Bulletin of the National Salmon
Resources Center, No. 2 : 1-8
December 1999

Recoveries of Thermally Marked Maturing Pink Salmon
in the Gulf of Alaska in the Summer of 1998
Morihiko Kawana*', Shigehiko Urawa*', Gen Anma*', Yoshihiko Kamei*z,
Takayuki Shoji*3,Masa-aki F ~ k u w a k a *Kristen~,
Katherine W. Myers*6, and Edward V. Farley, JT.*~*'Research Division, National Salmon Resources Center, Fisheries Agency of Japan,
2-2 Nakanoshima, Toyohira-ku, Sapporo 062-0922, Japan(kawana.morihiko @ salmon.affrc.go.j p )*' Faculty of Fisheries, Hokkaido University,
3-1-1 Minato, Hakodate 041-8611, Japan*3 Graduate School of Pharmaceutical Sciences, Hokkaido University,
Nishi 6, Kita 12, Kita-ku, Sapporo 060-0812, Japan*I Suburctic Fisheries Resources Division, Hokkaido National Research Institute of Fisheries,
116 Katsurakoi, Kushiro 085-0802, Japan*s CWT & Otolith Processing Laboratory, Alaska Department of Fish and Game,Box 25526, Juneau, A K 99802, USA*6 Fisheries Research Institute, School of Fisheries, University of Washington,
Box 357980, Seattle, WA 98195-7980. USA*7AukeBay Laboratory, Alaska Fisheries Science Center, National Marine Fisheries Service,11305 Glacier Highway, Juneau, AK 99801-8626, USA
Abstract.

We detected otolith thermal marks induced by Alaskan hatcheries to determine theocean distribution and migration of Alaskan pink salmon (Oncorhynchus gorhuscha) in the Gulf of
Alaska. Twenty-nine thermally marked pink salmon were found among 383 maturing fish (1996
brood year class) caught along two offshore transects (145'W and 165'W) during June and July
1998. Along the 145'W transect, 25 thermally marked fish from three Prince William Sound hatcheries (PWS, southcentral Alaska) were found (8.1%, n=307 fish), and their origins were Armin F.
Koernig Hatchery (AFK, n=8 fish), Cannery Creek Hatchery (CCH, n=9 fish), and Wally H.
Noerenberg Hatchery (WHN, n=8 fish). Along the 165"W transect, four thermally marked fish
were found (5.3%, n=76 fish), and their origins were AFK (n=l fish), CCH (n=2 fish), and WHN(n=l fish). PWS hatchery fish were more abundant in northern waters than in southern waters along
both transects, which corresponded to the direction of their homeward migration. Observed differences in distribution of male and female PWS hatchery fish may be caused by sexual differences inthe timing of homeward migrations. The recovery of four thermally marked PWS hatchery fish in
the Gulf of Alaska (47-50°N, 165'W) is a southwestward extension of the known ocean range ofmaturing southcentral Alaskan pink salmon in summer.
~

Key words : otolith thermal marking, pink salmon, hatchery stocks, distribution, Gulf of Alaska

Introduction
Mass marking of hatchery salmon (Oncorhynchus spp.) using otolith thermal marks has become
increasingly popular technique for inshore fisheries
Contribution A No. 10 from the National Salmon
Resources Center.
0 1999 National Salmon Resources Center

management in Alaska (Hagen et al. 1995; Geiger
and Munk 1998). Thermal marks are also an effective tool for stock identification in high-seas andcoastal waters (Farley and Munk 1997; Ignell et al.
1997; Farley et al. 1999; Urawa et al. 1999). Salmon
otoliths are thermally marked by exposing fish toalternating (relatively lower and higher) temperatures (Volk et al. 1990), whereby a "thermal ring"(dark ring) is induced by exposure to the lower temperature ( M u n k e t al. 1993). Different thermal

