27NOAA Technical Report NMFS 27

Proceedings of the Eleventh
U.S.-Japan Meeting on
Aquaculture,
Salmon Enhancement,
Tokyo, Japan,
October 19-20, 1982
Carl J. Sindermann (Editor)
Under the U.S.-Japan Cooperative Programin Natural Resources (UJNR)

Panel Chairmen:
CONRAD MAHNKEN - United States
NOBUHIKO HANAMURA - Japan

March 1985

U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Marine Fisheries Service

NOAA TECHNICAL REPORTS NMFS
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NOAA Technical Report NMFS 27

Proceed ings of the Eleventh
U.S.-Japan Meeting on
Aquaculture,
Salmon Enhancement,
Tokyo, Japan,
October 19-20, 1982
Carl J. Sindermann (Editor)

Under the U.S.-Japan Cooperative Programin Natural Resources (UJNR)March 1985

u.s. DEPARTMENT OF COMMERCE
Malcolm Baldrige, Secretary

National Oceanic and Atmospheric Administration
John V. Byrne, Administrator

National Marine Fisheries Service
William G. Gordon, Assistant Administrator for Fisheries

PREFACE
The United States and Japanese counterpart panels on aquaculture were formed in 1969 under the UnitedStates-Japan Cooperative Program in Natural Resources (UJNR). The panels currently include specialists
drawn from the federal departments most concerned with aquaculture. Charged with exploring and developing bilateral cooperation, the panels have focused their efforts on exchanging information related toaquaculture which could be of benefit to both countries.
The UJNR was started by a proposal made during the Third Cabinet-Level Meeting of the Joint UnitedStates-Japan Committee on Trade and Economic Affairs in January 1964. In addition to aquaculture, current subjects in the program are desalination of seawater, toxic microorganisms, air pollution, energy, forage
crops, national park management, mycoplasmosis, wind and seismic effects, protein resources, forestry, andseveral joint panels and committees in marine resources research, development, and utilization.
Accomplishments include: Increased communications and cooperation among technical specialists;
exchanges of information, data, and research findings; annual meetings of the panels, a policy coordinative
body; administrative staff meetings; exchanges of equipment, materials, and samples; several major
technical conferences; and beneficial effects on international relations.

Conrad Mahnken - United States
Nobuhiko Hanamura - Japan

ii

CONTENTS
Papers presented by U.S. panel members:
DICKHOFF, W. W., C. SULLIVAN, and C. V. W. MAHNKEN. Methods of measuring and controlling the parr to smolt transformation (smoltification) of juvenile salmon ....
FOX, A. C. The importance of the environment, stress, and disease relationship in aquaculture ..
GOULD, R. W., A. N. PALMISANO, So Do SMITH, C. V. W. MAHNKEN, W. S. ZAUGG, and E. F. PRENTICE. Seawater
acclimation of premigratory (presmolt) fall chinook salmon: A possible new management strategy?
HEARD, W. R. Chinook salmon fisheries and enhancement in Alaska: A 1982 overview .....
HERSHBERGER, W. K., and R. N. IWAMOTO. Systematic genetic selection and breeding in salmonid culture and enhancement programs ..
MONAN, G. E. Advances in tagging and tracking hatchery salmon ids: Coded wire tags, multiple-coded and miniature radio
tags, and the passi ve integrated transponder tag ..
ROGERS, D. E., and E. O. SALO. Trends in natural and hatchery production of chinook salmon o.
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Papers presented by Japanese panel members:
HIROI, O. Hatchery approaches in artificial chum salmon enhancement
IRIE, T. The migration and ecology of young salmon in early marine life.
KATO, M. Recent knowledge on europium marking technique for chum salmon
KOGANEZA WA, A., and M. SASAKI. Development of seawater net-cage culture and release of chum salmon
MA YAMA, H. Technical innovations in chum salmon enhancement with special reference to fry condition and timing of
release .....
MURAl, To, T. AKIYAMA, and T. NOSE. Nutritional studies for the development of formulated diet for salmon fry
SHIRAH ATA, S. Strategies in salmon farming in Japan ....
UEDA, K. An electrophysiological approach to the olfactory recognition of homestream waters in chum salmon .
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The National Marine Fisheries Service (NMFS) does not approve, recommend or endorse any proprietary product or proprietary material
mentioned in this publication. No reference shall be made to NMFS, or
to this publication furnished by NMFS, in any advertising or sales promotion which would indicate or imply that NMFS approves, recommends
or endorses any proprietary product or proprietary material mentioned
herein, or which has as its purpose an intent to cause directly or indirectly
the advertised product to be used or purchased because of this NMFS
publication.

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Statement of Eleventh Joint Meeting of the UJNR
Aquaculture Panel, Salmon Enhancement,
Tokyo, Japan, October 19-20, 1982
The Eleventh Joint Meeting of the UJNR Aquaculture Panel was held on October 19-20, 1982, atthe Shiba Yayoi Convention Hall in Tokyo, Japan. Dr. Nobuhiko Hanamura, Japanese Panel
Chairman, and Mr. Conrad Mahnken, U.S. Panel Chairman, presented welcoming addresses andopening greetings. Panel members, guests, and observers were introduced by the respective
chairmen.
The business meeting was chaired by Dr. Hanamura, and symposium moderators were Dr.
Hanamura, Mr. Mahnken, and Dr. Fujiya. Rapporteurs for the meeting were Mr. Ben Drucker and
Dr. Takeshi Murai.

I. Scienti.l'fs ExchanRt'
The Panel concluded that the scientist exchange program sponsored by the UJNR has been an effective means of advancing aquaculture science and the exchange of information between the twocountries. This program was continued between the Tenth and Eleventh UJNR meetings.
During this period:a). Six members of the U.S. Panel of the UJNR and eleven scientists as observers attended the
Eleventh UJNR Meeting.
b). Dr. Hiroshi Motoh, Central Laboratory of Marine Ecology Research Institute, visited theBrowns Ferry Biothermal Research Station in Athens, Alabama, the Environmental Protection
Agency Laboratory in Duluth, M innesotd, and NOAA's Northwest and Alaska Fisheries Center inSeattle, Washington. He also attended the International Symposium on the genus Chionecetes in
Anchorage, Alaska.
c). Dr. Susumu Ito, Director of the Aquaculture Center, Aomori Prefecture, visited a vallety oflaboratories, commercial growers, fish hatcheries, and research urganizations in the Pacific Northwest. He also attended the Annual Meeting of the North American Shellfish Association held in
Olympia. Washington.
d). Dr. Nagahisa Uki, Tohoku Regional Fisheries Research Laboratory, will visit a variety of
research agencies from 19 November to 18 December, 1982, to meet with U.S. scientists and exchange information on molluscan culture in general, but specifically on abalone culture.
e). In 1983. Dr. Isao Yano will visit the U.S to do research on reproductive physiology ofprawns, and arrangements for this visit will be made by the U.S. Panel members.
f). Efforts for M r. Osamu Fukuhara's visit to the U.S. in 1983 will be made by the JapanesePanel.
g). Arrangement for Dr. William Seaman's visit to Japan in \98~ will be made by the Japanese
PJnel.
h). Dr. Hanamura expressed his deep appreciation for the kind arrangements provided for theJapanese scientists by the U.S. side at the Tenth Joint Meeting.
2. Literature Exchange
For the period 1981-82, the U.S. Panel sent to the Japanese Panel 107 scientific papers. During
this same period, the Japanese Panel sent to the U.S. Panel 78 scientific papers.
Proceedings of the symposium "Seaweed Aquaculture," which was held in 1977, was publishedin 1981 as a Technical Report of the National Marine Fisheries Service, NOAA, and 6 copies were
mailed earlier to the Japanese Panel. An additional 20 copies have been sent, and 20 more copies
will be sent to the Japanese Panel in the near future.
In the future, 100 copies of each publication will be sent to the Chairman of the Japanese Panel.
Sixteen copies of the Annual Report on Japan's Fisheries (a Summary for Fiscal Year 1981)
were presented to the U.S. Panel members.
This program has been very useful for both countries and should be continued.
3. Cooperative Studies
The discussion concentrated on two elements: I) ongoing programs and 2) suggested new programs.
Ongoing Programs
a. ReRistry of Marine Path%/?I'
By combining the talents of the United States in detection of disease in wild stocks of fishes, withthat of the Japanese for recognition of disease in cultured fishes, an opportunity existed for the

UJNR to develop a registry of marine pathology. To that end, a collection of slides from Japan andthe United States is being assembled by Drs. Murchelano and Matsusato which will be available toall researchers. The achievement of this goal is nearly complete, and hopefully will be completed by
the Twelfth UJNR Meeting.
b. Disease Resistance of u.s. Oysters in Japan
Strains of disease resistant oysters have been sent to Japan and comparisons have been madewith cultured populations. The results have been sent to the United States, and the program was terminated with success.
c. Abalone Culture
Dr. Uki, Tohoku Regional Fisheries Research Laboratory, will be visiting the United States during November-December 1982. At that time he will discuss with U.S. workers the status of abalone
culture. A determination will be made at the Twelfth UJNR Meeting whether or not to start thiscooperative program.
Suggested New Programs
The United States proposed a study entitled "Sea Ranching of Western Pacific Pink and Chum
Salmon in the Western Atlantic." The purpose will be to determine the best donor storks for transplantation to the Western Atlantic (coast of New England). The approach would be to obtain stocksof Asian origin from Japan and North America (controls). These stocks would be reared, released,
and recaptured in Maine.
Also, Japan is interested in the transplantation of North American stocks and will develop acooperative study with the United States. Details of the project will be developed between the
United States and Japan by the next meeting.
As a test shipment, approximately 350,000 chum salmon eggs from stock in Japan will be shipped in the fall of 1982 to the United States. This transplantation project is being funded by the National Science Foundation which will enhallce the credibility of the program and allow the UnitedStates to pay all costs of the transplantation experiment in New England.
After consideration of the results of the test shipment and development of a plan, the newly proposed project should be adopted at the Twelfth Meeting.

4. Second Five- Year Plan
For the second five-year plan, a modification was proposed and accepted as follows:Year 2 (1983)
Year 3 (1984)
Year 4 (1985)
Year 5 (1986)

U.S.A. Reproduction/Maturation/Seed production
Japan Environmental quality in aquaculture systems
U.S.A. Aquaculture engineering
Japan Marine ranching

5. Publications
The slow progress in publishing papers presented at past UJNR meetings is a matter of concern toboth the U.S. and Japanese panels. At the Tenth Annual UJNR Meeting in Delaware last October,the panel made two decisions that should speed the process of publication: I) all manuscripts must
be presented to the panel chairman at the time of presentation at the Joint Meeting, and 2) the U.S.
side would publish all annual proceeding as NOAA Technical Reports. Progress since last Octoberin publishing the results of past meetings is as follows:a. Proceedings of the Sixth U.S.-Japan Meeting (1977) have been published.
b. In September, the U.S. Chairman received the four Japanese papers delivered at the Seventh
U.S.-Japan Meeting held in Tokyo, Japan, in May 1978 (marine finfish culture). These will be
combined with the U.S. papers and submitted to the NOAA editorial office within the next 2
months.
c. Proceedings of the Eighth U.S.-Japan Meeting held in Bellingham, Washington, in October
1979 (freshwater finfish culture) have been edited, galley proofs approved, and will be published asa NOAA Technical Report in November 1982.
d. Papers presented at the Ninth U.S.-Japan Meeting held in Kyoto, Japan, in May 1980 (shrimp
culture) were received by the U.S. Panel Chairman in September. These seven papers will be combined with the papers from the Tenth U.S.-Japan Meeting held in Rehoboth, Delaware, in October
1981 (molluscan culture), and will be submitted to NOAA for publication by early spring, 1983.
e. Papers from the Eleventh U.S.-Japan Meeting on Aquaculture, Tokyo, 1982 (salmon enhancement) will be edited and submitted for publication to NOAA by late winter, 1982. Because of theimportance of this subject matter, the papers will be published in both Japanese and English, with
the U.S. responsible for the English version and the Japanese Panel responsible for publishing theversion in Japanese.

2

6. Other Matters
The United States side proposed a study for the "Experimental Transplantation of Japanese
Scallops (Patinopectin yessoensis) to Puget Sound." The purpose would be to determine growth andsurvival of scallops. A shipment of a small number of scallops will be made to be brought back to
the United States in October 1982 for disease certification. After being certified, additional live
scallops will be imported for experimental purposes in the winter of 1982 and placed in a variety of
Puget Sound environments to determine their adaptability. The number involved would be about
1,600 scallops at 2.5 g each. The scallops should never have resided on the sea floor.
The Japanese side approved this experimental planting and will have the juveniles and several
adults ready to be taken back to the United States at the end of the field trip. It was requested that
the Science Counselor/Fisheries Attache of the U.S. Embassy, formally request the subsequent
winter shipment from the Japanese Fisheries Agency.
7. Field Trip
The schedule of the field trip was announced by Dr. Nose, and Dr. Hanamura thanked Drs.
Kobayashi and Koganezawa for their cooperation for the field trip.
8. Next Joint Meeting
As the theme of the twelfth Meeting has been changed, details of the schedule for that meeting
will be decided in the near future.
Respectfully submitted
Conrad Mahnken - United States
Nobuhiko Hanamura - Japan

3

Methods of Measuring and Controlling the Parr to
Smolt Transformation (Smoltification)of Juvenile Salmon
WALTON W. DICKHOFF,I CRAIG SULLIVAN,2 and CONRAD V. W. MAHNKEN3

INTRODUCTION

factors other than the physiological readiness of the fish forseaward migration or for seawater entry. In those cases where thedevelopment (degree of smoltification) has been considered, thecriteria used most often have been body coloration (silvering) or
size. Recent studies have indicated that these criteria are imprecise (Gorbman et al. 1982; Folmar et al. 1982). Furthermore, itis evident that smoltification can be abnormal when fish areraised under artificial conditions (Bern 1978; Nishioka et al.
1982). During the last 10 yr, research on developing methods forthe precise determination of the progress of smoltification has
provided many measurements of physiologic change which could
be useful for indicating smolt development (smolt quality).
Among these methods three have been applied most widely:
Seawater challenge, gill Na'-K' ATPase activity, and plasma
thyroxine (T 4) concentration.

In net-pen culture and hatchery enhancement of salmonid
fishes it is important that reliable methods are available tomeasure the parr to smolt transformation of anadromous
salmon ids, since incompletely developed fish may die or not growwhen they enter seawater. There are many methods which may be
useful for the measurement of smoltification; however, threemethods have been used most widely: Seawater challenge, gill
Na+-K+ adenosinetriphosphatase (ATPase) activity, and plasma
levels of the hormone thyroxine (T 4 ). Smoltification can bedivided into two broad physiological processes: Osmoion regulation and metamorphic development. Seawater challengemeasures osmo-ionregulation, while monitoring plasma levels of
T 4 provides information on metamorphic development. Gill
ATPase activity measurements may be an indicator of both
osmoregulation and development. Studies on smoltification using
all three methods simultaneously suggest that smoltification of a
population of salmon may be synchronous or asynchronous. For
example, maximal osmoregulatory performance as measured byseawater challenge may occur at a time when gill ATPase activity
is low. Therefore, measurement of smoltification of salmon inaquaculture operations should use at least two of the methods.
Smoltification is naturally controlled by changes in photoperiod
and temperature. Artificial control of these environmental conditions in order to regulate the rate or completeness of smoltificationis possible. Alternatively, smoltification may be controlled bytreating fish with hormones. Experiments using thyroid hormonesin the diet of salmon undergoing smoltification have suggested
that some aspects of smoltification may be controlled in this manner Thyroid hormone in the food stimulates morphologicalchanges and growth, among other aspects; but this hormonal treatment may not increase the fish's ability to regulate its blood ionlevels when the fish enters seawater. Hormonal treatment procedures for increasing or accelerating osmoregulatory abilities ofsmoltifying salmon will not be available until more is known
about the physiology of osmoregulation. Additional studies onother methods of hormonal control of smoltification are needed.

Seawater Challenge
The seawater (SW) challenge test of Clarke and Blackburn(1977, 1978) measures the hypo-osmoregulatory ability of fishtransferred from freshwater (FW) directly into SW. Analysis of
the blood plasma Na+ concentration of the transferred fish indicated that highest Na' levels are attained 24 h after SW entry.
Thus, in typical application of the test, blood levels of Na' aremeasured at 24 h. Hatchery reared smolts may have plasma Na+
values in the range of 150 to 160 mmol at the 24-h timepoint(Clarke and Blackburn 1978). Other studies of hatchery smolts
have indicated that plasma Na+ may reach 170 mmol or higher 24
h after SW entry (Folmar and Dickhoff 1981). Perhaps it is best to
consider relative differences between control and treated groupsof fish subjected to SW challenge rather than assign some absolute
24-h Na+ value as the criterion for smolt status of individual
groups of fish.
The SW challenge test compares the degree to which fish arepreadapted to withstand the hyperosmotic stress of direct entry
into full-strength (30%) SW. In a sense this test is artificial in that
under natural conditions salmon ids may spend some time inbrackish water in the estuary at the end of their downstream
migration. Studies on chum salmon behavior suggest that adaptation to full-strength seawater requires at least one tidal change (6h) or longer during which the fry remain in the estuarine mixing
zone between fresh and saltwater where salinity is approximately
one-third that of SW (Iwata et al. 1982). In other studies it is apparent that adaptation to fUll-strength SW is facilitated if the fish
are adapted to dilute SW for differing times (Gould et al. 1985).
These results suggest that gradual adaptation to SW is an important component in the development of hypo-osmoregulatory ability in salmonids. Nonetheless, the SW challenge test provides
important information about the smolt status of anadromous
salmonids.

METHODS OF MEASURING
SMOLTIFICATION
The decision on when to release juvenile salmon from hatcheries or when to transfer them to seawater has often been based on'School of Fisheries. University of Washington, Seatlle. WA 98195 and Northwest and Alaska Fisheries Center.
'University of Washington. Seatlle, W A 98195.
'Northwest and Alaska Fisheries Center, National Marine Fisheries Service,
NOAA, 2725 Montlake Boulevard East, Seatlle, WA 98112.

5

Gill ATPase Activity

osmoregulatory potential of the fish, since the gill is an important
regulator of this process.

Measurements of the ouabain-sensitive Na+-K' ATPase of thegill reveal cycles of activity during smoltification in FW and increases in activity 4 to 5 d after the fish enter SW. The point ofhighest ATPase activity generally coincides with the peak insmoltification. The changes in ATPase activity in FW are potentially of greater value than those in SW because of their predictive
value. A significant correlation has been found between peak
ATPase activity and the number of returning adult salmon (Wahle
and Zaugg 1982). Changes in gill ATPase activity in fish in SW
occur after the fish's initial adaptation to SW. Patterns of gill
ATPase activity during smoltification are variable among genetic
stocks of fish and from year to year in a single stock (Zaugg
1982). These differences in ATPase pattern are probably due tovariations in rearing conditions. Some evidence indicates that thegreatest degree of smoltification based on survival in SW in agroup of fish occurs near the peak of their gill ATPase activity,
although sometimes smoltification is greatest during increasing or
decreasing ATPase activity (Zaugg 1982; Ewing and Birks 1982;
Mahnken et al. 1982).
The functional significance of the gill Na' - K' ATPase a(:tivity
has not been established clearly. Some have suggested that this enzyme activity represents the "sodium pump" that participates inblood ion regulation. However, the increased activity of this enzyme in FW is not closely associated with changes in blood levels
of ions in the fish. The increase in gill ATPase acti vity in fish
shortly after entering SW does not appear to be closely related to
the level of the enzyme activity in fish in FW. It is quite possible,then, that ATPase activity measured in FW is associated with an
enzyme activity that differs from the ATPase in fish in SW. The
direction of sodium transport by the gill in FW is opposite indirection from sodium transport in SW. Most likely the increased
ATPase activity measured in gills of fish in FW is a develop·
mental event associated with general changes in metabolic activity of the gill and not the "sodium pump." On the other hand, gill
ATPase activity in FW may be an important indicator of iono-

Thyroxine (T 4 Surge)
The surge in blood plasma concentration of T 4 that occurs inanadromous salmon ids is coincident with the time of smoltification. Studies on yearling salmon indicate that smoltification ismost complete in a population after about 80% of the T 4 surge hastranspired in FW (Folmar and Dickhoff 1981). Studies of T 4
surges during smoltification of salmon at various latitudes suggestthat T 4 peaks frequently may be associated with the time of the
new moon (Grau et al. 1981). Comparison of the T 4 surge in different genetic stocks during the same year and in the same stocks
over several years reveals a large variation in the patterns ofchange in plasma hormone concentration. This situation is similar
to that for gill ATPase changes and suggests that the T 4 surge issubject to many environmental and genetic influences.
The specific functions of thyroid hormones in salmon duringsmoltification are not completely understood, although thyroid
hormones have been implicated in many physiological, morphological, and behavioral processes in juvenile salmonids (Folmar
and Dickhoff 1980). Evidence is strongest for a role of the thyroid
in integumentary pigmentation (e.g., body silvering), growth,
metabolism, and some behavioral aspects such as salinity preference. The importance of thyroid hormones for osmoregulatory adjustments is still unsettled.

COMPARISON OF METHODS
Generalizing from studies on SW challenge, gill ATPase activities, and plasma T 4 surges in coho salmon, a hypothetical pattern of the relationships of these measures can be presented (Fig.
I). The plasma T 4 surge occurs just prior to the highest ATPase
values which, in turn, are coincident with the greatest hypoosmoregulatory ability. Data that support the hypothetical scheme
shown in Figure I have been presented (Folmar and Dickhoff

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Figure I.-Typical pallerns ofchan~e in blood plasma thyroxine (T.) concentration, gill Na'/K' ATPase activity,and plasma Na' levels 24 h after seawater challenge of yearling coho salmon during the parr to smolt transforma·
tion.

6

transferred directly into seawater net-pens. It may be advantageous to mimic some aspects of downstream migration in a
hatchery by exercising fish or exposing them to alternative
sources of freshwater when possible.

1981). On the other hand, different relative patterns of the threemeasured parameters have been observed. In other words, thepeak level of gill ATPase activity may occur at the same time oreven before the 1'4 surge. Furthermore, the timing of these two
events (1'4' ATPase) may appear to be unrelated to the development of hypo-osmoregulatory ability. Thus, the normal or appropriate pattern of l' 4' ATPase, and osmoregulatory performance remains open to question. Perhaps the occasional disparity in therelative patterns of the three indices of smoltification may be explained by the possibility that smolt development in a population
may not be synchronous. In other words, gill ATPase, 1'4 changes,
and hypo-osmoregulatory development may be controlled independently and may not be coordinated. The basis for asynchronous smoltification is not known at this time; however, it isprobably due to some aspects of artificial conditions for rearing
salmon ids in hatcheries. The effects of particular hatchery practices on various indices of the parr-smolt transformation are areas
for future studies.
A common assumption in studies of smoltification is that thisbiological transformation may come to completion within theconfines of a hatchery. There are several indications that downstream migration to the estuary and entry into seawater may be
important elements which complete the development of a true
smolt. We have already discussed the behavior of salmon fry inosmotic gradients in the estuary and the beneficial effects ofadapting fish to dilute seawater (see above). Additional examples
of modification of smolt indices after the fish's release from thehatchery but while still in the river may be given.
Gill ATPase activities of migrating coho salmon captured in theestuary have been shown to be higher than the values obtained
from the same population of fish maintained in the hatchery(Zaugg 1982). In chinook salmon nigrating in an artificial
stream, gill ATPase levels may occur earlier and reach values thatare higher than those obtained from the same stock of fish retained in the hatchery (Hart et al. 1981). These observations suggestthat maximal development of gill ATPase activity cannot berealized in fish maintained in a hatchery. The mechanism responsible for the elevated ATPase of migrating fish is not known but
may be related to reduced rearing density, better water quality, or
swimming exercise.

METHODS FOR CONTROLLINGSMOLTIFICATION
Smoltification is a developmental process which is the expression of an endogenous rhythm synchronized by photoperiod andaffected by temperature (Wagner 1974; Hoar 1976; Wedemeyer
et al. 1980; Eriksson and Lundqvist 1982). Methods for controlling or increasing smoltification would involve optimizing photoperiodic events and increasing temperature. While these methods
are simple and cost effective, alternative ways of controlling andenhancing smoltification are possible. The natural endogenous
cycle and the photoperiodic influence on that cycle undoubtedly
involve neuroendocrine and endocrine pathways. Other potentially effective, low cost methods for artificial control of smoltification would involve the use of those hormones which respond tophotoperiodic information to direct the physiological transformation of salmonid parr. Thyroid hormone administration would
appear to be an attractive method in this regard considering therelation between thyroid hormone surges and smoltification.
The most expedient method for administration of thyroid hormones to large numbers of salmon is incorporation of triiodothyronine (1'3) into the diet. Several studies on the effectiveness of
thyroid hormones for stimulation of growth of fish in general andsmoltification of salmon ids in particular have been published (seerecent reviews by Donaldson et al. 1979; Higgs et al. 1982;
McBride et al. 1982). The dosage of thyroid hormone is important, since large doses can cause growth anomalies or inhibition of
growth. The most effective dosages incorporated into the dietwhich do not produce undesirable side effects range from 4 to 20
mg/kg of 1'3' The optimal dose is dependent on several factors
including age of the fish, rearing temperature, ration, and species(Higgs et al. 1982).
In a study on the effectiveness of dietary 1'3 (12 mg/kg and 4
mg/kg) for stimulating smoltification of coho salmon, we wereable to control the proportion of smolts as determined by morphological criteria by regulating the dose of 1'3 (Fig. 2). In thisstudy of yearling coho salmon, 1'3 treatment was initiated on 10
January, 4 mo p~ior to the peried of smoltification. Treatment
with 1'3 was continued throughout the experiment. Plasma levelsof 1'4 increased earlier in the group treated with the highest doseof 1'3 (Fig. 3). Although these findings suggest stimulation ofsmoltification by 1'3' the results of a seawater challenge test
revealed no significant increase in hypo-osmoregulatory performance of the treated fish (Table 1). The results of this experimentindicate that some, but perhaps not all, aspects of smohification
may be stimulated by exogeilOusly administered thyroid hormone.
The development of methods for artificial control of some aspectsof smoltification (e.g., hypo-osmoregulatory ability) must await abetter understanding of the basic biological mechanisms regulating the parr to smolt transformation.

Similar studies of 1'4 levels in migrating fish have shown that
increases or decreases in blood hormone concentration can occur
after the fish are released from the hatchery (Dick hoff, unpublished). There is some basis for speculation on the mechanisms
responsible for modification of plasma 1'4 levels in migrating fish.
Coho salmon which are forced to swim at speeds up to two bodylengths per second show elevated plasma 1'4 levels within 90 minof forced exercise. Increased swimming in rapidly flowing streams
may be responsible for increases in 1'4 levels in migrating fish.
Another factor which may influence plasma 1'4 levels in migrantfish is the effect of novel freshwater (Dickhoff et al. 1982). Whensalmon are exposed to freshwater which differs from that in which
they are reared, a transient rise in plasma 1'4 occurs. This response
is seen only during smoltification and is due presumably to someas yet undefined chemical factor or balance of factors in the new
freshwater. Since thyroid hormones may be involved in homing
imprinting, this response to different freshwater may be a part of
the homing imprinting mechanism operative in downstream
migrating fish.
The modification in gill ATPase activity and plasma 1'4 levels
in migrating fish are relatively less important in hatchery-rearedfish which are released into streams compared with fish which are

LITERATURE CITED
BERN, H. A.
1978. Endocrinological studies on normal and abnormal salmon smoltification. In P. J. Gaillard and H. H. Boer (editors), Comparative endocrinology,
p. 97-100. Elsevier/North Holland Biomedical Press, Amsterdam.

