Bulletin of the National Salmon
Resources Center, No. 3: 29-38
December 2000

REVIEW
Japanese Salmon Research in the Ocean:
A Review and Future Issues
Shigehiko Urawa"', Yukimasa Ishida**,and Masa-aki Fukuwaka*2* 'Research DiTision, National Salmon Resources Center, Fisheries Agency oj Japan,
2-2 Nakanoshima, Toyohira-ku, Sapporo 062-0922, Japan(urawa@salmon.affrc.go.jp)*2HokkuidoNational Fishei-ies Research Institute, Fisheries Agency ofJapan,
116 Katsurakoi, Kushiro, Hokkaido 085-0802,Japan

Abstract.- This paper provided a review on the results of Japanese salmon research conducted in
1993-2000 under the Science Plan decided by the North Pacific Anadromous Fish Commission(NPAFC). Recent developments of stock identification techniques and high-seas salmon population
surveys provided new information for the ocean distribution of chum salmon: Japanese chum salmon
inhabit the Okhotsk Sea in the early ocean life, pass the first winter in the western North Pacific
Ocean, and then migrate to the Bering Sea by the next summer. Coastal surveys suggested that major
salmon mortalities occur in the early ocean life, but the causes of juvenile mortalities have not been
well understood. Scale pattern analysis suggested that Japanese chum salmon suffer from growth
reduction in the Bering Sea, resulting in increase of age at maturity. A long term biologicalmonitoring i n the subarctic North Pacific Ocean found a negative relationship between macrozooplankton and pink salmon biomass. A similar biological monitoring should be necessary in the
Bering Sea. The extremely low lipid contents in the muscle of overwintering salmon indicated a great
difficulty for them to survive in winter. Future research issues are (1) juvenile salmon studies in the
Okhotsk Sea, (2) winter salmon studies in the North Pacific Ocean, (3) salmon ecology studies in the
Bering Sea, and (4) monitoring of major salmon stocks. These issues are indispensable for thesustainable stock management of Pacific salmon.

Key words: Pacific salmon, life history, population dynamics, distribution, ocean ecosystem, review

Introduction
The North Pacific Anadromous Fish Commission(NPAFC) was established under the Convention for theConservation of Anadromous Stocks in the North
Pacific Ocean, signed on February 1 1,1992 and enteredinto force on February 16, 1993 by Canada, Japan, theRussian Federation and the United States. The primary objective of NPAFC is to promote the conservationof anadromous stocks in the North Pacific Ocean andadjacent waters.
At the 1993 NPAFC annual meeting, the Committee
on Scientific Research and Statistics (CSRS) identified
two critical issues for research by the parties: (1) facContribution A No. 20 from the National Salmon
Resources Center.
02000 National Salmon Resources Center

tors affecting current trends in ocean productivity, and(2) factors affecting changes in biological characteristics such as growth, size and age at maturity, oceanic
distribution, survival, and abundance of Pacific salmon.
The CSRS developed the NPAFC Science Plan toaddress these two critical issues by three components:(1) life history of salmonids, (2) salmonid population
dynamics, and (3) salmonid habitat and ecosystem.
Each component has several items that identify questions relating to the two critical issues (Appendix 1).
Under the NPAFC Science Plan, the Parties make eachresearch plan, cooperating in the scientific research.
Abstracts of the recent results by Japanese salmon
research were compiled by Fisheries Agency of Japan(1997) and Urawa and Ishida (1998, 1999). The purposes of this paper are to review the results of Japanesesalmon research related with the present NPAFC Science Plan in 1993-2000, and to propose future research

30

2 if . 2 -6~$???B!-ki 9 -Uf% Bull. Natl. Salmon Resources Center, No. 3, 2000

for the appropriate conservation and utilization ofPacific salmon.

