Fishery bulletin of the Fish and Wildlife Service - NOAA

FISHERY BULLETIN OP THE FISH AND WILDLIFE SERVICE 283
covery of only one and six fish, respectively ; hence, the percentage returns are unreliable.
As the size of the migrants increases with age, the data indicate that the larger
migrants have the highest survival value.
In the second experiment (table 32) 21,791 migrants were marked, 659 were
recovered, and a calculated total of .at least 4,582 marked .fish returned from this
experiment (at least 21.0 percent). The incomplete returns from the marked 2-, 3-,
4-, and 5-year seaward migrants were 0.0, 20.5, 23.0 and 28.6 percent, respectively.
The returns from the two experiments agree closely except for the 2- and 5-year
fish of which few were marked. If the data are. combined as one experiment, 46,791
seaward migrants were marked, 1,399 were recovered, and a calculated total of at
least 9,733 fish returned (a minimum of 20.8 percent). ",
Age of seaward migrants
marked
2 -- -
3
4
5'
Total
Calculated
number of
each age
marked
{ «
TABLE 32.—Data for lhe second 19&6 marking experiment
| 16, 730
| 4, 925
{ «
21, 791
Age of fish
returning
from 1926
migration
1 Based on incomplete data, see text.
4i
61
4s
5|
e,
7,
4i
5j
6i
7..
6:
7j
Calculated
number of
each age
group examined
1,509
2,690
168, 042
4,627.
44,264
279
221, 311
Number of
marked flsh
of each ago
group found
3
458
5
188
í
059
Percentage
occurrence
of marked
fish in fish
examined
0.112
.273
.110
.425
.792
EXPERIMENTS IN 1927 AND 1928
Calculated
number of
flsh of each
age group
returning
9,934
8,836
43, 551
1, 236, 953
325, 643
20.
1,040
47.298
254, 138
14,294
895
1, 325
1, 943, 927
Calculated
number of
marked fish
returning
49
3,377
52:
1,080
24
»4,582
Percentagereturn
Total per-
at various
centage
ages return
0.3
20.2
1.1
21.9
28.8
} '0.0
1 «20.6
j «23.0
} 28.8
Fifty thousand seaward migrants were marked in both 1927 and 1928. However,
the curtailment of commercial fishing m 1929 and 1930 made it impossible to adequately
sample the runs of those years for the presence of marked fish, and the data
are consequently not included here.
EXPERIMENTS IN 1929
In 1929 (table 33), 50,061 sea ward, migrants were marked by the amputation of
the adipose and both ventral fins, 1,315 fish were recovered, and a calculated total of
11,157 marked fish returned from this experiment (22.3 percent) 1 . The return from
the Зт, 4-, and 5-year marked seaward.migrants was 18.3, 24.4,..and 13.5.percent;
respectively. As very few 5-year seaward migrants were marked and only 3 recovered,
the latter figure cannot be considered reliable; however, considering the returns of the
3- and 4-year seaward migrants, it is again apparent that the older and larger migrants
had the highest survival value.