No.1 No.2 No.3
No.4 No.5 No.6
- Bull. National Salmon
Resources Center 8, 2006
- Geographical Distribution and Seasonal Occurrence of Myxobolus kisutchi
(Myxozoa: Myxosporea) in the Central Nerve Tissues of Chinook and Coho Salmon in
the Columbia River and Its Vicinities. Shigehiko Urawa, Lee Harrell, Conrad. W.
Mahnken, and Katherine Myers. pp. 1-7. (1,193KB)
myxosporean parasite Myxobolous kisutchi Yasutake and Wood, 1957 infected
in the medulla oblongata and spinal cord of Chinook (Oncorhynchus tshawytscha)
and coho (O. kisutch) salmon. The parasite occurred in restricted
areas of the Columbia River basin and its vicinities (Minter Creek and Chehalis
River) in Washington, but not in other major Chinook salmon populations in North
America and Asia. The prevalence of parasite spores in Chinook salmon smolts
migrating down through the McNary Dam in the Columbia River was 20-37% in May
(spring type),dropped to 1.3%-1.7% in June(mainly fall type),and increased again
to 29% in July (fall type). The prevalence of spores in adult Chinook salmon
captured in the lower mainstream of The Columbia River was 43-65% for spring
runs, but lower (8-11%) for fall runs. Among juvenile Coho salmon reared at the
Minter Creek Hatchery, the spores of M.kisutchi first appeared in June,
and the prevalence increased to 97% in July, being sustained at almost 100%
until the smolt stage in the next spring. The parasite was redescrided based on
- Origins of Juvenile Chum Salmon caught in the Southwestern Okhotsk Sea
during the Fall of 2000. Shigehiko Urawa, Jiro Seki, Morihiko Kawana, Toshihiko
Saito, Penelope A. Crane, Lisa W. Seeb, Masa-aki Fukuwaka, and Elena Akinicheva.
stock identification (GSI) and thermal otolith marking techniques were used for
determining the stock origin of juvenile chum salmon (Oncorhynchus keta)
(age 0.0) caught in the southwestern Okhotsk sea (48-51°N,
in October 2000. The GSI results using an Asian baseline indicated that the
stock composition of juvenile chum salmon was 21% Japan, 22% Amur River, 25%
Sakhalin, and 31% northern Russia (Magadan/Kamchatka) stocks. Seven otolith
marked chum salmon (3.4%) were found among the samples. These marked fish were
released from the Bereznykovsky Hatchery (n=6) in Sakhalin and the Ozerky
Hatchery (n=1) in western Kamchatka. These results suggested that Russian stocks
were dominant among juvenile chum salmon in the sampling area in the fall of
- Seasonal Changes in the Total Lipid Content of Immature
Chum Salmon in the Bering Sea and North Pacific Ocean
during the Summer and Fall of 2002-2004. Tetsuichi Nomura, Shigehiko Urawa, Morihiko Kawana, Shunpei
Sato,Tomonori Azumaya, Masa-aki Fukuwaka, Kazuhiro Hida, Ayumi Nakajima, Tadayoshi Tojima, and Nancy D. Davis.
This study reports the total lipid
(TL) content in the white muscle of chum salmon by age group from fish caught in
the Bering Sea and North Pacific Ocean in summer (June-July) and fall
(September), 2002-2004. The TL was extracted from the muscle of 1,282 immature
chum salmon using chloroform and methanol and then measured gravimetrically. The
TL content of young fish (ocean age-.1) caught in the summer was significantly
lower than fish of the same age caught in the fall. The mean TL content of ocean
age-.1 fish caught during the summer of 2002, 2003, and 2004 was 1.8 % (n=48),
2.1% (n=89), and 2.4% (n=58), respectively. The mean TL content of ocean age-.1
chum salmon caught during the fall of 2002 and 2003 was 7.3% (n=180) and 5.2%
(n=198), respectively. Low lipid contents of young (ocean age-.1) chum salmon
caught during summer suggests this is a period when young fish grow at the
expense of lipid storage. High lipid content of fish caught in the fall suggests
this is a period when lipid is stored at the expense of growth, which likely
promotes survival of the fish through the winter. Total lipid content was
significantly and inversely correlated with moisture content, which together
with lipid content totaled about 80% of the white muscle. We recommend continued
monitoring seasonal and agespecific lipid content of chum salmon during their
oceanic migrations as an indicator of their growth potential and body condition.
- Demand System Analysis of Wholesale Price of Salmon
in Japanese Market. Ikutaro Shimiz. pp. 27-35. (In Japanese with English summary)(169KB)
The price elasticity of demand in
Japanese salmon market was measured by Almost Ideal Demand System-Error
Correction Model analysis to clarify the substitute and complement relations
among monthly wholesale prices of salmon between 1996 and 2003. Commercial
salmon circulated in central wholesale markets in ten consuming areas in Japan
are classified statistically into six items: fresh "Sake", domestic frozen
"Sake", salted "Sake", frozen "Masu", salted "Masu" and import frozen "Sake".
