さけ・ます資源管理センター
研究報告 第 5 号 33-36頁
2002年12月

Bulletin of the National Salmon
Resources Center, No. 5: 33-36
December 2002

RESEARCH NOTE
Biological Characteristics of Fall-Run Chum Salmon(Oncorhynchus keta) caught in the Lower Amur River
Kazumasa Ohkuma*1, Toshiya Suzuki*1, Kei Yurano*2,
Sergey F. Zolotukhin*3, and Victor G. Markovtsev*4*1

Research Division, National Salmon Resources Center,
2-2 Nakanoshima, Toyohira-ku, Sapporo 062-0922, Japan(ohkuma@salmon.affrc.go.jp)*2
Fisheries Agency of Japan, 1-2-1 Kasumigaseki, Tokyo 100-8905, Japan*3
Khabarovsk Branch, Pacific Research Fisheries Centre,
9 Shevchenko Street, Khabarovsk 680000, Russia*4
Pacific Research Fisheries Centre, 4 Shevchenko Alley, Vladivostok 690600, Russia
Abstract. − Biological characteristics were examined for fall-run chum salmon (Oncorhynchusketa) caught by test and local fisheries in the lower Amur River during September 2000. Age 0.3
fish (56%) were the most abundant age group, followed by age 0.4 fish (38%). The average fork
length and body weight were 66.8 cm and 3.91 kg for females, and 69.3 cm and 4.54 kg for males,respectively.
Key words : Amur River, chum salmon, fall run, biological characteristics

Introduction
The Amur River, one of the biggest rivers ineastern Asia, is famous and important for its summer- and fall-run chum salmon (Oncorhynchus keta).
The name keta means fish in the language ofthe Nanai people who live along the Amur River(Salo 1991). The first Japan-Russia cooperative
research program on Amur River chum salmon wasconducted in 1999 for summer-run fish (Ishida et al.
2001). They investigated the biological characteristics of the summer-run chum salmon and reported
large deviations in the sex ratio between sampling
locations. We continue the cooperative research byexamining the fall-run of chum salmon that returnedin 2000 by describing biological characteristics suchas fork length, body weight, gonadosomatic index,
age, and sex ratio of fall chum salmon caught in thelower portion of the river. We compare these characteristics with previous information from older
Contribution A No. 32 from the National Salmon
Resources Center.
© 2002 National Salmon Resources Centerstudies and from recent data for summer-run chumsalmon surveyed in 1999.

Materials and Methods
A total of 306 chum salmon were caught by drift
gillnet (size: 6 m × 150 m) in the lower Amur Riverand the Amgun River on September 9-10, 2000 (Fig.
1). The stretched mesh size of the gillnet was 140mm (70 mm by the Russian method of mesh measurement). The 247 fish caught at Tatarsk weremeasured for fork length (FL), scales were collected
for age determination, and the sex was determinedby visual examination. The European system wasused to designate the fish's age, where counts offreshwater annuli and ocean annuli are identified andseparated by a period. A subsample of 126 fish wasmeasured for body (BW) and gonad weight (GW).
Another sample of 40 fish caught at Tyr and 19 fishfrom the Amgun River, about 1 km upstream fromthe junction with the Amur River, were examined for
FL, BW, and GW. Fork length was measured to thenearest 1 cm and BW was weighed to the nearest 0.1kg. Gonad weight was weighed to the nearest 1 g
using an electronic balance. The condition factor

34

さけ・ます資源管理センター研報 Bull. Natl. Salmon Resources Center, No. 5, 2002

(CF) and gonadosomatic index (GSI) were calculated using following formulae:
CF=106 BW/FL3
GSI=GW/BW/10
Body weight and FL of age 0.3 and 0.4 fish werecompared by sex using t-tests. The chi-square wasused to test for differences in sex ratios.

Results

Fig. 1. Location of sampling sites in the lower Amur Riverfor collection of fall-run chum salmon in September 2000.

Table 1. Sex ratio of fall-run chum salmon caught in the lower Amur River in September 2000.
Number ofLocation

Female (%)

Male (%)

Tatarsk

60.3

39.7

247

Tyr37.562.5

40Amgun

47.4

52.6

19

Total

56.5

43.5306

samples

The sex ratio was 60.3% female and 39.7% malefor chum salmon caught at Tatarsk, and 37.5%
female and 62.5% male for the sample collected atTyr (Table 1). In the Amgun River, the sex ratio wasapproximately even, although the sample size wassmall (n=19). Sex ratios were statistically significant
by fishing location (chi-square, p<0.05).
Total average fork length and body weight were
66.8 cm and 3.91 kg for females, and 69.3 cm and4.54 kg for males, respectively (Table 2). Average
condition factor was the same for males and females.
The average gonadosomatic index is 10.6 and 4.04
for female and male fish, respectively. Those index
show that the fish of both sexes were not fully
matured yet.
The most abundant in the Tatarsk samples wasage 0.3 fish, followed by age 0.4 (Fig. 2). At Tyr,the age composition had a high proportion of age 0.3
fish, followed by age 0.4 fish. The most abundant
age class in the Amgun River sampls was age 0.3,
followed by age 0.4 fish.

