kerosene and repeating the treatment 

 twice as often on clean, dry webbing. 



TREATMENTS FOR GILL NETS 



Investigations on the preservation of gill nets have been conducted 

 by the bureau's technologists on gill nets which have been exposed in 

 Lake Erie waters, where losses are more serious than generally in 

 fresh water. In Lake Erie a green slime accumulates upon gill 

 nets, and, while it appears to have a minor influence upon the tensile 

 strength, the fouling lessens the catch. A net covered with green 

 slime lasij be restored to ordinary condition by thorough washing 

 and then exposing upon a reel to bright sunlight. Continued ex- 

 posure of this nature is detrimental, and so after the washed net is 

 thoroughly dried, it should be hung in the shade. 



The more serious fouling of nets in Lake Erie waters is due ta 

 two cellulose digesting bacteria which have been isolated from so- 

 called red slime. Microscopic examinations reveal that the bacteria 

 are found in the lumen of the cotton hairs and, apparently, there is 

 a progressive deterioration of the cellulose material from the lumen 

 outward. Gill-net webbing on which a red slime appears may 

 disintegrate within a few hours unless the slime is washed off. 



The following treatment (identical with that for pound or trap 

 nets) may be used to advantage : 



Pounds 



Copper oleate 30 



Gasoline or kei'osene (about 9% gallons) 70 



This treatment reduces the danger from red slime but increases the 

 liability of knots slipping when the fish are removed from the net. 

 To overcome this objection as far as possible the bureau's technol- 

 ogists have developed the following treatment: 



Pounds 



Copper oleate 20 



Copper resinate 10 



Gasoline or kerosene (about 91/2 gallons) 70 



The copper oleate should contain not less than 8 per cent copper^ 

 Another preservative treatment for gill nets consists of the follow- 

 ing ingredients: 



Pounds 



Coal tar 12 



Wood tar 6 



Kerosene (about 10 gallons) 76 



Fine red oxide of copper 6 



