PRESERVATION OF FISH NETS. 33 



GENERAL COMMENTS. 



Onlj'^ the more important and widely used or promising processes 

 for the preservation of nets have been considered. To anyone "who 

 has searched literature it would be a surprise if a great numy other 

 methods and processes were not found to have been tried. The list 

 given by Jessen includes, besides barking, smoking, alum, train oils, 

 tallow, grease, bluestone, potassium bichromate, various compounds 

 of mercury, iron vitriol, pine tar, wood oils, coal tar, aniline dyes, 

 and various other products of gas works, salt, resins, soaps, lime, etc. 

 But all the recorded data found that will have a material value have 

 been included in this paper. 



It should be obvious to most people that nets should always re- 

 ceive some preservative treatment. Coarse nets, pound nets, and the 

 like should be both barked with catechu or quercitron, mordanted 

 with potassium bichromate, and then tarred. Where it is not pos- 

 sible or suitable to tar the nets, they should receive the catechu or 

 quercitron treatment and the mordant. It is preferable to use two 

 baths of quercitron, the first containing only one-half the total 

 amount to be used. 



Though no actual figures have been brought forth to prove it, 

 there is little doubt that nets are destroyed more rapidly in warm 

 climates and warm weather than in cold. Fishermen should take 

 note of this fact and be accordingly more careful of their nets where 

 the weather is warm. It is also likely that foul, dirty water works 

 more rapid destruction on nets than clean water. 



One of the possible ways to avoid the disintegration of nets is, of 

 course, the chance of using some material that is not subject to de- 

 cay — metals, for example. A person signing the initials C. J. (1912) 

 describes briefly in the Dansk Fiskeritidende some experiments with 

 aluminum, brass, copper, and galvanized-iron wire for boAv nets. The 

 aluminum proved to be best. 



Xo important results have come from efforts to substitute metals 

 for plant fibers for nets. 



CARE OF NETS. 



When nets are piled up wet — especially if they are foul with slime, 

 blood, fat, etc. — the rapid oxidation heats the net. Even if the net 

 does not take fire the heat generated may very well cause a great 

 weakening. This weakening will not be visible, but will tell in a 

 much shorter life of the net. However carefully the net is barked 

 or tarred, a very short life can be looked for if the net has been 

 heated. 



For a temporary preservative, where it is not possible to dry the 

 nets, it is customary to salt them. This is a useful treatment, as far 

 as it goes. Salt is not in itself poisonous or injurious to small 

 organisms or bacteria (for they live in the sea which contains much 

 salt) if the concentration is not too great. But it is well known that 

 when any watery organism is exposed to a salt solution stronger than 

 its own juice water will })e extracted and usually the organism dies. 

 The salt is injurious to living things not because of its saltiness, but 

 because of its concentration ; not because it is poisonous, but because 



51700°— 2 L 22 



