612 BULLETIN OF THE BUREAU OF FISHERIES 
Table 7. — Length frequencies of scallops collected at Pivers Island, October 17, 1926, to January 25, 
1928 — Continued 
1926 
1927 
1928 
Length 
No- 
De- 
Jau 
Feb- 
Sep- 
Oc- 
No- 
De- 
Jan- 
milli- 
October 
vem- 
cem- 
ru- 
March 
April 
May 
June 
July 
August 
tem- 
to- 
vem- 
cem- 
meters 
ber 
ber 
ary 
ber 
ber 
ber 
ber 
17 
30 
17 
1 
15 
17 
i 
19 
5 
20 
* 
18 
4 
19 
3 
25 
8 
23 
2 
22 
6 
20 
11 
9 
23 
25 
i 
i 
2 
2 
2 
5 
7 
4 
5 
18 
4 
1 
1 
4 
1 
1 
3 
8 
10 
10 
6 
9 
5 
3 
2 
i 
5 
5 
4 
2 
6 
6 
2 
1 
1 
i 
3 
3 
4 
9 
8 
11 
6 
8 
5 
1 
2 
5 
8 
4 
9 
10 
9 
4 
i 
1 
6 
12 
7 
7 
9 
17 
3 
1 
2 
1 
1 
1 
4 
8 
7 
8 
7 
8 
8 
i 
2 
1 
i 
2 
8 
9 
7 
9 
18 
6 
2 
2 
1 
1 
1 
i 
6 
3 
5 
8 
13 
11 
1 
2 
1 


1 
1 
l 
1 
1 
2 
2 
10 
6 
12 
4 
11 
8 
5 
4 
2 
1 
1 
1 
1 
1 
1 
4 
8 
4 
5 
8 
6 
8 
4 
5 
3 
1 
1 
1 
2 
1 
1 
6 
1 
15 
7 
14 
11 
10 
8 
1 
1 
3 
3 
1 
1 
1 
1 
5 
4 
12 
10 
15 
4 
11 
6 
3 
3 
2 
2 
7 
2 
2 
1 
3 
4 
6 
6 
5 
14 
7 
9 
4 
2 
8 
9 
2 
4 
1 
9 
2 
2 
10 
5 
11 
7 
7 
6 
5 
2 
6 
4 
7 
3 
1 
2 
4 
7 
2 
12 
14 
a 
10 
6 
3 
3 
O 
7 
3 
3 
2 
2 
5 
3 
7 
8 
10 
8 
4 
6 
10 
15 
n 
8 
3 
1 
3 
9 
2 
3 
1 
5 
10 
13 
7 
8 

5 
12 
8 
6 
5 
1 
1 
1 
1 
2 
5 
3 
5 
2 
6 
13 
4 

6 
9 
11 
13 
14 
3 
2 
I 
2 
2 
1 
3 
3 
3 
5 
3 
13 
14 
9 


8 
6 
11 
8 
7 
6 
1 
2 
1 
1 
1 
1 
1 
3 
5 
13 
n 
6 
8 
4 
n 
8 
9 
5 
2 
2 
1 
1 
i 
2 
3 
6 
16 
ii 

8 
7 
9 
8 
12 
4 
3 
4 
5 
1 
1 
1 
2 
5 
12 
8 

6 
i 
10 
5 
13 
10 
11 
9 
2 
2 
1 
1 
1 
i 
1 
i 
6 
9 
3 
2 
6 
1 
8 
4 
9 
8 
6 
1 
1 
1 
1 
5 
5 
3 
1 
6 
5 
8 
13 
16 
2 
6 
3 
1 
1 
2 
1 
1 
1 
2 
1 
4 

3 
1 
1 
7 
10 
8 
6 
10 
3 
1 
1 
1 
1 
3 
1 
4 

1 
3 
11 
2 
7 
8 
10 
12 
4 
2 
1 
2 
1 
1 
1 
i 
2 
2 

1 
1 
2 
5 
4 
5 
6 
2 
2 
1 
1 
4 
7 
9 
8 
9 
5 
1 
1 
2 
4 
1 
1 
1 
1 
2 

2 
2 
8 
8 
12 
1 
1 
1 
1 

1 
4 
4 
5 
7 
5 
2 
1 
2 
1 
1 


4 
2 
5 
2 
3 
1 
1 
1 
2 
1 
1 
1 
1 
2 
3 
3 
1 
1 
9 
1 
1 
1 

1 
1 
3 
3 
1 
3 
1 
2 
1 
5 
3 
9 
1 
5 
1 
1 
2 
1 
1 
1 
1 
2 
2 
1 
7 .. 
1 
1 
1 
1 

1 
i 
1 
1 

i 
1 
... 
.... 

1 

2 
1 
1 
1 

1 

}_ 
1 
51. 
52. 
53. 
54. 
55. 
56. 
57. 
58. 
59. 
60. 
61. 
62. 
63. 
64. 
65. 
66 . 
67. 
68 . 
69. 
87. 
Usually in the fall, rarely in the summer or as late as early winter, there is formed 
the only growth line which is present consistently. On the average and perhaps 
nearly always it represents an age of very close to 1 year and reasonably may be termed 
a 1-year line or annual-growth line. Its cause is not easy of determination. 
This first-year line has been found, although rarely, as early as September. One 
old scallop was found in July with what appeared to be a second annual -growth line 
or 2-year line. Because the line presumably is formed by interruption of growth and 
because growth is continued through the winter (see fig. 27) it is evident that the 
growth cessation is not due to too low a temperature. 
Seasonal plankton change is another conceivable explanation. Although against 
it may be brought not all the arguments against temperature, at present there is no 
direct, positive evidence in its favor and no sufficient basis for its acceptance. 
In regard to spawning or spawn production the case is less indefinite. The line 
typically is a fall line; spawning occurs principally in the fall. Karely a newly formed 
line is found in summer or early winter; the spawning season begins in the summer 
and extends to early winter. In individual cases, however, no close correlation 
between the amount of new growth — that is, growth outside the line — and the state of 