’;. C/’ . 5 -$‘&h?BB+2 9 -@f% Bull. Natl. Salmon Resources Center, No. 2 , 1999

2

marks are made by varying the number and spacingof thermal rings. For brood-year 1996 stocks, about
490 million pink salmon (0.gorbuscha) were thermally marked and released from southcentral andsoutheastern Alaskan hatcheries. About 99% of
thermally marked fish were released from Prince
William Sound (PWS) hatcheries in southcentral
Alaska, where all hatchery pink salmon were thermally marked (McNair 1998; Munk and Geiger
1998). To investigate the ocean distribution of PWS
hatchery fish, we detected thermally marked otoliths
from maturing pink salmon caught in the Gulf of
Alaska in the summer of 1998.

Materials and Methods
Releases qf thermally markedfish
For brood-year 1996 stocks, thermally marked
pink salmon were released from four PWS hatcheries: Solomon Gulch Hatchery (SGH, n=188.86
million fish), Cannery Creek Hatchery (CCH,n= 136.84 million fish), Wally H. Noerenberg Hatchery (WHN, n=106.44 million fish), and Armin F.
Koemig Hatchery (AFK, n=51.56 million fish). In
addition, about 5.90 million pink salmon with thermal marks were released from Gastineau Hatchery(southeastern Alaska, Table 1; McNair 1998; Munkand Geiger 1998).

from 383 fish. Scales were also collected for age
determination.
The catch per unit effort (CPUE) was calculated
as total catch (number of fish) per one set of nonselective varied research mesh gillnet (30 tans, 1 tan=50 m long and approximately 6 m depth; Takagi
1975; Walker et al. 1998). A gonadosomatic index(GSI) was calculated as 100 x gonad weight (g) /body weight (g) to examine maturity. Fork length,
body weight, gonad weight, and GSI were compared
between marked and nonmarked pink salmon using
Student’s t-test (equal variance) or Welch’s t-test.

Otolith Analysis
The left sagittal otoliths were mounted on individually labeled glass slides using thermoplastic
cement. If the left otolith was missing or groundthrough the primordia, then the right otolith wasused. Otoliths were ground to expose the primordia
and examined under a microscope. Thermal marks
were recorded in the RBr code structure (Munk andGeiger 1998). If the same RBr code was used for abrood year class at different hatcheries, thenmicrostructural patterns were compared with voucher specimens that were collected from the hatcheries
before release. All otoliths were read independently
by two readers.

Results
Fish samples
A total of 813 maturing pink salmon were caught
by gillnets (non-selective varied research mesh, traditional commercial mesh, and experimental mesh)in two offshore transects (145’W and 165’W) by the
T/S Oshoro maru in the Gulf of Alaska during June
and July 1998 (Walker et al. 1998). Fork length(mm), body weight (g), sex, and gonad weight (g)were recorded and sagittal otoliths were collected

Twenty-nine thermal marks were found among
383 maturing pink salmon examined (Table 2, Fig.
1). Along the 145OW transect, 25 thermally marked
fish were found (8.1%, n=307 fish), and their origins
were AFK (n=8 fish), CCH (n=9 fish), and WHN(n=8 fish) in PWS, southcentral Alaska. Along the165’W transect, four thermally marked fish were
found (5.3%, n=76 fish), and their origins were AFK

Table 1. A list of thermally marked pink salmon fry (1996 brood year class) released from Alaskan hatcheries (revised fromGeiger and Munk 1998). AFK, Armin F. Koemig Hatchery; CCH, Cannery Creek Hatchery; GH, Gastineau Hatchery; SCH,
Solomon Gulch Hatchery; WHN, Wally H. Noerenberg Hatchery.
Mean bodyweight at
release (9)Number of
releases(million)