Life History of Salmonids
Spatial distribution
Intensive high-seas tag releases showed approximate
ocean distribution of Japanese chum salmon (Oncorhynchus keta) (see Ogura 1994), but the ocean migration route was not been decided especially during theearly ocean life period and winter season. Recent
developments of stock identification techniques andsalmon population surveys have provided new information for the ocean distribution of chum salmon (seea review by Urawa 2000).
In coastal waters of northern Japan, juvenile chumsalmon change their spatial distribution from inshore to
offshore regions with their growth (Kaeriyama 1986;
Fukuwaka and Suzuki 1998a). Juvenile chum salmon
migrate from Japanese coasts to the Okhotsk Sea in thefirst summer, and reside there by late fall (Ueno 1998;
Urawa et al. 1998b). When the sea surface temperature(SST) decreased less than 5'C in the Okhotsk Sea,
juveniles migrated to the western North Pacific Ocean,
where they overwintered with other Asian juvenile
stocks (Urawa and Ueno 1997, 1999; Urawa et al.
1998b). In summer, Japanese immature and maturingchum salmon were abundant in the Bering Sea, butrarely in the North Pacific waters (Urawa et al. 1997;
Urawa 2000). In the following winters, Japanese immature chum salmon were mainly distributed in the Gulf
of Alaska (Urawa et al. 1997).
Seawater temperature should be an important factor
to affect the ocean distribution of salmon, but favorite
temperatures differ depending on fish species and season. In winter, most salmonids were captured in northem waters of the North Pacific Ocean at SST 4-8'C(Ueno et al. 1999). Planktophagous salmonids may
have a survival strategy to stay in such cold waters inorder to reduce their energetic consumption, because
zooplankton as prey i s not abundantly available in winter (Nagasawa 2000).
In the Bering Sea, CPUE of pink salmon (0. go^
huscha) was extremely higher in odd years than in evenyears, while chum salmon showed opposite CPUE
trends. Chum salmon shifted their distribution to southeastward in odd years. These results suggest that the
spathial distribution of chum salmon may be affectedby abundance of pink salmon (Azumaya et al. 1999).
Maturing salmon with depth-sensing ultrasonictransmitters moved in particular directions and maintained their ground speeds and directions during day
and night (Ogura and Ishida 1995; Ogura 1999).
Archival tags showed that maturing chum salmon

dived into mid-waters (about 50 m in depth) and roseto surface waters very frequently at daytime, whichmight be related to location and orientation for theirhoming migration (Wada and Ueno 1999). In the
Pacific coasts of northern Honshu where SST was over
20'C in fall, adult chum salmon frequently dived todepths exceeding 100-400 m before returning to thenative river (On0 2000; Tanaka et al. 2000). Durationof deep dives tended to be prolonged as the thermal difference between sea surface and bottom water
increased, indicating that salmon sought the coolest
thermal refuge that they could exploit by verticalmovement. Thermal refuge could be a way for salmon
to minimize metabolic energy cost (Tanaka et al.
2000).
It is still unclear why Japanese chum salmon concentrate in the Okhotsk Sea at juvenile stage and in the
Bering Sea at immature and maturing stages. Further
studies are necessary to clarify relations between
oceanographic conditions, productivity of food organisms, and salmonid distribution.

Growth and maturity
Density dependence is one of possible causes for the
recent increase of age and decrease of size at maturity
for chum salmon in the North Pacific Ocean (Ishida etal. 1993; Kaeriyama 1996a). Limited prey resources in
the ocean may lead to density-dependent growth ofPacific salmon during rapidly growing season (Ishida
et al. 1998).A scale pattern analysis showed that Japanese chum salmon suffered from growth reduction after
the second year of ocean life (Kaeriyama 1998). Urawa(2000) estimated that these growth reduction may
occur in the Bering Sea, where chum salmon density
increases in summer. A growth reduction of chumsalmon in the third year of ocean life may be partly due
to a requirement of immature age 0.2 fish to consume
a large amount of prey (Ishida and Davis 1999).
Techniques to estimate somatic growth or age ofchum and sockeye salmon (0. nerka) have been
improved using otolith or scale patterns (Fukuwaka
1996; Fukuwaka and Kaeriyama 1997; Endo et al.
1998), while biochemical approach is also useful toassess somatic growth. Contents of nucleic acids orlipids suggested that strategies of resource allocation
for somatic growth i s different among Pacific salmon,
and growth characteristics depend on life stages(Azuma et al. 1998). The total lipid content and lipid
classes in the muscle and liver of pink and chumsalmon were examined for estimating their trophic condition in the ocean (Nomura et al. 1999, 2000). The
extremely low lipid contents in winter suggest thatchum and pink salmon are confronted with a great difficulty to live during this season. Further studies of sea-