Sign conditions of the own price elasticity of all items in Japanese salmon
market supported the Marshallian low of demand that the demand quantity
decreased when the price of goods increased. The value of own price elasticity
of domestic frozen "Sake" was less than 1 and domestic frozen "Sake" showed a
characteristic of necessary goods. On the other hand, the value of cross price
elasticity of salted "Masu" was bigger than 1 and there were many substitute
goods of salted "Masu". That accounted for the value of own price elasticity of
salted "Masu" was bigger than 1. It was suggested that the price elasticity of
supply of fresh "Sake" influenced the price elasticity of demand of salted
"Sake" and the demand of fresh "Sake" and salted "Sake" of autumn salmon was
stabilized by the increase of price elasticity of supply.
Temporal Changes of Vertical Distribution of Zooplankton Communities during
Spring and Early Summer in the Nemuro Strait Coastal Waters Off Shibetsu,
Eastern Hokkaido. Seki Jiro, Toshihiko Saito, and Ikutaro Shimizu. pp. 37-46. (In
Japanese with English summary) (2,019KB)
This paper reported the temporal
changes of zooplankton biomass, characteristics of their distribution pattern
and succession of items in the coastal waters off Shibetsu, eastern Hokkaido.
Zooplanktons were collected with simultaneously horizontal tow nets form 2-6
different layers from May to mid July in 2001 and 2002. The zooplankton wet
weight (mg/m3) in 2001 was 2 to 16 times higher than that in 2002. The number of
zooplanktons in 2001 was always superior that in 2002. The zooplankton
compositions were categorized clearly between 2001 and 2002 by principal
component analysis. The cold living type zooplanktons (Acartia
Pseudocalanus spp.) were dominant from May to mid
or late June, while they were replaced by the warm living ones (Evadne
Fritillaria sp.) in late June to July. The change
of these dominated items in 2001 was 10 days later than that in 2002. Three
dominated items of A. longiremis,
and E. nordmanni had
different distribution pattern of vertically and horizontally.
- Bibliography of Salmonids published in Japan (19): 2004. Shigehiko Urawa.
- Bull. National Salmon
Resources Center 7, 2005
- Study of Characteristic of Feeding Habitat of Juvenile Chum Salmon
and Their Food Environment in the Pacific Coastal Waters, Central Part of Hokkaido. Jiro Seki.
(In Japanese with English summary)(4,295KB)
Abstract-This study is to
investigate the ecological characteristics of juvenile chum salmon and the
behavior of zooplankton during spring and early summer in the Pacific coastal
waters off the coast of Hokkaido. The coastal waters were covered with the
Coastal-Oyashio in early spring, and surface temperatures increased to 10℃
in early-mid June and above 13℃ in July. Juvenile chum
salmon scattered extensively at surface temperature 8℃
, and the fish abundances decreased when over 13℃ .
Instantaneous growth rates of fish were -0.0025 to 0.0138 in the coastal waters.
Zooplankton biomass peaked from late May to early June. Cold-water zooplankton
species dominated at all times. Four types of diel vertical migrations of
zooplankton were recognized. The mean distances between peaks of zooplankton
number were almost 80 to 140 m. Zooplankton body lengths decreased in later
periods. Due to the increased water temperature, zooplankton biomass and growth
rate of fish in this area, it is desirable for fish to be released at fork
length 56 mm at a surface temperature of 5℃.
- Economic Factors Effecting Salmon Fisheries in Japan. Ikutaro Shimizu.
Salmon fisheries in Japan are
facing a serious crisis and are being pressed to enact structural reforms.
Though there has been a decline in high seas salmon fisheries, the total amount
of salmon catches has increased year after year with a success of salmon
enhancement. Salmon markets in Japan have consequently been globalized, and the
price of domestic salmon in wholesale markets has dropped. In this paper, I
described the fluctuation of salmon prices in the landing markets in Hokkaido in
order to make clear the factors of price change, from both the short-term and
long-term standpoints. Factors regarding the price formation of salmon in the
wholesale market in Japan were analyzed by the econometric method. The wholesale
price of fresh salmon fell when the inventory of frozen salmon or imported fresh
salmon increased, and also the prices of fresh salmon have dropped when the
inventory of salted salmon roe and fresh salmon increased in recent years. Since
there was an increase in the amount of imported fresh salmon produced by salmon
aquaculture in winter, there was an increase in the inventory of fresh salmon.
In order to reduce inventory and stabilize the wholesale price, it is necessary
to expand the market for domestic salmon by maintaining its freshness,
developing new processed food, and ensuring its safety. Furthermore, analysis of
the trend of consumers’tastes for salmon and a grasp of consumers’needs will be
important for the supply side, such as Fishermen’s Cooperatives and related
organizations engaged in enhancement of salmon resources.
- Synergistic Effects of Thyroxine and Cortisol on the Seawater
Tolerance of Sockeye Salmon (Oncorhynchus nerka).
Masatoshi Ban. pp. 117-121.
