PROGRESS IN BIOLOGICAL INQUIRIES. 1937 Ql 



Ohf<erva-'wyis on f<pawning. — In the 1937 survey of the 3-mile sec- 

 tion of the South Branch 205 sniallmouth nests (68.5 per mile) were 

 found on May 14 and 15, as compared with 142 nests found in this 

 section during the 1936 survey. Tliese nests were at an averagje depth 

 of 33.2 inches and the average distance from shore was 9 feet. The 

 eggs were counted in 10 nests and found to average 1,700 to each 

 nest. Very few dead eggs were found. 



In the Cacapon River, the average number of nests per mile was 

 13.75 and in the Shenandoah River there was an average of five nests 

 per mile. Owing to the turbidity it is probable that some nests 

 escaped observation. Fry counts made later along the same section 

 indicated that the number of nests must have been considerably 

 greater than observed. On the North Fork of the Shenandoah River 

 an average of five nests per mile were observed in the experimental 

 section. 



In spite of these unfavorable conditions, a considerable number of 

 older bass w^ere taken for scale studies. In the South Branch of 

 the Potomac River the average length of bass in their second year 

 was 6.69 inches, in their third year 8.75 inches, in their fourth year 

 10.13 inches, in their fifth year 10.81 inches, in their sixth year 16.0 

 inches, and in their seventh year 17.0 inches. In other words, small- 

 mouth bass in the South Branch did not attain the legal length of 

 10 inches until their fourth year and of the fish of this age more than 

 42 percent were under legal size. 



In the Cacapon River the meager data available indicate that the 

 situation is even less favorable. Of 24 smallmouth bass taken by 

 angling on June 1, not a single fish was of legal size and the largest 

 fish taken (9.75 inches) was in its fifth year. A 6-year fish was only 

 9.5 inches long. 



On the other hand, bass in the North Fork of the Shenandoah 

 River were found to make much more rapid growth. Here 2-year 

 fish averaged 7.69 inches in length, 3-year fish 10.52 inches, and 

 fish taken in their fourth year showed an average length of 12.13 

 inches. It is interesting to note that the North Fork is very nearly 

 the size of the South Branch. 



During 1937, progress was made toward placing field observations 

 on a quantitative basis. Counts of bass in three sections of the South 

 Branch of the Potomac River varying in length from 3 to 4.6 miles 

 agreed very closely, showing, respectively, 105, 107, and 124 fish per 

 mile. In contrast only 19 bass per mile were noted in the North 

 Fork of the Shenandoah River. 



It is of interest to note that in these rivers all of the bass appear 

 to spawn at one time and there is no evidence of later spawning ex- 

 tending into the month of June. In the South Branch of the 

 Potomac, where the extent of natural spawning is greatest, the fry 

 disappear with extreme rapidity and there seems little doubt that the 

 bass themselves are largely responsible for the losses. 



Growth studies. — Fingerling bass in the South Branch of the Po- 

 tomac attained an average length of 64 mm by mid-September while 

 the trend in the growth of fiugerlings in the Shenandoah River (no 

 collections made after July 30) indicated that the bass in this stream 

 again would have easily outstripped those from the South Branch 

 had they maintained the growth rate shown by fish collected up to 

 July 30, when the- average length was 59.5 mm. In the Cacapon. 