Urawa et al. - Ocean salmon research in Japansonal and spatial variation in lipid content among
North Pacific salmonids may better estimate changes introphic conditions experienced by salmon during theirhigh seas residency.
Endocrinological studies found that homing migration relates closely to gonadal maturation of Pacificsalmon (Fukaya et al. 1998; Kitahashi et al. 1998a,
1998b; Ueda 1998). The fecundity of mature female
chum and sockeye salmon was positively correlatedwith their fork length, but the egg size did not show any
correlations with the body size (Ishida et al. 1995;
Kaeriyama et al. 1995). However, it is not known how
growth variations affect maturation and reproduction.
Feeding ecology
In coastal waters, juvenile chum salmon fed more onlarge zooplankton such as copepods or polychaetes,
when such organisms were abundant or when stomach
fullness of fish was high (Suzuki and Fukuwaka 1998).
In inshore waters (5-15 m in depth) where juvenile
chum salmon were distributed, prey zooplankton wasless than at deeper layer (30 m) in offshore waters (Sekiand Shimizu 1998).
In the central North Pacific and the Bering Sea, age
0. I chum salmon fed a relatively high proportion ofamphipods as compared to the other age groups, while
prey composition was similar among older chumsalmon (age 0.2 to 0.5) (Ishida and Davis 1999). In thesame regions, chum salmon changed their dominant
diet from gelatinous zooplankton (such as pteropods,
appendicularians, or jellyfishes) in 1991, when pinksalmon were abundant, to a diet of crustaceans (such as
euphausiids, copepods, or amphipods) in 1992, whenpink salmon were less abundant (Tadokoro et al. 1996).
Local crustacean biomass had significant negative correlation with the CPUE of pink salmon in 1991 and thatof chum salmon in 1992.

Salmonid Population Dynamics
Ahundunc.e, monitoring, and forecasting
The synchronous decreasing body size and increasing age at maturity of Hokkaido chum salmon occurredin face of rising marine survival rates and ocean conditions favorable for growth, suggesting that reduced
growth and increasing age at maturity was due to density dependent intraspecific competition and high abundance of chum salmon in the North Pacific Ocean(Kaeriyama 1996~1,1996b, 1998).
Every summer, salmon stock assessment researches
were conducted in the North Pacific Ocean and Bering
Sea. Abundance of salmon in offshore areas based on
CPUE of research gillnet operations may be used todevelop pre-season forecasts of Japanese chum salmon