TM 1D

RBr

I I-May-97
27-May-97-13-Jun-97
7-May-97-26-May-97

0.47
1.22
0.26

16.25
35.31
136.84

AFK96early
AFK96late
CCH96

1 :1.4 f 2.3

23-Apr-97,5-May-97
I-May-97
7-Jun-97
12-May-97

0 39
0.35
1.51
0.55

188.86
75.87
30.57
5.90

SGH96
WHN96early
WHN96late
GH96

RegionFacility

Stock

Release site

Date of release

Southcentral Alaska
Southcentral Alaska
Southcentral Alaska

AFK
AFK
CCH

WHN
WHN
CCH

Sawmill Cove
Sawmill Cove
Cannery Creek

Southcentral Alaska
Southcentral Alaska
Southcentral Alaska
Southeast Alaska

SGH
WHN
WHN
GH

SGH
WHN
WHN
GH

SGH
LakeBay
LakeBay
Gastineau Channel

1.1.4

1:1.3, 2.2
1:1.3, 2.3
l:I.4, 2.3
1:1.6
1:1.8
1:1.8+2.3
1:1.4

Kawana et a1.- Thermally marked pink salmon in the Gulf of Alaska(n=l fish), CCH (n=2 fish), and WHN (n=l fish).
Marked pink salmon released from southeast Alaska
were not found along each transect. The CPUE of
marked fish caught in research gillnets indicated that
PWS hatchery fish were more abundant in the northern part of each transect than in the southern part(Fig. 2). Along the 145'W transect, PWS hatcherymales were found in northern waters (55-56'N) but
not in southern waters (49-52'N), although the proportions of males in nonmarked fish were 30-48% in
southern waters. In contrast, PWS hatchery females
were found in both northern (55-56'N) and southern(50-52'N) waters. The mean GSIs of PWS hatcheryfish were lower than those of nonmarked fish except
for 165"W males (Table 3, Fig. 3). In addition, themean body sizes and gonad weights of 145'W hatch-3

ery males were smaller than those of nonmarked
males (Table 3, Fig. 3).

Discussion
All thermally marked pink salmon detected in thepresent study were from PWS, where all pink salmon
released from four hatcheries were thermally marked(McNair 1998; Munk and Geiger 1998). The CPUEof marked fish caught in research gillnets indicatedthat PWS hatchery fish were more abundant in thenorthern part of each transect than in the southern
part. This corresponds to the northward direction of
their homeward migrations.
A model of ocean distribution and migration patterns of pink salmon based on recoveries of tagged

Table 2. A list of thermally marked pink salmon recovered in the Gulf of Alaska during gillnet operations conducted by the T/SOshoro maru in June and July 1998. F, female; M, male; FL, fork length; BW, body weight: GW, gonad weight; AFK,
Armin F. Koemig Hatchery; CCH, Cannery Creek Hatchery; WHN, Wally H. Noerenberg Hatchery; Gear A, traditionalcommercial mesh; Gear C, non-selective varied research mesh.
No

Date ofcatch

1
9-JuI-98
2
5-Jul-98
3
4-Jul-98
4
4-Jul-98
5
8-Jul-98
6
5-JuI-98
7
5-Jul-98
8
4-Jul-98
9 27-Jun-98
10 10-Jul-98
1 1 10-Jul-98
12 5-Jul-98
13 5-Jul-98
14 5-Jul-98
15 5-Jul-98
16 4-Jul-98
17 4-Jul-98
18 4-Jul-98
19 28-Jun-98
20 28-Jun-98
21
9-Jul-98
22
5-Jul-98
23
5-Jul-98

24
5-Jul-98
25 4-Jul-98
26
4-Jul-98
27
4-Jul-98
2X
4-Jul-98
29 29-Jun-98

Latitude(N)

Longitude
(W)

Gear
(mm)

Sex

5 1 OOO'
55"OO'
56"OO'
56"OO'
52°00'
55"OO'

145'00'
14S000'145"OO'
145"OO'
145"OO'
145'00'145"OO'
145"OO'165"OO'
145"OO'
145"OO'
14S000'

14S000'145"OO'