(T4) and cortisol (F) were investigated for their synergistic effects on the
seawater tolerance of sockeye salmon (Oncorhynchus nerka) at Chitose
Hatchery, Hokkaido, Japan. Juvenile sockeye salmon were separated into four
groups (an untreated control, F, T4, and F and T4 in combination). Each
treatment group received hormone orally via diet supplementation at a dose of 10μg
per body weight (1 g) for two weeks. The untreated control group was fed only
the commercial diet. Seawater tolerance after hormonal treatment was estimated
by gill Na+,K+-ATPase activity (gill-ATPase) and plasma sodium concentration
(plasma-Na) following seawater transfer for 24 h. Furthermore, chloride cells
observed in the primary gill lamellae were assessed immunohistochemically. The
F-treated group showed a two-fold higher level of gill-ATPase and a
significantly lower plasma-Na than those of T4-treated and control groups. A
treatment with F and T4 combination had larger effects compared with a single
treatment of either F or T4. The number of chloride cells observed in the
F-treated group increased about two-fold more than in T4-treated and control
groups. These results suggest that cortisol promotes seawater tolerance
including activation of Na+,K+-ATPase accompanied with differentiation of
chloride cells. F and T4 have a synergistic effect in promoting seawater
tolerance in sockeye salmon.
- Bibliography of Salmonids published in Japan (18): 2003. Shigehiko Urawa.
- Bull. National Salmon
Resources Center 6, 2004
- Effects of Import and Inventory Amounts of Salmon on
Wholesale Price Function of Fresh Salmon in Japan. Ikutaro Shimizu. pp. 1-11. (In Japanese with English summary)(364KB)
Relationships between annual variation in the wholesale price of fresh salmon
and annual variation in the fishery production, import and inventory amounts of
salmon were analyzed by econometric methods to elucidate factors on wholesale
price function of salmon caught in Japan. The wholesale price of fresh salmon
was affected not only by fishery production of fresh salmon but also by import
and inventory amounts of fresh salmon in sync. The wholesale price of fresh
salmon decreased when inventory or import amount of fresh salmon increased, and
it also decreased when inventory amount of salted salmon roe and fishery
production of fresh salmon increased. An increase in the inventory amount of
fresh salmon in recent years was caused by mass import of farmed fresh salmon in
- Participation of Thyroxine in Smoltification of
Sockeye Salmon (Oncorhynchus nerka).
Masatoshi Ban. pp. 13-21. (127KB)
In order to
describe effects of thyroxine on smoltification of sockeye salmon (Oncorhynchus
nerka), seasonal patterns of smoltification were investigated. Factors
assessed include seawater tolerance, fin margin blackening, condition factor and
changes in plasma thyroxine concentration (plasma-T4). Juvenile sockeye salmon
reared under natural photoperiod gradually developed seawater tolerance from
January to May in two consecutive years (1991 and 1992). Fin margin blackening
and decreases in condition factor were observed in May. Plasma-T4 showed
significant elevations in concert with an increase in photoperiod from January
to March, followed by rapid decreases. Temporary elevation of plasma-T4 was also
induced by switchover of artificial photoperiod from short day (8/16 h
light/dark cycle) to long day (16/8 h). With this hormonal surge, fish developed
seawater tolerance and transformed to smolt out-of-season. However, a single
administration of thyroxine supplemented in a commercial diet for twenty days
did not induce seawater tolerance. These results suggest that thyroxine has a
role as an enhancer of smoltification in sockeye salmon and operates at an early
phase of this process indirectly.
- Bibliography of Salmonids published in Japan (17): 2002. Shigehiko Urawa.
- Bull. National Salmon
Resources Center 5, 2002
Investigation of the Transmission Stage of the Microsporidian Kabatana
takedai in Salmonids. Isao Fujiyama, Shigehiko Urawa, Hiroshi Yokoyama, and
Kazuo Ogawa. pp. 1-6. (96KB)
In order to
examine the transmission route of the microsporidian Kabatana takedai to
salmonid fish, experimental challenges to rainbow trout (Oncorhynchus mykiss)
was tried by three methods (oral intubation, intraperitoneal injection, and
immersion) using K. takedai mature spores isolated from infected fish.
However, the experimental infection was not successful by any methods. To
estimate the size of the transmission stage, masu salmon (O. masou) were
exposed to infectious river water filtered by three sets of nylon meshes with
openings of 300μm, 100μm and 40μm. As a result, K. takedai infections
occurred among all fish groups. These results suggest that the transmission of
K. takedai to fish is not due to the direct spore transmission, but might
due to the unknown infectious stage smaller than 40μm.
- Infection of Salmincola californiensis (Copepoda: Lernaeopodidae)
on Juvenile Masu Salmon (Oncorhynchus masou)
from a Stream in Hokkaido.
Kazuya Nagasawa, and Shigehiko Urawa. pp. 7-12. (389KB)
parasitic copepod Salmincola californiensis infected 18 (94.7%) of 19
masu salmon juveniles collected from the Bekanbe-ushi River in eastern Hokkaido
in the springs of 1982 and 1983, while the parasite was not found on
white-spotted charr nor Sakhalin taimen from the river. The mean intensity of
the parasite on masu salmon was 10.3 (intensity range, 1-26). There was a
significant increase in intensity of infection as the size of the host fish
increased. Most of the copepods found were mature adult females, followed by
chalimus larvae and young adult females. The mature adult females were attached
almost exclusively to the gills and the inner surface of the operculum. The
chalimus larvae were found on the gills. The distal ends of the gill filaments
attached by adult females were damaged, but there were no significant
correlations between condition factor and intensity of infection. This paper is
the first confirmed record of S. californiensis from Hokkaido.