31

and Bristol Bay sockeye returns (Ishida and Ito 1998).
Mortaliq
Fukuwaka and Suzuki (1998b) calculated that in the
Sea of Japan the early ocean mortality of chum salmon
accounted for 97.4% of their total ocean mortality.
However, few studies clarified the causes of ocean
mortalities in juvenile salmon.
Field and experimental studies showed that theectoparasitic flagellate Ichthyobodo necator cause highmortalities among juvenile chum salmon soon after
migrating into the coastal seawater (Urawa 1993,
1996a, 1996b). Further studies should be conducted toevaluate other pathological organisms as the cause ofnatural mortalities of salmon.
Although over 90 fish species have been reported tooccur with chum salmon juveniles, there is no evidence
that fish predation has much impact on the number ofreturning adult chum salmon in Japan (Nagasawa andKaeriyama 1995; Nagasawa and Mayama 1997; Nagasawa 199Yb). On the other hand, rhinoceros auklets(Cerorhinca rnonocemta) and black-tailed gulls (Larus
crassirosti-is)have been recorded as predators of juvenile chum salmon. These seabirds abundantly breed innorthern Japan, and the impact of their predation onchum salmon populations may be significant (Nagasawa 1998b). More field and experimental works arenecessary to assess the mortality of juvenile chumsalmon caused by fish and seabird predation.
Relatively high positive correlation coefficients were
found between the survival rate of Russian pink salmon
and SST in the Okhotsk Sea and the waters off the East
Kamchatka during fry emigration period in August(Azumaya et al. 1998). The survival rate of Alaskanpink salmon was also positively related to SSTs in thewaters along the west coast of North America inAugust. These results suggest that the survivals of pinksalmon are affected by SST changes.
Salmon shark (Larnna ditropis) occupy the highest
trophic level in the food web of subarctic waters, where
salmonids are their major prey item. Nagasawa (1998a)
estimated that salmon sharks consumed 73-146 x lo6
salmonids from spring to autumn in 1989, which corresponded to 12.6-25.2% of the total annual run ofPacific salmon for that year. Salmon shark may highly cause the ocean mortality of immature and maturingsalmon.
Stork irzteraction
Kawamura et al. (1998) showed potential feeding
interactions between chum salmon and fat greenling(Hexagrarnmos otakii) juveniles along the northerncoast of Hokkaido. In the Okhotsk Sea, prey species(diet niche) overlap was highest between pink and32

5 L? . d $g&?g5LE+ 9 -@f% Bull. Natl. Salmon Resources Center, No. 3, 2000

chum salmon, but inter-specific competition might belesser importance in their diets (Tamura et al. 1999).
Hiyama et al. (1999) suggested that there were density-dependent effects on the body size and spawningsuggest that macrozooplankton biomass remained low
when pink salmon were abundant due to the intense feeding impact of pink salmon, which in turn allowed phytoplankton biomass to remain high as a result of the lesser

success of pink salmon in the Japan Sea. It is suggest-grazing effect of macrozooplankton (Shiomoto et al.

ed that an interaction between pink and chum salmon
changes the spatial distribution of chum salmon in theoffshore waters (Azumaya et al. 1999).

1997). Similar relationships among phytoplankton,
macrozooplankton,and salmonid biomass were observed
along the north-south transect in the North Pacific Ocean
and Bering Sea in the summers of 1992 and 1993 (Nagasawa et al. 1999).
East-west distributions of total and size-fractionatedchlorophyll a concentration and primary productivity
were determined at the surface in the subarctic North
Pacific during November and December 1992. This survey suggested that more turbulent water column conditions induced by high wind velocity was an advantageous
factor for survival of large phytoplankton in the surface
layer, and hence the high total chlorophyll a concentration and primary productivity were achieved in the western and central subarctic North Pacific (Shiomoto et al.
1999).

Stock identification
Scale characters of chum salmon collected in Japanese and Russian local stocks were compared to establish a stock identification technique and baseline dataon scale characters (Niita and Ueno 1999). These
results demonstrated that scale characters used in thisstudy were effective for stock identification of age 4
maturing fish and not sufficient for of age 3 maturing
fish. Other new characters are necessary to identify thestock origin of chum salmon.
A genetic stock identification technique using
allozyme variations has been well developed, and thistechnique is frequently applied for the stock identification of high-seas chum salmon (Urawa and Ueno
1997, 1999; Urawa et al. 1997, 1998b, 2000a).
The continental origins of chinook salmon ( 0 .
tshawytscha) in the North Pacific Ocean and Bering
Sea were successfully estimated by using two freshwater parasites (Myxobolus arcticus and M . kisutchi) as
biological tags (Urawa et al. 1998a). However, parasite
species useful as biological tags are limited.
Recently thermal otolith marking has been applied tohatchery-released juvenile salmon for their identification in the western coasts of North America. Many thermally marked chum and pink salmon were recaptured
in the Gulf of Alaska (Kawana et al. 1999; Urawa et al.
2000a). Japan also started thermal mark releases in thespring of 1999. An initial aim of the thermal mark program is to provide information for the ocean migrationand survival of each regional salmon stock in Japan.
The number of thermal mark releases from hatcheries
in Japan are planned to increase year by year (Urawa
et al. 2000b).