A115
C106
A121
C082
C 106
C082
A 121
C 106
C093
A1 15
A115
C093
C 106
C072
C082
A1 2 1
A 121
C 106
c121
C093
C106
'2106
C063

14S'OO'
145"OO'
145O00'
145'00'
14S000'
165'00'

C082
COX2
C 106
C I06
C106
A1 15

F
F
F
M
F
M
F
M
M
F
F
F
M
M
M
F
M
M
M
F
F
M
F
M
M
F
M
M
F

55'00'

56"OO'
50"oo'

5o"oo'
5O"OO'
55°00'
55"oo'
55"OO'

55"oo'56OOO'
56O00'
56"OO'
4n030'
48"30'
5 1"OO'55"OO'
55°00'
55"OO'
56"OO'
56"OO'
56"OO'
56"OO'
47"OO'

14S000'145"OO'
145"OO'
14S000'
14S000'
14S000'
16S00O'165 00'

145'00'

502
454
432
462
486
447
487
460
454
49 1
498
412
448
486
431
505
48 1
442
470
517
483
461
469
45 8
447
sin
476
470
451

1580
1080
900
I040
1480
I040
1240
1220
1240
1520
1400
1360
1000
1 I60
960
1540
1320
960
1260
IS40
1280
1160
1020

1060
1020

I540
1300
1200
1060

GW
(8)

Age

RBr

HatcheryOrigin

54
27
37
11
48
18
41

0.1
0.1
0.1
0. I
0.1
0.1

1: 1 . 4 f 2 . 3

1

0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1

1:1.8
1:1.8

AFK96early
AFK96early
AFK96early
AFK96early
AFK96late
AFK96late
AFK96late
AFK96late
AFK96late
CCH96
CCH96
CCH96
CCH96
CCH96
CCH96
CCH96
CCH96
CCH96
CCH96
CCH96
WHN96early
WHN96early
WHN96early

1:1.8
1:i.n
1:l.g
1.1.8
1:1.8+2.3
1.1.8f2.3

WHN96early
WHN96early
WHN96early
WHN96early
WHN96late
WHN96late

29
46
56
105
11
15
13
49
15
8

0.1

0.1

0.1
0.1

15

0.1

22
32
23
28

0.1
0. I
0.1
0.1

18
21
42
13
12
25

0.1
0.1
0.1
0.1
0.1
0.1

1:1 . 4 f 2 . 3

I : 1.4+2.3
1:1.4+2.3
1:1.4

1:1.4
1:1.4
1:1.4
1:14
1:1.3,2.3
1: 1.3,2.3
1:1.3,2.2
1: 1.3,2.3
1: 1.4,2.3
1 :1.4,2.3
1:1.4,2.3
1:1.4,2.3
1:1.3,2.3
1:1.3,2.3
1 :1.3,2.3

1:l.X

2 If . 3 $@'i&?gB-k
2 9 -68% Bull. Natl. Salmon Resources Center, No. 2, 1999

4

Female
65" N

d
fish

60" N

55" N

50" N

45" N

-

Pacific

W

Ocean
40" N
180"

170"W

160"W

150"W

140"W

130"W

120"w

Male

Fig. 1. Hatchery origins and composition of thermally marked maturing pmk salmon caught along the 145'W and 165OW transects in the Gulf of Alaska in June and July 1998. Numerals indicate the number of thermally marked fish. A, A m i n F.
Koemig Hatchery; C, Cannery Creek Hatchery; G, Gastineau Hatchery; S, Solomon Gulch Hatchery; W, Wally H. Noerenberg Hatchery.

Kawana et a1.- Thermally marked pink salmon in the Gulf of Alaska

5

0 Other pink salmon

W 60-

3

8

40-

20-

I

0
49" N

r

1

50" N

51"N

52" N

55"N

56"N

2obJL-n045'30N47"N48'30N

50"N

LatitudeFig. 2. Catch per unit effort (CPUE) of themally marked pink salmon, which were Prince William Sound (PWS) hatchery origincaught along the 145"W (upper) and 165"W (lower) transects in the Gulf of Alaska in June and July 1998. The CPUE values
are based on the catch (number of fish) per one set of research mesh gillnets (30 tans).

