CXLII REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



eggs, in four equal lots, were employed to demonstrate the critical 

 periods j two lots were picked daily to remove dead eggs; the other two 

 lots were picked only on the first, third, twenty-second, twenty-fourth, 

 and forty-first days, so as to avoid the critical times. The percentages 

 of loss in the first two lots were 56 and 32, respectively, and in the 

 second two 11 and 9, respectively. 



A number of tests indicated that even after a fish has been dead in 

 the water for a comparatively long time the contained eggs remain in 

 good condition. On November 25 a female salmon that had died below 

 the spawning rack was selected for experimentation. Eggs were taken 

 and fertilized at periods of 2. 4, 6, 8, and 24 hours after its death. In 

 the case of the first four lots the percentages fertilized were 99, 98, 92, 

 and 92, respectively, and at the end of 26 days the eggs were healthy. 

 The eggs taken after a lapse of 24 hours were not sound, and although 

 most of them were fertilized, the entire lot died within 2 weeks. On 

 the 13th of November eggs were obtained from 2 fish that had died in 

 the water, one having been dead 2 hours and the other over 6 hours ; 

 of the former, 97 per cent and of the latter 85 per cent hatched and 

 produced healthy fry. 



LAKE SUPERIOR. 



The investigations of Mr. A. J. Woolman in Lake Superior began in 

 April, 1897, and referred to in the last report, were continued until the 

 latter part of August, 1897. They had for their object the determina- 

 tion of the food-supply of the fishes of the lake and its relation to the 

 abundance and movements of the commercial fishes. Large collections 

 of the minute animal life, which directly or indirectly constitutes the 

 principal food of the fishes, were made with fine-meshed nets used at 

 the surface, bottom, and intermediate depths on the fishing-grounds 

 along the south shore. The study of the collections has not yet been 

 completed . 



Different regions were found to differ very materially in the variety 

 of small aquatic animal forms inhabiting them and in the abundance of 

 those forms. Some extensive areas were shown to be abundantly sup- 

 plied with minute animals in great variety, which in other areas were 

 almost completely absent. If further observations show that the dis- 

 tribution of the minute animals is in any way constant in given areas, 

 informatio.i of value in the planting of fish fry will have been obtained. 



One noteworthy feature of the inquiries was the discovery of small 

 crustaceans (Diaptomus) in large numbers in certain very deep waters 

 where there has recently been a remarkable increase in the abundance 

 of the bluefin whitefish (Argyrosomus nigripinnls).* These crustaceans 

 occur in large quantities only in deep water (100 to 130 fathoms), where 

 they are the predominating animals of this class. Another observation 

 was that apparently well-defined areas are occupied by cladocera, as 



* See Report U. S. Fish Commission for 1897, pp. cxxi, cxxn. 