7

100

{:;, T

80

Table I.-Plasma sodium of control- or triiodothyronine (T,)-treated coho salmon 24 h after entry into
seawater. Treated fish received T, in the diet at4 and 12
mg/kg for 3 mo prior to seawater challenge.

o Controlo T3 (4mg/kll)
3(/2 mq/kg)
Group(N=17)

Average plasma
sodium

95% confidence
interval

ControlT, (4 mg/kg)
T, (12 mg/kg)

174
170
169

169-179
165-175
165-173---_._--60
0

E

'"

.....
..
..

C
u

40
CLARKE, W. c., and J. BLACKBURN .
1977. A seawater challenge test to measure smolting of juvenile salmon.
Fish. Mar. Serv., Tech. Rep. 705, 11 p.
1978. Seawater challenge lests performed on hatchery stocks of chinook andcoho salmon in 1977. Fish. Mar. Serv., Tech. Rep. 761, 19 p.
DICKHOFF, W. W., D. S. DARLING, and A. GORBMAN.
1982. Thyroid function during smoltification of salmonid fish. In Institute of
Endocrinology, Gunma University (editor), Phylogenic aspects of thyroid
hormone action, Vol. 19. p. 45-61. Gunma Symposia on Endocrinology,
Center for Academic Publications Japan, Tokyo.
DONALDSON, E. M., U. H. M. FAGERLUND, D. A. HIGGS, and J. R. McBRIDE.
1979. Hormonal enhancemeot of growth. In W. S. Hoar, D. 1. Randall, and J.
R Brett (editors), Fish physiology, Vol. VIII. p. 456-598. Acad. Press, N. Y.
ERIKSSON, L.-O., and H. LUNDQVIST.
1982. Circannual rhythms and photoperiod regulation of growth and smolting
in Baltic salmon (Sa/rna sa/ar L.). Aquaculture 28: 113-121.
EWING, R. D., and E. K. BIRKS.
1982. Criteria for parr-smolt transformation in juvenile chinook salmon(Oncorhynchus /showy/scha). Aquaculture 28: 185-194.

Q.

C
0

~

20

o
500

1000

1500

2000

Cumulative temperature units (0 Fl

Figure 2.-Mean percent of the population which were smolts (as determined bymorphological criteria) during the parr to smolt transformation of coho salmon.
A greater proportion of smolts were observed in groups treated with dietarytriiodothyronine IT,> at concentrations of 4 mg/kg and 12 mg/kg.

25

20

0 Control
0 T3 (4m\l/kg){:;,

E

T (12 mg/klll
3

"'

0'

....
C

c

15

...>.

0

.c;

t-

.,
E

10

'"
0

a.
5

JAN

FEB

APRIL

MAY

Figure 3.-Blood plasma thyroxine (T.' concentration in coho salmon during smoltification. An earlier
increase in plasma T. occurred in fish treated with 12 mg/kg triiodothyronine (T.,) in the diet for 3 mo.

8

FOLMAR. L. c.. and W. W. DICKHOFF.
1980. The parr-smolt transformation (smollification) and seawater adaptation in salmon ids. A review of selected literature. Aquaculture 21:1-37.
1981. Evaluation of some physiological parameters as predictive indices ofsmoltification. Aquaculture 23:309-324.
FOLMAR. L. c.. W. W. DICKHOFF. C. V. W. MAHNKEN. and F. W. WAKNITZ.
1982. Stunting and parr-reversion during smo1lification of coho salmon(Oncorhynchus kisutch). Aquaculture 28:91-104.

HOAR, W. S.
1976. Smolt transformation: evolution. behavior and physiology. 1. Fish.
Res. Board Can. 33:1234-1252.
IWATA. M.• T. HIRANO. and S. HASEGAWA.
1982. Behavior and plasma sodium regulation of chum salmon fry duringtransition into seawater. Aquaculture 28:133-142.
MAHNKEN, C.. E. PRENTICE. W. W AKNITZ. G. MONAN, C. SIMS. and J.
WILLIAMS.
1982. The application of recent smoltification research to public hatcheryreleases: an assessment of size/time requirements for Columbia River
hatchery coho salmon (Oncorhynchus kisulch). Aquaculture 28:251-268.
McBRIDE. J. R.• D. A. HIGGS. U. H. M. FAGERLUND. and J. T. BUCKLEY.
1982. Thyroid and steroid hormones: potential for control of growth andsmoltification of salmonids. Aquaculture 28:201-209.
NISHIOKA. R. S., H. A. BERN. K. V. LAI. Y. NAGAHAMA, and E. G. GRAU.
1982. Changes in the endocrine organs of coho salmon during normal andabnormal smoltification-an electron-microscope study. Aquaculture 28:
21-38.
WAGNER. H. H.
1974. Seawater adaptation independent of photoperiod in steelhead trout(Salrno Rairdneri). Can. J. Zoo!. 52:805-812.
WAHLE. R. 1.. and W. S. ZAUGG.
1982. Adult coho salmon recoveries and their Na'-K' ATPase activity at
release. Mar. Fish. Rev. 44(11): 11-l3.
WEDEMEYER. G. A.• R. L. SAUNDERS. and W. C. CLARKE.

GORBMAN. A.• W. W. DICKHOFF. J. L. MIGHELL. E. F. PRENTICE. and F. W.
WAKNITZ.
1982. Morphological indices of developmental progress in the parr-smolt
coho salmon. Oncorhynchus kisutch. Aquaculture 28:1-19.
GOULD. R. W .. A. M. PALMISANO. S. D. SMITH. C. V. W. MAHNKEN. W. S.
ZAUGG. and E. F. PRENTICE.
1985. Seawater acclimation of premigratory (presmolt) fall chinook salmon:
A possible new management strategy? In C. J. Sindermann (editor), Proceedings of the Eleventh U.S.-Japan Meeling on Aquaculture. Salmon Enhancement. Tokyo. Japan. October 19-20. 1982. p. 15-19. U.S. Dep. Commer..
NOAA Tech. Rep. NMFS 27.
GRAU. E. G.. W. W. DICK HOFF. R. S. NISHIOKA. H. A. BERN. and L. C.
FOLMAR.
1981. Lunar phasing of the thyroxine surge preparatory to seaward migration
ofsalmonid fishes. Science (Wash .• D.C.) 211:607-609.
HART. C. E.• G. CONCANNON, C. A. FUSTISH. and R. D. EWING.
1981. Seaward migration and gill (Na'K)-ATPase activity of spring chinook
salmon in an artilicial stream. Trans. Am. Fish. Soc. 110:44-50.
HIGGS. D. A., U. H. M. FAGERLUND. J. G. EALES. and J. R. McBRIDE.
1982. Application of thyroid and steroid hormones as anabolic agents in fishculture. Compo Biochem. Physio!. 73B: 143-176.

1980.

Environmental factors affecting smoltification and early marine sur-vival of anadromous salmonids. Mar. Fish. Rev. 42(6j: 1-15.
ZAUGG. W. S.
1982. Some changes in smoltification and seawater adaptability of salmonids
resulting from environmental and other factors. Aquaculture 28:143-151.

9

The Importance of the Environment, Stress, andDisease Relationship in Aquaculture
ALFRED C. FOXI

degree of stress to which fish can adapt through these mechanisms
is important to a definition of the environmental quality requiredfor optimum fish health for hatchery and wild populations.
Although fishes can usually physically survive unfavorable environmental conditions for limited periods because of their homeostatic capabilities, these should not be used as an excuse for
operating aquacultural systems under marginal conditions. Instead, these abilities should be used to help set priorities and limits
for the environmental conditions that will promote optimal fish
health and quality.
Because of the many physiological, chemical, and behavioral
factors which affect a fish's response to stressors, it is difficult todevise a detailed list of environmental conditions, temperatures,water flows, etc., which would minimize stress and promote fish
health under all conditions. Unfortunately, most of the waterchemistry information available concerns fish toxicity rather thanfish health.
The synergistic effects of dissolved minerals on fish health offera promising avenue of approach. For example, work at the Seattle
National Fishery Research Center with nitrite toxicity has
demonstrated than increasing the water hardness to above 50
mg/I, or adding calcium chloride or sodium chloride to increase
the chloride level to 50 mg/l will protect steelhead trout against up
to 2 mg/l of nitrite. This has important implications for reusehatcheries using soft water where chronic low level nitrite exposure is frequently a fish health problem.
Another aspect of water chemistry for disease control which
has received attention at the Seattle National Fishery ResearchCenter is ozonation-both for pathogen removal and in terms of
its fish toxicity. The ozone dosage to destroy enteric redmouth(Yersinia ruckeri), furunculosis (Aeromonas salmonicida), and the
IPN and lHN viruses is substantially less than the chlorine thatwould be required, and persistent residuals are less of a problem.
In addition, ozone shows considerable promise as a replacement
fungicide for malachite green in the control of fungus(Saprolegnia) during egg incubation.
One of the most insidious effects of stress in aquaculture (andone that is also receiving serious attention as a method of
biological monitoring for environmental quality) is increased
susceptibility to fish diseases (Esch and Hazen 1980; Walters andPlumb 1980; Ellis 1981). Experience has shown that the mere
presence of most fish pathogens, unless present in overwhelming
numbers, will not result in epizootics unless unfavorable environmental conditions also exist that have compromised the fish's
defense system (Walters and Plumb 1980).
Thus, infectious fish diseases are not single-caused events, but
are one outcome of the continuing interactions between theaquatic environment, the fish, and their pathogens. If the hostenvironment-pathogen relationship is balanced, the result will begood fish health, growth, and survival. If it is marginal, diseaseproblems will begin to become evident and reduced fish condition, growth, and survival will result. If it is unbalanced, chronic

A necessary starting place in understanding the physiology offish in intensive culture is a consideration of normal conditions in
the aquatic environment itself. Fishes commonly live under somewhat demanding chemical and physical conditions, many ofwhich have no analogue in the terrestrial environment. It is truethat they are physiologically adapted to these conditions, but
adaptation does not imply the absence of an energy cost (Lugo
1978). First, fishes must expend a significant number of calories(from the diet) to overcome frictional drag during swimming andto move water over the gills to obtain oxygen. Second, the amountof dissolved oxygen available for respiration is quite limited; it isnormally only about 10-12 mg/l, is frequently much less, and canfluctuate widely. The respiratory medium (water) also acts as adialyzing medium for the blood. Thus, when additional oxygen isneeded, the increased gill circulation results, as well, in an increased water influx. The blood electrolyte loss during the resulting
diuresis can be life-threatening (Hunn 1982).
Thus, fishes are continually challenged by the normal physiochemical demands of the aquatic environment itself. Added to thismay be stress from habitat alterations, and intra- and interspecificinteractions such as social hierarchies (Schreck \981).
Fish in aquacultural facilities are usually under some degree ofadditional stress because of required operating procedures such as
handling, crowding, hauling, drug treatments, and (particularly
during stocking) unfavorable or fluctuating temperatures andwater chemistry (Piper 1982). This stress is superimposed on that
due to the previously mentioned "normal" conditions in theaquatic environment. When recirculation systems are in use,
unique conditions of water chemistry occur that can cause anadditional metabolic load. These include chronic exposure to low
or fluctuating levels of un-ionized ammonia, nitrite, nitrate, carbon dioxide, and gas supersaturation; frequently accompanied byelevated water temperatures (to accelerate growth). Furthermore,environmental conditions and population densities are often dictated more by economic than biological considerations. All ofthese conditions, together with any fright response that accompanies them, can impose a considerable load, or stress, on the normal metabolism of fish. Although individual stress factors inaquacultural systems are usually sublethal in themselves, stressors
are more commonly multiple and the resulting physiological load
can reduce growth, impair fish health and quality, and result in
decreased survival and increased costs.
A fish's survival in the face of environmental stress depends
upon its ability to regulate physiological processes so as to achieve
compensation. Any stress requiring an adjustment in excess ofability to accommodate will eventually become lethal; either
directly or indirectly as a result of disease. An understanding of
the mechanism of response to environmental changes and the'Director, National Fishery Research Cenler, U.S. Fish and Wildlife Service, Bldg.
204, Naval Station, Seattle, WA 98115.

IIdisease problems can be expected. Examples of fish diseases thatare stress-mediated in freshwater aquaculture are those due tofacultative bacterial fish pathogens such as aeromonads, pseudomonads, and the myxobacteria, which are continuously present inmost natural waters. A classic example is bacterial gill disease,which frequently can be treated successfully by simply reducing
the fish population density. Other infectious fish diseases whichindicate that tolerance limits to stress are being exceeded include
vibriosis (Vibrio anguillarum), bacterial hemorrhagic septicemia(Aeromonas and Pseudomonas spp.), and protozoan parasite andfungus infestations such as costiasis (Costia necatrix) and
Saprolegnia (Wedemeyer et al. 1976). As judged by its physiological consequences, viral erythrocytic necrosis may be a potentially useful indicator disease in the the estuarine environment(MacMillan et al. 1980). Fish disease incidence can, of course, bemost easily used as an index of unfavorable conditions in aquacultural facilities which have relatively controlled environmental
conditions.
Certain stress-mediated fish diseases have now also been identified as offering particular promise (in biological monitoring) as
indicators of unfavorable conditions in the marine environment.
These include chromosomal and morphological abnormalities of
eggs and larvae, skeletal anomalies, neoplasms, fin erosion, andepidermal ulceration (Malins et al. 1980; Sindermann 1980). A
more detailed discussion of stress-mediated diseases, together
with a description of the stress factors Implicated in their occurrence, is presented in Wedemeyer et al. (1980).
In the special case of anadromous species, a fish health problemof particular significance is the impact of stress on the parr-smolt
transformation. A discussion of the physiological changes occurring during smoltification, of particular relevance to aquaculture,is given by Folmar et al. (1982) and Mahnken et al. (1982). Environmental factors such as changes in water chemistry, temperature, or photoperiod may result in inhibition of the developmentof one or more of these physiological functions (Wedemeyer et al.
1980). For example, the normal development pattern of the gill
ATPase enzyme system of coho salmon, Oncorhynchus kisutch,
paIr is affected both by water temperature and by otherwise
sublethal amounts of dissolved heavy metals. Chronic exposure tocopper at only 20-30 ~lgll partly or completely inactivates gill
ATPase function (Lorz and McPherson 1976). The consequence isreduced seawater tolerance and, thus, survival. An equally significant behavioral consequence is that normal migratory behavior isinhibited.
In addition to trace heavy metals, anadromous salmonid parrare also affected by contaminants such as the herbicides andnitrates now increasingly common in surface waters as the resultof intensive forest and range management, and agricultural practices. For example, both picloram and the dimethylamine salt of
2,4-D used for weed control on non crop lands inhibit the migratory behavior of juvenile coho salmon (Lorz et al. 1978). Other
formulations, such as Endothal and the 2,4-D esters used to control Eurasian water milfoil, may also inhibit seawater tolerance
and migratory behavior of smolts (Liguori et al. 1983). Such effects, which are otherwise sublethal at the individual fish level,
may have serious consequences in terms of seawater survival(Mahnken et al. 1982).
In the case of water temperature, the effects can be to suppress
the onset of smoltification, or to accelerate both smolting and parrreversion. The development of smoltification in anadromous rainbow trout (steelhead) is particularly sensitive to water temperature-which thus provides a useful sublethal index for biologicalmonitoring. Gill ATPase development is essentially blocked attemperatures above 13°C while other physiological parameters,such as growth, can be enhanced (Zaugg and McLain 1972). Cohosalmon suffer a retarded pattern of ATPase development at 6"C,and a premature development pattern at 20°C (Zaugg and McLain
1972). Temperatures up to 15°C do not adversely affectsmoltification and accelerate growth sufficiently so that minimum
size requirements can be met in one rearing season. However,parr-reversion is also accelerated which shortens the time period
during which the smolts can successfully convert to seawater. The
parr reversion of juvenile chinook salmon due to elevated watertemperatures can be substantially reduced if they are reared atsalinities of up to 20 ppt (Clarke et al. 1981).
A final aquaculture stress factor to consider that adversely affects smolt performance capability, is crowding and handling(Specker and Schreck 1980; Fagerlund et al. 1981; Sandercock
and Stone 1982). The population level effect of significance isreduced seawater survival which renders it of particular importance in ocean ranching.
Of all the environmental stress factors predisposing salmonid
fishes to disease problems in intensive culture, crowding, i.e., approaching or exceeding the maximum carrying capacity of thewater, is probably one of the most important. The number of fish
which can successfully live and grow in a given water supply
depends on its pathogen load, the dissolved oxygen level,
metabolic rate of the fish, feeding ,ate, and how fast the water isbeing exchanged, which in turn governs the rate at whichmetabolic wastes accumulate. In a recirculating system, nitrateaccumulation must also be considered. This would be a function of
the efficiency of the biological filter. The fish pathogen load is ~usually neglected, but very important, factor affecting both thecarrying capacity and the health of the fish being reared. In recirculating systems, pathogens can be controlled by water sterilization J(,vlces using ozone or ultraviolet light, but in the usual
hatchery situation, pathogen loads are frequently only indirectly
under the control of the fish culturist.
As an additional complication, fish loadings also should be
evaluRted in terms of the stress they cause. For example, moving
juvenile coho salmon held in soft, 10°C water from the relatively
Jightloading of 8.0 kg/m J (0.5 Ib/ft J ) (density index 0.1) to either
96 or 192 kg/m J (6 or 12 Ib/ft 3 ) causes acute stress which can last
up to lad. A loading of 64 kg/m 3 (4 Ib/ft 3 ) (density index 0.8)
causes only minimal blood chemistry disturbances. For fish distribution trucks, this would correspond to about 0.06 kg/l (0.5 lb/gal)of water. However, moving smolting coho salmon at population
densities greater than about 16 kg/m 3 (1 Ib/ft 3 ) or 0.0 1 kg/l (0.1
Ib/gal) in hauling trucks causes severe stress and can activate
latent kidney disease.
A critical consideration in any discussion involving fish
diseases is recognizing that there are still problems in being able
to adequately recognize good fish health when it is achieved.
Obviously, fish health is far more than the mere absence of fish
disease. Growth and survival are also frequently used as measuresof health but they are satisfactory only as a first approximation.
The problem is especially difficult in the ocean ranching ofanadromous fishes because producing smelts of maximum healthand quality is critical to maximizing ocean survival and thus
returns to the hatchery.
In conclusion, better information on the physiology of fish inintensive culture would assist in mitigating stress, improve fish
health and quality, and improve overall survival through disease
prevention. The following is recommended:
12I) Maintain water quality within recommended guidelines forthe species of interest.
2) Regulate population density to prevent crowding stress.
3) Recognize that multiple stress from crowding, handling, anddisease treatments is additive or synergistic.
4) When multiple stress is unavoidable, allow an adequate
recovery time based on the species, and severity of theresulting physiological disturbances.
5) Use the occurrence of stress-mediated fish diseases as an indicator of adverse conditions and take corrective action.

Heidolph (editors), Aquatic toxicology and hazard assessment: Sixth symposium, ASTM, STP, 802, p. 530-544. Am. Soc. Tes!. Mater., Philadelphia,Pa.
LORZ, H., S. GLENN, R. WILLIAMS, C KUNKEL, L. NORRIS, and B. LOPER.
1978. Effect of selected herbicides on smolting of coho salmon. U.S.
Environmental Protection Agency, Grant Rep. R-804283. Oreg. Dep. Fish
Wildl., Corvallis, 482 p.
LORZ, H. W., and B. P. McPHERSON.
1976. Effects of copper or zinc in fresh water on the adaptation to sea waler
and ATPase activity, and the effects of copper on migratory disposition ofcoho salmon (Oncorhynchus kisu/ch). J. Fish. Res. Board Can. 33:20232030.
LUGO, A. E.
1978. Stress and ecosystems. In J. H. Thorp and J. W. Gibbons (editors),
Energy and environmental stress in aquatic systems, p. 62-101. Technical
Information Center, U.S. Dep. Energy.
MacMILLAN, J. R., D. MULCAHY, and M. LANDOLT.
1980. Viral erythrocytic necrosis: some physiological consequences of infection in chum salmon (Oncorhynchus keta). Can. J. Fish. Aquat. Sci. 37:
799-804.
MAHNKEN, C, E. PRENTICE, W. WAKNITZ, G. MONAN, C SIMS, and J.
WILLIAMS.
1982. The application of recent smoltificalion research to public hatcheryreleases: an assessment of size/time requirements for Columbia River
hatchery coho salmon (Oncorhynchus kisulchl. Aquaculture 28:251-268.
MALlNS, D. C, B. McCAIN, D. BROWN, A. K. SPARKS, and H. O. HODGINS.
1980. Chemical contaminants and biological abnormalities in central andsouthern Puget Sound. U.S. Dep. Commer., NOAA Tech. Memo. OMPA-2,
292 p.
PIPER, R. G.
1982. Fish hatchery management. Am. Fish. Soc. Spec. Publ., 450 p.
SANDERCOCK, F. K., and E. J. STONE.
1982. A progress report on the effect of rearing density on subsequent survivalof Capilano coho. In B. Melteff and R. Neve (editors), Proc. North Pac. Aquaculture Symp., p. 82-90. Univ. Alaska Sea Grant Rep. 82-2, Fairbanks,
Alaska.
SCHRECK, C B.
1981. Stress and compensation in teleostean fishes: response 10 social andphysical factors. In A. D. Pickering (editor), Stress and fish, p. 295-321.
Acad. Press, Land.
SINDERMANN, C J.

A better understanding of the physiology of fish in intensive
culture, including disease as one physiological consequence of an
unfavorable aquatic environment, would provide the factual foundation required for improving efficiency in aquaculture as it has inother branches of animal husbandry. Specifically:I) Species-specific tolerance limits to multiple environmental
alterations are needed (e.g., salinity, oxygen, temperature).
For example, at what point do otherwise sublethal temperature increases become stressful when dissolved oxygen isalso unfavorable?
2) Improved hatchery procedures to mitigate stress, particularly
for Atlantic salmon, striped bass, and intermediate temperature fishes, are needed.
3) Performance challenge tests are needed to allow a more efficient assessment of the impacts of stress, evaluate genetic
strains, and allow a more rapid assessment of overall fish
health and quality.

LITERATURE CITED
CLARKE, w C, J. E. SHELBOURNE, and J. R. BRETT.
1981. Effect of artificial photoperiod cycles, temperature, and salinity on
growth and smolting in underyearling coho (Oncorhynchus kisUlch), chinook(0. /shuwy/schal, and sockeye (0. nerka) salmon.
Aquaculture 22: I05-116.
ELLIS, A. E.
1981. Stress and the modulation of defense mechanisms in fish. In A. Picker109 (editor). Stress and fish, p. 147-170. Acad. Press, Lond.
ESCH, G W .. and T C HAZEN.
1980. Stress and body condition in a population of largemouth bass: Implications for red-sore disease. Trans. Am. Fish. Soc. 109:532-536.
FAGERLUND. U. H. M., J. R. McBRIDE, and E. T. STONE.
1981
Stress-related effects of hatchery rearing density on coho salmon.
Trans. Am. Fish. Soc. 110:644-649.
FOLMAR. L. C, W. W. DICKHOFF, C. Y. W. MAHNKEN, and F. W WAKNITZ.
1982. Stunting and parr-reversion during smoltification of coho salmon(Oncarhynchus kisurchl. Aquaculture 28:91-104.
HUNN. J. B.
1982. Urine flow fate in freshwater salmon ids: a review. Prog. Fish-Cult.
44:119-125.
LIGUORI, Y., V. VAKOUR, M. LANDOLT, and F. FELTON.
1983. Toxicity of the herbicide Endothal to juvenile chinook salmon(Oncorhynchus /shawYlScha). In W. E. Bishop, R. D. Cardwell, and B. B.

1980. The use of pathological effects of pollutants in marine environmental
monitoring programs. Rapp. P.-V. Reun. Cons. lilt. Explor. Mer 179:129134.
SPECKER, J. L., and C B. SCHRECK.
1980. Stress responses to transportation and fitness for marine survival incoho s.lmon (Oncurhynchus kislllch) smolts. Can. J. Fish. Aquat. Sci.
37:765-769.
WALTERS, G. R., and J. A. PLUMB.
1980. Environmental stress and bacterial infection in channel catfish,
Ic/ulurlls punc/allls Rafinesque. J. Fish BioI. 17:177-185.
WEDEMEYER, G. A., F. P. MEYER, and L. SMITH.
1976. Environmental stress and fish diseases. TFH PubL, Neptune City,
N.J., 192 p.
WEDEMEYER, G. A., R. L. SAUNDERS, and C. C. CLARKE.
1980. Environmental factors affecting smollification and early marine
survival of anadromous salmonids. Mar. Fish. Rev. 42(6): 1-15.
ZAUGG, W. S., and L. R. McLAIN.
1972. Changes in gill adenosinetriphosphatase activity associated with parrsmall transformation in steelhead trout, coho, and spring chinook salmon.
J. Fish. Res. Board Can. 29:167-171.

13

Seawater Acclimation of Premigratory (Presmolt) Fall
Chinook Salmon: A Possible New Management Strategy?
ROWAN W. GOULD,· ALDO N. PALMISANO? STANLEY D. SMITH,2
CONRAD V. W. MAHNKEN,3 WALLY S. ZAUGG,3 and EARL F. PRENTICPABSTRACTAt selected points in their life history, juvenile fall chinook salmon, Oncorhynchus tshawytscha, were accli·
mated in diluted seawater, 15 ppt salinity, for different times before they were challenged with undiluted
seawater. In successive months, the weight and length of the fish and percent mortality after acclimation in
diluted seawater for 0, 6, 24, and 168 hours were as follows: February (1.2 g, 51 mm), 97,90,71, and IS; March(2.1 g, 59 mm), 77, 67, 46, and 5; April (3.7 g, 70 mm; Na'-K' ATPase levels rising) <7 in aU groups. In July(well after normal April hatchery release) when fish averaged 20 g and 115 mm, mortality after seawater
challenge was 25% after 0 or 6 hours acclimation, 8% after 24 hours acclimation, and nil after 168 hours acclima·tion. For the population of juvenile faU chinook salmon used in these experiments, ability to withstand direct
seawater exposure corresponded to levels of gin Na'-K' ATPase.
Growth in seawater was monitored for survivors of each treatment group from the March and April
seawater challenges. After 4 months, no significant differences in fish length and weight were observed.

