Fishery bulletin of the Fish and Wildlife Service - NOAA

192 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE
the season, and also prevented their continuation into August. Thus, there was less
opportunity for taking large larvae corresponding to the eggs and small larvae of the
earlier cruises. However, the cruises did thoroughly cover the major portion of the
season of maximal spawning and subsequent larval development; so there need be
only a treatment which excludes from comparison the large larvae early in the season
and the eggs and young larvae late in the season which were not proportionately
represented in the other stages of their planktonic existence.
This was done by taking the average numbers of eggs and larvae per cruise for
the several cruises that spanned the period of maximal numbers of each stage of egg
and larva. 19 The selection of cruises for these averages was as follows: for egg stages
A to C, cruises I to IV; 3-mm. larvae, cruises II to V; 4- to 7-mm. larvae, cruises III
to VI; 8- to 9-mm. larvae, cruises IV to VII; 10- to 12-mm. larvae, cruises V to VIII;
13- to 15-mm. larvae, cruises VI to IX; 16- to 22-mm. larvae, cruises VII to IX; and
23- to 50-mm. larvae, cruise IX.
Egg stages:
Categories '
В .
с
Fish lengths (millimeters) :
3.2
4 S
6
7
8
9
10
11
12
13 ......
14
15
16
17
18
19
20
21
22
23
24
25
30.
40
60
TABLE 7.—Survival of young stages of mackerel in 1938
Duration
of category
»
Day* 2.63
2.32
2.38
5.14
6.86
6.48
4.66
3.91
3.41
3.04
2.73
2.48
2.28
2.10
1.96
1.82
1.71
1.60
1.62
1.43
1.37
.27
.24
.19
.14
.09
8.65
6.86
5.72
Average
age of
category*
Days 1.3
3.7
6.0
9.9
16.0
22.1
27.1
31.3
34.9
38.1
41.0
43.6
46.0
48.2
60.2.
62.1
53.8
55.6
57.1
58.5
69.9
61.3
62.5
63.8
64.9
66.0
71.0
78.9
85.0
Frequencies
Average per
Average cruise adper
cruise' Justed for duration
of category
'
Number
16,900
12,600
12,600
9,310
4,270
1,760
717
403
192
73.5
18.4
7.70
4.96
2.98
3.38
1.72
1.10
1.10
1.70
1.10
.633
.600
.467
1.300
.300
.800
3.900
.300
.100
Number
6,080
5,430
6,260
1,810
622
321
157
103
66.3
24.2
6.74
3.10
2.17
1.42
1.73
.945
.643
.688
1.118
.769
.389
.388
.377
1.092
.263
.734
.451
.0437
.0175
Survival per million newly spawned eggs
Logarithmic values
Empirical
ï
Log
5. see
5.776
6.761
5.299
4.835
4.647
4.237
4.054
3.791
3.425
2.870
2.532
2.377
2.193
2.279
2.016
1.849
1.879
2.090
1.927
1.631
1.630
1.617
2.078
1.461
1.907
1.695
.681
.284
Computed
•
Log
6.916
4.759
5.609
5.354
4.957
4.559
4.233
3.959
3.724
3.516
2.960
2.483
2.372
2.271
2.179
2.092
2.013
1.935
1.861
1.797
1.733
1.668
1.613
1.563
1.602
1.462
1.222
.868
.677
Arithmetic values
Empirical
Number
735,000
697,000
576,000
200,000
68,400
35,200
17,300
11,300
6,180
2,660
741
340
238
156
190
104
71
76
123
85
43
43
41
120
29
81
60 62
ï The categories of egg stages are defined on p. 178, the categories of larval lengths are the midpoints of the class interval.
> See text p. 179.
* See text p. 192.
* Items In the third column divided by the Items In the first column.
> Logarithms of the Items in the fourth column plus the constant 2.041.
* These are the values represented by the heavy lines of fig. 17.
Computed*
Number
822,000
674,000
406,000
226,000
90,600
36,200
17,100
9,100
6,300
3,280
891
304
236
187
168
124
103
86
72
63
64
47
41
36
32
28
1774
This selection provides a series that approximately follows the eggs of cruises I
to IV through their subsequent stages. Since by far the largest numbers of eggs were
11 Beforn the averages were drawn an adjustment was made in the numbers of larvae from cruise TV on which a group of stations,
Fonwick I, Wlnterquarter I, TI, and III, and Chesapeake I and III had been omitted. These stations were located in the area where
only 2 days previously there had been found most of the 5- to 11-mm. larvae and the omission of these stations caused a marked,
deficiency of these sizes in the totals of cruise IV (note in table 6, column 4, the abrupt drop In numbers from the 3- to the 5-min.
class). Since these particular stations were occupied at the very end of cruise III, growth and mortality In the few Intervening days
before cruise IV would have only slightly altered the catches at these stations by the time of the latter cruise. Therefore, to restore
the deficiency, the catches of cruise Ш at these statical were added to the cruise IV totals, giving new values of 6381,1998, 682, 160,
67,31,6, and 8 for the 4- to 11-mm. classes In the 4th column of table 6.