Fishery bulletin of the Fish and Wildlife Service - NOAA

208 FISHERY BULLETIN OF THE FISH AND WILDLIFE SEKVICE
be even greater than its value for predictions. These separate correlations would
provide a basis for determining the size of spawning stock necessary to maintain an
undepleted fishery. Efficient utilization will be possible when a reliable estimate can
be made of the proper size of spawning reserve. Until then, there will always be
danger of reducing the annual take, on the one hand, by attempting to preserve more
spawners than needed, or, on the other hand, by catching more spawners than can
be spared from the stock needed for adequate reproduction.
APPENDIX
METHODS OF DETERMINING SIZE AT MATURITY
Samples of fish were taken at various times at Woods Hole, Provincetown, and
Sagamore, Mass., during the period June 24 to July 21,1925. The fish were measured
to the nearest half centimeter on a straight line from tip of snout to the extremity of
the midcaudal rays. Gonads of the males were graded by eye as small translucent,
small opaque gray, enlarged white, running milt, and spent. The last three grades
were classified as mature. Gonads of females were graded by eye as small translucent,
small granular, enlarged granular, translucent spots, running ripe, and spent. The
last three grades were classified as mature. The results are summarized in table 13.
TABLE 13.—Size of mackerel at, maturity as indicated by 1,116 individuals taken by traps in the
vicinity of Woods Hole, Mass., and in Massachusetts Bay during the period, June #4 to July SI,
1925
Length, centimeters
220
22.5
230
235 ..
Total
24.0 .
24.8
28.0
286
28.0 — - -
26.8
27.0
27.5
28.0
28.6
29.0
29.5
80.0
30.5
81.0
31.6
32.0
32.8
33.0 ...
33.8
34.0
34.6
36.0
35.6
36.0
Total
Total Л
Total
Total
Total
Immature
Number 111
10
13
16
22
27
26
37
127
35
17
18 7
10
87
14
12
16 99
60
7
11 556
33
6
в 7
3
2
24
Males
Mature
Number
2
2
1
1
1
2
2
7
6
7
4
3 2
21
6
7
8
11 5
36
15
29
26
28
20
117
Mature
Percent
2
26
62
83
9
Immature
Number 1
3
6
10
8
16
32
33
46
134
47
22
27
20
14
130
21
16
21
17
14
89
13
12
1497
66
6
8 1
4 2
20
Females
Mature
Number
--
1
2
5
6
6
17
6 7
14 8
11
45
Mature
Percent
2
24
•
69