INTRODUCTION

this paper. Other investigators have determined that gradualacclimation to low salinities results in early tolerance to fullstrength seawater. Wagner et al. (1968) gradually acclimatedBonneville-stock, fall chinook salmon, using 5-d, 5 ppt salinity
increments up to 30 ppt salinity to realize> 80% survival ofjuveniles 100 d old. Nonacclimated fish were reared 140 d before
survival exceeded 80%. Similar results were observed in springchinook salmon. Kepshire and McNeil (1972), who acclimated66-d old fall chinook salmon to seawater by incremental salinity
increases, each lasting 18 d, before transfer to undiluted seawater,
reported a slight reduction in growth of saltwater-adapted fishcompared with that of control fish held in freshwater.
The objective of our work was to determine how soon fallchinook salmon can adapt to seawater after acclimation in diluted
seawater (15 ppt salinity) and the length of time required foradaptation. At the same time, we compared seawater growth ofsmall, saltwater preadapted fish to seawater growth of fish
naturally acquiring seawater tolerance. This effort is the first stepin assessing the value of presmolt seawater adaptation as amanagement tool.

Public and private anadromous salmonid aquaculture in
America, especially sea ranching, has reached a significant crossroad insofar as further expansion is concerned. Several economicand environmental factors limit growth of the industry. In the last
5 yr, maintenance, building, and operation costs have soared, allin direct conflict with demands for production of greater numbersof low-cost smolts. Coupled with increased commercial andrecreational demand for publicly and privately reared fish, a limit
is being approached to the number of adult salmon that originate
from hatcheries, at least in the states of Washington, Oregon,
Idaho, and California.
Environmental factors play an important role in production ofhealthy smolts. Supplies of high quality freshwater, already oversubscribed, are used at unrealistic carrying capacities, resulting inovercrowding and disease. New sources of suitable freshwater are
increasingly difficult to locate and appear to be the single, mostimportant biological variable limiting salmonid aquaculture.
Man's manipulation of the environment is also a limiting factor. Multiuse of existing water supplies has adversely affectedmigrations of both smolts and adults. Dams, water removal, andpollution are the primary causes of mortality. These problems arepotentially devastating for all fish, particularly poor-quality
hatchery fish.
New salmonid-rearing strategies are needed to improve efficiency, increase operational flexibility, allow for multiple-species
rearing, and optimize use of existing freshwater. One strategy,
early seawater acclimation of small, presmolted, and premigratory
fall chinook salmon, Oncorhynchus tshawytscha, is the subject of

MATERIALS AND METHODS
On 22 October 1981, fall chinook salmon at the eyed egg stage
were obtained from production lots at Spring Creek National Fish
Hatchery, and transported to Marrowstone Field Station, Seattle
National Fishery Research Center, located on Puget Sound near
Port Townsend, Wash. Eggs were disinfected in 100 ppm Argentine4 solution (pH 7) for 10 min, and placed in Heath-Techna
Incubator trays (about 3,000 eggs per tray). Each tray received
freshwater at the rate of 10 I/min. All fish were hatched by 16
November 1981, and were moved on 8 December 1981 to 12,80 I
troughs each receiving 4 IImin freshwater. On 5 February 1982,
random samples of 50 fish each were placed in 68 I glass aquaria

I National Fishery Research Center, U.S. Fish and Wildlife Service, Seattle. Wash.;present address: National Fishery Research and Development Laboratory, U.S. Fish
and Wildlife Service, R.D.#4, Box 63, Wellsboro, PA 16901.
'National Fishery Research Center, U.S. Fish and Wildlife Service, 7600 Sand
Point Way NE., Bldg. 204, Seattle, WA 98115.
'Northwest and Alaska Fisheries Center, National Marine Fisheries Service,
NOAA, 2725 Montlake Blvd. E., Seattle WA 98 I 12.

'Reference to trade names does not imply endorsement by the National Marine
Fisheries Service, NOAA. or Ihe U.S. Fish and Wildlife Service.

15

each receiving 2 l/min freshwater. Each aquarium received either
freshwater or seawater treated with ultraviolet light, pumped from
Puget Sound, or mixtures of both. Freshwater and seawatertemperatures as well as seawater salinity were monitored daily(Fig. I). Salinity was measured with a YSI Model 33 S-C-T meter.
Fish were fed Oregon Moist Pellet "ad libitum."

-U
Q
Q

->

"

~

j"

32

SALINITY

30

.....

.....
-_ ......

. -I.- ....- ..

28
26changed to diluted seawater (salinity about 15 ppt) for one ofthree acclimation periods-6, 24, or 168 h-followed by conversion to full-strength seawater. The experimental procedure was
begun on each of the following dates in 1982: 23 February, 23
March, 20 April, and 20 July. Specific exposure salinities for eachseawater challenge are summarized in Table I.
Numbers of dead fish in experimental tanks were recorded daily
until mortality subsided (a minimum of 10 d). Kidney samples
from about 25% of the dead fish were cultured for bacterial infection on Brain Heart Infusion Agar (Difco). Resulting bacterial
cultures were identified by using the API-20E (Analytical Products Industries, Plainview, N.Y.) bacterial identification system,
and following the manufacturer's recommended procedures.

24
22
20
18

TEMPERATURE

16"Freshwate; ...... :.:.......
-

14

-

12

~

10

"

!

..,

.

Growth Experiment- :-. ~ e.-0."" ,.;.: .'~,.....

From the 23 March challenge, two lots of 15 fish each wereformed from survivors of each treatment group. More fish survived the 20 April challenge, allowing selection of four 15- fish lots
from each treatment group. Each lot was moved to a 68 I aquarium
receiving 2 l/min undiluted seawater. Fish were fed Oregon Moist
Pellets at a percentage of their body weight based on manufacturer's recommendations and temperature. Growth was monitored
monthly for 5 mo. Fish were weighed to the nearest 0.1 g and fork
lengths measured to the nearest millimeter.

Seawater.... ~~~

F,b

May

M"

Juo

Aug

Jul

s,p

Ot;t

Experimental [Ime period (months)

Figure I.-Seawater salinity, seawater temperature, and freshwater tempera.
ture at Marrowstone Field Station from 1 February 1982 to 1 October 1982.

RESULTS
ATPase Determinations

Gill Na+-K+ ATPase Determinations

Sixteen aquaria containing 50 fish each and receiving only
freshwater were sampled for gill Na'-K' ATPase enzyme activity
to measure timing of smoltification. At about 2-wk intervals,
10-30 fish from one aquarium were removed and gill filament
tissue was excised. Each sample consisted of tissue from I to 3
fish, resulting in 10 replicated samples for each time period. Allfish tested for gill Na'-K' ATPase activity were weighed to thenearest 0.1 g and measured (fork length) to the nearest millimeter.
Sampling and gill Na' -K' ATPase determinations were according
to Zaugg (1982).

Gill Na' - K' ATPase acti vity for fall chinook salmon under the
given experimental conditions was low through February andMarch, averaging below 10 folmol Pi/mg Prot per h (Fig. 2). Activity began to increase in April and continued upward until about I
July, when it declined precipitously to nearly pre-April values,
only to quickly rise again in late July. The first two seawater
challenges came before ATPase activity increased and the third as
ATPase activity was increasing (Fig. 2). Gill Na'-K' ATPase
activity in late June-32 folmoi Pi/mg Prot per h-was high compared with values observed in several related studies at other locations on the same brood of fish. The 20 July challenge began at apoint when freshwater gill Na' -K' ATPase levels were depressed;
however, after 168 h, the activity was nearly equal to that observed during the third challenge. The bimodal nature of ATPaseacti vity for our experimental stock has been observed in past
years, but the duration of increased activity from April throughJune and the subsequent decline had not been previously noted.

Pre-exposure Study
We used 48 aquaria-12 aquaria for each of four seawater
challenge experiments-each containing 50 juvenile fall chinook
salmon in the pre-exposure study. During each challenge, threetanks were converted directly to seawater. Three tanks wereTable I.-Mean salinity during experimental seawater challenges. Also included are salinities of seawater used to acclimate
fall chinook salmon before seawater challenge.
Date (1982)
23 February
Acclimation

time (h)20 April

23 March

20 July95%
confidence
intervalMeansalinity
(ppt)

950k

Mean

95%

confidence
intervalMeansalinity(ppt)

confidence

salinity

confidence

interval(ppt)

interval

±0.2
±3.0
±1.4
±0.7

27.6
14.8
16.3
14.4

±0.5
±0.8
±I.I
±0.6

26.9
17.6
15.8
15.4

±1.0
±1.8
±3.1
±1.6

29.1
14.9
14.1
15.2

±0.6
±4.0
±1.6
±1.5

Mean

95%

salinity
(pp!)

27.2
16.0
13.5
14.5

o (undiluted
seawater)
6
24
168

16

Pre-exposure Study

36
32
~

Cumulative mortality in both the February and March seawater
challenges was high for unpreadapted fish and low for fish
preadapted to 15 ppt salinity for 7 d (Fig. 3). Preadaptation
resulted in reduced mortality after 6 h and a still further reduction
after 24 h.
In April, one of the normal release times for Spring Creek fallchinook salmon, most of the fish were able to withstand direct

28

:. 24

~

a:

20

~

~

16

.3

~ 12
>-

"

Feb

May

Jon

Aog

Jol

Figure 2.-Gill Na" - K- ATPase levels of fall chinook salmon held in freshwaterat Marrowstone Field Station from February 1982 to October 1982. Bars indkate 95% confidence intervals.

Sep

Experimental lime period (months)

FEBRUARY 23 SEAWATER CHALLENGE
100

MARCH 23 SEAWATER CHALLENGE

MEAN WT. 1.3 y
MEAN FORK LENGTH 52mm

90

100

MEAN WT. 2.1 9
MEAN FORK LENGTH 60mm

90

oro'"

'" ;:
'" '"

80

80

Eal

70

70

-;:;c
c :J
~

60

60

"'u
0.",
-x

50

50

"§8

40

40

0'"
E~

30

30

20

20

10

10

~'"
u~

oX

':::E

'"
1:'0

?"E
"'0

_ Q.
x
.2:
~'"
:J _.

E~

8"s

FEB 18

FEB 23

FEB 28MAR 5

MAR 10MAR 15MAR 20MAR 20MAR 25Experimental time period (days)

MAR 30

APR 4

APR 9

APR 19JUL Y 20 SEAWATER CHALLENGEAPRI L 20 SEAWATER CHALLENGE
100

100
MEAN WT. 3.7y
MEAN FORK LENGTH 70mm

90

APR 14

Experimental time period (daysl

MEAN WT. 20g
MEAN FORK LENGTH 130rnm

90

oro'"
'" ;:
"'''''"

-

80

80

Eal
o x

70

70

-;:;c
c :J

60

60

"'u
0.",
-x

50

50

40

40

30

30

~'"
:J-

20

20

u.~

10

10

u~

•

':::E

'"~o

?"E
"§8

OIRECT EXPOSURE TO SEAWATERo

6 HOUR EXPOSURE, 15 ppl.

6

24 HOUR EXPOSURE. 15 ppl.

o 168 HOUR EXPOSURE. 15 ppl.

0'"
E

a

"'0

.2: Q.

- x

E·~
:J.-

April19

April 24

April 29

May 4

May 9

May 14

May 19July 13

July 18

July 23

July 28

Aug 2

Aug 7

Aug 12

Experimental time period (daysl

Experimental time period (days)

Figure 3.-Cumulative mortality of juvenile fall chinook salmon challenged at various times with mixed freshwater-seawater (~15 ppt salinity) for 0, 6, 24, or 168 hbefore exposure to full-strength seawater (~29 ppt). Each curve represents combined cumulative mortality from three equally treated lots. Each lot contained 50 fish-a
total of 150 fish per treatment group.

17

seawater exposure (Fig. 3). Highest mortality in any group was
7%. The mortality pattern in July reflected the probable state ofsmoltification as indicated by ATPase levels: Much of the population had lost the ability to withstand direct seawater exposure.
Acclimation to diluted seawater for 6 h did not seem to increaseseawater tolerance, but 24-h acclimation improved survival. No
fish were lost after 168-h acclimation. These results might be areflection of the extremely rapid fluctuation in the ATPase levels
observed in July. In addition, we detected high gas supersaturation(110-115%) and low dissolved oxygen (4 ppm) in our freshwatersupply in July. During the 20 July seawater challenge, eventhough the mortality pattern between treatment groups was consistent with earlier challenges, stress on the fish could have affected mortality and gill Na+-K+ ATPase activity.
During all challenges, most kidney cultures resulted in nobacterial growth. Where growth occurred, the bacteria wereclassified as members of the genus Pseudomonas, which were probably secondary invaders after death of the fish.

was observed (Figs. 4, 5). There was also little, if any, growth difference between survivors of various acclimation groups. Growthof fish used to monitor ATPase (maintained in freshwater) was
greater than that of fish in saltwater. The lengths and weights forthese fish follow: 66 mm, 3.0 g (12 April); 78 mm, 5.5 g (10May); 93 mm, 9.8 g (10 June); 108 mm, 16.4 g (10 July); and 125
mm, 27 g (10 August). These values cannot be compared withthose for saltwater growth because tanks receiving freshwatercontained different numbers of fish, handling was different, andexperimental environments were dissimilar.

DISCUSSION
Chinook salmon populations are experiencing increasing
exploitation rates and deteriorating environmental conditions. To
offset resultant declines, management agencies have called forlarge increases in hatchery production. Economic roadblocks, environmental degradation, and lack of suitable freshwater supplies
in the Pacific Northwest significantly limit hatchery capacity forrearing fall chinook salmon. Early preadaptation of fall chinook
salmon is a possible solution to these problems. Thinning releases
are now common at many hatcheries. For example,
Spring Creek National Fish Hatchery on the Columbia River, thesource of our experimental animals, released 9.6 million fallchinook salmon before smoltificalion; and the Abernathy Salmon
Culture Development Center, also on the Columbia River, released about 400,000 presmolts. Releases of presmolt chinook salmon
have historically contributed far fewer adults to the fishery thanwere contributed by larger smolted fish released at the usual timein April or May. Loss of these presmolted fish is known to occur
in river reservoirs and in the estuary, where small fall chinook
salmon may remain and feed for several weeks before entering the

Growth Experiment
Length and weight were determined for survivors of the 23
March and 23 April challenges. Little, if any, growth difference
120

110

100

25

A- SUI'I;YOfS of March seawater challenge
B- Survivors of Apr.1 seawater challenge
095% confIdence le ... el for lhe me • .,

90

20

E

.s
:I:

>-

"
~

80

lS

:§

A= Survivors of March seawale. challengeB- ')ufYlvQr, of April se"w'lIe. challenge
095% confidence level fOf (he- mean

I-

G

~
70

10

60

50

o"';:;:IO\D~:
A

-:

START

4112

B-

O"";:;:IO"'~:

A -:

B-

O";:;~IO"'~!!

A: B

o l&l~l&lIOlD;:;~

A

..:

B-

O\D;:;:e(:l"';:;~AI

OlD;:;~lOID;:;~

B

A

START

5110

6110

7110

8/10

:

B
I START

5110

SAMPLING DATE

O<D;:;~IO"';:;~

A

:

B

I

6110

0"';:;:.0"':::
A

-l

7110

B"

-

OUl;:;"'1:l"'~~

A

-,

,
I

8110

SAMPLING DATE

Figure 5.-Growtb comparison (weigbt) between two groups of fall cbinook
salmon, one (A) surviving a seawater cballenge on 23 March, and one (B) surviving a seawater challenge on 23 April. Each group contained four treatmentgroups, eacb acclimated for 0, 6, 24, or 168 b in diluted seawater (~15 ppt sallnity) before exposure to undiluted seawater.

Figure 4.-Growth comparison (length) between two groups of fall chinook
salmon, one (A) surviving a seawater challenge on 23 March, and one (B) surviving a seawater cballenge on 23 April. Eacb group contained four treatmentgroups, eacb acclimated for 0, 6, 24, or 168 b In diluted seawater (~15 ppt salinity) before exposure to undiluted seawater.

18

either an estuary site or directly into the river at the hatchery. Further experiments with direct seawater releases are required to
document the contribution of preadapted juveniles, as well as toanswer other related biological questions. An obvious ramification of preadaptation is impaired homing. Impaired homing
behavior, however, may have exploitable economic and biologicaladvantages. Fish may home to release sites, become confused, andremain in the area. Thus, release sites may serve as predetermined,
open-sea terminal fishing areas. Since preadapted fish are excess
to hatchery needs, heavy harvest is desirable. It is also possiblethat preadapted fish follow migration times and use rearing areas
different from those of normally released hatchery smolts or wild
smolts. If so, this behavior would allow fishery managers increased flexibility in setting harvest seasons and quotas protecting wild
and important hatchery stocks. (These suggestions are of course
highly speculative and require further research.)
Preadaptation of fall chinook salmon is by no means a primarystrategy for rearing fall chinook salmon. The worth of the procedure lies in the economical use of previously "wasted" progenyof existing runs. If freshwater systems continue to be adversely affected by man's manipulations, new strategies such as preadaptation may be the only means of maintaining an economical andbiologically sound harvest of anadromous salmon ids.

ocean (Dawley et al. 1981). Mortality-causing factors such aspredation or lack of food are believed to be important and might
be avoided by transporting fish to a brackish water environment
for short-term rearing and preadaptation, followed by release
directly into seawater. If successful, this strategy for releasing atleast a portion of fall chinook salmon hatchery production early intheir life cycle could provide several advantages:
1) Greater flexibility in the use of hatchery facilities for multispecies artificial propagation, i.e., rearing of both fallchinook salmon and coho salmon, Oncorhynchus kisutch.
2) More economical rearing operations because more fish canbe produced in existing hatcheries, or fish of better quality
can be produced because rearing densities can be reduced.
Studies now indicate that low-density rearing of coho salmon
increases survival in the hatchery and contribution to thefishery (Fagerlund et al. 1979, 1981; Sandercock andStoneS).
3)Maximum effective use of available freshwater.
4) Minimum effect on wild juvenile salmonids rearing in waterways.
5) Higher survival of premigrants resulting from direct releaseto saltwater, thereby avoiding fish and bird predation in the
freshwater reservoirs and estuary.
6) Possible avoidance of ocean density-dependent mortality on
wild stocks if some fish are released earlier than others.

LITERATURE CITEDBULLIV ANT, J. S.
1961. The influence of salinity on the rate of oxygen consumption of young
quinnat salmon (Oncorhynchus Ischawylscha). N.Z. J. Sci. 4:381·391.
CLARKE, W. C., 1. E. SHELBOURN, and J. R. BRETT.
1981. Effect of artificial photoperiod cycles, temperature, and. salinity on
growth and smolting in underyearling coho (Oncorhynchus kisulch), chinook(0. rshawylscha), and sockeye (0. nerka) salmon. Aquaculture 22: 105-116.
DAWLEY, E. M., R. D. LEDGERWOOD, T. H. BLAHM, and A. L. JENSEN.
1981. Migrational characteristics and survival of juvenile salmon ids entering
the Columbia River Estuary in 1981. Annual Report on Research to theBonneville Power Administration. Coastal Zone and Estuary Div]sion, Northwest and Alaska Fisheries Center, National Marine Fisheries Service, NOAA,
Seattle, Wash.
ERiKSSON, c., S. HALLGREN, and S. UPPMAN.
1981. Lekvandring hos odlad lax (Sa/rna salar) utsatt som smolt i Ljusan och
dess mynningsomrade. Laxforskningsinstitutet Meddedande 1981:3.
FAGERLUND, U. H. M., J. R. McBRiDE, and E. T. STONE.
1979. A test of 17a-methyltestosterone as a growth promoter in a coho
salmon hatchery. Trans. Am. Fish. Soc. 108:467-472.
198 t. Stress related effects of hatchery rearing density on coho. Trans. Am.
Fish. Soc. 110:644-649.
1l0KA, C.
1978. Summary of the report on the project of experimental exploitation ofimportant migratory resources (1977). Development of the technique of rearing and releasing young fish to increase the rate of return of the salmon.
Fish. Mar. Serv., Can. Trans!. Ser. 4417, 11 p.
1l0KA, c., 1. TERAJIMA, K. YAMAMOTO, S. OGAWA, S. SATO, and Y.
NAKAMURA.
1978. An examination of the release of seawater-reared fingerlings. Fish.
Mar. Serv., Can. Trans!. Ser. 4384, 58 p.
KEPSHIRE, B. M., and W. J. McNEIL.
1972. Growth of premigratory chinook salmon in seawaler. Fish. Bull., U.S.
70:119-123.
WAGNER, H. H., F. P. CONTE, and J. L. FESSLER.
1968. Development of osmotic and ionic regulation in two races of chinook
salmon, Oncorhynchus tshawyrscha. Compo Biochem. Physiol. 29:325-341.
ZAUGG, W. S.

The final indicator of success for any management strategy iscontribution to and long-term effects on the population. Our work
indicates that during the test period, acclimated presmolt fallchinook salmon (survivors of the 23 March seawater challenge)
grew as well as smolted fall chinook salmon (survivors of the 23
April seawater challenge) in seawater. This observation supports
the thesis that preadapted fish may also grow and react normallyas adults. Other authors (Kepshire and McNeil 1972; Sullivant
1961; Clarke et al. 1981) reported decreased growth forpreadapted fish. They may have observed normal growth reduction caused by transition to seawater. Clarke et al. (1981), for example, began their experiments using 1.2 g fall chinook salmon
held from early April to June. These fish would normally beapproaching smoltification but would still display retarded growthwhen moved to full strength seawater (29 ppt) after 6 wk (early
May).
There are few indications in the literature concerning the effects of early seawater entry on the contribution of adults.
Available evidence indicates that the contribution may be equal toor better than that of "normally" released fish. The Japanesechum salmon, Oncorhynchus keta, industry has made favorable useof river-mouth releases and short-term, saltwater-rearing
strategies for several years (lioka 1978; Iioka et al. 1978), indicating that releases in saltwater are feasible and practical.
Eriksson et al. (1981) demonstrated that smolts of Atlantic
salmon, Salrno salar, made a greater contribution to the fisherywhen released into seawater sites than did smolts released from
'Sandercock, F. K., and E. T. Stone. [Undaled.] The effect of rearing density on
subsequent survival of Capilano coho. Mimeogr., 2 p. Fisheries and Oceans,
Salmonid Enhancement Program, 1090 West Pender St., Vancouver, B.C. V6E 2P1
Canada.

1982. A simplified preparation for adenosine triphosphatase determinationin gill tissue. Can. J. Fish. Aquat. Sci. 39:215-217.

19

Chinook Salmon Fisheries and Enhancement in Alaska:
A 1982 Overview
WILLIAM R. HEARD I

ABSTRACT
Chinook salmon, Oncorhynchus tshawytscha, fisheries and enhancement programs have distinct characteristics in different regions of Alaska. Major commercial fisheries are found in southeastern Alaska, Bristol Bay,and the Arctic- Yukon-Kuskokwim (A.Y.K) regions; important recreational fisheries are in southeastern Alaska
and Cook Inlet, and subsistence fisheries are in Bristol Bay and the A- Y-K region. In many areas, chinook
salmon are caught in more than one fishery. For example, fish returning to western Alaska (Bristol Bay andA- Y-K) are also caught in foreign high-seas gill net and trawl fisheries. In Cook Inlet, the principal fishery isrecreational; however, commercial net fisheries that target on other species also catch some chinook salmon. In
southeastern Alaska, both commercial and recreational marine troll fisheries catch fish from stocks thatoriginate from Alaska, British Columbia, and the Pacific Northwest.
In 1982, 13 hatcheries were rearing chinook salmon in Alaska: 8 in southeastern Alaska, 3 in Cook Inlet, Ion the Alaska peninsula, and 1 in interior Alaska. At satellite projects associated with several hatcheries, fry,fingerlings, or smolts are heid in marine net-pens or are released in streams or lakes to produce anadromous
adult returns.
Five organizations, including the Alaska Department of Fish and Game, two regional aquaculture associa·
tions, the National Marine Fisheries Service, and the Annette Island Indian Reservation, operate chinook
salmon hatcheries. Transport of eggs to or from hatcheries and overall development of programs at eachhatchery are regulated by the State of Alaska.
Many chinook salmon hatcheries and satellite programs in Alaska are too new to be evaluated; however,two in Cook Inlet (Crooked Creek and Halibut Cove Lagoon) and three in southeastern Alaska (Crystal Lake,
Little Port Walter, and Deer Mountain) are contributing to regional fisberies. Different enhancement strategies
are used to meet different regional needs. In Cook Inlet, the recreational fishery is primarily in freshwater anddepends on mature adults returning to their natal area or release site. In southeastern Alaska, where chinook
salmon are caught only in seawater, the fisheries depend on actively feeding fish. Because fisheries in Alaska require different life·history stages, managers developing enhancement strategies must consider ocean migration
patterns, stock genetics, hatchery location, and specific fish·culture treatments that might infiuence maturation
patterns and contribution potentials.

INTRODUCTION

Regional allocation of salmon in western Alaska is interna·
tional because fish from the Yukon River can originate in Canadian provinces as well as in Alaska. Furthermore, high· seascatches of immature, western Alaska chinook salmon by theJapanese mothership fleet in the Bering Sea can exceed the total
inshore and river commercial harvest of mature fish in some years(Meacham and Arvey 1981; Major 1982).
These many controversies, in turn, directly affect research,
management, and enhancement efforts to improve stocks andfisheries. In southeastern Alaska, much of the current chinook
salmon research and enhancement effort is directed at resolving
complex issues associated with the interstate and international
allocation of depressed stocks.
The purpose of this report is to review major chinook salmon
fisheries in Alaska and enhancement efforts that relate to some ofthese fisheries.

Chinook salmon, Oncorhynchus /shawy/scha, are found alongmuch of the Alaskan coastline, from Dixon Entrance in the south
to Kotzebue Sound in the north. Some of these stocks spawn in
Alaska; others spawn in Washington, Oregon, California, Idaho,
British Columbia, and Asia and migrate through nursery areas
along the Alaskan coastline.
Often different fisheries in Alaska and elsewhere depend on thesame stocks of chinook salmon; thus, allocation of this valuable
fish can cause regional, interstate, and international controversy.
In Cook Inlet, the catch is allocated between a major recreational
fishery in freshwater streams and incidental catch in a commer·
cial gill net and seine fishery in the inlet. In southeastern Alaska
where the commercial troll and recreational marine fisheries
target on a complex mixture of stocks, incidental catches in commercial gill net and seine fisheries become an important issue. In
western Alaska, mature, returning chinook salmon are caught
commercially in an inshore gill net fishery in Bristol Bay and in
net fisheries in the Kuskokwim and Yukon Rivers. Throughout
western Alaska, in addition to commercial fisheries, there is aheavy subsistence use of chinook salmon.

STOCKS AND FISHERIES
Major fisheries in Alaska can be categorized into four
geographic areas: Southeastern, Cook Inlet, Bristol Bay, and theArctic- Yukon-Kuskokwim region (A- Y-K) (Fig. 1). The commercial catch in Alaska in 1980 and 1981 is representative of catches
in recent years (Table 1)-670,1 00 chinook salmon in 1980 and
820,000 in 1981. Most of these fish were caught in Southeastern,
Bristol Bay, and A- Y-K regions; however, major management

1 Northwest and Alaska Fisheries Center Auke Bay Laboratory, National Marine
Fisheries Service, NOAA, P.O. Box 155, Auke Bay, AK 99821.

