NET DETERIORATION IN LAKE ERIE • 151 



Through the cooperation and generosity of I. H. Kolbe, of Erie, Pa., 

 arrangements were made for opening a laboratory at his plant for 

 conducting detailed bacteriological and chemical studies when funds 

 should be available. In the summer of 1928 it became possible to 

 establish a laboratory at this point; Prof. W. H. Wright of the depart- 

 ment of agricultural bacteriology of the University of Wisconsin, was 

 associated with the bureau's workers in order that the problem might 

 be attacked from a sound basis of microbiological experience and 

 knowledge. J. M. Fogelberg and E. M. Hildebrand, likewise from 

 the University of Wisconsin, performed the greater part of the 

 experimental work with praiseworthy energy and skill. 



EFFECT OF RED SLIME ON NETTING 



During the summer, certain species of hydra become very abun- 

 dant in Lake Erie, of which one with a red color is most common. 

 These small animals drift about the lake, stinging the fish and driving 

 them ''wild." ^ They settle upon nets where they remain as a source 

 of annoyance to the fishermen, whose hands often swell as a result of 

 the irritation caused by handling the nets thus contaminated.*^ This 

 red slime represents practically all the actual gross fouling that affects 

 nets in Lake Erie. The growth of algae — the green organisms found in 

 nearly all waters — is generally not very great, though often a factor 

 to be considered. The amount of grass and weeds is not at all com- 

 parable with the growths found at Beaufort, N. C, for instance, 

 where luxuriant growths occur during the warm weather. 



In Figure 2 will be seen a composite net made from a number of 

 vertical strips treated with different preservatives. The treatment on 

 the left is composed of tar applied to the twine while hot. This is the 

 usual treatment for trap and pound nets; and the section is heavily 

 fouled with red slime, as can be seen by comparing the size of the 

 twine in the first section with that in the next two which are treated 

 with preservatives containing cuprous oxide. 



The fishermen believe that this red slime rots the nets. However, 

 when one considers the mode of life of hydra this does not seem prob- 

 able, for these organisms merely use the net as an anchoring place 

 and derive their sustenance from material brought to them by the 

 currents in the water. It was thought that possibly formic acid or a 

 similar product caused the hydra to "sting" and that this acid might 

 hydrolyze the cellulose of the cotton, but colorimetric measurements 

 failed to show any great amount of acidity in a beaker of water in 

 which hydra were allowed to rot. 



In order to make sure what part is played by the larger forms of 

 life and what part is played by the microscopic forms such as bacteria, 



5 "July 30, 1927, commercial fishermen at St. Joseph, Mich., complain that at irregular intervals (that is, 

 the slime does not appear every year) a red slime accumulates on their nets and after a storm it may he 

 found in water up to 40 fathoms "deep. They first noticed the red slime here 40 years ago. This slime is 

 usually found in shallow water. They assert that this slime produces a soreness of the hands and wherever 

 it occurs in abundance no fish can be taken. The informants assert that the slime makes the fish wild and 

 drives them away. Gill nets fished here in the shallower water generally take whitefish, but when the 

 slime is present no whitefish can be taken. For about two weeks this spring (1927) trout were very scarce 

 and it was noticed that the red slime was present in abundance." Field notes by Dr. John Van Oosten . 



Beardsley, in the Bulletin of the U. S. Fish Commission for 1902, Vol. XXH, pp. 157-160, records a case 

 where hydra killed trout fry. 



« See also W. A. Clemens, Science LV, pp. 445-6 (1922), in which is stated— " Fishermen had frequently 

 spoken about a poisoning which often affected them while handling the nets during the process of cleaning 

 and mending. They said this occurred chiefly after the nets had dried and were covered with a fine dust 

 which they called tar dust. No poisioning was observed during this summer, but the men stated that 

 their hands and faces became inflamed and swollen especially if there were any cuts." 