- Factors on Short- and Long- Term Changes in Wholesale Prices
of Salmon in Hokkaido. Ikutaro Shimizu. pp. 13-19. (In Japanese with English summary)(277KB)
short-term and long-term changes in the wholesale price of salmon at the main
landing ports in Hokkaido were examined. The wholesale price increased in the
year when the landing amount of salmon decreased from the previous year. A
negative correlation between the landing amount and prices of salmon at the
landing port indicated that the prices of salmon were influenced by the landing
amount. It was also clarified that the import amount of salmon influenced the
wholesale price of salmon. The wholesale price of salmon in the entire Hokkaido
showed the long-term variability depending on the amount of imported salmon, and
the wholesale price of salmon in the regions showed the short-term variability
depending on the amount of landed salmon.
- Diurnal Variations in the Upstream Migration of Adult Masu
Salmon (Oncorhynchus masou) in Rivers of Hokkaido
during the Spawning Season.
Hiroshi Mayama. pp. 21-26. (In Japanese with English summary)(262KB)
variations of adult masu salmon (Oncorhynchus masou) were observed at the
trapping sites in the lower reaches of the Sarubetsu River, a tributary of the
Tokachi River, and the Mena River, a tributary of the Shiribetsu River in
Hokkaido during the spawning season. Significant differences in daily movement
patterns were found between masu salmon and the other species of salmon, chum (O.
keta) and pink salmon (O. gorbuscha) under same environmental
conditions. It seems that upstream migration of masu salmon which select
spawning sites generally in the upper reaches of stream occurs mainly in daytime
to find out obstacles in rapids.
- Effects of Cortisol and Growth Hormone on the Seawater
Tolerance of Sockeye Salmon (Oncorhynchus nerka).
Masatoshi Ban. pp. 27-31. (99KB)
In order to determine hormonal effects on the seawater tolerance of sockeye
salmon (Oncorhynchus nerka), cortisol or growth hormone (GH) were
administered via intraperitoneal injection at 1 μg per body weight for two weeks
in March and May in the laboratory. In March, the gill Na+, K+-ATPase activity
of the cortisol group was 1.5-fold higher than that of the control group
injected only with saline. Plasma sodium concentrations 24 h after transfer to
seawater for the cortisol and GH groups declined to 164.3 mM and 153.5 mM,
respectively, while the control group had 191.1 mM. In May, however, the gill
Na+,K+-ATPase activity in all these treatments elevated to 16.8 - 17.1 μmols
Pi/mg pro/h and the plasma sodium concentrations decreased to 148.0 - 154.5mM.
Admin stration of cortisol and GH had no effect on seawater tolerance in May.
These results indicate that cortisol and GH are important hormones promoting
seawater tolerance in sockeye salmon, while effects of these hormones may vary
with administration time.
- Biological Characteristics of Fall-Run Chum Salmon
(Oncorhynchus keta) caught in the Lower Amur River. Kazumasa Ohkuma, Toshiya Suzuki, Kei Yurano,
Sergey F. Zolotukhin, and Victor G. Markovtsev. pp. 33-36. (112KB)
characteristics were examined for fall-run chum salmon (Oncorhynchus
keta) 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.
- Bibliography of Salmonids published in Japan (16): 2001.
pp. Shigehiko Urawa.
- Bull. National Salmon
Resources Center 4, 2001
- Effects of Handling Stress on Osmoregulation of JuvenileSockeye Salmon (Oncorhynchus
nerka) in Seawater. Masatoshi Ban. pp. 1-5. (143KB)
Effects of handling stress on
osmoregulatory ability of juvenile sockeye salmon (Oncorhynchus nerka)
were investigated to assess responses of fish sampled for physiological studies.
Yearling juveniles were initially reared in either fresh water (May) or natural
seawater (August), and subsequently separated into three treatment groups. For
each treatment, fish were placed in artificial seawater (33 ppt) using one of
three handling methods. Fish were either carefully transferred to the seawater
(Group 1), hung on a fishing hook and suspended in the seawater (Group 2), or
confined in a small net and dipped into the seawater (Group 3). Serum sodium
concentration and gill Na+,K+-ATPase activity were measured 4 hrs after transfer
of fish. In May and August, the serum sodium concentrations of Groups 2 and 3
fish were significantly higher than that of Group 1 fish, whereas there was no
significant difference in the gill Na+,K+-ATPase activity among three groups.
These results indicate that handling stress may disturb osmoregulatory ability
of fish in seawater without activating enzyme in the gills and that the serum
sodium concentration increases in a short period.
- Occurrence of Kabatana takedai (Microspora) in Juvenile Masu Salmon (Oncorhynchus
masou) reared at Varying Water Temperatures in a Hatchery. Shigehiko Urawa.