21

Figure I.-Four geographic regions of Alaska with importantchinook salmon fisheries.
IMPORTANT ALASKA CHINOOK FISHERIES

issues also occur in Cook Inlet because of conflicts between
recreational and commercial fisheries.
Two other areas, Copper River and Alaska Peninsula, also havea significant commercial harvest of chinook salmon; however,neither area has special management concerns associated with thefisheries. In the Copper River, most chinook salmon are caught ina gill net fishery at the mouth of the river. On the Alaska Peninsula, most chinook salmon are caught along the northern peninsula and are associated with the outer districts and migration
approaches to Bristol Bay. Some stocks originate from thesouthern Alaska Peninsula area, notably on Kodiak Island and at
Chignik, but they usually make up a small part of the total Alaska
Peninsula catch.

commercial harvest of chinook salmon recorded. Since 1953, theannual catch has averaged about 13,500 fish.
The recreational catch of chinook salmon in the Cook Inlet area
has been steadily increasing. The Cook Inlet area has the highest
recreational fishing effort in Alaska because of population
demographics in the state. In 1979, 125,000 recreational fishermen spent 766,556 d fishing in the Cook Inlet area and caught
25,800 chinook salmon (Cook Inlet Regional Planning Team
1981). On the Kenai River alone, recreational fishermen spend
nearly 100,000 d annually fishing for chinook salmon that weighan average of 14 kg (30 lb) and frequently exceed 27 kg (60 lb).
Most chinook salmon caught in Cook Inlet are mature adults
approaching or in their natal streams. Only a few ocean-feeding
salmon are caught in marine recreational fisheries in the outerpart of Kachemak and Resurrection Bays, fisheries similar toother recreational fisheries in southeastern Alaska and southward
along the North American coast. Rough marine waters and few
launching and berthing facilities limit marine recreational fishingin Cook Inlet; however, there is a small, specialized marine
recreational fishery for mature chinook salmon along beaches of
the Kenai Peninsula south of Deep Creek. Wild stocks andhatchery stocks of chinook salmon from Oregon, Washington,
British Columbia, and southeastern Alaska use Lower Cook Inlet
a~ an ocean nursery area (Wallis 1980), and a small marine
recreational fishery on immature, ocean-feeding chinook salmon
in the outer part of Kachemak Bay provides valuable recovery
information on coded-wire tagged chinook salmon.

Cook Inlet Area

Southeastern Alaska

Chinook salmon from the Susitna, Kenai, Kasilof, Ninilchik,and Anchor Rivers, and Deep Creek all contribute to the Cook Inlet fisheries; however, most fish originate from the Susitna River.
Commercial fisheries for chinook salmon in Cook Inlet include"
purse-seine fishery in Lower Cook Inlet, and drift gill net and set
gill net fisheries in Upper Cook Inlet. Between 1933 and 1953,
the average annual commercial harvest in Cook Inlet was morethan 90,000 fish (Cook Inlet Regional Planning Team 1981).
However, the commercial catch has been declining since 1951,
the year that 187,513 fish were caught and the highest annual

Commercial and recreational fisheries in southeastern Alaska
harvest chinook salmon from stocks that are endemic to the areaand stocks that originate as far south as Oregon (Parker andKirkness 1956). From analyses of recovered coded-wire tags, theNorth Pacific Fisheries Management Council tentatively assigned
the origin of stocks contributing to the southeastern Alaska
chinook salmon fishery as follows: 40% Canada; 40% Washington, Oregon, and Columbia River; and 20% Alaska. The major
endemic stocks of chinook salmon from southeastern Alaska arefrom the Taku, S,ikine, Alsek, Chilkat, Situk, Unuk, and Chicka-

Table I.-Preliminary commercial catch of chinook salmon in
Alaska by area, 1980 and 1981.'
Area

1980

1981

Southeastern
Copper River and vicinity
Cook Inlet
Alaska Peninsula and vicinity
Bristol Bay
Arctic- Yukon-Kuskokwim
Total

320,600
8,700
12,90024,70095,700207,500
670,100

270,800
21,40010,60031,900239,000
246,300
820,000

I

Data compiled by the Alaska Department of Fish and Game.

Di vision of Commercial Fisheries.

22

Principal stocks in the Yukon River, largest river in Alaska andfourth largest in North America, have been characterized according to their spawning grounds: Lower (Andreafsky, Anvik, andNulato Rivers), Middle (Koyukuk and Tanana River tributaries),and Upper (Big Salmon, Nisutlin, and Teslin Rivers) (McBrideand Marshall 1983; Arvey 2). An unknown portion of the chinook
salmon in the Upper Yukon River spawn in Canada, and, in 1981,
an estimated 5,500 chinook salmon were commercially harvested
in the Canadian portion of the Yukon River (Meacham and Arvey
1981). Subsistence catches of chinook salmon are also significant
in the A- Y-K region. In 1981, the subsistence catch of chinook
salmon was estimated at 50,000 for the Yukon River and 65,000
for the Kuskokwim River (Meacham and Arvey 1981).
In 1980, the Japanese mothership fishery caught 703,798
chinook salmon in the high-seas fishery, primarily in the Bering
Sea. Major (1982) has estimated that 380,417 or 54% of thesefish originated from western Alaska, mainly from the Yukon andKuskokwim Rivers and Bristol Bay. Most of these fish were immature (0.2 ocean age) when caught and would have matured 1-3
yr later. The loss of chinook salmon to U.S. fishermen was
estimated to be 5.62 million kg (12.4 million lb) (Major 1982).

min Rivers. Other stocks exist, but they are small or their current
status is unknown.
Most chinook salmon are caught by the commercial power-troll
and hand-troll fleets, which concentrate in certain inside and outside waters of southeastern Alaska (Gunstrom 1980). Sportfisheries for chinook salmon are in urban-area marine waters
principally around Juneau, Sitka, Ketchikan, Petersburg, andWrangell. The recreational harvest, estimated at 17,096 chinook
salmon in 1977 (Mills 1979), represented about 5.6% of the total
catch of chinook salmon in southeastern Alaska; whereas theharvest of chinook salmon in the commercial troll, gill net, andseine fisheries represented about 89.9, 2.7, and 1.7%, respectively, of the chinook salmon harvested in southeastern Alaska inthat year.
The Magnuson Fisheries Conservation and Management Act of1976 led to development of Fishery Management Plans which
regulate ocean fisheries for chinook salmon in jurisdictional
waters of the United States. In southeastern Alaska, the commercial troll fishery and recreational fishery are partly dependent onchinook salmon originating from outside the region. The North
Pacific Fisheries Management Council and the Alaska Board ofFisheries implemented the first Fisheries Management Plan forsoutheastern Alaska during the 1979 fishing season. The firstupper-limit Optimum Yield for southeastern Alaska was set at
320,000 fish/yr; however, the Optimum Yield has since beenadjusted downward and was set at 255,500 chinook salmon for
the 1982 season. Because many stocks of chinook salmon that
contributed to the troll fishery in southeastern Alaska were declining, new regulations for this fishery included reduced fishing
periods, minimum-size limits, and catch quotas. Gunstrom (1980)
gave a detailed account of the southeastern troll fishery and included the history, management problems, objectives, anddevelopment of the Fishery Management Plan.

CHINOOK SALMON ENHANCEMENT
Although chinook salmon enhancement is presently concentrated in southeastern Alaska and Cook Inlet, there are two projects in other areas. By the end of the 1982 spawning season, 13
hatcheries were rearing chinook salmon (Fig. 2): 8 in southeastern
Alaska, 3 in Cook Inlet, and I each in the Alaska Peninsula andinterior Alaska. One new facility, Trail Lakes Hatchery on the
Kenai Peninsula, was scheduled to receive 1982-brood chinook
salmon eggs but had construction delays. Many of these programs
are in early stages of brood-stock development, and only small
numbers of eggs or fingerlings are being cultured.
The 13 chinook salmon hatcheries in Alaska are operated by
five organizations: The Alaska Department of Fish and Game
operates nine, and the two regional aquaculture associations, theNational Marine Fisheries Service and the Annette Island Indian
Reservation, each operate one. The State of Alaska controls thetransport of chinook salmon eggs to or from hatcheries and thedevelopment of the overall program at each hatchery.
In satellite projects associated with several hatcheries, chinook
salmon fry, fingerlings, or smolts are held in marine net-pens or
are released in streams or lakes to produce returns of anadromous
adults. In a few projects, mostly in the Anchorage urban area andon the Kenai Peninsula, chinook salmon fry are planted in landlocked lakes for a recreational fishery.
In programs producing anadromous chinook salmon, broodstocks for the hatcheries and satellite projects are carefully
selected so that wild spawning populations are protected andmaintained, and the particular enhancement needs in the area aremet. Brood stocks usually come from the region where thehatchery is located, and most hatcheries are placed where chinook
salmon are not endemic. Only one hatchery project has beendeveloped on a stream with a large, wild population of spawningchinook salmon: At Crooked Creek, a tributary of the KasilofRiver, on the Kenai Peninsula of Cook Inlet, the same stock thatspawns in the stream is used in the hatchery and in several
satellite projects in the region. In another stream, Ship Creek, near

Bristol Bay
In Bristol Bay, all of the principal river systems, including the
Naknek, Kvichak, Nushagak, Togiak, Egegik, and Ugashik Rivers,
support one or more stocks of chinook salmon. Since the 1950's,
70% of the commercial harvest in Bristol Bay has come fromNushagak District, and in 1981, the commercial gill net catch of
chinook salmon in the Nushagak District was 195,000 fish.
Recreational fisheries for chinook salmon in Bristol Bay are notsignificant; however, subsistence catches of mature fish in rivers
draining into Bristol Bay are significant. In 1981, an estimated
15,000 chinook salmon were caught in this subsistence fishery,
which is primarily a gill net fishery (Meacham and Arvey 1981).
A recent escapement model for Nushagak chinook salmon (Alexandersdottir and Mathisen 1981) recommends building a stronger
data base for commercial and subsistence fisheries, a data basethat takes into account selectivity of different meshes of gill nets
used in these fisheries and increasing the precision of escapement
estimates.

Arctic- Yukon-Kuskokwim Region
The large A- Y-K region has many stocks of chinook salmon.
Some originate from short, lowland coastal streams; others
originate from the 3,700 km (2,300-mi) long Yukon River, which
has its source in British Columbia, Canada. Most chinook salmon
commercially caught in this region are from the Kuskokwim andYukon Rivers.

2W. D. Arvey, Regional Research Supervisor, Commercial Fisheries Division,
Alaska Department of Fish and Game, 333 Raspberry Road, Anchorage, AK 99502,
pers. commun. December 1982.

23

1.
2.
3.
4.
5.

ALASKA DEPARTMENT OF FISH
AND GAME
Clear
Ship Creek
Crooked Creek
Trail lakes
Kitoi Bay

6. Snettisham
7. Hidden Falls
10. Crystal Lake
12. Deer Mountain

8.

NORTHERN SOUTHEAST REGIONALAOUACULTURE ASSOCIATION
Medvejie

9.

NATIONAL MARINE FISHERIESSERVICE
Little Port Walter
SOUTHERN SOUTHEAST REGIONAL
AQUACULTURE ASSOCIATION

11. Wtlllman Lake
AN~EnE

Figure 2.-Location and agency affiliation of hatcheries raisingchinook salmon In Alaska.

IScAND INDIAN
FlESERVATI0N

11. Tarnga5

J.
LOCATION AND AGENCY AFFILIATION OF HATCHERIESIN ALASKA CULTURING CHINOOK SALMON

Anchorage, wild chinook salmon spawn in the stream; however.
most adult chinook salmon in that stream apparently originate
from hatchery production. Fish from other areas have also beentransplanted to Ship Creek.
Before considering some enhancement projects more closely, 1will briefly review the freshwater biology of Alaska chinook
salmon. Smolts migrate into seawater in April, May, and June
(Meehan and Siniff 1962; Kissner 1977; Raymond 19813), andmost migrate in May and June. Juvenile chinook salmon can have
two life history patterns, generally referred to as ocean type or
stream type. The ocean type migrate to seawater during their firstyear; the stream type migrate after remaining 1 or 2 yr infreshwater (Gilbert 1912). (The terms "ocean-type" and "streamtype" are similar to the terms "fall" and "spring"; however, theterms "fall" and "spring" apply to the time of spawning migrations.) Most chinook salmon in Alaska have a stream-type biology(Yancey and Thorsteinson 1963; Rowland 1969; Waite 1979;
Kissner 1981, 1982); however, recent research on chinook salmon
in the Kenai River raises questions on the age that juveniles enterseawater in that system (Dave Wangaard4 ). In North America,
ocean- and stream-type chinook salmon are probably different
genotypes rather than environmentally regulated phenotypes and,because of different ocean-migration traits, have different potentials for contributing to specific fisheries (Healey 1983).
On the Taku River in southeastern Alaska and on Crooked
Creek in Cook Inlet, O-age chinook salmon fry move downstream
during mid- to late-summer and early fall (Kissner 1977; Waite
1979) and apparently remain overwinter in downstream freshwater areas some distance from the spawning area. Presumably,other siblings remain overwinter in upstream waters closer to theirnatal areas. Other stocks of stream-type chinook salmon also havethis behavior (French and Wahle 1959; Royal 1972).
Chinook salmon in Alaska spawn in July, August, and September. Most spawn in August, and in many large Alaskan rivers,chinook salmon are the first spawning salmon to appear eachyear.

Cook Inlet
The three hatcheries in Cook Inlet that .:ulture chinook salmon-Ship Creek, Crooked Creek, and Trail Lakes-ea.:h have aslightly different enhancement strategy. Because of arctic wintersin Cook Inlet, most overwinter culture of chinook salmon is at
Ship Creek Hatchery, which uses warm water from the coolingponds of a large power plant. Eggs are collected from racks on
Crooked Creek and Ship Creek in the fall, transported to Ship
Creek Hatchery, and raised 6-8 mo in warm water to O-age
smolts. Smolts are released either in the stream of origin or insatellite projects in the region. Some fish from almost all releases
are coded-wire tagged to evaluate the projects. In /981, some
Crooked Creek chinook salmon eggs were retained at the Crooked
Creek Hatchery, where, because of cooler water, most smolts arescheduled to be released as yearlings.
At the Trail Lakes Hatchery, located on the headwaters of the
Kenai River System, eggs will be incubated and reared to only
early stage fry. This modular hatchery was designed to simultaneously culture several stocks in isolation. The fry will beplanted in areas with unused rearing potential in the Cook Inlet
area. In 1982, it remained undecided as to which stocks would be
used at this hatchery and where the fry would be planted.
Chinook enhancement at Crooked Creek has had some success:From 0.9 to 1.5% of the released smolts returned to Crooked
Creek as adults, including jacks (WaiteS). In 1982, 74% of the
3,503 fish returning to the Crooked Creek Hatchery were
estimated to be hatchery fish, and an estimated 79% of the 2,800
fish caught in a recreational fishery at the stream mouth werefrom the hatchery.
Evaluating adult chinook salmon returns at Crooked Creek (andother areas) from either hatchery or wild stocks is complicated by'Raymond, J. A. 1981. Outmigration of salmon smolts from Clear Creek, Alaska.
Unpubl. rep., 19 p. Alaska Dep. Fish Game, Div. Fish. Rehabilitation, Enhancement.
Dev., Juneau, AK 99801.
'D. B. Wangaard, Fishery Biologist, U.S. Fish anJ W,lclife Service, 1011 East
Tudor, Anchorage. AK 99503, pers. commun. July 1981.

'D. C. Waite, Fishery Biologislll, FRED Division, Alaska Department of Fish anJ
Game, P.O. Box 3150, Soldotna, AK 99669, pers. commun. October) 982.

24

four factors: 1) Inadequate sampling of precocious males returning
after I or 2 yr in the ocean; 2) the long-lived nature of the species(some mature and return only after 6, 7, or even 8 yr); 3) a fisherythat captures different numbers of multiple age groups thatoriginate from the same brood; and 4) highly variable marine survival of smolts from different broods.
In 1975, the first release of smolts from Crooked Creek included only 3,679 smolts. Since then, from 50,000 to 380,000 smolts
have been released annually. Average smolt sizes at release haveranged from 15 to 35 g.
The number of Crooked Creek chinook salmon caught in commercial and recreational fisheries is largely unknown because,
presently, neither fishery is systematically sampled for marked
fish. The recreational fishery, especially along Cook Inlet beaches
approaching the Kasilof River, has increased significantly inrecent years. The Crooked Creek chinook salmon enhancement
program needs a careful, critical analysis to accurately measure its
effectiveness and determine whether or not the hatchery programis adversely affecting wild stock production on that stream.
Three satellite projects in the Cook Inlet area, the Whittier,Seward, and Halibut Cove Lagoon projects, all use smolts rearedin warm water at the Ship Creek Hatchery. Age-O smolts are
released into local waters, and in some cases, are kept in marine
net-pens before release to improve imprinting to the release site.
The project at Whittier, in Prince William Sound, began in
1981 when smolts were released to provide adults for a recreational marine fishery and eggs for some Prince William Sound
hatcheries.
In 1976-79,442,000 smolts from the Seward project were released into Box Canyon Creek to establish a self-sustaining run fora local marine recreational fishery. The 14-31 g smolts from fourbroods of Ship Creek and Crooked Creek stocks were released inJune each year from 1976 to 1979. Although no adults have beencaught in the recreational fishery, 132 spawners, mostly age 0.3
from the I978-brood releases in 1979, have returned to Box Canyon Creek and spawned (McH enry 6).

The satellite project at Halibut Cove Lagoon, in Kachemak Bay
across from Homer, has been one of the most successful projects
in Alaska, as measured by the nUillber of returning adults. The
Halibut Cove Lagoon project is evaluated from the percentage ofadults returning to the release site that have coded-wire tags.
About 100,000 tagged smolts have been released at Halibut Cove
Lagoon over an 8-yr period, and over 900 tags have been
recovered near the release site. Return rates (including jacks) for
smolts released from five broods ranged from 0.8 to 7.3% andaveraged 2.7% (Dudiak 7 ). Returning adults are snagged (legal inseawater) in a local fishery in the terminal marine area, and in
1982, more than 2,500 fish from this project were caught.
However, Halibut Cove Lagoon tags have not been recovered in
the marine recreational fishery that catches ocean-feeding
chinook salmon only a few miles away in outer Kachemak Bay(Fig. 3).

Southeastern Alaska
Chinook salmon enhancement in southeastern Alaska differs
considerably from that in Cook Inlet because fisheries in southeastern Alaska are restricted to marine waters, and most arecaught by trolling, which requires feeding fish. A successfulenhancement program must, therefore, produce chinook salmon
that are actively feeding in specific marine waters in southeastern
Alaska. Most chinook salmon in southeastern Alaska are cultured
to age-l rather than O-age fish. All chinook salmon hatcheries insoutheastern Alaska rear transplanted stocks, and several aresituated in remote, roadless areas. All except one, the Snettisham
Hatchery, are located on islands. One hatchery, Little Port Walter,
is a research facility operated by the National Marine FisheriesService and the Alaska Department of Fish and Game, and since
1976, a variety of chinook salmon enhancement techniques havebeen studied at this facility.
Four of eight hatcheries in southeastern Alaska-Whitman
Lake, Hidden Falls, Medvejie, and Tamgas Hatcheries-started
raising chinook salmon only within the past 3 yr, and their pro-

6E. T. McHenry, Fishery Biologist III, Sport Fish Division, Alaska Department ofFish and Game, P.O. Box 285, Seward, AK 99664, pers. commun. October 1982.

'N. C. Dudiak, Fishery Biologist lII, FRED Division, Alaska Department of Fish
and Game, P.O. Box 234, Homer, AK 99603, pers. commun. October 1982.

ALASKAALASKA
1. Little Port Walter
2. Crystal Lake

BR ITiSH
COLUMBIA

BRITISH COLUMBIA
3. Atnarko (wild)
4. Puntledge

5. Robertson Creek
6. Nitinat (wild)

WASHINGTON
7. Skagit
8. Priest Rapids
OREGON

Figure 3,-Recoveries of immature chinook salmon with coded- wiretags from Oregon, Washington, British Columbia, and Alaska
stocks in outer Kachemak Bay, Cook Inlet, Modified after Wallis

9. Marion Forks
10. South Santiam (5)(1980)RECOVERIES OF CODED WIRE TAGGED
IMMATURE CHINOOK SALMON

25

grams cannot be evaluated. Medvejie and Tamgas HatclH::riesbegan culturing chinook salmon from 1982-brood eggs.
Three other southeastern hatcheries, Crystal Lake, Little Port
Walter, and Deer Mountain Hatcheries, all show promise because
chinook salmon from these hatcheries are contributing to therecreational and commercial troll fisheries in the region. Effective
programs began at Crystal Lake and Little Port Walter in 1976
and at Deer Mountain in 1977.
Crystal Lake Hatchery was first operated in 1972 and was
designed to use recirculating warm water heated by oil furnaces.
After dramatic increases in world oil prices, however, the facility
has used single-pass, ambient-temperature water similar to othersoutheastern hatcheries.
Five stocks of chinook salmon are being raised in hatcheries insoutheastern Alaska. Two stocks, Andrew Creek stock from the
Stikine River and Cripple Creek stock from the Unuk River, aremost widely used, both in number of eggs and number ofhatcheries. These two stocks and three 0ther stocks (from the
Chickamin, King Salmon, and Situk Rivers) all originate fromsoutheastern Alaska. Heard (1982) has reviewed in detail the useof specific chinook stocks at southeastern Alaska hatcheries
through 1981. Presently, Crystal Lake Hatchery is using only the
Andrew Creek stock, and Deer Mountain Hatchery is using only
the Cripple Creek stock. The Little Port Walter Hatchery is conducting some research with three stocks (Cripple Creek, Chickamin River, and Situk River stocks). At Little Port Walter, stocks
are maintained separately and returning adults are spawned according to specific matings.
Hatcheries in southeastern Alaska have used different strategies
for rearing and releasing smolts. Age-O smolts (11.4 g) from the
1976-brood were released from Crystal Lake after they werereared in heated water. Smolts from two different 1976-broodstocks were released at Little Port Walter in nine separate groups
including one age-O (36.0 g) and eight age-I smolt (63.0-82.8 g)groups. Yearling smolts (7.4-10.1 g) from the 1977-brood werereleased from the Deer Mountain Hatchery.
Preliminary adult returns and contribution to the fisheries areavailable for 1976-brood releases at Cry~tal Lake and Little Port
Walter, and 1977-brood releases at Deer Mountain. Preliminary
overall survival rates (return to hatchery and fishery contributions) of 1976-brood smolts through 5-yr-old fish (1981) was
6.8% for Crystal Lake releases and 7.1-7.3% for Little Port Walterreleases (Table 2). Survival of the nine smolt groups at Little Port
Walter ranged from 1.0 to 14.1 % (Table 3). This includes both
adult returns to the hatchery and estimates of contributions tocommercial and recreational fisheries. From preliminary analysesof recoveries from 1977 -brood at Deer Mountain Hatchery,marine survival (through age-5 adults in 1982) will be about
6.0%. The I 976-brood releases from Crystal Lake and Little Port
Walter contributed a significant number of 4-yr-old immaturechinook salmon to fisheries throughout the northern part of southeastern Alaska. At Crystal Lake, many mature 4-yr-old females
returned with 4-yr-old males to the hatchery from age-O smolts(Zorich 8 ); however, at Little Port Walter, only males matured andreturned as 4-yr-olds from yearling smolts. In 1982, about 50
5-yr-old females that returned to Deer Mountain Hatchery were
spawned for the first filial (F-I) generation of eggs taken at thatfacility. Collectively, in 1982, about 1.4 million .::hmook salmon
eggs were taken from adults returning to Crystal Lake. Little Port
Walter, and Deer Mountain Hatcheries.
Two satellite projects for enhancing chinook salmon in southeastern Alaska began in 1982. Both projects are designed to determine whether natural rearing areas can be used to increase smoll
production. In the first project, eggs from 1981-brood Chickaminstock were cultured to early fry stage at Whitman Lake Hatchery,a Southern Southeastern Regional Aquaculture Association
Hatchery, and the fry were then planted in the Carroll River. In
the second project, fry from 1981-brood Chickamin River stock
were reared at the Little Port Walter Hatchery and planted into
two small nearby lakes.

Table 2.-Preliminary marine survivals through age S of 1976-brood chinook
salmon smolts released at Crystal Lake Hatchery· and at Little Port Walter insoutheastern Alaska.

Sto.k
Crystal Lake Hatchery:
Andrew Creek
Little Port Walter:
Cripple Creek
Chickamin River. Survival (%) .

SmoltsAdultsreleasedrecoveredAll

A~('.-'_

(No.)

(No.)

smoltssmolts

166.030

11,363

6.&

22.50818,431

1,598
1,344

7.1
7.3

Other Areas------ ._.- -The two other chinook salmon enhancement projects in Alaska
are at Kitoi Bay and Clear Clear Hatchery (Fig. 2) is located at

7.1
9.7

'R G. ZOIich, FiShery Biologist II, FRED Division, Alaska Department of Fish
and Game, Swanson Building, P.O. Box 667, Petersburg, AK 99833. pers. commun.
October 1981.

'Data provided by Bob Zorich, Alaska Department of Fish and Game, Crystal
Lake Hatchery.

Table 3,-Marine survival through age S of nine 1976-brood chinook salmon smolt groups
released at Little Port Walter in southeastern Alaska.
Treatmentgroup'

N

C-5
U-IO
U-Il
C-12
C-l3
C-14
U-15
U-16
U-17

5,034
4.918
4,536
4,552
4,4 72
4.373
4.108.. ,462

4,184

No. recovered

Release
date

Size
~g)

Age 2

8-21-77
4-12-78
4-13-78
4-14-n5-11-78
5-12-78
5-13-78
5-10-78
6-07-78

36.0

0

Total

(%)

II
46
26
29
156
202
132
87
74

49
107
103
134
543
618
547
487
354

1.0
2.2
2.3
2.9
12.1
14.1
12.4
10.9
8.5

64.~

63.9
72.2
64.2
84.6
645
647
82.8

Survival--------AbC 3 Age 4 Age 5------7
1
1
0
18
23
45

8
0

2
5
55
fio

64

37
56
62
104
382
411
342
311
170

---------_._-~-------'Ident; fies stock "nd tag cedes C = Chickam:n River stcck; U = Unuk River stock.

26

biology of chinook salmon, specific enhancement objectives, andregional and international sociopolitical issues.
One of the more challenging and complex aspects of chinook
enhancement in Alaska is to meet the needs of diverse fisheries
throughout the state. The needs of the chinook salmon fishery insoutheastern Alaska, for example, are different from those in
Halibut Cove Lagoon. In southeastern Alaska, the troll fishery isdependent on ocean distribution and migration patterns ofspecific stocks of chinook salmon. Hatchery programs contributing to this fishery must produce chinook salmon that actively feed in marine waters where the fishery occurs. In Halibut Cove
Lagoon, a highly successful program has developed based on
returns of maturing chinook salmon that have completed theirocean-feeding phase. Healey (1983) pointed out that ocean trolling is more effective in harvesting immature than mature chinook
salmon. An excellent example of this is seen in lower Cook Inlet
where ocean feeding chinook salmon from many North Americanstocks are caught in the small sport-troll fishery in outer
Kachemak Bay ~Fig. 3); yet, no fish from the nearby Halibut Cove
Lagoon project have been caught in this fishery. Ocean-type andstream-type stocks, because of different ocean-migration traits,
may have different potentials for contributing to troll fisheries~Healey 1983); therefore, stock genetics, location of hatcheries orsatellite projects, and enhancement techniques will influence how
well different stocks contribute to specific fisheries that havediverse needs in different parts of Alaska.

