104 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
over voluntarily. We would expect this, as the connection between the two pools 
is quite deep, though swift. It is even remarkable that no more than 17 per cent 
passed to the lower pool. It is conceded that the estimates in the tables above are 
liable to considerable errors. There are always some unknown quantities in the 
equations, yet the results appear trustworthy. 
Pool I) is below the lower railroad bridge, and was quite unimportant. It was 
seined but once, a large rock at the lower end of the pool making seining impracti- 
cable. Six young salmon were taken. It was one of these six that was taken in 
the first haul in Pool E. The two pools are continuous. 
Pool E is a portion of the river about 75 yards long, immediately below and not 
separated from D, ending above a long riffle. It was the only pool that could be 
entirely covered by the seine. The bottom is mostly covered with cobblestones, and 
there are large rocks along one shore. These afforded hiding-places for the young 
salmon while the seine was being drawn. It was seined many times in August. 
The following table gives the record of the catch at each haul of the seine made 
in the pool, giving (1) the date, (2) the number caught, (3) the number previously 
marked and released in the pool, (4) (lie number of marked fishes taken, (5) the 
estimate of (lie number of young salmon in the pool, and (6) the variation of this 
estimate from the average estimate. On the 16th and 17th of August (lie seining 
was carried on continuously, the time required for making a haul and counting and 
marking the parrs being from 20 to 30 minutes. The marked specimen taken in the 
first haul was one of ( lie six from Pool D. 
Record of seine hauls in Pool E. 
Date. 
N umber 
of young 
salmon 
caught. 
N umber 
pre- 
viously 
marked. 
Number 
marked 
fish 
caught. 
Estimated 
number 
of young 
salmon 
in pool. 
Variation 
of esti- 
mate from 
average 
estimate. 
66 
1 
1 
14S 
66 
13 
751 
-271 
.1411 
197 
30 
992 
- 30 
August 1 7, a. m 
82 
312 
38 
682 
-340 
47 
357 
19 
883 
—139 
1!) 
385 
4 
1 , 804 
+782 
64 
4011 
25 
1,024 
+ 2 
1411 
439 
62 
.1,055 
+ 33 
71 
525 
41) 
932 
- 90 
35 
556 
15 
1,297 
+275 
August 1.7, p. m 
111 
576 
9 
1,216 
+194 
3 
586 
3 
586 
-436 
Total for 24 hours 
850 
586 
259 
■ ■ 1.022 
August 18 
0 
(1 
September 18 
178 
97 
« 1,075 
October 18 
29 
"Average. 
The purpose of the work in this pool was to determine the number of young 
salmon that might be found in a pool. The estimates are made in the same way as 
in the case of Pools B and C. The third haul, as noted in the table, may be taken 
as an example: 30, the number of marked fishes taken, is to 197, the number marked 
previous to this haul, as 146, the total number taken, is to 992 , the total number 1 in 
the pool. The estimates vary from 586 to 1,829, but several of them are not far from 
a thousand. The average of the estimates is 1,022, which is probably near the truth. 
September 18 we seined the pool again, catching 178 young salmon, 97 of which, 
a little over half, had been marked. By looking at (lie table above it can be seen 
that a little over half of the estimated number in the pool were marked in August — 
586 out of 1,022. If an estimate is made of the number in the pool in September, by 