Table 3. A comparison of body and gonad measurements between maturing thermally marked Prince William Sound (PWS)
hatchery pink salmon and nonmarked pink salmon caught along the 145OW and 16SoW transects in the Gulf of Alaska in
June and July 1998. Values are given as the mean+SD. Numbers in parentheses are sample sizes. FL, fork length (mm);BW, body weight (g); GW, gonad weight (g); GSI, gonadosomatic index= 100 x gonad weight &)/body weight (8).
Sex

Measurement

145"Wtransect
Female
FL
BW
GW
GSI

Male

FL
BW
GW
GSI

165"W transect
FemaleFLBW

Male

PWS hatchery stocks

Other stocks

Probability

483f24 (12)1328+227 (12)4 7 f 2 1 (12)3.54k 1.41 (12)485+25 (155)1443f302 (155)
82f37 (1.55)
5.56k2.05 (155)p=0.84p=0.20p<o.001p<o.01

460f16 (13)1111k123 (13)14+6 (13)1.26k0.53 (13)495f35 (126)1575+408 (126)
41+29 (126)2.50k 1.43 (126)p<o.001p<o.001p<o.o01p < 0.001

4 8 7 f 4 2 (2)1300f339 (2)465k33 (46)1244f273 (46)p = 0.35
p=0.70GW

24+2 ( 2 )6 5 f 3 1 (46)p=0.07GSI

1.89k0.66 (2)5.28 f 1.99 (46)p<0.05

FL
BW
GW
GSI

4 6 2 i 1 1 (2)1250f14 (2)2 2 f 1 0 (2)1.76i0.81 (2)474f40 (26)1271 +304 (26)37+28 (26)2.74+ 1.95 (26)p = 0.67
p = 0.93~ ~ 0 . 4 7
p = 0.49

3 I f . 'd ?@%%?@-I?
2 9 -6$@ Bull. Natl. Salmon Resources Center, No. 2, 1999

6

r

0

l2

8rc

145OW

6 0

0

01
400

I

I

500

600

r

l2

145OW

Male

0
0
0

0

01
400

-0

I

600

8I

165OW
Female
0

0

0

0

t

a

700
165OW
Male

0

6

0

I

I

500

0
0
0

0
U
m
K
0

0

.

0
0
0

0

0

0

c3
0

01
400

I

I

500

600

Fork Length (mm)

01
300

0

0

I

I

400

500

I

600

Fork Length (mm)Fig. 3. Relationships between gonadosomatic index and fork length (mm) in maturing pink salmon caught along the 145'W and165'W transects in the Gulf of Alaska in June and July 1998. Closed and open circles show Prince William Sound hatcheryand other pink salmon, respectively.

fish in 1956-1992 (Myers 1994, updated from Takagi et al. 1981) indicated that pink salmon originating
in southwestern, central, and southeastern Alaska are
not distributed south of 50"N in the vicinity of165"W. However, we recovered four thermallymarked PWS hatchery pink salmon at 47-50'",
165OW, which is a southwestward extension of the
known ocean range of maturing southcentral
Alaskan pink salmon in summer.
Marked SGH fish were 39% of the total releases
from four PWS hatcheries of pink salmon with goodquality thermal marks (Joyce et al. 1997; Munk andGeiger 1998). During a May 1998 salmon survey
along the 145"W transect, marked SGH fish werecaught in northern waters (5Zo59'-55O03'N), andthree other hatchery stocks were caught in southernwaters (42'57'-46'58'N, Farley et al. 1999). In 1998,