Infections with the microsporidian
parasite Kabatana takedai (Awakura, 1974) were monitored for juvenile
masu salmon (Oncorhynchus masou) held at various water temperatures
controlled using river and spring waters in the Chitose Hatchery, Hokkaido,
Japan. In the summer of 1999, the hatchery water became over 15℃
due to unusual increase of water temperature in the Chitose River. In
consequence, heavy microsporidian infections occurred among juvenile masu salmon
temporally transplanted from the Shiribetsu and Shizunai rivers, discontinuing
back releases of these fish into their native rivers to prevent the parasite
diffusion. These juveniles (approximately 100,000 fish) were killed by the late
November. The present survey also indicated that the cyst formation of K.
takedai could occur at low temperatures less than 13℃.
A rearing experiment confirmed that the parasite cysts were residual within the
muscle and heart of hosts over 7 months.
- Variation in Lipid Content in the Muscle of Chum and Pink Salmon in the Gulf
of Alaska in May 1999. Tetsuichi Nomura, Katherine W. Myers, Christine M. Kondzela, James
M. Murphy, Hiromi Honma, and H. Richard Carlson. pp. 13-18. (259KB)
We report on a study of the total
lipid content (TL) of chum and pink salmon in the Gulf of Alaska in May 1999.
Chum and pink salmon were caught by surface trawl net in the Gulf of Alaska
during a spring cruise of the F/V Great Pacific. TL was extracted from
the muscle of 99 chum and 50 pink salmon by Folch's method using
chloroform/methanol and measured gravimetrically. A significant difference in
the total lipid content by ocean age was observed in chum salmon. Younger chum
salmon (ocean age-.1 and .2) had lower lipid content than older fish (ocean
age-.3 and .4). Mean TL in pink salmon was 2.6% in females and 2.7% in males.
Our results suggest that low lipid content, previously observed in high-seas
salmon during the winter season, is prolonged into the spring in young chum and
- Structural Factors on Changes in the Supply and Demand of Salmon in Japan.
Ikutaro Shimizu. pp. 19-29. (734KB)
Japanese salmon fishery is facing
a juncture of existence and is pressed for the improvement of a constitution.
The decline of high-seas salmon fisheries was taken and the import amount
increased rapidly. In addition, domestic salmon production by coastal set net
fisheries has increased with a success of salmon enhancement in Japan. Salmon
market has internationalized consequently, decreasing wholesale prices of
domestic salmon in Japan. Domestic salmon prices are determined by inventory and
import amounts and current salmon fishery production, and wholesale prices of
domestic salmon were influenced by prices of imported salmon. Though there are a
lot of consumption of salmon in the northern and eastern part of Japan, there
may be a capability of demand expansion in the western part of Japan. Freshness,
commodity-making, development of new markets for consumer and conservation of
food safety will be important for the stability of wholesale prices of domestic
- Bibliography of Salmonids published in Japan (15): 2000. Shigehiko Urawa.
- Bull. National Salmon
Resources Center 3, 2000
- Distribution and Biological Characters of Pink (Oncorhynchus gorbuscha)
and Masu Salmon
(0. masou) in the Sea of Japan. Kazumasa Ohkuma, Yukimasa Ishida, Oleg A. Rassadnikov,
and Viktor G. Markovtsev. pp. 1-10. (523KB)
Distribution and biological
characters of pink (Oncorhynchus gorbuscha) and masu salmon (O. masou)
in the Sea of Japan in spring were summarized based on the data obtained
from the research cruises carried out from 1993 to 1999. Though pink salmon
showed higher CPUEs within the 8-13℃ SSTrange, they
were caught even in lower temperature around 5ﾟC. In
contrast, masu salmon were caught only in 8-14℃ SST
range waters. The body size of pink salmon excluding the result in 1997 were
larger in the odd years and smaller in the even years. Though the sex ratio of
pink salmon were almost even, about 70% of total catch were female in masu
salmon. From the results of age determination, 64% of masu salmon were
identified as age 1.1 fish and 36% were age 2.1.
- Easternmost Record for Ocean Distribution of Masu Salmon (Oncorhynchus
masou). Kazumasa Ohkuma, Shigehiko Urawa, Yasuhiro Ueno, and Nancy D. Davis.
Masu salmon (Oncorhynchus masou)
was caught in the central North Pacific Ocean (46ﾟ00'
N, 180ﾟ00') on June 27,1998 during a high-seas
salmonid research cruise by the R/V Wukatuke maru. The species was
identified by morphological and genetic analyses. The capture location was far
to the east from the previously recorded catches of masu salmon in the North
Pacific Ocean (45-50ﾟN, 157-162ﾟE).The
masu salmon was a maturing male (age 1. 1), whose fork length was 540 mm and
body weight was 2,460 g. Considering the location and date of capture, it is
likely that the fish had strayed from its usual distribution and wandered far
eastwards to the mid Pacific Ocean.
- Natural Reproduction of Chum Salmon in the Horonai Stream:
Spatial Segregation of Redd Formation between Chum Salmon and Other Salmonids.
