162 



V. S. BUREAU OF FISHERIES 



Table 2. — Tempt natures , oxygen content, and reaction (pH) of Lake Erie water at 

 locations where nets were set 



Date 



Course and distance from 

 Erie 



Depth 



Tem- 

 pera- 

 ture 



Oxygen, 

 parts per pH 

 million 



Remarks 



1928 I 

 Aug. 15 X. by E. 164 miles'. 



Aug. 16 N. by E. 16 miles 1 



Aug. 17 .N". by E. li E. 16 miles' . 



.\ug. 21 N. by W. 1^2 W. 14 miles' 



Aug. 22 I N. by W. '/2 W. 15 miles'. 



Aug. 28 N. i;f E. Smiles' 



Sept. 7 I X. 'i E. 16 miles ' 



Sept. 8 X. 16 miles' 



Sept. 15 X. 'i E. 14 miles '.... 



Sept. 6 3 mile,s from harbor K 



Sept. 14 do ■ 



Surface 



15 fathoms . 



23 fathoms 2. 

 Surface 



12 fathoms.. 



24 fathoms K 

 Surface 



13 fathoms.. 

 22 fathoms K 

 Surface 



14 fathoms 2. 



Surface 



13 fathoms 2. 



Surface 



13 fathoms 2. 



Surface 



11 fathoms.. 

 21 fathoms. - 



Surface 



11 fathoms.. 

 19 fathoms K 



Surface 



9 fathoms.. - 

 18 fathoms.. 



Surface 



4 fathoms. . . 

 7 fathoms . . . 



Surface 



7 fathoms 



18.5 

 18.2 



8.8 

 19.3 

 17.4 

 11.2 

 19.7 

 18.5 



9.5 

 21.1 

 20.2 

 20.0 

 20.9 

 21.2 



8.5 

 8.5 

 8.8 

 8.4 

 8.4 

 8.9 

 8.0 

 7.7 

 9.4 

 8.3 

 7.8 

 8.3 

 8.3 

 8.4 



8.7 

 9.1 

 8.7 

 8.8 

 9.1 

 8.7 

 8.7 

 9.2 

 8.5 



Thermometer and pH outfit 

 not available. 



8.1 

 8.4 



8.3 

 7.7 

 8.2 

 7.9 

 8.0 

 7.8 



Unusual for gill nets to be 

 fished so near shore. 



Thermocline between 16 and 

 21 fathoms. 



7.9 

 8.5 

 8.2 



8.0 



8.0 



8.1 



7.7 

 8.2 

 7.9 



1 Gill nets. 



2 Bottom. 



3 Pound nets. 



As a random experiment small pieces were cut from some dried 

 gill nets, which had been out of the water for a period of time between 

 one and two weeks, and put into Dubos medium for incubation. At 

 the end of several days bacterial growth was noticed, and the usual 

 bacteria were found by microscopic examination. Transfers were 

 made from this culture to other tubes of media, which produced some 

 of the most active cultures found in the work. The conclusion follows 

 that contaminated nets handled in the accepted way still harbor 

 destructive organisms for some time. The bacteria may slowly 

 continue to cause deterioration during the period of winter storage 

 until the nets become so dry that the organisms die. 



The part played by bacteria during the months when the nets are 

 not being used should be investigated further. It seems probable that 

 much deterioration can take place unless the nets are clean and dry at 

 the time they are put away for the winter. 



PRESERVATIVE TREATMENTS 



Bacteria differ with respect to the kind of food they thrive upon 

 best. Some utihze meat, others starch, sugar, or fat. The bacteria 

 in which we are interested utilize cellulose as their favorite food. 

 It is the process of converting the cellulose so generally found in the 

 lake that makes the bacteria injurious to net twine. As long as the 

 cellulose is derived from debris of wood or rotting grass, this proc- 

 ess does not concern the fisherman; but unfortunately the thread of 

 gill nets can also serve these bacteria as food. Not only do the bac- 

 teria feed on the fibers of the net, but they also find the threads an 