Clear Air Force Station, near Anderson, and like Ship Creek
Hatchery, uses warm water from cooling ponds of a power plant.
Juvenile salmon from Clear Hatchery are released into a nearby
tributary of the Nenana River, which flow[ into the Tanana River,which in turn flows into the Yukon River.
In 1981, eggs were collected from fish in the Salcha River, atributary of the Tanana River, and transported to Clear Hatchery.
The chinook salmon were cultured to O-age smolts (3.4 g), and103,000 were released at the hatchery in May 1982 (Raymond 9 ).
Twenty-five thousand smolts were coded-wire tagged and represent the first marked juveniles and the first chinook salmon
enhancement effort in the A-K- Y region. This experimental program is also exploring the feasibility of enhancing runs of chinook
salmon in the interior arctic Alaska.
The Kitoi Bay Hatchery has a satellite project at Lake Rose
Tead, Kodiak Island. Beginning with the 1975 brood, chinook
salmon eggs were collected from the Chignik River stock on the
Alaska Peninsula, transported to Kitoi Bay Hatchery, and cultured
to the early fingerling stage. Fingerlings were then released into
Lake Rose Tead to produce adult returns for a local recreational
fishery (Murrayi°). Some adults returning to Lake Rose Tead (F-ladult returns) were used as a brood stock. In 1981, about 25% of
the 133,000 eggs collected were from F-l adults returning to
Pasagshak River, the outlet stream to Lake Rose Tead (McMullin
and Kissel 1982). In 1982, about 37,000 of the eggs taken for the
project were from returning F-I adult. (Murray footnote 10).
In an earlier Kodiak Island project similar to the one at Lake
Rose Tead, chinook salmon fry were transplanted to Frazer Lakefrom Kitoi Bay Hatchery to establish a self-sustaining
anadromous run (Blackett 1979). The Karluk River stock, also on
Kodiak Island, was used to establish the run at Frazer Lake.

LITERATURE CITEDALEXANDERSDOTTIR, M., and O. A. MATHISEN.
1981. Nushagak Bay king salmon escapement model. Univ. Washington,
Fish. Res. Inst. Final Rep. FRI-UW-8114, 43 p.
BLACKETT, R. F.
1979. Establishment of sockeye (Oncorhynchus nerka) and chinook (0.
Ishawvlscha) salmon runs at Frazer Lake, Kodiak Island, Alaska. J. Fish.
Res. Board Can. 36: 1265-1277.
COOK INLET REGIONAL PLANNING TEAM.
1981. Cook Inlet regional salmon enhancement plan 1981-2000. Alaska
Dep. Fish Game, Soldotna, 122 p.
FRENCH, R. R., and R. J. WAHLE.
1959. Biology of chinook and blueback salmon and steelhead in the Wenatchee River system. U.S. Fish Wildl. Serv., Spec. Sci. Rep. Fish. 304, 17 p.
GILBERT. C. H.
1912. Age at maturity of Pacific coast salmon of the genus Oncorhynchus
Bull. U.S. Bur. Fish. 32: 1-22.
GUNSTROM, G.
1980. The troll fishery in Southeast Alaska. Alaska Dep. Fish Game, Fish.
Inf. Pamphlet I, 8 p.
HEALEY, M. e.

DISCUSSION
Of the five species of Pacific salmon, chinook salmon provide
the fewest fish to Alaska's varied fisheries; however, they are themost valuable and highly 'prized species in all the fisheries.
Although most fisheries in Alaska are still based on naturalchinook salmon production, hatchery fish are contributing tofisheries in Cook Inlet and southeastern Alaska. In southeastern
Alaska, however, much of the hatchery contribution comes fromoutside the region. Increased enhancement activity in Alaska hasdeveloped partly to provide more chinook salmon to thesefisheries.
In Cook Inlet, new recreational fisheries have developed fromhatchery or satellite projects, such as the Crooked Creek Hatcheryand the Halibut Cove Lagoon project. Other satellite enhancement
programs should increase production or develop new natural runsof chinook salmon. Although sampling is incomplete and varied,in 1982, between 8,000 and 10,000 adult chinook salmon from
Alaska enhancement programs were caught in Alaska fisheries,
divided about equally between Cook Inlet and southeastern
Alaska. The full potential for enhancement of chinook salmon in
Alaska may not be realized for several years because many programs are still developing and will be influenced by the complex

1983.

Coastwide distribution and ocean migration patterns of stream andocean type chinook (Oncorhynchus tshaWYlscha).
433.
HEARD, W. R.
1982.

Can. Field-Nat. 97:427-

Chinook salmon enhancement and research activities in southeastern

Alaska. In Third Alaska Aquaculture Conf., Cordova, p. 93-109. Univ.
Alaska Sea Grant Rep. 82-8.
KISSNER, P. D.
1977. A study of chinook salmon in Southeast Alaska. Alaska Dep. Fish
Game Completion Rep. Study AFS 41-5, 63 p.
1981. A study of chinook salmon in Southeast Alaska. Alaska Dep. Fish
Game Annu. Rep. 1979-1980, Project F 9 23, AFS 41-8, 35 p.
1982. A study of chinook salmon in Southeast Alaska. Alaska Dep. Fish
Game Annu. Rep. 1980-1981, AFS 41-9, 36 p.
MAJOR, R. L.
1982. Yield loss of western Alaska chinook salmon resulting from the large
Japanese mothership catch of 1980. Document submitted to annual meeting Int. North Pac. Fish. Comm., Tokyo, Jpn., Oct. 1982,27 p.
McBRIDE, D. N., and S. L. MARSHALL.
1983. Feasibility of scale pattern analysis to identify the origins of chinook
salmon (Oncorhynchus Ishawylscha Walbaum) in the lower Yukon River

OJ. A. Raymond, Fishery Biologist III, FRED Division, Alaska Department of Fish
and Game, 1300 College Road, Fairbanks, AK 9970 I, pers. commun. May 1982.
,oJ. B. Murray, Fishery Biologist III, Sport Fish Division, Alaska Department ofFish and Game, Kashevaroff and Mission Roads, P.O. Box 686, Kodiak, AK 99615,
pers. commun. October 1982.

27

commercial gillnet fishery, 1980-81. Alaska Dep. Fish Game. Inf. Leafl.
208.64 p.
McMULLIN, J., and M. W. KISSEL (editors).
1982. Alaska Dep. Fish Game, Div. Fish Rehabilitation, Enhancement, Dev.
1981 Annu. Rep., 101 p.
MEACHAM, C. P., and W. D. ARVEY.
1981. Western Alaska chinook salmon synopsis. Rep. to U.S. Section, Int.
North Pac. Fish. Comm., 26 Sept. 1981, 15 p.
MEEHAN, W. R, and D. B. SINIFF.
1962. A study of the downstream migrations of anadromous fishes in the
Taku River, Alaska. Trans. Am. Fish. Soc. 91 :399-407.
MILLS, M. J.
1979. Statewide harvest study. Alaska Dep. Fish Game, Sport Fish Div.
Annual Performance Rep. Alaska Statewide Sport Fish Harvest Studies,
SW-I-A, Vol. 20, 112 p.
PARKER, R R., and W. KIRKNESS.
1956. King salmon and the ocean troll fisheries of southeastern Alaska.
Alaska Dep. Fish Game, Res. Rep. I, 64 p.

ROWLAND, R. G.
1969. Relation of scale characteristics to river of origin in fouf stocks ofchinook salmon (Oncorhynchus Ishawytscha) in Alaska. U.S. Fish Wildl.
Serv., Spec. Sci. Rep. Fish. 577, 5 p.
ROYAL, L. A.
1972. An examination of the anadromous trout program of the Washington
State Game Department. Spec. Consultant Rcp. Wash. Dep. Game, Olympia, 192 p.
WAITE, D. C.
1979. Chinook enhancement on the Kenai Peninsula. Alaska Dep. Fish
Game, Fish. Rehabilitation, Enhancement, Dev. Div. Completion Rep.,
Anadromous Fish Studies AFS-46-1, 51 p.
WALLIS, J.
1980. Marked chinook salmon in Kachemak Bay, Alaska. In 1979 Northwest
Fish Culture Conference, Portland, Oreg., December 1979, p. 5.
YANCEY, R M., and F. V. THORSTEINSON.
1963. The king salmon of Cook Inlet, Alaska. U.S. Fish Wildl. Serv., Spec.
Sci. Rep. Fish. 440, 18 p.

28

Systematic Genetic Selection and Breeding in
Salmonid Culture and Enhancement Programs 1 ,2
WILLIAM K. HERSHBERGER and ROBERT N. IWAMOT03

INTRODUCTION

ply a more systematic approach to the genetic improvement ofthese fish for intensive culture.
Very little basic genetic selection and breeding work has been
conducted with Pacific salmon (Oncorhynchus) species. As
previously mentioned, chinook salmon have been selectively bred
(Donaldson and Menasveta 1961), largely to change the age atreturn to spawn. Other short-term and largely nongeneticallyoriented reports have suggested the hereditary nature of a numberof traits (see review by Ricker 1972) and their potential response
to selection and breeding. However, few have involved a genetic
assessment of the traits studied or satisfactorily measured a
response to selection.
A large part of this lack of research can be attributed to the inability to control the entire life cycle of the salmon and to assure
adequate returns for breeding. Without these capabilities, it is notpossible to obtain accurate measurement of the genetic component involved in traits important to intensive culture. With thedevelopment of the technology necessary to raise Pacific salmon
species in marine net-pen enclosures (Novotny 1975), these two
problems were largely negated. In addition, commercial interest in
raising and marketing Pacific salmon utilizing this approach provided an impetus to develop a more systematic and predictableapproach to selection and breeding of these species.

Genetic selection and directed breeding have been a part ofanimal husbandry for perhaps 10,000 yr. The benefits of theseprocedures are quite apparent in the production realized fromdomesticated agricultural animals. While a large part of theseaccomplishments were achieved without any real knowledge ofgenetic principles and concepts, the approach used was one ofbasic genetic management. The practices employed included
choosing superior individuals for breeding, culling of inferior individuals, development of specific strains, and cross-breeding ofstrains to improve specific traits. These techniques are still
employed as part of the genetic management of agricultural
animals and continue to playa major role in improvement of theirproduction.
Some of these same procedures have been practiced in theculture of salmonid fishes. However, because of the relatively
short history of successful culti vat ion of these species in captivity,changes beneficial to the intensive cultivation of this group offishes have been slow to be realized.
Because control can be exercised over the entire life cycle byrearing in a hatchery, most of the selection and breeding work
conducted on salmon ids has been with Salrno and Salvelinus
species. Significant gains in performance characteristics havebeen realized with these species. Early work with brook trout,
Salvelinus jontinalis, demonstrated the efficacy of the genetic approach to improve disease resistance (Embody and Hayford
1925). Lewis (1944) reported alteration of the life history traits ofrainbow trout, Salrno gairdneri, by use of selection. Perhaps themost long-term selection program reported to date on salmonids isthat of Donaldson (1968) on rainbow trout and chinook salmon,
Oncorhynchus tshawytscha. Gains in a number of traits importantto culture of these species were reported after 35 + yr of selective
breeding.
All of these studies were based on the concept of selective
breeding, generally, the process whereby the reproducing adults
are chosen only on the basis of their phenotype. While this approach has been demonstrably successful, it has several
undesirable characteristics. From a commercial point of view, themost important of these are I) unpredictability of selection
response, 2) the inability to monitor genetic change, 3) more likely probability of inbreeding problems, and 4) the slow response ofsome less heritable traits. By application of more systematic selection and breeding methods (Falconer 1960), these problems canbe largely avoided. Thus, it would seem desirable to attempt to ap-

MARINE NET-PEN CULTURE PROGRAM
In the United States, marine net-pen culture of Pacific salmon
began in 1970 (Novotny 1975). The industry that developed was,and still is, based almost exclusively on the production of immature 350-400 g coho salmon, O. kisutch. Details on the cultureof these fish and related technology can be obtained in the reportby Novotny (1975). The choice of species was based largely on
hardiness and general adaptability to production conditions. Also,
because of a large emphasis on culturing this species in state andfederal hatcheries, a ready supply of eggs and sperm was initiallyavailable. However, there was soon a realization that to improvethe efficiency of production and minimize associated costs, itwould be necessary to develop a "domesticated" stock adapted toconditions of complete captive culture.
In 1978 we initiated a program to develop a coho salmon
broodstock for the marine net-pen industry. This cooperative program between the University of Washington, the Sea Grant Program, and Domsea Farms, Inc., had a long-range goal to develop a
coho salmon stock with desired characteristics for marine pen
culture. Specific traits chosen for genetic improvement, based on
economic considerations of the industry, were I) freshwater
growth rate, 2) saltwater growth rate, and 3) smoltification. Thus,
the breeding goals were defined and limited to the traits thatwould be of maximum economic benefit.
Since no information was available on the genetics of these
traits in coho salmon, the first step was to estimate the genetic andphenotypic parameters associated with the expression of these'Contribution No. 608 from the School of Fisheries, University of Washington,
Seattle, Wash.
'This research was supported by grant no. NA8IAA-D-000 from the National
Oceanic and Atmospheric Administration to the Washington Sea Grant Program,
University of Washington.
'School of Fisheries, University of Washington, Seattle, WA 98195.

29

traits. Determination of these values was necessary to I) indicate
the likelihood of a selection program to change the genetics of atrait, 2) devise the appropriate selection scheme, and 3) predict
the amount of change that could be expected. We found that adequate genetic variability (expressed as heritability (h 2 for all
three traits existed in this stock, thus assuring a reasonable
response through a selection program. Heritability estimates for
freshwater and saltwater growth measurements are shown in
Table 1. These values agree very favorably with data reported on

estimated to provide information on the relationships of the traits
and to give guidance on the types of selection that would yield the
maximum gain (Hershberger et aI. 1982; Iwamoto et aI. 1982;
Saxton et aI. 1982).
Based on these data and the production needs of Domsea Farms,
a selection scheme was devised that would provide the best selection results with the physical facilities available. The selection
program developed is shown in Figure 1. This selection strategy
includes independent culling during incubation followed by family selection during the saltwater phase. Family selection is basedon a selection index incorporating both freshwater and saltwater
performace traits. At maturity, spawners from the selectedfamilies are chosen on the basis of individual merit and mated ac..
cording to a circular mating design (Fig. 2). The specific mating
design was chosen to minimize the increase in inbreeding per
generation « 0.1 % per generation).
This system has been used on two odd (BY 1979 and BY 1981)
and two even (BY 1980 and BY 1982) year cycles of coho salmon
in this program. Gains in the areas of improving freshwater andsaltwater growth have exceeded our original expectations (Hershberger et aI. 1982; Iwamoto et al. 1982; Saxton 1980). For example, as a result of one generation of selection, realized gains infreshwater growth were 97% and 52% in progeny from the 1979
and 1980 brood years, respectively. These values can be comparedwith a maximum predicted gain of 46% for the 1979 brood year
progeny. While these gains cannot be totally attributed to genetic
change because of the lack of an appropriate control population,»

Table I.-Heritability estimates (based on sire component) on fresbwater and saltwater growth measurements for progeny from adults spawned in 1977 and1978.
Measurement
date
Freshwater
Apr. (4)'
MdY (5)
July (7)Saltwater
Nov. (I i)Mar. (15)

T..it

BY 1977

BY 1978

WeightWeIghtLengthWeightLengthStage)

0.61±0.3I'
0.38±0.25
0.30±0.24
0.25±0.22
0.22±0.21
0.29±0.19

0.36±0.21
0.47±0.22
0.56±0.25
0.26±0.20
0.37±0.21
0.31 ±0.09

WeightLengthStage'
WeightLength

0.17±0.15
0.19±0.16
0.25±0.14
0.19±0.11
0.18±0.11

0.31 ±0.18
0.38±0.20
0.32±0.11
0.62±0.21
O.45±0.17

IMonths postfertilization.
2Standard error.
'Based on morphological smolt index (0 = Parr.
Smoll).

these traits in othcr salmonids (Aulstad et ai. 1972; Chevassus
1976; Refstie and Steine 1978). In addition to h] estimates,
several other genotypic and phenotypic parameters were

FAMILYtJ~J--~t~1

SElECTlCN PRX.AA"IEll FflMlLlES() R.U-SIlY----

3 HALF-SIB
lNO£ATI~PERF~CE\ . <UFf<MILlES

5\~ ''''IllESl(J ' ..... ILlES

Fffl LV

6ty~t ~J~~r~ J

FISH I'.!:!...

fl87~~~y10 SELECT'"ocx
liD 'A".ILlES''''ILlE~ EAO<WIl><(IDPRl.GENY

3 HALF-SIB;() ''''ILlES~

Ff<MILlES

Figure I.-Diagram of the selection program used to llevelop a coho salmon
stock for marine pen culture. The single line indicates rearing in freshwater andthe double line rearing in saltwater. The underlined numbers indicate a"relative selective value" of the groups "rejected."

Figure 2.-Diagram of the mating system used in spawning selected individuals
to develop a coho salmon stock for marine pen culture.

30

survival to the "swim-up" stage averaged 70.5% and 80.0% for
those adults transferred to freshwateri.n 1980 and 1981, respectively. In comparison, fish spawned directly from saltwater
exhibited an average uf 30.2% in 1980. The overall success ofthese procedures can be seen in Table 2. Substantial progress has
been realized in improving survival in all stages of rearing, including mature adults.

the improvement is substantial and meaningful for commercial
production.
Another critical area of production in which substantial improvement has been realized is survi val on transfer to saltwater.
Under natural circumstances this movement is volitional and isprobably controlled by the ability of the fish to physiologicallyfunction in a saltwater environment (Hoar 1976). However, inmarine net-pen culture the fish are directly transferred to saltwater, with no previous opportunity for adaptation. In the pastthis technique has resulted in very low survival rates «30%). In
1981 progeny from selected parents were compared with an
unselected group of coho salmon from Washington Department of
Fisheries hatcheries. After identical incubation and rearing conditions, 95% of the fish from the selection program were ready totransfer to marine net pens, versus 67% of the control group. This
reflected a substantial improvement in this area of production
after one generation of selection. Further, since readiness totransfer to saltwater seems to be a function of size (Mahnken
1973; Saxton 1980), this result also indicates a more rapid andconsistent growth rate.
In addition to the directly selected traits, it has been necessary
to develop procedures for improving other areas of fish culture toassure the continuation of the program. The most crucial of thesehas been the technique of maintaining maturing adult fish in captivity. Because of the "pioneering" nature of this work, little
research had been conducted on such basic problems as broodstock nutrition, disease treatment, and specific husbandry requirements. These areas have been approched in a number of different
ways. A Sea Grant funded program is currently underway todevelop a broodstock diet to improve gamete quality and viability.
Preliminary results indicate several dietary components have major effects on gamete quality. The major disease problems inmaturing adults (vibriosis and bacterial kidney disease) have been
controlled by use of a vaccination program using a bivalent vibrio
vaccine (Schiewe and Hodgins 1977) and an erythromycin injection during the first spring and second summer of saltwater
growth, respectively. Mimicking the natural life history of coho
salmon by returning them to freshwater for final maturation andspawning has increased egg quality dramatically. For example,

POTENTIAL ENHANCEMENTAPPLICATIONS AND
FUTURE DIRECTIONS
The major emphasis of this program has been to improve traits
desirable to the commercial net-pen culture of coho salmon.
Because of this focus, a majority of the information is not directly
applicable to the free-ranging characteristics of salmon used forenhancement or ocean ranching. However, there are a number ofareas where data gleaned from this program can be applied. The
first is in the freshwater culture of young salmon. Our stock
development program has shown that substantial genetic
variability exists for fresh water growth characteristics, and thesecan be substantially improved by selection (Iwamoto et al. 1982).
Size prior to migration to saltwater has been shown to be a major
factor in the success of smoltification (Mahnken et al. 1982).
Thus, by improvement of growth in freshwater the potential exists
for greater survival in saltwater (Saxton et al. 1982).
Related to this, we found in one brood year (1978) a relatively
high correlation of freshwater growth with subsequent saltwater
growth (Hershberger et al. 1982). Although this result ispreliminary and needs further verification, it suggests that increased growth in freshwater may be accompanied by a similar
response in saltwater. Thus, selection in the hatchery may result ina greater growth in saltwater. This would be a definite benefit inharvest of adult fish.
Finally, successful culture of adult Pacific salmon in captivity
can provide two major benefits. First, investigation of the processes involved with gamete maturation and reproductive physiology, which are necessary for a captive breeding program, will give
us a better understanding of the requirements for optimum

Table 2.-Summary of percent survival values at different rearing stages of the various cohorts
from selected families in the coho stock development program.

Swim-uprearing t

Percent survi val
initial saltwater
rearing 2

72.0
53.5
'78.9

94.9
82.2
86.9

60.5
51.5

87.9
92.9

Freshwater

Odd year line
BY 1977
BY 1979
BY 1981Marketsize

Adult'

Adult'

41.5
81.0
88.5

54.3
80.8

22.7
29.6

9.8
12.1

55.2
94.1

70.2
662.5

21.6

7.6

Even year line

BY 1978
BY 1980
I

No. at end of freshwater rearing.
No. ponded

2No. surviving 3 rno postsaltwater transfer.

No. at end of freshwater rearing)

No. surviving to spawn

No. transferred to saltwater"No. surviving to spawn.

No. eggs incubated'Reflects improvement resulting from transfer of adults to freshwater.
6Reflects mortalities in the fall of 1981 from infection by gill parasites (Sarcodina and Coslia spp.).

31

LITERATURE CITED

reproduction. Second, this technology will provide the opportunity to maintain endangered, or threatened stocks without fearof extinction, and may give us a tool for conducting more precise
selection programs for ocean ranching concerns. One of the problems in conducting selection and breeding programs for ocean
ranching is the uncertainty of retrieving an adequate sample ofbrookstock for reproduction purposes. Maintaining a crosssection of selected families in marine net-pens for spawning purposes may solve this problem.
Caution must be expressed in applying the data from the present program to ocean ranching too extensively, however. Conditions in the two situations are very different and, consequently,
may largely negate any cross-use of genetic information.
Considerable success has been achieved through the combined
use of systematic genetic selection and breeding and culture technique modifications during the short tenure of this project.
However, several areas need further work and continued investigation, and the program must be flexible enough to meet production requirements. One of the most important aspects to be addressed this next year is the evaluation of the genetics of the traitsemphasized during the course of this program. Continued selection will alter the genetic factors determining a trait (Pirchener1969), which will concomitantly change the response to selection
and type of selection needed to realize a constant response. Thus,
monitoring of genetic changes is necessary to assure continued
success in improving the stock.
A further aspect to be considered is genetic analysis of additional traits that are important to production. Several are currently
being investigated for possible incorporation into the selection
program. These include flesh color, yield at processing, and adultreproductive characteristics. The first two are important to the
production and marketing of the coho salmon. It has been shownthat flesh color is one of the main factors in consumer differentiation of salmon and trout (Ostrander et al. 1976), and thus will
have a large influence on the price of the product. Improvement inyield at processing (dress-out weight) has the potential to increase
the efficiency of growing a marketable product, and thus decrease
production costs. Finally, rainbow trout has shown adequate
genetic variability in some reproductive traits to expect some
responsc to selection (Gall and Gross 1978). W{, are now
evaluating several adult reproductive traits for possible incorporation into the selection program in order to impnwe the quality
and quantity of gamete production.

AlILSTAD, D., T. GJEDREM, and H SKJERVOLD.
i 972
Gt:netic and environmental :>ources of variation in length and weightof rainbow trout (Sa/rna gairdneri). J. Fish. Res. Board Can. 29:237-241.
CHEVASSUS, B.
1976. Variabilite et hc;ritabilite des performances d~ croissance chez la truits
arc-en-ciel (Salrno gairdneri Richardson). Ann. Genet. set. Anim. 18:278-

283.
DONALDSON, L. R.
1968. Selective breeding of salmonid fishes. In W. J. McNeil (editor), Marine
aquiculture, p. 6.~-74. Oregon State Cniv. Press, Corvallis.
DONALDSON, L. R., and D. MENASVETA.
196!. Selective breeding of chinook salmon. Trans. Am. Fish. Soc. 90: 160164.
E.MBODY, G. C, and C. O. HA YFORD.
19:5. The advantages of rearing brook trout fingerlings from selected
breeders. Trans. Am. Fish. Soc. 55: 115-148.
FALCONER, D. S.
j 960.
Introduction to quantitative genetics. Ronald Press Co., N.Y., 365 p.
GALL, G. A. E., and S. J. GROSS.
1978 A genetic analysis of the performance of three rainbow trout bro<Xistocks. Aquaculture 15: I 13-127.
HERSHBERGER, W. K., R. N. IWAMOTO, and A. M. SAXTON.
i 982. G'netic potential ior fresh- and seawater growth of net-pen cultured
coho salmon. In B. R. Melteff and R. A. Neve (editors), Proceedings of theNorth Pacific Aquaculture Symposium. p. 185-192. Alaska Sea Grant
Program, Fairbanks.
HOAR, W. S.
1976. Smolt transformation: evolution, behavior and physiology. 1. Fish.
Res. Board Can. 33:1234-1252.
IWAMOTO, R. N., A. M. SAXTON, and W. K. HERSHBERGER.
1982. Genetic estimates for length and weight of coho salmon (Oncorhynchus
kisulch). J. Heredity 73:187-191.
LEWIS, R. C.
1944. Selective breeding of rainbow trout at Hot Creek hatchery. Calif. Fish
Game 30:95-97.
MAHNKEN, C. V. W.
1973. The size of coho salmon and time of entry into sea water: Part I,
Effects on growth and condition index. Twenty-fourth Annual Northwest
Fish Culture Con f., Wemmes, Oregon, p. 30-31.
MAHNKEN, C., E. PRENTICE, W. WAKNITZ, G. MONAN, C. SIMS, and J.
WILLIAMS.
1982. The application of recent smoltification research to public hatcheryreleases: an assessment of size/time requirements for Columbia Ri verhatchery coho salmon (Oncorhynchus kisu!ch).

Aquaculture 28:251-268.

NOVOTNY, A. J.
1975. Net-pen culture of Pacific salmon in marine waters.

Mar. Fish. Rev.

37(1):36-47.
OSTRANDER, J., C. MARTINSEN, J. LISTON, and J. McCULLOUGH.
1976. Sensory testing of pen-reared salmon and troul. J. Food Sci. 41:386-

390.
PIRCHENER, F.
1969. Population genetics in animal breeding.

SUMMARY

W. H. Freeman and Co., San

Francisco, 274 p.