Toshihiko Saito. pp. 15-24. (In Japanese with English summary)(878KB)
Spawning migration and redd
formation of chum salmon (Oncorhynchus keta), masu salmon (O. masou),
white-spotted charr (Salvelinus leucomaenis), and brown trout (Salmo
trutta) were investigated in the Horonai Stream along the Pacific coast of
Hokkaido during the fall of 1998, in order to evaluate reproductive interactions
between straying chum salmon and other fall-spawning salmonids. Fish trapping
and redd observation revealed that their spawning timing was similar among four
salmonid species. However, the stream reaches where redds were constructed
differed between chum salmon and the other species. Of 24 redds of the latter,
23 concentrated on a similar spawning ground, within a 1.1 km stretch downstream
of a weir, although those of the former were limited to only three in the
sameground. Other chum redds (9 redds) were found further 0.7-1.3 km downstream
from the spawning ground, where no other species spawned except for one masu
salmon escaping from the latter ground. We found no difference in depth and
velocity for all redds among four species, indicating that their spawning
microhabitats were not determinants of their spawning ground choice. This study
demonstrated that spatial segregation of spawning might exist between chum
salmon and other fall-spawning salmonids in the Horoni Stream, even though the
reason was unknown.
Effects of Photoperiod and Water Temperature on Smoltification of Yearling
Sockeye Salmon (Oncorhynchus nerka). Masatoshi Ban. pp. 25-28. (286KB)
The effects of photoperiod and
water temperature on smoltification of yearling sockeye salmon (Oncorhynchus
nerka) were investigated. Yearling sockeye salmon separated into six
groups (A to F) were reared under artificial photoperiod conditions from January
to April. The photoperiods of groups A and D simulated natural day length.
Groups B and E and groups C and F were kept at 13 h and 15 h of daylight,
respectively. Throughout the experiment, groups A, B and C were supplied with
river water (3-5℃) and groups D, E and F were
supplied with well water (7-8℃). The serum sodium
concentration 24 h after transfer to seawater in groups C and F decreased from
196 mEq/l in January to nearly 160 mEq/l in April. The gill Na+,K+-ATPase
activity of groups E and F showed a much higher increase from nearly 3μmols
Pi/mg protein/h in January to 15 and 21
protein/h in April. Fin margin blackening was observed in 6% of fish in group E
and 45% of fish in group F in April. These results indicate that smoltification
of yearling sockeye salmon may be affected by increases in photoperiod and
higher water temperature accelerates the parr-smolt transformation.
- Japanese Salmon Research in the Ocean:A Review and Future Issues. Shigehiko
Urawa, Yukimasa Ishida, and Masa-aki Fukuwaka. pp. 29-38. (840KB)
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 biological monitoring in 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 the sustainable stock management of Pacific salmon.
- Bibliography of Salmonids published in Japan (14): 1999. Shigehiko Urawa.
- Bull. National Salmon
Resources Center 2, 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, Takayuki Shoji, Masa-aki
Fukuwaka, Kristen Munk, Katherine W. Myers, and Edward V.
Farley, Jr. pp. 1-8. (471KB)
We detected otolith thermal marks
induced by Alaskan hatcheries to determine the ocean
distribution and migration of Alaskan pink salmon
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ﾟW
and 165ﾟW) during June and July 1998.
Along the 145ﾟ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ﾟW
transect, four thermally marked fish were found (5.3%, n=76
fish), and their origins were AFK (n=1 fish), CCH (n=2 fish),
and WHN (n=1 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 in the timing
of homeward migrations. The recovery of four thermally marked
PWS hatchery fish in the Gulf of Alaska (47-50°N, 165ﾟW)
is a southwestward extension of the known ocean range of
maturing southcentral Alaskan pink salmon in summer.
Temporary Residence of Precocious Sockeye Salmon (Oncorhynchus
nerka) in the Ocean. Shigehiko Urawa, Masahide Kaeriyama.
Ten precocious males of sockeye
salmon (age 1.0, 190-220 mm in fork length) were captured in the
Bibi River of the Abira River system along the Pacific coast of
Hokkaido, Japan, during July and August 1994. Their origin was a
hatchery-reared sockeye salmon stock (84-146 mm in fork length)
released in the river in the middle May of the same year. Most
of precocious males captured in the river were infected with the
marine digenean parasites (Bruchyphallus crenatus and/or
Lecithaster gibbosus), indicating their ocean residence.
The scale patterns suggested that they rapidly grew in the ocean
for at least 2 months. This may be the first
report evidencing the seaward migration of yearling precocious
sockeye salmon and their temporary residence in the ocean
Seawater Tolerance of Lacustrine Sockeye Salmon (Oncorhynchus nerka)
from Lake Toya. Masatoshi Ban, Hiroyuki Haruna, and Hiroshi Ueda.
External changes and seawater
tolerance related to smoltification of yearling lacustrine
sockeye salmon (Oncorhynchus nerka) originating from Lake
Toya (LSS) were investigated monthly from March to July 1993.