Table 2. Average fork length (FL), body weight (BW), condition factor (CF), and gonadosomatic index (GSI) of fall-run chumsalmon caught in the lower Amur River in September 2002.
FemaleMale

Tatarsk

Tyr

Amgun

Total

Tatarsk

Tyr

Amgun

Total

mean

66.7

68.2

66.0

66.8

69.3

69.4

70.0

69.3

SD

4.03

2.73

1.66

3.87

6.39

5.68

5.54

6.16

n149

15

9

173

98

25

10

133

mean

3.94

4.06

3.40

3.91

4.70

4.34

4.24

4.54

SD

0.81

0.56

0.36

0.76

1.14

1.23

1.08

1.16

CF

mean

12.9

12.7

11.8

12.8

12.912.7

12.1

12.8

SD

0.89

0.60

0.65

0.89

0.98

1.10

0.75

1.01

GSImean

10.8

8.9

11.9

10.6

4.1

4.1

3.8

4.04

SD

2.38

1.91

2.58

2.44

0.78

0.59

0.86

0.74

n75

15999

51

25

1086

FL (cm)BW (kg)Ohkuma et al. − Biological characteristics of fall-run chum salmon in the Amur River

35Fig. 2. Percent age composition of fall-run chum salmon caught in the lower Amur River in September 2000.

While the mean size of male chum salmon
increased from age 0.2 fish to age 0.5 fish (Table 3),
Table 3. Average fork length (FL) and body weight (BW) offall-run chum salmon caught in the lower Amur River in September 2000.
AgeFL (cm)BW (kg)mean

SDnmean

SDn

0.5

68.2

2.7

6

3.30

0.28

2

0.4

66.7

3.9

69

3.91

0.87

44

0.3

66.7

4.0

94

3.93

0.68

51

0.2

66

1

3.1

Female

1Male
0.5

76.0

2.0

3

5.30

0.26

3

0.4

71.0

6.7

45

4.77

1.24

33

0.3

68.4

5.8

76

4.41

1.09

44

0.2

65.0

3.4

7

3.13

0.69

4

the mean size of female did not increase by age somuch. Sample sizes of age 0.3 and 0.4 fish werelarge enough for statistical analysis, and age 0.4
males were significantly larger than age 0.3 males(p<0.05). However, no significant difference wasobserved in mean FL of females at age 0.3 and 0.4(p=0.50). Differences among male (p=0.09) andfemale (p=0.45) mean BW were not significant.

Discussion
Comparison of our age composition with datafrom 1959 (81.8% for age 0.3 and 7.2% for age 0.4;
Sano 1966) shows the proportion of age 0.4 fish hasincreased since the earlier study and confirms theincrease in mean age observed by Ishida et al.
(1993). Regarding fish size, Ishida et al. (1993)
reported the decreasing trend in body weight fromthe 1970s to 1980s. Our mean BW values for age
0.3 chum salmon caught in the lower Amur River36

さけ・ます資源管理センター研報 Bull. Natl. Salmon Resources Center, No. 5, 2002

exceed the values obtained in the 1959 study (3.40 kg
for female and 4.16 kg for male, Sano 1966).
In 1999 the proportion of female summer-runchum salmon was low (32-34%) at Tyr (Ishida et al.
2001). In autumn 2000 the proportion of females
collected in Tyr was lower (37.5%) than the 60%
females caught at Tatarsk. Male fish ascend the river earlier than female fish during their spawningmigration (Bakkala 1970). However, it was difficult
to conclude that female chum salmon outnumbered
the males at Tatarsk, which is further up stream thanTyr. The predominance of females further upstream
may be explained by the small number of fish examined at Tyr. Further studies are needed to clarify
these issues.

Acknowledgements
We thank Captain Pavel T. Matushkin and thecrew of the R/V Prof. Soldatov for their assistanceand sincere kindness during the research cruise. Wethank Dr. Vladimir A. Belyaev, Director, TINRO,
Khabarovsk Branch for his coordinating efforts andsupport for this research, and Mr. Yaichi Miyamotofor his translation services during this excursion.
We also appreciate Dr. Yukimasa Ishida, National Research Institute of Fisheries, and Ms. Nancy D.
Davis, University of Washington for their assistancein revising the manuscript.

References
Bakkala, R. G. 1970. Synopsis of biological data on
the chum salmon, Oncorhynchus keta (Walbaum)

1792. FAO Fish. Synop. 41, U.S. Fish Wildl. Serv.
Circ. 315, 89 p.
Ishida, Y., S. Ito, M. Kaeriyama, S. McKinnell, andK. Nagasawa. 1993. Recent changes in age andbody size of chum salmon (Oncorhynchus keta) in
the North Pacific Ocean and possible causes. Can.
J. Fish. Aquat. Sci., 50: 290-295.
Ishida, Y., T. Takahashi, T. Tagaki, S. F. Zolotukhin,
and V. G. Markovtsev. 2001. Biological characteristics of summer run chum salmon in the Amur
River. Bull. Hokkaido Natl. Fish. Res. Inst., 65: 17.
Salo, E. O. 1991. Life history of chum salmon(Oncorhynchus keta). In Pacific salmon life history(edited by C. Groot and L. Marolis). University ofBritish Columbia Press, Vancouver. pp. 231-309.
Sano, S. 1966. Chum salmon in the Far East. InSalmon in the North Pacific Ocean. Part IV.
Spawning populations of the North Pacific salmon.
Int. North Pac. Fish. Comm. Bull., 23: 23-42.
アムール川下流域で採捕した秋サケの生物学的特徴
大熊一正・鈴木俊哉・由良野圭・
Sergey F. Zolotukhin・Victor G. Markovtsev
2000年9月にアムール川下流域において秋サケの生物学的調査を行った．採捕された秋サケの鱗による年齢査定を行ったところ，0.3年魚（4年魚）が56％を占め，次いで0.4年魚（5年魚）が38％を占めた．調べたサケの平均体長および平均体重は雌で66.8 cm，3.91 kg，雄では69.3 cm，4.54 kgであった．