The use of a systematic selection and breeding program todevelop a coho salmon broodstock for the marine net-pen industry
has shown that such an approach can be applied beneficially to
improve production traits. Freshwater growth, saltwater growth,and smoltification have all been increased by a greater extent than
predicted. Further, by use of the appropriate design, genetic
changes over time can be monitored, production needs can be met,
and potential inbreeding effects can be minimized. Some of theresults obtained with the marine net-pen system can be used as indicators for possible gains in ocean ranching endeavors, but acautious approach must be used in generalizing the data. Additional studies are needed on other desirable production traits toenhance the marine net-pen culture of coho salmon. Throughlong-term, systematic selection and breeding programs on
salmonid, and other species important to aquaculture, significant
gains in desirable traits can be realized to enhance production ofthese species.

REFSTIE, T., and T. A. STEINE.
1978.

Selection experiments with salmon. I'll. Genetic and environmental

SOl1rc..es of variation in length and weight of Atlantic salmon in the freshwaterphase.

Aquaculture 14:221-234.

RICKER, W. E.
1972. Hereditary and environmental factors .ffecting certain salmonid populations. In R. C. Simon and P. A. Larkin (editors), The stock concept in
Pacific salmon, p. 27-160. Univ. British Columbia, Vancouver.
SAXTON, A. M.
J 980. Smoltification in the net-pen culture of coho salmon (Oncorhynchus
kisutch). M.S. Thesis, Univ. Washington, Seanle, 81 p.
SAXTON, A. M., R. N. IWAMOTO, and W. K. HERSHBERGER.
1982. Smoltification in the net-pen culture of accelerated coho salmon,
Oncorhynchus kisutch Walbaum: prediction of saltwater performance. 1.
Fish BioI. 22:363-370.
SCHIEWE, M. H., and H. O. HODGINS.
1977. Specificity of protection induced in coho salmon (Oncorhynchus
kisulch) by heat-treated components of two pathogenic vibrios. J. Fish. Res.
Board Can. 34:1026-1028.

32

Advances in Tagging and Tracking Hatchery Salmonids:
Coded Wire Tags, Multiple-Coded and Miniature Radio
Tags, and the Passive Integrated Transponder Tag
GERALD E. MONANI

ABSTRACT
An overview of four advanced fish tags that can be used effectively by aquaculturists and biologists working
with hatchery salmonids is given. The four tags are: The coded wire-rare earth tag, the multiple-coded radio tag,the miniature radio tag, and the passive integrated transponder tag. Descriptions of each tag and its relaledequipment as well as a discussion of each tag's capabilities are given.

INTRODUCTION
Aquaculturists and fishery biologists working with Pacificsalmon. Oncorhynchus spp., and steelhead, Sa/rna gairdneri, have avital interest in the fish they raise and study. They need to know:
How much they grow, how they survive, where they migrate, andhow they behave. To obtain this information, they must have ameans of distinguishing one group of fish from another and/or one
fish from another within the group.
A variety of marking and tagging techniques have been developed to provide a means of identifying specific fish or groups offish (Konstantinov 1977). These include but are not limited to:Complete or partial fin clipping (Rounsefell 1963); various
passive tags like the Petersen tag, Atkins tag, body-cavity tag,strap tag, internal anchor tag, and spaghetti tag (Jensen 1962);
tattooing (Chapman 1957); branding (Raymond 1974); subcutaneous injection (Thresher and Gronell 1978); coded wire tags
(Bergman et al. 1968); and sonic and radio tags (Monan et al.
1975). The tags have developed from simple external visual identifiers to sophisticated electronic devices that can provide a variety of information about the tagged fish and its surroundings.
The objective of this paper is to provide an overview of four ofthe latest fish tags developed in North America that can be usedeffectively by aquaculturists and biologists working with hatcherysalmon ids. The tags to be discussed are the coded wire tag (CWT),
the multiple-coded radio tag, the miniature radio tag, and thepassive integrated transponder (PIT) tag.

A

Magnified color-coded (A) and binary(8) wire tags
(actual size 1 x 0.25 mm)
Fig"re I.-·Coded wire tags.

The coded wire identification tag (CWT) was developed byJefferts et al. (1963); B~rgman et al. (1968) and Hager and Jewell(1968) evaluated lhe tag. The CWTs greatest attributes are that it
can be applied to fish as juveniles and recovered when they are
adults, it has an almost unlimited number of codes, and it has aminimum effect on the behavior of th~ fish.
The CWT, as it is used on Pacific salmon and steelhead in the
Pacific Northwest, is a 1 x 0.25 mm magnetized stainless steel
wi.re that is either color coded or binary coded (Fig. I). The wire is

injected into the snout of the juvenile fish where it can be carried
for life. Overall tag loss during growth of fish from juvenile toadult size can be as low as 3% (Ebel 1974). A half-tag has also
been developed that is suitable for fry such as pink salmon, O. gorbuscha (KaiiJ2).
Tagging is fast and easy; anesthetized fish are positioned nose
first into a specially formed head mold that positions the fish in
the proper relationship to the tag injector. The pressure of the fishagainst the mold triggers the injector in one system, whereas theoperator presses a button in another, and the tag is injected into
the cartilaginous wedge of chondrocranium located in the fish's
snout anterior to the eyes. Head molds that fit the snouts of thesize and species of fish being tagged are critical to effective tagging. An experienced tagger can tag up to 1,000 fish/h.
Appropriate detectors can determine if a fish is carrying a
CWT. These detectors are equally effective with juvenile fish rightafter tagging or years later when the tagged fish has reached adulthood. The detection system can be a hand held device that is pass-

I Northw(;st and Ala3k'J Fishel1~s Center, National Marin~ Fisheries Service.
NOAA, 2725 Montla!:e Boulevard East, Seattle, WA 98! ! 2.

2M. Kalil, Alaskd Department of Fish and Game. 333 Raspberry Road, Anchorage, AK 99502. pers. commun. October 1982.

CODED WIRE TAGS33

ed over the fish or it can be a more sophisticated de vic.: that can
automatically detect tagged fish and separate them from untagged
fish (Ebel 1974).
In the automatic separator widely used on the Columbia River(Ebel 1974), adult fish that were tagged as juveniles ascend a fish
ladder and after passing over a false weir slide down a chutethrough the detector coil. If a tag is detected, a gate is acti vateddeflecting the fish into a holding pen; untagged fish simply returnto the fish way to resume their migration.
Once the tagged fish has been detected, the tag must be removed from the fish's snout for decoding. This is usually accomplishedby removing a plug of flesh from the fish's snout. The plug withthe tag inside is then placed in a concentrated solution ofpotassium hydroxide to free the tag which is then read with the aidof a microscope. Freeing the tag and reading the code is a relatively slow process-an experienced worker can extract and read10- 15 tags/h.
The cost of tags is approximately $16 to $25/thousand, a tagging machine costs about $20,000 to $23,000, and tag detectors
cost from about $3,600 to $9,300.
To increase the usefulness of the CWT by eliminating the needto remove the tag from the fish is the objective of research being
conducted by National Marine Fisheries Service (NMFS) scientists in Seattle, Wash. (Park 3 ). The major goal of NMFS scientists
is to produce a tag and detector that will allow a tagged fish to be
detected and its code determined automatically without the fishleaving the water.
The system they have developed involves coating the tag with
one or more rare earth metals (e.g., cerium, lutetium, etc.).
Presently at least 45 codes are available at a cost of about $25/
thousand tags. The tags are applied with a regular CWT tagging
machine. At this stage of development, detection and decoding are
in two steps. The tags are detected with a conventional magnetic
detector. Once the tagged fish is in hand, the fish is placed in amoist tray and subjected to X-ray fluorescent spectroscopy. The
X-ray process takes 5 to 15 s, and the fish is out of water for a
total of about 30 s. Following the X-ray treatment, the systemanalyzes the data, determines the tag code, indicates the results ona video screen, and makes a permanent record on punched tape.
In 1980, the system correctly identified all 15 adult chinook
salmon, O. tshawytscha, returning from a group of juveniles taggedwith rare earth tags in 1979. In addition, the system has correctly
identified numerous juvenile fish tagged with rare earth tags.
An automatic system of in-water identification, while deemedfeasible, will probably not be developed by NMFS scientists in thenear future because of funding restraints. Nevertheless the system
as developed has significant merit in that: 1) The fish is not sacrificed; 2) faster tag identification (tag would not have to be extracted from the fish); 3) computerizing data in real time-reducing errors and decreasing processing time; and 4) genetic studies
where selected groups of adults could be tagged, identified as totheir genetic makeup prior to spawning and selected genotypes
mated.

subsequently obtained relies on either seeing an external tag insitu or after recovery, sacrificing the fish to recover an internal
tag. Since fish live in an environment that is not easily penetrated
by man's normal senses, most data collection relies on recaptureof the tagged fish. Basically, this provides information at two
points-the point of release and the point of recapture. If a
researcher wants to know about the fish's activities between thes.:
two points, a variety of electronic tags are available.
Electronic tags generally fall into two categories-those operating on radio frequencies (operative in freshwater only) and those
operating on ultrasonic frequencies (operate in fresh or saltwater).
Within these two categories, the tags can be further grouped as
simple beacon or pinger tags (tags that can be remotely tracked)
and telemetry tags. Telemetry tags not only allow the researcher totrack the fish but also can provide a variety of biologically and environmentally important factors, e.g., compass heading (Mitson etal. 1982), salinity of the surrounding water (Priede 1982),
temperature (Coutant and Carroll 1980), depth (Luke et al. 1973),
heart rate (Priede and Young 1977), tail beat (Ross et al. 1981),
swimming speed (Voegeli and Pincock 1980), etc.
Several excellent reviews of electronic tags have been published(Stasko and Pincock 1977; Ireland and Kanwisher 1978; Nelson
1978; Harden Jones and Arnold 1982). In addition, the Underwater Telemetry Newsletter published an extensive bibliography ofunderwater telemetry in biological applications in its initial issue-Volume I, Number I-in April 1971. This bibliography has
been continuously updated in subsequent issues. 4
In this paper, I will discuss two recently developed radio tags
and their related tracking systems and a new electronic tag being
developed.

Multiple-Coded Radio Tag For Adult Salmonids
Radio tags developed by NMFS personnel were first used in thefield to study the behavior of adult spring chinook salmon in the
Columbia River as they approached a major hydroelectric dam
interrupting their upstream migration (Monan and Liscom
197 IS).
The tag initially used was a battery powered, high-frequency
radio transmitter that operated on a carrier frequency of approximately 30 MHz, had a 167 mW input and an effective tracking
range of 0.8 km or more, and was operational for about 15 d. Taglife was variable and could be extended to up to 60 d if desired.
The transmitter and batteries were sealed in a plastic capsuleabout 89 mm long and 19 mm in diameter (Fig. 2). Each tag
weighed about 28 g in water and was carried in the stomach of the
fish except for a small wire antenna that extended from the tag,through the fish's esophagus, and was attached to the roof of the
fish's mouth. The tags were frequency coded. There were nine
separately identifiable codes (30.17, 30.18, ... , 30.25 MHz) andherein was a major area that needed improvement. Nine codes
were not enough to permit sufficient numbers of fish to be tracked
during the limited migration periods of the salmon being studied.
Development of a multiple-coded radio tag and decoding
receiver was a significant advance in fish tracking capabilities.

ELECTRONIC TAGSThe problem with conventional tags is that for all practical purposes, once the fish has been tagged and released, any information'Issues are available by writing: Dr. Charles Coutant, Editor UTN, Environmental
Sciences Division, Oak Ridge National Laboratory, P.O. Box X, Building 1505, Oak
Ridge, TN 37830.
'Monan, G. E., and K. L. Liscom. 1971. Radio tracking of adult spring chinook
salmon below Bonneville Dam, 1971. Natl. Mar. Fish. Servo North Pac. Fish. Res.
Cent., Seattie, Wash., Final Rep. to U.S. Army Corps Eng., Delivery Order NPPSUPR-71-2617.

'D. Park, Northwest and Alaska Fisheries Center, National Marine Fisheries Ser'/ice, '<OAA, 2725 Mont!ake Blvd. East, Seattie, WA 98112, pers. commun.
September 1982.

34

The cost of radio tags for adult salmon is about $1 00-1401tag, abasic receiver and antenna unit is approximately $2,000, and adecoding receiver is about $5,000.

RADIO TAG FOR ADULT SALMONIDSNo.

Miniature Radio Tag

00762
R£WARO\""" Ground band/

The tags described previously are suitable for adult salmon andsteelhead to carry in their stomachs without noticeable modification of their behavior. However, to track smaller fish, particularly
salmon and steelhead smolts, a much smaller tag was needed. To
fill this need, NMFS researchers designed a miniature tag 26 mm
long by 9 mm wide by 5 mm thick weighing 2.6 g in water (Fig.
4). The transmitter is assembled on a hybrid circuit substrate andis powered by two silver oxide batteries. Once assembled, the tag
is coated with a mixture of paraffin and beeswax and sealed indental acrylic. The tags operate on a carrier frequency of approximately 30 MHz and have a battery life of 72 h. The tags can befrequency coded (9 codes) or multiple-coded (720 codes) depending upon application. The effective tracking range is about 300
m when the tagged fish is near the surface; the range decreases
rapidly when the fish is deeper than 9 m. The cost of each tag is
about $100-140.
Prior to using the miniature tag in the field, testing was carriedout with juvenile coho salmon, O. kisutch, using sham tags (samesize, shape, and weight but inoperable). The tag was inserted into
the fish's stomach through the esophagus, and the 125 mm longantenna wire was allowed to trail out of the fish's mouth. The tagged fish were placed in a holding tank with untagged coho salmon
and observed for 30 d. After recovering from the anesthetic andhandling, they appeared to feed and behave normally. Whentested in a swimming chamber, there was no difference in the performance of tagged and untagged fish. The tagged fish ranged infork length (FL) from 150 to 160 mm.

Encapsulated tag

Attachment device

o

2

4

3

5

7

6

8

9

10 cm

Figure 2.-Multiple-coded radio tag suitable for adult salmonids.

With the new tag and equipment, it is possible to identify up to 80
tags/frequency or 720 total.
The multiple-coded tag uses a pair of pulses to establish its
code. The first or main power pulse is 15 ms in duration; a 5 mscode pulse follows. The time between the two pulses varies from
0.5 to 40 ms (Fig. 3) and dictates the code of the tag. The size,
weight, and external appearance of the multiple-coded tag are
essentially the same as the initial radio tag.
Special decoding receivers were designed; pulses from a 2 kHz
oscillator were gated into a register starting at the trailing edge ofthe 15 ms power pulse and stopped at the trailing edge of the 5 mscode pulse. The decoding receiver decodes the tag and prints thefrequency and code of the tag, and a conventional receiver andantenna are used to determine the location of the tagged fish.
Code determinant:each 0.5 ms = 1 code numberr----oI~I\\~

pUlse.pe';OdI600mSI-1

L

Code pulse (5 ms)
Coding penod (1 to 40 msl

Figure 3.-Pulsing sequence used to establish code of multiplecoded radio tag.

Power pulse (15 msl

PULSE

SEOUENCEMINIATURE RADIO TAGS
Finished

Prior to coating
Batreries

Encapsulated tag

Figure 4.-Mlnlature radio tag for juvenile saImonids.

35

The miniature radio tag was used in three field studies tomonitor the behavior of downstream migrating juvenile salmon
and steelhead as they approached a major hydroelectric dam in the
Columbia River (Sims et al. 1981;6 Faurot et al. 1982 7 ). A total of
99 smolts (63 chinook salmon-145 to 192 mm FL and 36 steelhead-161 to 220 mm FL) were tracked. Tracks normally lasted
from 4 to 6 h.
Because of the short range of the tag, new tracking procedures
were developed. Tracking involved two, two-man crews (a boat
operator and a tracker) in two separate boats. Operators used conventional receivers with di·rectionalloop antennas to establish thelocation of the fish in relation to the boat. They then determined
the positions of the boats using horizontal sextants to take bearings to markers accurately positioned strategically along the shore.
The fish's location was indicated on an accurate scale chart of thestudy area. A series of these plots were then connected by a line,
and a record of the fish's movement was established. The technique provides accuracy within about 25 m, which is somewhat
less accurate than obtained with the more sophisticated fixed
shore stations and central plotting and control station (Fig. 5) used
when tracking adult salmon (Monan et al. 1975). Automaticrecording of date, time, direction of travel, and tag code for tagged
fish passing an appropriately located monitor is also possible.

sive tag that can provide better data than the CWT but at less costthan the radio tag.
The passive integrated transponder (PIT) tag being developed
by Identification Devices Inc., of Denver, Colo.,s for identification of livestock is currently being evaluated for use on fish byscientists of the NMFS (Prentice 9 ).
The PIT tag is basically a silicon computer chip and an antenna
encapsulated in ceramic material (Fig. 6). The 32-bit chip willstore code information for about 4.3 billion unique codes. During
manufacture, groups of tags may be batch coded or each tag could
have a unique code in a serial sequence. The theoretical life
expectancy of the tag is about 100 yr. The manufacturer estimatesthe initial fish tag will be about 4.2 mm long by 1.6 mm indiameter. It is expected that the length subsequently will be reduced by 50%. Currently a sham tag is being evaluated for tagging
location, retention, physiological acceptance, etc. at the Manchester Marine Experimental Station.
The tag can be placed by an injection device similar to that used
for CWT's. However, unlike the CWT, it is unimportant how the
tag is oriented in the fish. Therefore, a number of areas other thanthe 'l1out are being evaluated, e.g., the abdominal cavity and themusculature under the dorsal fin.
Detection and decoding of the tag are done with a data scanner.
The data scanner, when activated by the operator, sends out asignal which is received by the tag's antenna. The signal is converted to power which drives the tag's chip. The unique preprogrammed signal is sent back to the scanner where it is instantly
visually displayed in a numeric format. Current tests indicate thetag can be detected when the fish is surrounded by up to 16 cm ofwater and the scanner is 30 cm away. The fish can pass at any
reasonable speed and in .any orientation.
More sophisticated versions of the scanner can have addedfunctions such as:

Passive Integrated Transponder Tag
Coded wire tags provide a relatively inexpensive means to
obtain basic release and recapture data from large numbers of fish.
Radio tags provide a means to get behavioral and physiologicalinformation on a limited number of fish-but at a substantial co,!.
Aquaculturists and fisheries researchers need a relatively inexpen'Sims, C. W., J. G. Williams, D. A. Faurot, R. C. Johnsen, and D. A. Brege. 1981.
Migrational characteristics of juvenile salmon and steelhead in the Columbia River
Basin and related passage research at John Day Dam Vol. I. Natl. Mar. Fish. Servo
Northwest and Alaska Fish. Cent., Seattle, Wash. Final Rep. to U.S. Army Corps
Eng., contracts DACW57-80-F-0394 and DACW68-78-C-005I, 61 p.
'Faurot, D. A., L. C. Stuehrenberg. and C. W. Sims. 1982. Migrational characteristics of juvenile salmon and steelhead trout in the Columbia River System, 1981,
Vol. 11. Radio tracking juvenile salmon ids in John D.y Reservoir. Natl. Mar. Fish.
Servo Northwest and Alaska Fish. Cent., Seattle. Wash. Final Rep. to U.S. Army
Corps Eng., .:ontract DACW57-81-F-0342, 24 p.

'Reference to trade names or products does not imply endorsement by the National Marine Fisheries Service, NOAA.
9E. Prentice, National Marine Fisheries Service, Manchester Marine Experimental

Station, P.O. Box 38, Manchester, WA 98353, pers. commun. June 1982.

Figure 6.-Passive integrated transponder (PIT) tag (approximately 4.2
mm long )( 1.6 mm in diameter).

Figure 5.-Tracking coordinator in the control station plotting locations ofadult salmon tagged with radio tags.

36

LITERATURE CITEDI) a logic module, so signals from more than one tag can be
decoded and counted "simultaneously" but displayed in thesequence of arri val;
2) a 32-128 K-bit internal memory that will allow the operator
to obtain tag information in the field, store it in the scanner,and bring it back to the laboratory for processing; and
3)a RS 232 plug to make the scanner compatible with ADP.

BERGMAN, P. K., K. B. JEFFERTS, H. F. FISCUS, and R. C. HAGER.
1968. A preliminary evalualion of an implanted, coded wire fish tag. Wa;h.
Dep. Fish., Fish. Res. Pap. 3(1 ):63-84.
CHAPMAN, D W.
1957. AI' improvec portable tatooing device. Prog. Fish-Cult. 19:182-184.
COUTANT, C. c., and D. S. CARROLL.
1980 Temperatures occupied by ten ultrasonic-tagged striped bass in freshwater lakes. Trans. Am. Fish. Soc. 109:195-202.
EBEL, W. J.
1974. Marking fishes and invertebrales. til. Coded wire tags useful in aUlOmalic recovery of chinook salmon and steelhead trout. Mar. Fish. Rev.

When cost of tagging and decoding are considered, the cost of
the system is reasonably comparable with the CWT system. Costof the tag is currently estimated at about $5/tag, but quantity
manufacturing can be expected to reduce this figure. The data
scanner used with livestock costs $1,500 to $3,000 depending
upon options.
The PIT tag has a great potential for use in salmon aquaculture
and research because of the following:

36(7): I0- I3
HAGER, R. C., and E. D. JEWELL.
1968. Field evalualion of c<'ded wire lag delection and recovery lechniques
Wash. Dep. Fish., Res. Div., Suppl. Prog. Rep.. Mar. Fish. Res. Manage.,
Coded Wire Tag Invest., 20 p.
HARDEN JONES, F. R , and G. P. ARNOLD.
1982. Acoustic telemelry and the marine fisheries. Symp. Zoo I. S"e. Lond.
49:75-93.
IRELAND, L. c., and 1. W. KANWISHER.
1978. Underwaler acouslic biotelemetry: procedures for obtaining information on the behavior and physiology of free-swimming aquatic animals intheir natural environments. In D. I. Mostofsky (editor), The behavior of fish
and other aquatic animals, p. 341-379. Acad. Press, N.Y.
JEFFERTS, K. B., P. K. BERGMAN, and H. F. FISCUS.
1963. A coded wire identification system for macro-organisms. Nature(Lond.) 198:460-462.
JENSEN, A. C.
1962. Marking and tagging fishes. U.S. Fish Wildl. Serv., Fish. Lean. 534,
8 p.
KONSTANTINOV. K. G.
1977. Modern methods of fish tagging. 1. Ichthyol. (Eng!. transl. Vo p !.
Ikhliol.) 17:924·038.
LUKE, D. McG., D. G. PINCOCK, and A. B STASKO.

I) virtually unlimited number of tag codes;2)tag detection and decoding accuracy ~ 95%;
3) detection and decoding can be done while the fish is in thewater without handling or sacrificing the fish;4) injection system can be simpler and less costly than the CWT
injector; and5) data can be directly fed into a computer-greatly reducing
time lag, errors, and cost of data processing.
If the development of the PIT tag for fish is successful, a new
era in tagging will have been reached.

SUMMARY

1973.

Pressure-sensing ultrasonic transmitter for tracking aquatic animals.

J Fish. Res. Boa.,d Can. 30:1402-1404.
MITSON, R. B., T. J. STORETON-WEST, and N. D. PEARSON.
1982. Trials of an acoustic Iransponding lag compass. Oiotelem. Patient
Monit. 9(2):69-79.
MONAN, G. E., J. H. JOHNSON, and G. F. ESTER BERG.
1975. Electronic lags and related tracking techniques aid in study of migrating salmon and sieelhead trout in Columbia River Basin. Mar. Fish. Rev.
37(2):9-15.
NELSON, D. R.

Tags available to aquaculturists and fishery biologists are
increasing and becoming more sophisticated. Researchers are nolonger restricted to visual identifiers but have a variety of advanced tags available-largely due to the rapidly expanding field ofelectronics.
In the preceding portion of the paper, four advanced tags werediscussed that may be used effectively with salmon ids: The coded
wire-rare earth tag, multiple-coded radio tag, miniature radio tag,and PIT tag. Each tag represents advances and has distinct advantages, but none represent the ultimate in tag development. The
rare earth coded wire tag makes decoding the tag possible without
removing it from the fish, but the fish must be handled. The
multiple-coded radio tag makes monitoring the behavior of large
numbers of separately identifiable, free-swimming adultsalmonids possible. Miniaturization of the radio tag allows studiesof the behavior of free-swimming juvenile salmonids. The PITtag, when fully developed, will provide a means of individually
identifying fish (once they are tagged) from juveniles to adults
without sacrificing or handling them-if fully developed, it willallow the acquisition of data heretofore impossible or impracticalto obtain.

1978. Telemetering techniques for the study of f[<e-ranging sharks. In E. S.
Hodgson and R. F. Malhewson (editors), Sensory biology of sharks. skales,
and rays, p. 419-482. U.S. Dep. Navy, Off. Naval Res., Arlington, Va.
PRIEDE, I. G.
1982. An ultrasonic salinity telemetry transmitter for use on fish in estuaries.
Biotelem. Patient Monit 9(1):1-9.
PRIEDE, I. G., and A. H. YOUNG.
1977. The ultrasonic telemelry of cardiac rhythms of wild brown troul (Salma(rulla L.) as an indicator of bio-energetics and behavior. J. Fish BioI. 10:
299-318.
RAYMOND, H. L.
1974. Marking fishes and invertebrates. I. State of the art of fish branding.
Mar. Fish. Rev. 36(7): 1-6.
ROSS, L. G. W. WATTS, and A. H. YOUNG.
198 I. An ultrasonic biolelemetry syslem for the continuous monitoring oflail-beal rale from free-swimming fish. J. Fish BioI. 18:479-490.
ROUNSEFELL, G. A.
1963. Marking fish and invertebrates.
549,12 p.
STASKO, A. B., and D. G. PINCOCK.

ACKNOWLEDGMENTS

U.S. Fish Wildl. Serv., Fish. Leaf!.

1977. Review of underwater biotelemetry, with emphasis on ultrasonic techniques. 1. Fish. Res. Board Can. 34:1261-1285.
THRESHER, R. E., and A. M. GRONELL.

I would like to acknowledge Donn Park for his work on the rareearth tag; Charles Bartlett, Gordon Esterberg, Kenneth Liscom,
Lowell Stuehrenberg, Donald Thorne, and Charles Volz for theirparts in development of the multiple-coded and miniature radio
tags; and Earl Prentice for his vision and pursuit of a PIT tag forfish.

1978. Subcutaneous tagging of small reef fishes.
VOEGELI, F. A., and D. G. PINCOCK.

Copeia 1978:352-353.

1980. Determination of fish swimming speed by ultrasonic telemetry.
telem. Parient Monit. 7(3-4):2 I 5-220.

37

Bio-

Trends in Natural and Hatchery Production of
Chinook Salmon
DONALD E. ROGERS and ERNEST O. SALOl

INTRODUCTIONCATCH AND ESCAPEMENT

Chinook salmon, Oncorhynchus tshawytscha, are the least abundant but the oldest and heaviest at maturity of the Pacific salmon.
They are sought by commercial and recreational (sport) fishermenbecause they are large and they are more vulnerable to salmon
fisheries because they have a long ocean life, typically 3-4 yr andsometimes 5-6 yr at sea (Major et al. 1978). They are also uniqueamong the Pacific salmon because a very high proportion of them
are caught in high seas and coastal troll fisheries while immature,and often at long distances from their home streams. This fact
makes it difficult to determine the status of individual stocks
along the North American and Asian coasts.
Fredin (1980) reviewed the historical trends in the catches ofPacific salmon through 1977. The pink, O. gorbuscha, chum, O.
keta, and sockeye, O. nerka, catches in most fisheries were at ahistorical low in the 1970's, whereas catches of coho, O. kisutch,
and chinook salmon remained relatively stable or increased in the
1970's. Since 1978 there have been some dramatic changes in thecatches and abundances of Pacific salmon.
We will examine the recent trends in chinook salmon abundance largely on the basis of catch statistics because numbers offish in escapements are either unknown or imprecisely known
over much of the chinook salmon's range. The production ofchinook salmon in Alaska and Asia is almost entirely from wild
stocks whereas hatcheries produce a significant portion of thechinook salmon from California to Washington and these fish
enter the fisheries in British Columbia and southeastern Alaska.