Ocean-run sockeye salmon (OSS) originating from the Bibi River
were examined for comparison. As an external index of smolting,
dorsal and caudal fin margin blackening was observed in more
than 80% of LSS and OSS during May and June, while it was below
55% during other months. The serum sodium concentration of LSS
and OSS 24 h after transfer to seawater decreased below 165 mEq/L
from April to June and from April to May, respectively. The gill
Na+, K+-ATPase activity of both groups in fresh water showed a
rapid increase from March and reached the maximum level of about
18μmols Pi/mg pro/h in May, followed
by a gradual decrease. These results indicate that yearling LSS
smolt, like OSS, are maximally seawater tolerant in May.
Predation of Juvenile Masu Salmon (Oncorhynchus masou) and Brown Trout (Salmo trutta)
on Newly Emerged Masu Salmon Fry in the Chitose River. Hiroshi Mayama.
(In Japanese with English summary)(513KB)
Predation of piscivorous fishes on
masu salmon (Oncorhynchus masou) fry at the period of
emerging from the spawning redds in the upper reaches of the
Chitose River, Hokkaido, was monitored by stomach content
analysis. Thirty-six % of masu salmon juveniles (63-117 mm in
fork length (FL)) and 24% of brown trout (Salmo trutta )
(54-189 mm in FL) fed on masu salmon fry, with average of 1.4
and 2.6 fry per stomach, respectively. Brown trout included two
age groups, and an occurrence of fry (67%) in diet of 2-year-old
fish (≧129 mm in FL) was significantly
higher than that of smaller yearlings (12%). An estimated size
of masu salmon fry consumed was 16.7- 45.3% of the predator
length. Newly emerged masu salmon fry are much vulnerable to
predation, because they cohabit with the predators in deep and
slow-flowing areas without habitat segregation. The
establishment of effective stocking techniques to avoid
predation is an important issue to increase the survival of
hatchery-released masu salmon fry.
Estimation of Survival Rate of Juvenile Chum Salmon and Evaluation
of Salmon Ranching Practice
in Hokkaido, Japan. Kazutoshi Watanabe. pp. 29-37.
(In Japanese with English summary)(522KB)
Survival rate of juvenile chum
salmon (Oncorhynchus keta), released from five regions
around Hokkaido, was estimated by using the simple deterministic
model of survival process. The survival rates of juvenile in
each region were higher in the year classes after mid-1980's
than in those before mid-1960's. The return rates of adult
correspondingly changed with the survival rates. This means that
juvenile survival largely contributes the abundance of year
class and the adult return in chum salmon. Index of efficiency
of salmon enhancement practice (E) was derived from
relative number of juvenile released and that of adult
returning. E increased in different manner between
regions after the introduction of the program of "release fed
juvenile at the period of suitable environmental condition for
juvenile" in 1962. In the regions, where the return rates were
lower before the start of the program, E increased faster
and larger. Otherwise, increase in E was not so fast or
large in the regions of higher return rates. The program was
successful in enhancement of chum salmon stocks around Hokkaido,
as a whole.
Bibliography of Salmonids published in Japan (13): 1998. Shigehiko Urawa.
- Bull. National Salmon
Resources Center 1, 1998
Turbidity on Feeding Behavior of Juvenile Masu Salmon (Oncorhynchus
masou). Hiroshi Mayama. pp. 1-11. (In Japanese with English summary)(771KB)
Field surveys and laboratory
experiments were conducted to determine the effects of turbidity
on the feeding behavior of juvenile masu salmon (Oncorhynchus
masou) in running water.Feeding rate of newly emerged
juveniles collected in a stream of the Mena River, showing high
turbidity(28-67 nephelometric turbidity units, NTU), tended to
be declined compared to those at the lower turbidity levels (5-7
NTU), while no significant difference was found in yearling
juveniles between clear and turbid waters. Results from the
analysis of stomach content and drifting fauna indicate that
large yearling juveniles shifted their feeding sites from faster
waters to slower-flowing places near shore where many other
animals also might gathered during high water with high
turbidity, and took sufficient amount of food by foraging for
these animals. On the other hand, the feeding ability of
underyearling juveniles might be decreased in high turbid water,
because their main prey were limited to smaller size. Foraging
rates for artificial dry food and the percentage of fish feeding
at 5 levels of turbidity (0-105 NTU), using two types of
suspended sediment (white kaolin and red-clay), were reduced
significantly only in red-clay turbidity. Active feeding tended
to occur at the intermediate turbidity levels (13-29 NTU)
compared to the clear condition (<1NTU).
Diel Migration of Zooplankton and Feeding Behavior of
Juvenile Chum Salmon in the Central Pacific Coast of Hokkaido.
Jiro Seki, Ikutaro Shimizu. pp. 13-27. (In Japanese with English summary)(910KB)
In the Pacific coastal waters of
Hokkaido, zooplankton were collected with simultaneously
horizontal tow nets from 7 different layers on sunset,
mid-night, sunrise, and noon of May 14-15 and June 13-14, 1991.
