164 



U. S. BUREAU OF FISHERIES 



in the treatment would not be the same as in the lake. Moreover, 

 the supply of food to the bacteria and the removal of their waste prod- 

 ucts would not be ideal, and hence the bacterial population would 

 not reach a very high level. The results, therefore, could only be 

 expected to be qualitative. Nevertheless, the experiments were 

 initiated and carried through. The results are shown in the follow- 

 ing table. The first column indicates the effect of the treatment, 

 cold, upon previously sterilized twine; columns 2 and 4 show the effect 

 of bacteria upon twine previously treated with the material under 

 study, then sterilized in an autoclave, and finally inoculated with 

 destructive bacteria. Columns 3 and 5 show the effect of steriliza- 

 tion upon the treated twine. 



Table 3. — Effect of preservatives on gill-net twine under laboratory conditions 



Description of treatment 



Untreated control _ 



Tannic acid, 1 per cent; copper sulphate, 10 per cent 

 Tannic acid, 1 per cent; phenol, 5 per cent; ferrous 



sulphate, 10 per cent 



Salicylic acid, 10 per cent in cupric chloride dissolved 



in ethyl alcohol 10 per cent 



Zinc sulphate, 10 per cent 



Tannic acid, 1 per cent; cupic chloride, 10 per cent... 

 Lead acetate, 10 per cent; potassium dichromate, 10 



per cent 



Tannic acid, 1 per cent; cupric acetate, 5 per cent 



Copper sulphate, 10 per cent; sodium carbonate, 10 



per cent 



Cresote (beechwood), full strength 



Phenol, 5 per cent; crystal violet, 1:1,000 



Phenol, 5 per cent 



Beta naphtol, 10 per cent in alcohol. 



Cupric chloride, 10 per cent; potassium dichromate, 



10 per cent- 



Cupric chloride, 10 per cent; sodium carbonate, 10 



per cent 



Beta naphtol, 10 per cent in alcohol; cupric chloride, 



10 per cent 



Proprietary compound 



Tar-kerosene 



Cuprous oxide, 6 per cent; coal tar, 6 per cent; pine 

 tar, 3 per cent; water-gas-tar oil, 85 per cent (treat- 

 ment No. 28.')0) 



Crystal violet 1: 1,000.. 



Cuprous o.xide, 6 per cent; coal tar, 20 per cent; 

 water-gas-tar oil, 74 per cent (treatment No. 284) - - 

 Cuprous oxide, 6 per cent; coal tar, 13!-^ per cent; pine 

 tar, 6% per cent; water-gas-tar oil, 74 per cent (treat- 

 ment No. 288) 



Copi)er resinate, 29 per cent; water-gas-tar oil, 71 per 



cent (treatment No. 2817). 



Mercuric oxide, •% per cent; ferric oxide, 6 per cent; 

 coal tar, 13 per cent; wood tar, 7 per cent; water- 

 gas-tar oil, 73 per cent (treatment No. 2819) 



Tensile strength in pounds 



Chemical 



effect of 



treatment 



3.00 

 2.30 



2.83 



2.88 

 2.98 

 2.27 



1.67 



2.47 



1.84 

 3.13 

 2.95 

 2.90 

 2.90 



1.18 



1.32 



2.78 

 3.22 

 3.13 



3.10 

 3.10 



3.33 

 3.08 



Inoculat- Treated 

 ed with ! and ster- 

 bacteria j ilized in 

 in Dubos ' Dubos 

 media I media 



0.91 

 2. 17 



2.73 



2.98 

 2.95 

 1.81 



1.52 

 2.30 



2.30 



.83 



2.90 



2.90 



2.88 



1.13 



2.15 



2.85 

 3.17 

 2.00 



3.10 

 3.13 



3.19 

 3.31 



2.78 

 2.12 



2.71 



1.86 

 2.71 

 2.30 



1.52 

 2.60 



2.15 

 2.93 

 2.90 

 2.90 

 3.03 



1.29 



1.92 



2.15 

 2.93 

 3.08 



2.83 

 3.15 



2.93 

 3.29 



3.15 



Inoculat- 

 ed with 

 bacteria 

 in lake 

 water 



2.88 

 2.24 



2.95 

 2.34 

 2.37 



1.79 

 2.54 



2.20 

 1.83 

 3.00 

 3.03 

 2.80 



1.11 



3.08 

 3.63 

 3.05 



2.83 

 3.10 



3.19 



3.31 

 3.63 



3.45 



Treated 

 and ster- 

 ilized in 

 lake 

 water 



2.95 

 2.20 



2.63 



1.94 

 2.78 

 2.24 



1.45 

 2.40 



1.79 

 3.10 

 2.98 

 2.98 

 3.15 



1.01 



1.65 



2.63 

 3.08 

 3.15 



3.10 

 2.95 



3.10 

 3.48 



The treatments tested include many not heretofore used. Some 

 are not suitable for practical use upon nets, but were tried in order to 

 learn more about the characteristics of the cellulose-digesting 

 bacteria. 



It appears that phenol affects the bacteria adversely; however, it 

 can not be used on account of its solubility. Betanapthol is effective, 

 but creosote has little effect. The inefficiency of creosote for this 