Salmon Habitat and Ecosystem
Physical-biological inter-action and productivity
Year-to-year variations in biomass of phytoplankton
and macrozooplankton, and abundance of pink salmon
were examined in summers from 1985 to 1994 in the subarctic North Pacific Ocean. After 1989, phytoplankton
biomass and pink salmon abundance showed corresponding yearly patterns, whereas the pattern shown bymacrozooplankton biomass was always the inverse ofthat shown by phytoplankton and salmon. These patterns

Climate change effects
During the period from the mid-1970s to the late 1980s,
the Aleutian Low Pressure Index (ALPI) was high, butboth sea surface temperature and zooplankton biomass in
the Oyashio region remained low. Although the annual
catch of pink salmon along the east coast of Sakhalin
gradually increased from the 1960s to 1977, it declined
from 1978 to 1984 despite decreasing catches by theJapanese high-seas salmon fishery. The coastal catch
trend was similar to long-term changes in zooplankton
biomass in the Oyashio region, suggesting that east
Sakhalin pink salmon production was affected by climate
and zooplankton production in this region (Nagasawa
1998c; Nagasawa et al. 1999). Pink salmon catch on theeast coast of Sakhalin declined from mid-1970s to the late1980s but sharply increased in 1989. Catch of pinksalmon on the Hokkaido coast showed a similar trend anddramatically increased 1991. Pink salmon from theseregions stay as juveniles in the Okhotsk Sea. The low
catch for the mid-1970s through the 1980s was closely
related to increased sea-ice cover in the southern
Okhotsk Sea in response to intensifying of the ALPI. The
1989-1991 sharp increase in catch was in accordancewith decreased sea-ice cover in the southern Okhotsk Sea
corresponding to weakening of the ALPI (Nagasawa et
al. 2000). Return rates of Japanese chum salmon did notindicate a significant relation with the ALPI. However,carrying capacity estimated for odd-year pink salmon in
the North Pacific Ocean indicated a significant relation
with the ALPI (Kaeriyama 1997). Because the impact of
the ALPI differs between regions in North America andAsia, and also among salmon species,research on climate

Urawa et al. - Ocean salmon research in Japanchange and ocean production is needed on both regional
and whole North Pacific scales (Nagasawa 1998~).

33

salmon# Population size and survival estimates of overwin-

tering salmon

Future Salmon Research
Several questions identified in the NPAFC Science
Plan have been resolved in cooperation with scientistsof Canada, Russia and the United States, while others
are not yet settled (Appendix I). The major purpose ofJapanese salmon research is to accomplish sustainablefisheries, balancing the conservation and use of salmon
stocks in the North Pacific ecosystem. Recent studies
are showing the main ocean distribution of Japanesechum salmon. They inhabit in the Okhotsk Sea in thefirst summer and fall, overwinter in the western North
Pacific Ocean, and migrate to the Bering Sea by thenext summer. Immature chum salmon migrate to theGulf of Alaska for overwinter after intensive feeding in
the Bering Sea. In accordance with these seasonal
migration, we should concentrate future salmon studies to population dynamics and ocean ecosystems inspecific waters. These research are (1) juvenile salmon
studies in the Okhotsk Sea, (2) winter salmon studies
in the North Pacific Ocean, (3) salmon ecology studies
in the Bering Sea, and (4) monitoring of major salmon
stocks, The former three issues have been adopted into
the new NPAFC Science Plan (North Pacific Anadromous Fish Commission 2000).