In addition, distribution and feeding habits or juvenile chum
salmon were investigated in the same area from late May to early
July of 1987 and 1988. Chum salmon juveniles were mainly
distributed in the coastal waters less than 20 m in depth, and
fed mainly on Evadone nordmanni, Eucalanus bungii, Neocalanus
spp., Pseiidocalanus spp., Eurytemora headmanii,
Metridia pacifica, Acartia longiremis, Acartia tumida,
Vivalvia, Fritlllaria SP. and Oikopleuridae. Plankton net
samplings indicated that these cold water type zooplankton
species were predominated in May, and their density was 2-15
times higher than in June. Most zooplankton species showed diel
vertical migration, being most abundant between surface and 10 m
in depth in May. In June, however, zooplankton became most
abundant at layer of 30 m in depth, and the density of
zooplankton decreased remarkably near surface layers where
juvenile chum salmon might migrate for feeding. Despite at, the
feeding condition was successful in chum salmon juveniles which
were distributed in shallow waters (5-15 m in depth). The prey
organisms might be supplied to salmon juveniles in coastal
shallow waters by the limited vertical migration of zooplankton
and by up welling.
Detection of Infection Hematopoietic Necrosis Virus Using
RT-PCR Combined with Tissue Culture. Toko Yoshinaka, Yuuka Hori,
Akira Motonishi, Kazuhiko Kasai, Atsushi Yamamoto, Kunio Suzuki,
Mitsuo Ugazin, Tetsuichi Nomura, and Mamoru Yoshimizu. pp. 29-34. (In
Japanese with English summary)(704KB)
Direct RT-PCR, tissue culture and
RT-PCR combined with tissue culture were compared for the IHNV
inspection in juvenile masu (Oncorhynchus masou) and
sockeye salmon (O. nerka). The detection rate or
IHNV from artificially infected rainbow trout (O. mykiss)
was also compared by using tissue culture and RT-PCR combined
with tissue culture. IHNV-infected salmonid fish were detected
highly using RT-PCR combined with tissue culture. This method
restrained inhibition of IHNV RNA extraction, because IHNV was
replicated in the inoculated cells and inhibition of IHNV RNA
extraction was diluted. The RT-PCR combined with tissue culture
is a good method for the routine examination of IHNV.
A Status of Lepeophtheirus salmonis (Copepoda:
Caligidae) on Seawater-cultured Coho Salmon (Oncorhynchus
kisutch) and Rainbow Trout (O. mykiss) in Japan.
Shigehiko Urawa, Teiichi Kato, and Akira Kumagai. pp. 35-38. (301KB)
Infection levels of the salmon
louse Lepeophtheirus salmonis were examined for coho
salmon (Oncorhynchus kisutch) and rainbow trout (O.
mykiss) cultured in seawater net pens in northern Japan. The
prevalence of L. salmonis on coho salmon gradually
increased from 59.2% in late June to 84.6% in August when fish
were harvested, but the mean intensity remained less than 3.2
parasites per fish. The prevalence of parasite on rainbow trout
increased to 92% in November with a mean intensity of 4.1
parasites per fish. The low infection levels of L. salmonis
among seawater cultured salmonids in Japan may be largely
attributable to the complete single year class culture system
harvested within one year, and to relatively low susceptibility
or host fish to the parasite.
A Record of Adult Coho Salmon (Oncorhynchus kisutch)
strayed into the Chitose River. Motohiro Kikuchi, Shigehiko
Urawa, Kazumasa Ohkuma, and Masahide Kaeriyama. pp. 39-43. (In Japanese with
adult coho salmon (Oncorhynchus kisutch) was accidentally
caught in the Chitose River, Hokkaido on December 3, 1997. The
morphology and allozyme pattern (sMDH-B1,2) of the specimen were
described to compare with these of other Pacific salmon. The
scale pattern suggested that it was wild coho salmon male (age
1.1). The fish had an unusual body color, indicating pigment
Burst Swimming Speed of Chum Salmon Fry measured with a
Simple Water Tunnel Apparatus. Kazumasa Ohkuma, Shogo Sasaki,
Arimasa Wada, and Tadayoshi Tojima. pp. 45-48. (In Japanese with English
Burst swimming speed (∪/b)
of chum salmon (Oncorhynchus kela) fry were measured with
a simple water tunnel apparatus at 8℃.
Examined fish were reared in a pond (length, 30 m; width, 5.4 m:
depth, 0.4-0.45 m) of the Chitose Hatchery from March 5 to April
20, 1994. ∪b of fry was
measured individually in a 20 mm diameter acrylic test tube with
a 30 cm long swimming space. Burst swimming speed increased with
fish length (FL) and the relationship could be expressed as∪b
(cm/s)=2.36FL (mm)-26.23 (n= 142, r=0.720. p<0.001) for
the absolute value and as ∪b
(FL/s)=0.15FL (mm) +11.12 (n=142, r = 0.266, p< 0.01) for
the specific value. These positive relations, especially the
increase in the specific value suggests rapid development and
improvement of swimming ability during the fry stage.
Bibliography of Salmonids published in Japan (10): 1995.
Shigehiko Urawa. pp. 49-60.
Bibliography of Salmonids published in Japan (11): 1996.
Shigehiko Urawa. pp. 61-71.
Bibliography of Salmonids published in Japan (12): 1997.
Shigehiko Urawa. pp. 73-82.