Commercial catches of chinook salmon have declined in recent
years in Oregon, southeastern Alaska, and central Alaska (Fig. I).
Since the 1960's the Cook Inlet fishery in central Alaska has been
severely restricted and the chinook salmon troll fishery in southeast Alaska has been restricted by quotas. About 75% of the commercial catch (1976-80) in the southern region (California tosoutheast Alaska) was made by troll fisheries operating on a mixture of stocks. The pronounced increase in British Columbia troll
catches has come largely from chinook salmon produced in
Oregon and Washington.
During 1976-80, Oregon and Washington had about 57% of the
1.1 million estimated average escapement in the southern region,
whereas the catch (commercial and sport) was only 34% of theregional average catch of 4.0 million (Table I). In contrast, theescapements to British Columbia constituted about 17% of theregional escapement, whereas the catches made up 41 % of theregional catch.
In the northern region, catches have increased since the 1960's
largely from increased exploitation by inshore fisheries in western
Alaska and the high seas fisheries (mainly in the Bering Sea). During 1976-80, the high seas catch constituted about 40% of thecommercial catch in the northern region.
Based on coastal catches of pink, chum, and sockeye salmon,these species are more abundant along the northern rim of the.6r:----,--------,------.-----r------,
Central'Western

AlaskaAlaskaCalifornia

OregonHigh Seas.4

DATA SOURCES
Catch statIstics through 1978 were obtained from Fredin(1980), International North Pacific Fisheries Commission (1979),
and INPFC Statistical Yearbooks. Catches for 1979 and 1980
were from internal reports of INPFC and state and federal
fisheries agencies of the United States and Canada. Catches for1981 and 1982 were available only for Alaskan fisheries and wereobtained from the Alaska Department of Fish and Game.
Although these were preliminary estimates, the final catches for1981 and 1982 are unlikely to be significantly different.
Estimates of chinook salmon escapements were obtained fromthe Pacific Fisheries Management Council's proposed management plan for 1981, internal reports of state fisheries agencies,
and personal communication with these agencies. Escapement
estimates for wild stocks are not as precise as catch statistics andin some cases are only order-of-magnitude estimates.

Washington

BritishColumbia

1.6

Southeast
Alaska

1.4
1.2

Years

'Fisheries Research Instilule. School of Fisheries. Universily of Washinglon,
Seattle, W A 98195.

Figure 1,-Annual commercial catches of chinook salmon by 5- yr periods beginning 1921-25 and ending 1976-80,

39

Table I.-Estimates of chinook salmon escapements (wild and hatchery),
1976-80. (Fish in thousands.)

Year

California

OregonWashington

BritishColumbia

Southeast
Alaska

Total

1976
1977
1978
1979
1980

'258
'258
290
269
216

593
660
702
581
643

164
224
196
177
'190

18
30
20
25
39

1,033
1,172
1,208
1,052
1,088

Coho

'1
6

1

4

0
1920

Average

1976-80

258

636

26

190

60

c

1,110

~
~

Average~~catch (all gear)
I

40

~

671

1,361

1,679

>:

4,050

339

Estimate from average of other years.

Chinook4

North Pacific than they are along the western coast of North
America (Fig. 2). There have been exceptionally large catches ofall species of salmon in western and central Alaska since 1978
and the catches of pink, chum, and sockeye salmon in 1981 were
historical records. Coho and chinook salmon have been much
more abundant in the southern region (Fig. 3). However, rates of
exploitation of these species have been much lower in the northern region because other species are so much more abundant

32~::::~::
0

1920

40

60

40

1920

60

80

Year

NGrthern region

Southern region

20

1
"

i

Figure 3.-Annual commercial catches of coho salmon (4-yr averages) andchinook salmon (S-yr averages), 1921-80. Northern region: Western and central
Alaska (black), Asian coastal (stippled), and high seas (open). Southern region:
Southeastern Alaska (black) and California to British Columbia (stippled).
Alaskan catches in 1981 and 1982 indicated by narrow bars.

PINK

18T

"

1 20

10 1

300

Yukon

River catches

200

40

60

80

1920

40

60

80
CHUM

40

300

Kuskokwim River

catches

3(
200

20

E

10

:JiiltoL.r-;.-........_~
1920

40

60

80

~

D

1920

40

10('

~

80

60

Z

0

SOCKEYE
300

~

1 920
Year

Northern region

40

60

200

80

100

Southern region
055

Figure 2.-Annual commercial catch of salmon, 1921-80 by 4-yr averages forpink and chum salmon and S-yr averages for sockeye salmon. Northern region:
Western and central Alaska (black), Asian coastal (stippled), and high seas
(open). Southern region: Southeastern Alaska (black) and California to British
Columbia (stippled). Alaskan catches in 1981 and 1982 indicated by narrow
bars.

60

65

70

80

Year

Figure 4.-Annual catches (commercial and subsistence) of chinool salmon
from the Yukon and Kuskokwim Rivers and estimates of the runs (catch andescapement) to the Nushagak River, 1952-82.

40

there. In 1982 there were historical record high catches of coho
and chinook salmon in western and central Alaska, whereas
catches in the southern region remained relatively stable in recent
years.
The Yukon, Kuskokwim, and Nushagak Rivers are the major
producers of chinook salmon in Alaska and for the Nushagak
River there have been annual estimates of the escapements since
1961 (Fig. 4). These rivers contribute a significant number of fish
to the high seas catches, ranging since 1961 from 116,000 to
642,000, except in 1980 when about I million chinook salmon
were caught. The inshore runs to the Nushagak River increased in1978 and the run in 1982 was 362,000.
Statistics from the Nushagak District of Bristol Bay are well
suited for examining the historical trends in the abundance ofsalmon because there has been extensive exploitation of chinook,
sockeye, and chum salmon since 1900 (Fig. 5). The late-summer
fisheries for pink and coho salmon have been sporatic dependingon the abundance of the runs and the early summer catches of theother species. However the catches of all species declined in theearly 1920's and the catches of the more abundant sockeye declined again in the early 1950's. The large runs beginning in 1978were unpredictable from either the abundances of parent
spawners or juveniles in freshwater. The cause of the large runs inrecent years seems to be from an increase in marine survival thatis related to a change in the climate over western and central
Alaska.
Winter temperatures in the Gulf of Alaska and Bristol Bay
declined in the late 1940's, were exceptionally cold in the early
1970's, and then beginning with the winter of 1976-77, temperatures have been comparable with those of the 1920's and 1930's(Fig. 6). The major changes in salmon abundance in western andcentral Alaska since 1920 have generally followed the changes in

0
-1

-2
-3

-,
·c -5
-6
-7
-8

-9
-10
-11

-12

1920

30

40

50

80

70

80

Yea r

Figure 6.-Average winter (November-March) air temperatures at Kodiak (top)and Bristol Bay (bottom) weather stations through the winter of 1981-82.

temperature. Although the biological mechanisms by whichchanges in climate affect the survival of salmon (particularly atsea) are unknown, the outlook for salmon production in Alaska isgood as long as temperatures remain mild.

12
10

Sockeye

12
10

Pink

8
6
4

0

.3

Figure S.-Annual commercial catches of salmon and estimates oflhe runs (catch plus escapement) where available for the Nushagak
District of Bristol Bay 1893-1982.

Coho

.4

Chinook.3.2

oL&_,,1900

1910

1920

1930

1940
Year

41

1950

1960

1970.

1980

HATCHERY PRODUCTION

release from nonpublic hatcheries increased from zero in 1977 toabout 14% of the total in 1981. This is expected to grow, especially in Alaska, although it has tapered off in Oregon and, except for
the Indian Tribes, releases from private hatcheries are not legal in
the State of Washington. Using the State of Washington as an
example, since the 1950's the releases of coho salmon have increased from about 15 million to over 40 million, while in thesame period the numbers of chinook increased from 15 million toover 70 million (Simenstad et al. 1982). Correspondingly thecatch of coho salmon has increased in Washington from1,250,000 in the 1950's to 2,800,000 in the late 1970's. The
catch of chinook salmon has increased from 600,000 in the early
1960's to over a million in the late 1970's. This includes therecreational (sport) fisheries (Fig. 7).
At the present time, approximately 44% of the coho salmon
harvest in the southern region is from natural production and 56%
is from hatcheries, while the chinook salmon harvest is 60% fromnatural production and 40% from hatcheries, although it is expected that the chinook salmon harvest will be about 50150,
natural and artificial, in the near future. In the last 70 yr, about
60% (54% from the Columbia River and 70% from the Sacramento-San Joaquin Rivers) of the chinook salmon spawning andrearing area has been lost in the Sacramento-San Joaquin andColumbia River systems, the principal producers of chinook
salmon (Salo and Stober 1977; Kjelson et al. 1982). Interestingly,

In the early 1900's there were large numbers of state andprivate hatcheries that propagated primarily coho, chum, andchinook salmon. This was followed by a dc-emphasis on
hatcheries in the 1930's and 1940's. In the 1950's and 1960's
there was an increase in the use of hatcheries for mitigation of lost
salmon and steelhead habitat and the production of coho andchinook salmon was emphasized. Currently in the states of Wash·
ington and Oregon, the hatchery releases in numbers of fish ofchinook and chum salmon are the largest followed by coho, pink,
and sockeye salmon, although the total production (biomass) (Ifcoho is the highest. In Alaska, the private aquaculture corpora·tions release large numbers of pink salmon in the north and chumand coho salmon in the south. The Alaskan goal is a billion fish
annually by 1990 (McNeil 1982).
In 1960 there were 72 hatcheries producing salmon and steel·head on the Pacific coast and by 1976 the number reached 154. In
1960 a total of 150 million fish were released from hatcheries on
the coast of the eastern Pacific. By 1977,377 million were released and for a I-yr period in 1980-81 this had increased to 935
milhon (Tables 2, 3). Thirty percent of this total was pink salmon
in Alaska and sockeye salmon from spawning channels in British
Columbia. The releases of chinook salmon increased fromapproximately 200 million in 1977 to 250 million in 1980
whereas coho releases increased from 90 to 140 million. The

Table 3,-Hatrhery releases of juvenile salmon in millions for a l.yr period in
1980-81. (From: McNeil 1982.)

Table 2.-Public hatchery juvenile salmon releases in 1977 in millions.
(From: National Aquaculture Plan 1980.)
Chum

Pink

Steelhead

Coho

Chinook

Total

65

73
15
0

Q

264
73
9

I

California

6
2
0
0
3

120
55

0
a
a

0
0
0
0
0

I

0
25

29

Total

66

a

II

90

209

376

Washington
OregonIdaho
AlaskaI

AlaskaBritish Columbia
Washington
OregonCalifornia
Idaho

I

Total

Chum

Pink

Sockeye

Cilho

61
93
67
6
0
0

141
6
5
0
0
0

25
143
0
0
0
0

4
5
95
35

227

152

168

Chinook

Total

I

0

19
153
40
29
6

232
266
320
81
30
6

14a

248

935

I

-----------_.-

2.5

9

CHINOOK

CO H0

8

j

2.0

6

II
II
I

1.5

5 I

I

7

I

I

0.50

f

4 VIr

f-

=
(D
=
<I:
U

1.0

3

0.25

2

0.5

.J.J

.+----.--....---.--....---.--...----..----+0
1980
1900
1940

l¥--....----.-----.------.--....----.----+O

1940

LL
Cl
0:::
W

1
1900

0.75

1980

iXI
?-:

=
=

YEAR
Figure 7,-Releases of artificially propagated salmon in Washington State (solid line) and Puget Sound salmon catches (dash line), 1901-79. From Simenstad et a\. (1982).

42the production of the Sacramento River has dropped about 70%(Kjelson et al. 1982). How much of this was due to fishing andhow much has been compensated for by hatcheries in the Sacramento River is not clear. The Fraser River in British Columbia has
a calculated optimum escapement of 200,000 chinook salmon
while the current escapements are 60,000-70,000. Overfishing of
the Fraser River stocks, in mixed stock fisheries where the contributions of Washington and Oregon hatcheries may be as much as
70-90% of the Canadian catch of chinooks, appears to be theprincipal cause of decline in Canada (Pearse 1982).

Himsworth (editors), Salmonid ecosystems of the North Pacific, p. 59-119.
Oregon State Univ. Press, Corvallis.
INTERNATIONAL NORTH PACIFIC FISHERIES COMMISSION SECRETARIAT.
1979. Historical catch statistics for salmon of the North Pacific Ocean.
INPFC Bull. 39, 166 p.
KJELSON, M. A., P. F. RAQUEL, and F. W. FISHER.
1982. Life history of fall-run juvenile chinook salmon, Oncorhynchus /showy/scho, in the Sacramento-San Joaquin estuary, California. In V. S. Kennedy(editor), Estuarine comparisons, p. 393-411. Acad. Press, N.Y.
MAJOR, R. L., J. ITO, S. ITO, and H. GODFREY.
1978. Distribution and origin of chinook salmon (Oncorhvnchus /showy/scho)
in offshore waters of the North Pacific Ocean. INPFC Bull. 38:1-54.
McNEIL, W. J.
1982. Salmon ranching in the Northeast Pacific: Status and outlook. Presented at ICES, Copenhagen, Denmark, 1982.
NATIONAL AQUACULTURE PLAN.
1980. See: Salmon species plan by E. O. Salo and R. L. Hardy. U.S. Department of Commerce, 1980.
PEARSE, P. H.
1982. Turning the tide. A new policy for Canada's Pacific fisheries. The
Commission on Pacific Fisheries Policy Final Report, Vancouver, B.C.,
292 p.
SALO, E. 0., and Q. J. STOBER.
1977. Man's impact on the Columbia River stocks of salmon. Proceedings ofthe conference on: Assessing the effecls of power-plant induced mortality onfish populations. Pergamon Press.
SIMENSTAD, C. A., K. L. FRESH, and E. O. SALO.
1982. The role of Puget Sound and Washington coastal estuaries in the life
history of Pacific salmon: An unappreciated function. In V. S. Kennedy(editor), Estuarine comparisons, p. 343-364. Acad. Press, N. Y.

SUMMARY
The sustained catches of chinook salmon in the southern regionof the North Pacific can be largely attributed to hatchery production that has replaced the declining production from natural
stocks. The outlook for chinook salmon production is good but
problems remain as to the allocation of the catch among thefisheries along the west coast of North America.
Catches of chinook salmon in the northern region, mainly fromwestern Alaska to Kamchatka, have increased since the 1950's
from increased exploitation of natural stocks; and, since 1977,
from an increase in marine survival that was associated with achange in climate. The outlook for future production is good aslong as temperatures remain mild.

LITERATURE CITED
FREDIN, R. A.
1980. Trends in North Pacific salmon fisheries. In W. J. McNeil and D. C.

43

Hatchery Approaches in Artificial
Chum Salmon Enhancement
OSAMU HIROPINTRODUCTION

fish since 1974, and over 20 million fish since 1979. The largest
return, about 30 million fish, was in 1981.
Annual changes in the percentage of adult returns in chumsalmon liberated from Hokkaido and Honshu Islands of Japan are
shown in Table 3. The percentage of adult returns of liberated
chum salmon fry have stabilized since 1968 in Hokkaido andsince 1976 in Honshu.

Almost all the chum salmon, Oncorhynchus keta, resources inJapan have been supported by artificial propagation. To promote
efficient artificial propagation of chum salmon, it is important for
us to make a model of some aspects of behavior in the life cycle ofthe fish, especially those concerned with migration, spawning,breeding, downstream migration, and feeding migration.

CHUM SALMON RESOURCES AND
REPRODUCTIVE EFFICIENCIES

Table I.-Annual changes in catch in the Japanese salmon fishery.

Annual Changes in Catches in theJapanese Salmon Fishery
Annual changes in catches in the Japanese salmon fishery are
shown in Table I. Almost all the coastal catches are due to artificial propagation in Japan. The percent of coastal catch in tons
has increased over 50% since 1978 to about 70% in 1981.

Annual Changes in Adult Returns and Return Percent
in Chum Salmon Liberated From Japan
Annual changes in adult returns in chum salmon liberated from
Hokkaido and Honshu Islands of Japan are shown in Table 2.
Adult returns in rivers and coastal seas totalled over 10 million
1 Hokkaido Salmon Hatchery, Fisheries Agency, 2.2, Nakanoshima, Toyohiraku,
Sapporo, Hokkaido, Japan 062.

Vear

Far seascatch(thousandtons)

Coastalsea catch(thousand
tons)

Total
(thousandtons)

Percentage
of coastal
catch

1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981

120
101
115
92
110
91
99
90
96
87
91
82
62
41
42
42
42

22
22
27
17
27
24
35
26
36
42
64
40
50
58
86
77
106

142
123
142
109
137
115
134
116
132
129
155
122
112
99
128
119
148

15.5
17.9
19.0
15.6
19.7
20.9
26.1
22.4
273
32.6
41.3
32.8
44.6
58.6
67.2
64.7
71.6

Table 2,-Annual changes in adult returns in chum salmon derived from Hokkaido and Honshu
Island of Japan (thousands),
Hokkaido
Year

Coastalsea

Rivers

1966
1967
1968
1969
197'0
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981

3,408
3,908
1,902
3,595
4,651
6,806
6,343
7,724
9,026
14,217
8,342
9,466
12,28417,751
13,786
20,296

396
592
236
578
627
845
614
597
601
1,557
463
742
863
1,151
1,660
1,630

HonshuTotal

Coastalsea

Rivers

3,804
4,500
2,138
4,173
5,278
7,651
6,957
8,321
9,627
15,774
8,805
10,20813,147
18,902
15,44621,926

451
370
260
313
424
652
698
616
901
1,550
1,344
1,977
2,667
4,518
5,873
7,251

187
142
115
134
149
245
229
238
224
362
270
374
394
608
1,099
727

45

Total
Total

Coastalsea

Rivers

Total

638
512
375
447
573
897
927
854
1,125
1,912
1,614
2,351
3,061
5,126
6,972
7,978

3,859
4,278
2,162
3,908
5,075
7,458
7,041
8,340
9,927
15,767
9,686
11,443
14,951
22,26919,65927,547

583
734
351
712
776
1,090
843
835
825
1,919
733
1,116
1,257
1,759
2,759
2,357

4,442
5,012
2,513
4,620
5,851
8,548
7,884
9,175
10,752
17,686
10,41912,55916,20824,02822,41829,904

Table 3.-Annual changes in the percentage of adult returns in chum salmon
liberated from Hokkaido and Honshu Islands of Japan .
.

Hokkaido

Year

Liberatedfry(thousand)

1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981

280,743
272,106
334,463549,278
272,036434,729
207,438
361,571442,101
575,986
475,805
445,510484,849
801,991
523,361
693,222779,261
873,489
1,146,047
1,079,708_-_._-

HonshuAdult
returns(year class)(thousand)Return
rates

3,025
4,983
2,119
2,572
5,943
8,110
4,881
8,737
10,11012,913
11,909
9,036
11,342
21,322
13,088(18,456)'

1.08
1.83
0.63
0.47
2.19
1.87
2.35
2.42
2.29
2.24
2.50
2.03
2.34
2.66
250
(2.66)'(%)

Adult
Liberated
returns
Returnfry(after 4 yr) rates(thousand) (thousand) (%)
138,267
116,476
139,575
109,836
196,469
161,240
121,193
139,536
144,673
211,464
224,943
271,223
271,708
343,988287,180
412,625
433,177
589,905
750,113738,055

718
572
415
497
653
987
1,017
1,004
1,295
2,112
1,764
2,651
3,311
5,606
7,282
8,408

0.52
0.49
0.30
0.45
0.33
0.61
0.84
0.72
0.90
0.99
0.78
0.98
1.22
1.63
2.54
2.04

INumerals in parentheses indicate number or fale up to 4-yr-old fish relurn::..

The recent rapid increases in adult returns and percentage ofreturns are due not only to an increase in number of liberated fry(by expansion and improvement of hatchery facilities, effective
use of spring waters, and full protection of river fish from control
of coastal catches), but also to regulation of fry-releasing times by
prolonged (I to 4 mo) feeding during artificial propagation.

final step of their anadromous migration to the home river fromthe far seas.
Maturation patterns of adult chum salmon in each of therivers of Hokkaido.-The period of freshwater life of adult chumsalmon up to full maturation after entering rivers differeddrastically in different home rivers, being 0 to 40 d in rivers of
Hokkaido. Differences in the period closely resembled that indegree of sexual maturation. There was no difference in the period
from year to year, but there was a definite seasonal change in eachof the rivers. From these differences in the period of freshwater
life after entering rivers, adult chum salmon in each of the homerivers were divided into three maturational groups-early, intermediate, and late maturing homing types.
In the early maturing homing type, adults migrate as a silvery,
maturing fish in the coastal sea near the home stream and ripen
after a prolonged period-about 25 to 40 d-of freshwater life. In
the intermediate maturing homing type, adults migrate as a silvery
or slightly nuptial-colored, maturing fish in the coastal sea near
the horne stream and ripen after a relatively long time, about; 0 to
25 d, of freshwater life. In the late maturing homing type, adults
migrate as a nuptial-colored, maturing or mature fish in the
coastal sea near the home stream and ripen after a short time,about 0 to 10 d, of freshwater life. Location of the ri vers includedin each of the types in Hokkaido is shown in Figure I. When theseedlings taken from adults in each of the home rivers were transplanted to other rivers, the returned adults had a tendency tofollow the same maturing homing type as that of the original river.

Reproductive Efficiencies of Chum Salmon
Fry in Japan
Recently, the ratios of liberated fry to eggs taken in chumslilmon are about 80% in Japan-a mortality of about 20% up to
fry-liberation (Hiroi 1981). In the 1979 to 1983 salmon enhancement program, adult returns of 38.6 million chum salmon was expected from 2,150 million fry liberated in the last year. Reproductive efficiencies and percentage of returns planned for theenhancement program have been exceeded already by the actual
values for the past 5 yr. In addition to maintaining a quantitative
increase in resources, we also have been selecting adult chumsalmon with a long freshwater life during anadromous migration.
These are valuable commercially because of silvery fish in coastal
seas near home streams.

TECHNICAL APPROACHES AND BASICSTUDIES FOR ARTIFICIALPROPAGATION OF CHUM SALMON
Sexual Maturation and Artificially
Induced Maturation

Changes in serum concentrations of steroid hormones,
thyroxine, and vitellogenin during anadromous migration ofchum salmon.-In order to clarify endocrine factors related tosexual maturation and osmoregulatory adjustments for entrance
into freshwater, serum concentrations of various steroid hom ones
(estradiol-17fJ, androgens, 17a, 20fJ-dihydroxy-4-pregnen--3-one)

Maturation in chum salmon progresses synchronously in thetesticular lobules of males (Hiroi and Yamamoto 1968) and in theovarian oocytes of females, Moreover, male and female chumsalmon, as well as males and females of other species belonging to
the genus Oncorhynchus, are destined to die after spawning, in the
46

v
a

o

Early MaturationalR·

Homing Type()

Middle Maturat lana L•

Late Maturational
Homing Type

Homing TypeToshibetsu

Bettog aR.

R..

Figure I.-Maturational pattern of adult chum salmon in each of the rivers of Hokkaido.

and thyroxine were measured with radioimmunoassay techniques,and vitellogenin was measured with radial immunodiffusion
methods during the anadromous migration of male and female
chum salmon (Hiroi et al. 1982; Veda et al. in press).
In females, estradiol-17(3 levels were high in fish taken at sea
and in midstream, but significantly decreased in fish at the time of
final maturation, including oocyte maturation and ovulation (Fig.
2). Changes in estradiol-17(3 levels coincided with those of serum
vitellogenin levels (Fig. 3). Thereby, these results provide strong
evidence that estradiol-17(3 is responsible for the synthesis ofvitellogenin in chum salmon.
Serum 17a,20(3-dihydroxy-4-pregnen-3-one (17a,20(3diOHprog) levels were low in maturing chum salmon taken at sea
and in midstream, but rose dramatically in mature and ovulating
females. This provides strong evidence that 17 a ,20(3-diOHprog isthe natural maturation-inducing steroid and relates to final oocyte
maturation in chum salmon females (Fig. 4).
Serum androgen levels in male and female chum salmon are
shown in Figure 5. The antiserum employed in the present study
binds both testosterone and 11- keto- testosterone. In females,
serum androgen levels were high throughout the course ofanadromous migration. The levels were much higher in females
than in males throughout the sampling period. Although theprecise roles of androgens in female fish are presently unknown,
the close relationship observed between estradiol-17(3 and androgen levels during late vitellogenesis in chum salmon supports
the suggestion that testosterone may act as a substrate for
estradiol-17(3 biosynthesis.
In males, serum androgen levels were high in maturing fish
taken at sea and in midstream during spermatogenesis, but declined sharply around the time of spermiation. This observation suggests that androgens are involved in the process of spermatogenesis rather than that of spermiation.

15

E
(Jl

C
......
10

Sea

River

pre-spctoNningperiodspawning
periodFigure 2.-Changes in serum estradiol-17/J levels during sexual maturation infemale chum salmon. The vertical hars represent the mean % SEM.

47

25

400

20

/Female........

-E

E

l Jl

c

E 300

-

15

01

'c

C
.......

(1)

lJl

VI

c

.Q
Qj

(1)

~

e 200

01

> 10·

"U

c

«

r-~--~

\

~Male

5
100

\
Sea

River
~wnin;;lspawnin;;lperiodperiodSea

River
pre-spawningperiodFigure 3.-Changes in serum vitellogenin ievels during sexual maturation in female chum salmon. The vertical bars
represent the mean ± SEM.

spawning
periodFigure S.-Changes in serum androgen levels during sexual maturation in40

female and male chum salmon. The vertical bars represent the mean ± SEM .

........

-

E

Serum l7a,20fJ-diOHprog levels in males, similar to females,
increased rapidly during spermiation, although the magnitude ofelevation in males was smaller than in females. This observation
provide~ strong evidence that l7a,20fJ-diOHprog is involved in
the process of spermiation (Fig. 6).
Serum thyroxine levels were highest both in females and males
collected in the coastal sea, and the levels decreased during
anadromous migration (Fig. 7). The present findings in chumsalmon, showing high serum levels of thyroxine during their life in
the coastal sea, raise the possibility that thyroxine is involved indetermining the readiness for the movement of the salmon fromthe sea to fresh water.

01

C.......
(1)

c
0

300

I

(\')

I

C

~

01

....

(1)

0.
I

200

-.:t

>.

e
-g.