most of the three other hatchery fish indicated low
GSI in July. The run-timing of SGH pink salmon isapproximately 3-4 weeks earlier than that of thethree other hatchery stocks. Therefore, in July SGH
pink salmon may be distributed closer to the coast of
PWS than other PWS hatchery stocks.
In general, the proportion of males in catches ofmaturing pink salmon at AFK is more than 80% during the last 10 days of July and decreases graduallyto the end of August in even year stocks (Mathisen
and Zheng 1994). The more northerly distribution of
PWS hatchery males compared to females that we
observed in offshore waters in late June to early Julymay be related to sexual differences in the timing of
their homeward migrations.
The total number of otolith-marked Pacificsalmon released into the North Pacific Ocean andKawana et al.- Thermally marked pink salmon in the Gulf of Alaska

adjacent seas is increasing (Munk and Geiger 1998).

In Japan, mass marking of hatchery salmon withotolith thermal marks began with 1998 brood-year
stocks, after US, Canadian, and Russian otolithmarking programs had already implemented. We aredetecting thermal marks on chum (0.ketu) and pinksalmon otoliths collected by Japanese salmon
research vessels during summer 1999 salmon surveys from a wide area of the North Pacific Ocean
and Bering Sea. Continued monitoring of the distribution of hatchery stocks by detection of otolith thermal marks is important for mixed-stock managementof Pacific salmon.

References
Farley, E. V., and K. Munk. 1997. Incidence of thermally marked pink and chum salmon in the
coastal waters of the Gulf of Alaska. Alaska Fish.
Res. Bull., 4: 181-187.
Farley, E. V., K. Munk, and P. T. Hagen. 1999. Incidence of thermally marked pink, chum, and sockeye salmon in the coastal waters of the Gulf of
Alaska, 1998. (NPAFC Doc. 446) Auke Bay Laboratory, Alaska Fisheries Science Center, NMFS,NOAA, Juneau, Alaska, USA. 24 p.
Geiger, H. J., and K. M. M u d . 1998. Otolith thermal mark release and mass-processing history in
Alaska (USA), 1988-1998. (NPAFC Doc. 368)
CWT & Otolith Processing Lab., Alaska Department of Fish and Game, Juneau, Alaska, USA. 9
P.
Hagen, P., K. Munk, B. VanAlen, and B. White.
1995. Thermal mark technology for inseason fisheries management: a case study. Alaska Fish. Res.
Bull., 2: 143-155.
Ignell, S. E., C. M. Guthrie 111, J. H. Helle, and K.
Munk. 1997. Incidence of the thermally-marked
chum salmon in the 1994-96 Bering Sea pollack
B-season trawl fishery. (NPAFC Doc. 246) Auke
Bay Laboratory, Alaska Fisheries Science Center,
NMFS, NOAA, Juneau, Alaska, USA. 16 p.
Joyce, T. L., D. G. Evans, and K. M. Munk. 1997.
Otolith thermal marking of pink salmon in Prince
William Sound salmon hatcheries, 1996. Exxon
Valdez oil spill restoration project annual report(Restoration Project R96188). Commercial Fisheries Management and Development Division,
Alaska Department of Fish and Game, Cordova,
Alaska, USA. 27 p.
Mathisen, 0. A,, and J. Zheng. 1994. Changing sex

