60 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



Green Lake, Me., May 26, 1894. 



Dear Sra: Your letter dated May 23, inclosing a copy of a report upon the larvae 

 sent, by the entomologist of the Agricultural Department, is at hand, and which I 

 was glad to receive. I am not prepared to say positively whether the larvae of the 

 large caddis fly intentionally fed upon the fry, or whether the web spun was for the 

 capture of the fry, but during a period of ten days they appeared in our supply and 

 hatching troughs in large numbers, spinning them full of this fine web, which would 

 naturally entangle a small per cent of the embryos. Clusters containing 25 or 30 of 

 the large larva? would be found all through the troughs, and invariably a fish would 

 be found in the middle, in some cases almost entirely devoured ; numbers would be 

 seen moving to and fro, hither and thither; also quite a lot of them would adhere 

 to the sides of the trough at water level. A single larva was noticed time and 

 again to attach itself to the sac and sometimes to the head of the fish ; the fish 

 would swim around as if in severe pain for a moment or two, and would settle to 

 the bottom dead or dying. 



Of course, in one of our hatching troughs, where we were carrying from 10,000 to 

 12,000 fry, with as many thousand larva) in it, it was natural to suppose that they 

 were feeding upon them, which they surely did; it might not have been from prefer- 

 ence but from necessity, as the troughs contained but very little else in the shape 

 of food that could be seen with the unaided eye, though I am of opinion that they 

 were feeding upon the sac of the embryo from preference, and I am sure that the 

 sac of the young fry would make very delicate food. After the fish arrived at the 

 age of 15 days, the larva was not able to entangle or capture them except in very 

 rare cases, as the fish by this time had developed sufficient activity to free them- 

 selves. The larvae of both the caddis and black fly have almost entirely disap- 

 peared. The fish is no longer the sufferer, but the fish-culturist, as the black fly 

 is in all of his glory. 



I am, very respectfully, E. M. Robinson, 



Superin tendent. 



Dr. Tarleton H. Bean, 



Assistant in Charge Division of Fish Culture, 



U. S. Fish Commission, Washington, D. C. 



Fungus and parasites. — The parasite referred to in the following let- 

 ter of Mr. Kobinson was not identified, but similar attacks have been 

 observed at other stations, and studies are now in progress looking 

 toward the identification of the species and the elucidation of its life 

 history, as well as the proper treatment of the fish affected. 



Green Lake, Me., May 30, 1S94. 



Dear Dr. Bean : For the past month or twenty days the loss in our salmon fry 

 began to be alarming, and at one time I feared the epidemic that caused so much 

 destruction at the Craig Brook Station, and gave Mr. Atkins so much trouble, was 

 upon us in its worst form. I first began to notice very fine fungus growth on the 

 fins and near the gill covers; the little fish so affected would huddle together in the 

 corners of the troughs and seemed to have no life about them, and in 24 or 36 hours 

 would die. The next trouble discovered was a small parasite, not on any particular 

 part of the body, but pretty generally distributed ; these parasites looked to the 

 unaided eye like very small warts, and showed white in the water. Whether the irri- 

 tation of the parasite on the body of the fish causes the fungus I can't say, but am 

 of the opinion it does. 



As soon as the fungus and parasites were discovered I had salt used very freely; 

 would have water cut off the troughs and drawn down to within 3 inches of 

 the bottom; then made a strong brine by dissolving 1 quart of salt in a pail for 

 each trough ; this brine would be poured in, and at the same time be thoroughly 

 mixed with the water and fish; all the little nooks and corners of the trough would 



