38 



U. S. BUREAU OF FISHERIES. 



6. Copper oleate alone here, as elsewhere, produced a very flexible 

 line; it held tensile strength during exposure about like the Dutch 

 method for cotton lines. Copper oleate excelled in wearing quality 

 but did not equal in this respect the combinations of copper oleate 

 and tar. 



7. The petroleum product No. 2 proved to be a poor preservative 

 in all respects studied. 



8. The Dutch method, in preservation of tensile strength and in 

 flexibility, was intermediate in value between the best and poorest; 

 in mechanical wearing quality it was inferior. 



9. The copper paints preserved -tensile strength well, greatly stif- 

 fened the lines, and wore poorly. 



SERIES EXPOSED IN FRESH WATER AT PUT IN BAY, OHIO. 



All the exposures of lines in water so far described were in sea 

 water at Key West, Beaufort, and Woods Hole. It is important to 

 determine how preservatives behave in fresh water also. Since Lake 

 Erie is the seat of one of om* greatest fresh-water fisheries, where the 

 art of constructing and using fishing nets has been brought to a high 

 degree of perfection, it seemed appropriate to make a series of experi- 

 mental exposures in its waters. Accordingly, a series identical with 

 the Woods Hole series in the lines and preservatives used was pre- 

 pared and placed in the water at the U. S. Bureau of Fisheries hatch- 

 ery at Put in Bay, Oliio, June 15, 1922. The series for cotton lines 

 was exposed till December 15, 1922. 



WATER CONDITIONS AT PUT IN BAY. 



The temperatm-es of the water at Put in Bay are shown in Table 16. 

 Table 16. — Temperature of water at Put in Bay, Ohio. 



It is well known that fresh water in Lake Erie is very severe in its 

 effect on lines. A red slime becomes deposited on the nets in the 

 summer season, and a strong deterioration of nets occurs at the same 

 time. This red slime consists of hydroids, colonies of small animals 

 that may or may not directly affect the nets. At any rate, decompo- 

 sition of the samples was rapid, as will be seen, and the order of effect- 

 iveness of the different preservatives differed considerably from that 

 of the salt-water experiments. 