7

ratios during spawning migration of pink salmon
in Southeast Alaska. In Proceedings of the 16th
northeast Pacific pink and chum salmon workshop. University of Alaska Fairbanks, Fairbanks.
pp. 137-145.
McNair, M. 1998. Alaska salmon program 1997
annual report. Commercial Fisheries Management
and Development Division, Alaska Department ofFish and Game, Juneau. 36 p.
Munk, K. M., and H. J. Geiger. 1998. Thermal marking of otoliths: the "RBr" coding structure of thermal marks. (NPAFC Doc. 367) CWT & Otolith
Processing Lab., Alaska Department of Fish andGame, Juneau, Alaska, USA. 19 p.
Munk, K. M., W. W. Smoker, D. R. Beard, and R.
W. Mattson. 1993. A hatchery water-heating system and its application to 100% thermal marking
of incubating salmon. Progressive Fish-Culturist.,
5 5 : 284-288.
Myers, K. W. 1994. New conceptual models of highseas migrations of pink and chum salmon. In Proceedings of the 16th northeast Pacific pink andchum salmon workshop. University of Alaska
Fairbanks, Fairbanks, Alaska, USA. pp. 83-96.
Takagi, K. 1975. A non-selective salmon gillnet for
research operations. Int. North Pac. Fish. Comm.
Bull., 32: 13-41.
Takagi, K., K. V. Aro, A. C. Hartt, and M. B. Dell
1981. Distribution and origin of pink salmon(Oncorkynchus gorbuscha) in offshore waters of
the North Pacific Ocean. Int. North Pac. Fish.
Comm. Bull., 40: 195 p.
Urawa, S., M. Kawana, G. Anma, Y. Kamei, T. Shoji, M. Fukuwaka, K. Munk, K. w. Myers, and E.
V. Farley. 1999. Stock origin of chum salmoncaught in offshore waters of the Gulf of Alaska
during the summer of 1998. (NPAFC Doc. 420)
National Salmon Resources Center, Fisheries
Agency of Japan, Sapporo 062-0922, Japan. 16 p.
Volk, E. C., S. L. Schroder, and K. L. Fresh. 1990.
Inducement of unique otolith banding patterns as apractical means to mass-mark juvenile pacificsalmon. Am. Fish. SOC.Symp., 7: 203-215.
Walker, R. V., K. Y. Aydin, G. Anma, H. Yamaguchi, Y. Kamei, T. Shoji, M. Kaeriyama, and s.
Urawa. 1998. The 1998 international cooperative
salmon research cruise of the Oshoro maru.
(NPAFC Doc. 349) FRI-UW-9812. Fisheries
Research Institute, School of Fisheries, Universityof Washington, Seattle, Washington, USA. 20 p.

さけ・ます資源管理センター
研報 Bul1.Nat1.SalmonResourcesCenter,No

州名 守彦 ・浦和茂彦

・安間

元 ・亀井佳彦・ 庄司

l45 度 定線では， 307 個体のうち 25 個体 (8． l%) がKOernigHatChery(CCH ， 9(AFK ， 8 個体 )， CannerycreekHaLChery個体 )， WallyH
NOerenbergHatChery(WHN ， 8 個

標識魚であ り，起源はArminF・・]998 年夏期にアラスカ 湾で再捕された 温度標識カ
ラフトマス成魚． 2， 1999

耳石温度標
識を利用して ，夏期アラスカ湾で流網 により採集

体) だった ． また西経 165 度 定線では， 76 個体のうち 4 個体 (5． 3%) が標識魚であ り，起源は AFK(@個体)， CCH ( 2 個体)， WHN( l 個体) だった．
両定線でpWS 岬化場魚の CPUE が、 母川回帰方向に相当する北方海域で 高かった． PWS 服化場魚の分布に雌雄差が 観察され， 母川 回帰時期の違いに 由された個体を 分析した． @998 年 6 月から 7 月にか来することが 示唆された ．

けてアラスカ 湾 (西糸引45 度と l65 度 ) で採集され沖合 (北緯47‑50 度 ) において PWS 由来の標識魚が4 個体再捕されたことは ，中央アラスカ 系 カラフト
マス成魚の既知の 分布域を南西方向に 拡張するも

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アラスカ 産 カラフトマスの 海洋分布と移動を調べるため， アラスカの 暇化場で施されたたカラフトマス 成甘、 383 個体のうち， 29 個体がプリンス・ウイリアム・サウンド

地域(PWS ， 中央アラスカ ) から放流された 温度標識 甘、 だった．西経

のであ った ．

また， 西経 l65 度 定 線の