# Survival strategies of salmon in winterSalnzon ecology studies iiz the Bering Sea

Recently, the depression of ocean growth wasobserved in salmon stocks originating both the Asianand American coasts. Current studies suggest that
salmon growth reduction may occur in the Bering Sea,
when many salmon migrate in the waters for their feeding and growth in summer. To clarify relations between
the growth and mortality of salmon and the carrying
capacity in the Bering Sea, we should focus the following research items:# Climate change and primary production# Production of food animals# Population size and distribution of major salmon
stocks#Feeding competition and growth change of salmon
Monitoring of major salmon stocks
A monitoring program should be continued to assess
the status of major salmon stocks in Japan for theirproper management.
# Annual changes in the number of adult returns# Annual changes in body size and age at maturity,and fecundity# Genetic monitoring for stock conservation

Jullenile salmon studies in the Okhotsk Sea

The previous studies indicated that Asian salmon
stocks inhabit in the Okhotsk Sea during summer andfall in the first year of ocean life. The early ocean lifein Pacific salmon may be the most critical period. Inorder to develop the demography of juvenile salmon,
we should concentrate the following research items:# Seasonal distribution and migration of juvenile
salmon# Population size and survival estimates of juvenile
salmon# Feeding competition and growth change of juvenile
salmon# Primary production and food animals
Winter salmon studies in the North Pacific Ocean
Recent winter salmon studies indicate that Japanesechum salmon stay in the western North Pacific Ocean
during the first winter, while in the Gulf of Alaska during the following winters. Biochemical analysis suggests that winter is one of the critical periods for salmon
population. To elucidate impacts of winter ocean environments on salmon survivals, future research issuesare:# Winter distribution and habitat environment ofReferences
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海洋における 日本のサケ 属 魚類に関する研究 : 総説と将来の 課題
浦和茂彦 ・石田行止・福者 雅卓

NPAFC

科学計画のもとに 1993‑2000

年に行われたサ・マス資源に 関する日本の 研究戊果を要約すると共に，サケ・マス類の持続的資源管理に 必要な将来の研究課題を 提案した．近年発達した系群識別技術と海洋での資源調査により 口水系サケの 海洋分布にケ関する新たな 情報が得られ ，日本系サケは 海洋生活

初期にオホーツク 海に生息し，北西太平洋で最初の越冬をした後，次の夏までにベーリング 海へ回遊す
ることがわかった． 海洋生活初期の 死亡が高いこと
が沿岸調査により ボ峻されたが，死亡要因は 十分解
明されていない．ベーリング

海で日本系サケの 成艮

速度が減少し 結果的に成熟年齢が 高くなったこと
が鱗相 分析により推定された．北太平洋亜寒帯での長期モニタリング 調査によると 大型動物プランクト
ン とカラフトマスのバイオマスには負の関係がみれれた． 同様の調査がベーリング 海でも必、
要であ ろう ．

越冬期のサケ・マス 類の筋肉申における 脂肪含量が極端に低いことから ，サケ・マス類にとって冬期に生残することは 非常に困難であ ることが示唆された．
将来の研究課題として ，(1)

オホーツク海におけるサケ・マス幼魚調査， □ ) 北尺平洋における 冬期サケ・マス調査， (3) ベーリング海におけるサケ・マ
ス 類生態調査， (4) 主要なサケ・マス 類系 群の モ二
タリングが上 @ヂ られる

Urawa - Bibliography of salmonids in 1999

31

Appendix 1. A contribution of Japanese salmon research to clarify questions identified in the NPAFC Science Plan.
Questions

