52 U. S. BUREAU OF FISHERIES 



River fingerling bass averajn:ed 69 mm in length by September 1, and 

 in the North Fork of the Shenandoah the average length on Septem- 

 ber 16, was 75 mm. 



The 1937 season proved a poor one for the collection of fish and 

 bottom organisms becanse of high water from freqnent rains. As a 

 resnlt samples could not always be collected at regular intervals, and 

 the number of fish caught was sometimes inadequate. 



There seems little doubt from general observation that forage 

 minnows are considerably more abundant in the Shenandoah River 

 and its North Fork than in the South Branch and Cacapon Rivers, 

 l3ut to date the quantitative methods employed have not established 

 this fact. 



One of the most important results of the studies on the Shenan- 

 doah and South Branch of the Potomac Rivers during the past 2 

 years is the evidence that the latter stream is at present overstocked 

 with bass. That this is the case is indicated by the large number of 

 bass nests observed and the slow growth of young bass in the South 

 Branch. In this stream smallmouth bass do not attain the legal 

 length of 10 inches until their fourth year and over 42 percent do 

 not reach this size until their fifth year. In contrast, bass in the 

 INorth Fork of the Shenandoah, which is comparable in size with the 

 South Branch, reach legal length in their third year and in their 

 fourth year average two inches longer than bass of the same age in 

 the South Branch. 



The large number of nests observed in the South Branch also leads 

 to some interesting speculations on the effect of stocking. As pre- 

 viously stated, an average of 68.5 nests per mile were observed in 1937 

 in the experimental section. Since the average number of eggs in 

 each nest was approximately 1,700 and there were very few dead eggs 

 it is evident that at least 115,000 fry per mile were produced. It is 

 not probable that all the nests were seen, since observations were 

 made only on two consecutive days, so that we may estimate the fry 

 produced in this section of the river at over 125,000 per mile. There 

 are approximately 75 miles of bass water in the South Branch and if 

 we assume that an average of 100,000 fry per mile were produced in 

 this area we find that it would require 7,500,000 fry to stock the 

 South Branch at the same rate as was done by nature. Even if we 

 reduce the estimate by 50 percent some 3,750,000 fry would be re- 

 quired, which would be a large order for any hatchery. 



Food studies on fi.ngerling smallmouth hass. — The stomach con- 

 tents of 1,076 fingerlings collected at monthly intervals in test sec- 

 tions of the South Branch and Shenandoah Rivers have been ex- 

 amined. These collections permitted seasonal comparisons of the 

 food of growing fingerlings from the time they rose from the nests 

 until the end of the growing season. It was surprising to find that 

 10 percent of the Shenandoah River fry, averaging 10 mm long, had 

 consumed fish. Many of these bass had not yet completely absorbed 

 their yolk material. The chief items of food, however, were nymphs 

 of the genus Boetis and midge larvae. As the bass increased in size, 

 fish became more important in the diet, except in the South Branch 

 where the data reflect a scarcity of forage minnows. 



Bottom fauna studies. — A quantitative study of the bottom fauna 

 in the Shenandoah and South Branch Rivers showed that the number 

 and weight of organisms per square foot was much less in the pools 