References

1. Life History of Salmonids
1.1 Spatial Distribution
When and where do salmon concentrate in highest density?
Does sea surface temperature regulate salmon distribution?
Does interaction between different species and different stocks affect the distribution?
Are juvenile salmon distributed in oceanographically protected waters?
Is salmon distribution related to distribution of predators or competitors?
Do oceanographic conditions and productivity of food organisms affect salmonid distribution, and is there a trend in this influence at various periods during their life
history?
1.2 Growth and Maturity
When and where does growth variation of salmon occur?
Which life history stages is the most important for determining growth variation (juvenile, immature, maturing, or returning adult)?
What factors (salmon density, sea temperature, food resources, competitors, predators) affect growth vanation?
How does growth variation affect maturation and reproduction?
1.3 Feeding Ecology (Diet)
Is salmon diet species-specific'?
Is the composition of food specific to salmon species?
Does salmon diet change by salmon density'?
Does salmon diet reflect the abundance of food items?
Does salmon diet affect salmon growth, and survival?
Does salmon diet relate to salmon distribution and population numbers?
Does salmon abundance regulate food supply or does food supply regulate salmon
abundance?

Azumaya et al. 1999; Urawa 2000
Ueno 1998
Azumaya et al. 1999
Ueno 1998
Azumaya et al. 1999

Ishidaet al. 1993,1998; Kaeriyama 1998
Kaeriyama 1998
Kaeriyama 1998

Ishida and Davis 1999
Tadokoro et al. 1996
Suzuki and Fukuwaka 1998

Shiomoto et al. 1999

2. Population Dynamics
2.1 Abundance, Monitoring, and Forecasting

Does salmon abundance on the high seas provide a good estimate of adult returns?
Where and When?
What are the most important and effective monitoring items?
How can carrying capacity be estimated?
What determines changes in carrying capacity of salmon?
How can a strategy of forecasting be determined for the commercial returns in various populations?
What factors are related to changes in carrying capacity?
Do changes in carrying capacity alter salmon abundance and production?
What are the environmental variables that control carrying capacity?
Does carrying capacity change with changing climate? If so, by what mechanism'?
Can the Ricker model be used to estimate the carrying capacity of salmon?
2.2 Mortality
What factors are related to salmon survival (return rate)?
Do predators and/or competitors affect salmon survival?
What is the relationship among starvation, disease, temperature, and mortality?
Does over-wintering affect mortality?
Which period is critical for determining the abundance of the various species, populations, and age-groups?
2.3 Stock Interaction
Does stock interaction affect growth, distribution, diet, and reproduction?

Ishida and Ito 1998

Ishida et al. 1995

Azumaya et al. I998
Nagasawa 1998a, 1998b
Urawa 1996a, 1996b;Nomura et al. 1999
Nomura et al. 1999; Nagasawa 2000
Fukuwaka and Suzuki 1998b
Kawamura et al. 1998; Tamura et al. 1999

3 1? . 2 %&;EE-B'c 9 -68% Bull. Natl. Salmon Resources Center, No. 3. 2000

38

Appendix 1. (continued)
Questions
2.4 Stock Identification
Are baseline data (genetic, parasite, etc.) stable?
What salmon stocks are identifiable with each of the various techniqucs?
How accurate and precise are the stock identification estimates?
3. Salmon Habitat and Ecosystem
3.1 Physical-biological Interaction and Productivity
Does the Aleutian Low affect production?
Does salmon abundance affect productivity?
Is productivity in the western, central. and eastern North Pacific different?
3.2 Climate Change Effects
Does sea ice affect salmon production?
What are the cffects on southern distribution limits of salmon?
What are the effects on food supply and predators of salmon'?
In what way do meteorological changes affeci productivity? Is there a trend?
3.3 Regime Effects (Temporal and Spatial)
How can regime shifts be detected?
Are ancient salmon otoliths and scales available for retrospective analyses?
Are regime shifts reflected in hard parts (scales, otoliths, etc.)'!
Are there other indicators (paramcters) that permit tracking the changes'!

References

Urawa et al. 1998a
Urawa et al. 200021
Niita and Ueno 1YYY: Urawaet al. 200021

Kaeriyama 1997
Shiomoto et al. 1997
Shiomoto et al 1999, Nagasawa 2000
Nagasawa ct al. 2000
Ueno eL al . 1999
Nagasawa 1998c