.s::.
i:S

8

In vitro effects of chum salmon gonadotropins (SGA) on
oocyte maturation in chum salmon.-To look for the
possibilities of artificially induced maturation, in vitro effects ofchum salmon gonadotropin (SGA) on estradiol-17fJ and l7a,20fJdiOHprog production by ovarian follicles and on the induction of

100

('oj

,f

I:'

.-

Sea

River

pre-spclM1in;;lperiodspcwring
periodFigure 4.-Changes in serum 17", ,20{3.dihydroxy.4.pregnen·3·
one levels during sexual maturation In female chum salmon. The
vertical bars represent the mean ± SEM.

48

germinal vesicle breakdown (GYSO) of oocytes were investigatedin maturing females captured in midstream, which were in the latevitellogenesis phase, about 10-15 d before ovulation (Hiroi et al.
1982).
Ovarian follicles of 10 oocytes, which had only thecal andgranulose cell layers, were incubated in vitro 18 h at 15°C in eachconcentration of SGA Ringer solution. Estradiol-17(3 was
obviously produced by the incubations (Fig. 8), but no significant
differences in production levels between the SGA treated groups
and the Ringer control solution were observed, thereby showingthat the levels were contained originally in follicles. On the other
hand, 17 Gl' ,20(3-diOHprog production levels, as compared withthat of the Ringer control, significantly increased with the increase in SGA doses. This provides strong evidence that 17 Gl' ,20(3diOHprog, under SGA stimulation, is produced in ovarian folliclesof the late vitellogenesis phase.
Fifteen oocytes were incubated in vitro 72 h at 15°C in various
doses of SGA Ringer solutions. Although the oocytes were notchanged by incubation in Ringer control (Table 4), oocyte matura-

1

QI

C

o

MB
I

c

QI

C

01

<II

0..I 6

-.t
I

>~
l"0

.c.>-4
i5I
~

--E

o

N

01

ri 2

C

~

QI

C

o

7c 5

10
~

Sea

--E

River
pre-spawning
per iodQI

c01

spawning
pe riod

-

014

I"

"1 3

C

<II

....

0-

~

r--.

. Figure 6.-Changes in serum 170,20fJ·dihydroxy.4pregnen.3-one levels during sexual maturation in malechum salmon. The vertical bars represent the mean ± SEM.

I

>)(
o
....

0

'6
0
........

"0

>:f
o

VI

UJ

2

I

~

o
N

15
R 0.01 0.1

1 jJg

~

1 J-lg

SGA--~E 10

,,

,
,

Male

/,{

QI

C
)(

....o

Female>.

.c.

~Figure 8.-Elfects or chum salmon gonadotropin (SGA) on estradiol.17fJ and
170,2O(J.dihydroxy.4-pregnen·3·one production by chum salmon roUicles. The
columns with obUque lines show the mean levels or ringer control. The verticalbars represent the mean ± SEM.

5

Table 4.-Elfects or chum saimon gonadotropin (SGA) on the
Induction or GVBD or chum salmon oocytes in vitro.

,,

SGA dose(}Jg/ml)

,

3.3
1.0
0.33
0.1
0.033
0.01
Ringer control

Sea

Oocyte condition (%±SEM)

Treatment,,

Migrated
GVBD

nucleus

Immature

100
80±12
100
47±29
0

0
20±12
0
53±29
100
7±7

0
0
0
0
0
93±7

0

0

100

River
pre-spawningperiodspawning
periodFigure 7.-Changes in serum thyroxine levels during anadromous migration inremale and male chum salmon. The vertical bars represent the mean ± SEM.

49

tion from migrated nucleus to GVBD were induced by the incubation of various doses of SGA solutions, showing 100% GVBD
over 0.33 fJg/ml dose of SGA. These results show that it is possible
to induce GVBD artificially (but not ovulation) by in vitro incubation of SGA in maturing oocytes of the late vitellogenesis
phase in chum salmon.

derived from the increase of cloudy water at the inner surface ofthe vinyl sacks apparently caused by diurnal temperature fluctuations of 2° to 9°C. Stored eggs inseminated with preserved semen
under the same conditions (Hiroi 1978) showed fry-liberation
rates over 97% after 2,8, and 15 h of storage, which were higher
than that of control eggs (96%). From I to 3 d, the fry-liberation
rates declined slowly to 75%, and dropped suddenly to 39% after 4

Retention of Gametes in Chum Salmon('10)

In order to promote effective utilization of gametes, including
the production of excellent stocks or the future development of
selective breeding, short-term retention of gametes and long-term
cryopreservation of sperm were investigated in chum salmon.

100
>-

a:

LL

0
W

I-

ffi

Changes in fry-liberation rates of short-term stored chumsalmon gametes.-Gametes were enclosed in vinyl sacks containing 0z-gas and stored in corrugated cardboard boxes at a room
temperature of 2 ° to 9°C or in a refrigerator (only sperm) at atemperature of 2 ° to 5°C.
Fresh eggs fertilized with stored sperm stabilized over 90% in
the fry-liberation rate up to 4 d after storage (Fig. 9), but after 5 dpreservation, fluctuated between 60 and 90% with a weakening in
sperm motility and gradual increase in microbial contamination
showing 75% after a 7-d retention. Preserved eggs inseminatedwith fresh semen showed fry-liberation rates over 90% up to 2 dafter storage. but after 3 d preservation, dropped gradually in fryliberation rate to 12% after 7 d storage. Almost all the mortality ofstored eggs was due to unfertilized eggs (Table 5) which were

(I)

:::;
LL
0

50

,,

;'!
z

\

w
u
a:
w

0 '-....,.,,....,..-:!""......-......- -......- -.....- -.....- -.....--~,-2815

qfO.JlS) 1

2

3

4

-----

l'el1ilizeJ eggs

Stillborn
eggs

Unfertilized
eggs

Early deadfertilized
eggs

Late deadfertilized
eggs

Entrance of

None

None

Present

Present

Activation with

None

Present

Present

Present

water supply
Blastodisc

None

PreslO:nt

Present

Presel'll

None

Present

Present

Present

None

None

Present

None

None

None

Present
Present

Extremely

lillie orLinle orExtremelynone

nollt.

sperms into
micropylefOffil3tion

Almost all theeggs coagulate
opaquewithin 24 h.
Multiplicationof fungi

6

7

DAYS STORED

Elements

Remarks

5

FigurP 9.-Changes of fry-liberation rate in chum salmon as inseminated fresheggs lIE) with presened sperm (PS), preserved eggs (PE) with fresh sperm (IS),and preserved eggs with preserved sperm.

rionsperm eggs

Physiologicaldegenerations
and Qvershocking duringholding period,'b..

Table 5.-Sources and types of dead egg, in chum salmol':.

Isotonic
regulationof chorion
Cleavages
Isotonic
regulation ofembryonic
body
Multiplying
frequencyof fungi
Sources,,a..

-----Types

FEx IS,

l!5

Water ,upply
before insemination. mixingof broken eggs
and stillborn
sperms atcollected eggs
Living aspects
up to shocking:;election rune
with faintpinkish color50

Probabie
accidenis of
incubator or
waler supply
and overshocking

Li ving aspects
after shocking
selection with
faint yellowish
color

Probable
accidents inincubation
process andmuhiplil:(trionof fungi
Multiplicationof fungi andopaquecoagulation soonafter dying withdefiniteembryonic body

be kept slow, under 10 cm/s, with periodic exchanges of new
water. In the present approaches, holding or rearing ponds withthe water supply welled up from the bottom are most suitable.

d and to 0.13% .after 7 d of storage. Among the stored eggs, inaddition to a gradual increase in unfertilized eggs, dead eggs
before insemination increased accompanying prolongation ofstorage, which was considered to be due to direct or indirect influences of microorganisms.
Counts of microorganisms in stored semen and coelomic fluid
increased rapidly accompanying prolonged storage (Table 6;
Nomura and Hiroi unpublished). The count in coelomic fluid(3.1 x 10 5 body/ml) was larger than that in semen (2.7 x 10 3
body/ml) in the initial control. The increase in microorganisms
after 7 d of retention was as much as 4,000 times in semen and
4,500 times in coelomic fluid compared with that of the control.

Various infectious viruses and Aeromonas salmonicida in
adult salmon in rivers in Hokkaido.-These data were citedfrom Nomura and Kimura (1981) and Kimura et al. (1982).
Infectious viruses and A. salmonicida were determined by usual
methods, mainly from the semen of males and coelomic fluids offemales, and from fresh kidney. Although the detection rates were
extremely low, four kinds of infectious viruses, IHN, OMV, CSV,
and VEN virus, were found in adult salmon in some rivers in Hokkaido from 1976 to 1981. IHN virus was found in only one sample of chum salmon adults in 1976 and 1977. CSV virus was
detected in only one sample from chum salmon adults in 1978.
OMV virus was determined in only one sample from Masu salmon
adults in 1980. VEN virus was observed in only I sample fromchum salmon adults in 1980 and in 8 samples from chum salmon
adults in four rivers and in 14 samples from pink salmon adults ofthree rivers in 1981.
The detection rates of A. salmonicida, which causes furunculosis, were unexpectedly high in chum salmon adults. The rates increased with prolongation of the holding period, reaching over
50% in some rivers, but showed no significant difference between
sexes.

Table 6.-Viable counts of microorganisms in the semen andcoelomic fluid of chum salmon.
Viable counts of microorganisms per 1 ml

Days
stored

o
3
7
I

Semen

Coelomie fluid

2.7x 10'6.3x 10' (x23)'
1.1 x 10' (x4.074)'

3.1 X 10'1.6x 10' (x 52')lAx 10' (x4.516)'

Numerals in parentheses show the times to control.

Cryopreservation of chum salmon sIJerm.-These data werecited from Kurokura et al. (1982).
Chum salmon semen was immediately diluted with extenderand DMSO, and cryopreserved in liquid nitrogen after freezing bymethanol-dry ice bath (Kurokura and Hirano 1980). Fertility tests
with sperm cryopreserved for 17 d gave about 19% eyed eggs.
ranging from 5.3 to 29.9% (Table 7). This result demonstrated thepossibility of long-term preservation of chum salmon sperm.

Sources and kinds of dead eggs in chum salmon.-Dead eggs
were divided originally into four types (Table 5; Hiroi 1981). A
large number of dead eggs were either stillborn or unfertilized.
Stillborn eggs were deprived of normal fertility before fertilization and were found in broods held a long time under poor conditions. They were SOUlces of fungi during artificial incubation of
the eggs, because of the absence of isotOnIC regulation by thechorion. The unfertilized eggs were activated only with a watersupply, without the entrance of the sperm into the micropyle, andaccomplished blastodisc formation and isotonic regulation of theegg chorion, but did not proceed through cleavage. The occurrenceof dead eggs was due to unskillful techniques in the artificial process of collecting eggs for insemination.
Among the fertilized eggs, dead eggs were divided into two
types, early and late mortalities, depending on the developmental
stage. The fertilized eggs which died in the early developmental
stage did so as a consequence of over-shocking, unsuitable water
currents, and defects in egg-incubation f<:cilities. The eggs whichdied in the late developmental stage after maintaining isotonic
regulation did so as a consequence of over about 200°C in daily
cumulative water temperature. They were sources of fungi
because of the solubility of the embryonic contents as a consequence of the loss of isotonic regulation of the chorion.

Table 7.-Fertility of cryopreserved chum salmon
sperm. (n=8, mean 18.6%, SE 8.9%.)
Sperm

Total eggs

Eyed eggs% eyedPreserved

417
419
472
347
570
445
465
384
468
612

24
41
53
60
122
105
134
115
411
579

5.8
9.8
11.2
17.3
21.4
23.6
28.8
29.9
87.8
94.6

Fresh

Technical Conditions and Mortality Factors Up to
Fry-Liberation During Artificial Propagation ofChum Salmon

Technical approaches to insemination.-Since chum salmon
are destined to die soon after their first spawning, eggs must be
obtained by the "incision method" rather than the stripping
method. Chum salmon eggs are activated instantaneously by contact with water. On the other hand, the sperm are activated immediately with ovarian coelomic fluids and effect entrance into themicropyle by their motility. However, the sperm can become abnormally mobile with water or Ringer solution. Because of this,eggs must be inseminated without water, namely the "drymethod" of insemination.

Basic conditions required for holding maturing chumsalmon in rivers.-Four basic conditions for holding maturing
fish in rivers are described. First, maturing adults must be held inhome stream waters because of their instinctive homing nature.
Second, we have to understand the seasonal changes in degree of
sexual maturation in the adults soon after entering each of therivers. Knowledge of the degree of maturation is necessary to
determine the holding time for optimum selection of mature fish
and collecting eggs. Third, maturing adults must be kept in optimum water temperatures of 6° to 12°C by mixing spring water
into the river water. Fourth, water currents in holding ponds must

Technical approaches during transfer of fertilized eggs toincubators.-Optimum washing times of eggs soon after fertilization were determined by mortality from a 2-h suspension of51

(010)

the water supply (Hiroi 1980). The mortality of fertilized eggs
decreased in proportion to the prolongation of washing times andbecame stable at over 25 min (Fig. 10). Therefore, eggs whichhave been recently artificially inseminated need to be washed forover 30 min in running water with an adequate current.
Fertilized eggs in the early developmental stage were weakened
by strong shocking, and almost all the eggs died. Resistance ofeggs to weak shocking is shown in Figure 11. Mortality of fertilized eggs was smaller up to 8 h after fertilization, but increased suddenly after 9 h, when the developing eggs initiated the firstcleavage at a water temperature of 8°C (Hiroi et al. 1973). Therefore, the fertilized eggs have to be transported gently and settled
into incubators within 8 h at 8°C after fertilization.

80
III

8w 70
0

w 60
N

--'
l-

~

~

50

n::

w
lJ.. 40
lJ..

0

>
I-

30

:::; 20
;!
~ 10
~

0

(Of. )

25

30

33 35

''o~'

"'5 '

202

243

268 283324

364,...,...,

,

,-,

50

55

'SODAYS

405

445

J,JJ6

·c

TREATED TI/'o£5 AFTER FERTILIZATION

1Il

<.9
<.9

10

Figure 12.-Change in mortality of developing chum salmon eggs by hardshock.

w

o

W
N

:J

and over 56 d at 8°C after fertilization, but became stable below
1% from 33 to 55 d. Therefore, eyed eggs can be detected from 35
to 55 d at 8°C (about 280° to 440°C in daily cumulative watertemperature) after fertilization.

i=

a:
~

5

o

Technical approaches used with sac-fry in fry ponds.Emerged fry must be hatched in artificial incubation beds modeled on natural conditions, especially with regard to sunlight, gravel,
and water supply including upwelled currents. Developing fry do
not seem to need sun, up to about 900°C in daily cumulative
water temperature, after fertilization at 8°C. Because of their lackof mobility after emergence, they remain on the bottom in the sacfry pond. It is necessary to maintain the water currents in the sacfry pond below 3 cm/s with upwelled currents. Gravel on thebottom of the pond is important in maintaining the upwelledcurrents.

•
5

10

15

20

25

30

35

40

WATER-WASHING TIMES

45 CONT(MINUTES)

Figure IO.-Changes in mortality of fertilized chum salmon eggs by 2-h suspension of water supply soon after the artificial fertilization in the Chitose (solid
circles) and Nljibetsu (open circles) Hatcheries.

(',,)

Technical approaches used with feeding fry in rearing
ponds.-Feeding fry require sunlight and water currents, with anadequate food supply, to accomplish their downstream migration
followed by their feeding migration to the sea. Feeding must be
initiated during the period of 900° to 960°C in daily cumulative
water temperature when the fry have functional digestive systems.
Water in the rearing pond must have currents, with both riffles
and pools like river streams, as well as an adequate exchange of
new water with suitable, dissolved oxygen (over 70% in theoutflow of ponds). Water currents as riffles in rearing ponds areespecially important for the fry to have full swimming ability.

14

8w

12

o
w

N
...J

~

tl.'

10

8

Bacterial gill disease and blue sac disease.-Bacterial gilldisease and blue sac disease are serious problems for chum salmon
fry. Almost all the fry-liberations from the lots exposed to bothdiseases resulted in little or no adult returns. Bacterial gill diseaseis infectious in a large number of fry, over about 850°C in daily
cumulative water temperature. They are caused by flat, long rodson the surface of gill filaments. As shown in Figure 13, from scanning electron microscope observations (Hiroi, Nomura, andDrawa, unpublished), long rods were always detectable on the surface of the gill filaments of the infected fry. This disease istreatable by bathing with 0.5 to 1 ppm of nifurpirinol for 1 h.
Blue sac disease is essentially a form of dropsy in which theyolk sac is a visible blue color. This is caused by exposure of

TREATED TIt<ES AFTER FERTILIZATION

Figure n.-Change In mortality of developing chum salmon eggs by weak
shock.

Technical approaches used with developing eggs in incubators.-Developing eggs must be incubated without lights by
upwelled currents of spring water with an appropriate constantwater temperature. Egg resistance to hard shocking similar to thehard-shocking selection of dead eggs in the eyed stage is shown in
Figure 12. Mortality of fertilized eggs was larger both up to 32 d
52

fry at the most suitable time to accomplish adequate feeding
migration to the northern Pacific Ocean from the home rivers.

LITERATURE CITEDHIROI, O.
1978. Studies on the retention of gametes of salmonid fishes-3. Changes infry. liberation rate of stored chum salmon eggs inseminated with sperms
preserved in same cor,ditions. [In Jpn., Eng!. summ.] Sci. Rep. Hokkaido
Salmon Hatchery 32: 19-26.
19RO. On the water-washing time of chum salmon eggs soon after the artificial fertilization. [In Jpn .. Eng!. summ.] Sci. Rep. Hokkaido Salmon
Hatchery 34: 115-120.
1981. Early mortality of chum salmon resources, especially on mortal elements up to the fry-liberation during the artificial propagation. [In Jpn.,
Eng!. summ.] Rep. F;,h. Res. Invest. Jpn. Gov. 22:53-66.
HIROI, 0., S. URAWA, H. UEDA, K. YAMAUCHI, and Y. NAGAHAMA.
1982. Changes in serlJrn ~oncentralions of steroid hormones accompanying
sexual maturation of the chum salmon, Oncorhynchus keta [In Jpn.] 1982
spring meeting of Jpn. Soc. Sci. Fish., April, Tokyo.
HIROI, 0, and K. YAMAMOTO.
1968. Studies on the maturation of salmonid fishes-I. Changes in the testisof the chum salmon, Onl--orhynchus keta, during anadromous migration.
Bul!. Fac. Fish., Hokkaido Univ. 19:173-184.
HIROI. 0., M YASUKAWA, T. SUETAKE, S SASAKI, T. TOMITA, and Y.
SATO.
1973. A preliminary report on the development of chum salmon (Oncurhvn·
chus ketu) egg kept in the spring water of 8°C. [In Jpn .. Eng!. summ.] Sci.
Rep. Hokkaido Salmon Hatchery 27:25-30.
KIMURA, T., M. YOSHIMIZU, M. TANAKA, S. SUZUKI, Y. EZURA, and T.
NOMURA.
1982. Incidences of infected virus (I 976 to 1981) and Aeromonas salmonicida(1979 to 1981) among anadromous salmonids in Hokkaido. [In Jpn.]"Synthetic studies on a techOical development of mass production in theanadromous salmonid fishes," Ministry of Agriculture, Forestry and Fisheries.
198;. Report of River Investigation Group, HokkaiJu Reg. Fish. Res. Lab.,
p 179-188.
KUROKURA, H., and R. HIRANO.
1980. Cryopreservation of rainbow trout sperm. Bul!. Jpn. Soc. SCI. Fish.
46:1493-1495.
KUROKURA, H., K. KAKU, and R. HIRANO.
1982. Studies in cryopreservation of salmonid sperms. [In Jpn.] "Synthetic
studies on a technical development of mass production in the anadromous
salmonid fishes," Ministry of Agriculture, Forestry and Fisheries. /981
Report of River Investigation Group, Hokkaido Reg. Fish. Res. Lab., p. 161171.
NOMURA, T., and T. KIMURA.
1981. Incidence of Aeromonas salmonidda among anadromous salmon ids in
Hokkaido, 1979. [In Jpn., Eng!. summ.] Fish Patho!. 16(2):69-74.
UEDA, H., O. HIROl, A. HARA, K. YAMAUCHI, and Y. NAGAHAMA.
In press. Changes in serum concentrations of steroid hormones, thyroxine andvitellogenin during spawning migration of the chum salmon, Oncorhynchus
keta. Gen. Compo Endocrino!.

Figure B.-Scanning electron micrographs of gill filament of infected chumsalmon fry to bacterial gill disease. On the surface of the giU filaments, Oat, longrods are detectable. Figure 13a, • 950; Figure 13b, .2,800.

developing eggs or fry to waters containing over 130% in nitrogengas. Almost all the waters with this gas content were due to pumpmalfunction rather than the original gas content in natural flowing
waters. At present, this disease is not treatable.
Timing of fry-liberation.-To prevent early mortality of chumsalmon in artificial propagation, it is important to release healthy

53

The Migration and Ecology of Young Salmon in
Early Marine Life
TAKAHIKO IRIEI

ABSTRACTThe ecology of juvenile chum and pink salmon is described for Abashiri Bay of tbe Okhotsk Sea and tbe
Pacific Ocean off Hokkaldo. Ecological and morpbological cbanges are discussed togetber witb developmental
stages. Juvenile cbum salmon development is divided into four stages. Tbe patterns and routes of offsbore
migration are discussed In relation to water masses. It is suggested tbat tbe migration routes of juvenile salmon
coincide wltb tbe distribution of the coastal water mass, and are connected wltb an Isothermal area with surface
water temperatures ranging from 8° to 13°C. Furtbermore, tbe timing of juvenlle salmon reiease is discussed,
considering environmental conditions and tbe developmental stage of tbe juvenlles. The most suitable time forrelease is wben the coastal water mass Is spreading along the coast. Optimal size of chum salmon at release wasconsidered to be over 5 em in fork length.

INTRODUCTION

Investigations were mainly carried out in Abashiri Bay andadjacent waters of the Okhotsk Sea, and in the Pacific Ocean off
Hokkaido in 1977-81 (Fig. 1). Oceanographic conditions in
Abashiri Bay are affected by the Soya Warm Current and thosealong the Pacific coast of Hokkaido are affected by both the
Tsugaru Warm Current and the Oyashio Current (Fig. 2).
To collect juvenile salmon. a small purse seine (117 m long.
2.6-9 m deep) was used during the day and a spoon net (5 m long.
40 cm diameter) with fish-gathering lamp (100 V, 2.5 kWj wasused at night.

Juvenile chum, Oncorhynchus keta, and pink salmon, O. gorbuscha, migrate from rivers into marine habitats and live incoastal waters for a few months. before they migrate toward offshore waters. In Japan, little has been known about the ecology
and morphology of young salmon during this period, and there arefew studies on the mechanism of migration toward offshore
waters (Sano and Kobayashi 1952, 1953; Mihara 1958; Okada
and Nishiyama 1970; Okada and Taniguchi 1971; Kobayashi
1977; Kobayashi and Abe 1977l.
In general, fish ctevelop in successive ontogenetic periods which
are morphologically. physiologically, and ecologicallydistinguishable. Furthermore, each period is divided into stages orphases (Nikolsky 1963; Balon 1975). In the general distinction ofdevelopment. chum and pink salmon in early marine life correspond to the juvenile period.
This paper deals with the migration and ecology of young
salmon in early marine life. The paper also discusses the developmental stages of juvenile chum salmon using comparisons of
ecological and morphological changes. Furthermore, patterns androutes of migration toward offshore waters. and the timing of
release in relation to the developmental stages are discussed. This
may not unly help in describiug an unknown period in the life
history of salmon, but may also be useful in determining the optimum time of release to reduce the mortality rates of juvenile
salmon.

Is.

JAPAN SEA

MATERIALS AND METHODSPACIFIC OCEAN

In recent years. we have obtained new information about theecology of young salmon in a special project, "Technical developmt'.nt of large-scale farming of anadromous salmons," sponsoredby the Agriculture, Forestry, and Fisheries Research Council. This
report is based on our recent studies and my own data (Kobayashi
et al. 1980; Irie et al. 1980, 1981 a, b, 1982; Irie 1982a, b).

I Hokkaido Regional Fisheries Research Laboratory. Fisheries Agency of Japan,
116 Katsura koi. Kushiro. Japan 085.

Figure I.-Map showing the iocation of Abashiri Bay and adjacent waters andthe Pacific Ocean off Hokkaido where investigations were carried out.

55

occurred within 1-2 km of the shore (Figs. 3,4, Table 2). They
were often found in schools or assembled in inlets and ports.
Under fish-gathering lamp, they were observed swimming in theextreme surface of the water (lrie et al. 1980, 1981 a).
From late June through early July, juvenile chum salmon of
4-12 cm FL and pink salmon of 4-1 cm FL were observed within
16 km of the shore (Figs. 3, 4, Table 2).
The number of juvenile salmon decreased with distance fromthe shore. The larger juveniles were distributed further offshore(lrie et al. 1980, 1981 a). Mishima, Yamamoto, and Shimazaki(1982) and Mishima, Shimazaki, Yamamoto, Ishii, Sasaki, andMeguro (1982) indicated a similar phenomenon. Reviewing pastreports published in Japan, Ito (I980) pointed out that the larger
chum salmon appeared further offshore even in coastal areas. The
same phenomenon was reported for pink salmon off the British
Columbia coast (Gilhousen 1962; Healey 1980).
Under fish-gathering lamp, the juveniles were observed swimming quickly in circles in schools just below the surface water(lrie et al. 1980, 1981 a). There were changes in the schooling andswimming behavior over time and with the stage of development.
Hoar (1976) stressed that schooling behavior was very importantin the evolution of the strongly migrant seagoing stocks ofoncorhynchids.
~.fost juvenile salmon had disappeared from Abashiri Bay by
early or mid-July (Figs. 3, 4). The results suggest that juvenile
salmon live first in the area adjacent to the shore and gradually extend to the area along the coast and further offshore.
Juvenile pink salmon were collected together with chumsalmon in Abashiri Bay (Figs. 3, 4). Similar phenomena werereported off the coast of the South Kuriles (Ibankov and Shershnev 1968) and off the British Columbia coast (Manzer 1956;°

Figure 2.-A schema of the upper structure of currents and waters around
Japan (after Dda 1935). A: Kuroshio water, B: Tsushima warm current, C:
Oyashio water, 0: Tsugaru warm current, E: Soya warm current, K: boundary
zone of the cold water and the warm water.

Table I shows the data from the investigations and collectionsof juvenile salmon. Oceanographic observations and plankton
sampling were made in each investigation. Table 2 shows the fork
length distribution of the juvenile salmon.

DISTRIBUTION PATTERN AND BEHAVIOROF YOUNG SALMON
In mid and late May in Abashiri Bay, juvenile chum salmon of
3-6 cm fork length (FL) and pink salmon of 3-5 cm FL generally

Table I.-Data from investigations and collections of juvenile chum and pink salmon by various methods in 1977-81.
Cruise
no.

no.
Year

PeriodArea

Sampling gear

tows

1977

19 July - 17 August

Japan Sea Okhotsk Sea

Isaac-Kidd mid-water trawl

12

Larva net

18

Gill nelSpoon net with fish lamp

5
8
13
4
16
2
2
7
2
6
5
9
17
3
21
2
20
2
7
13
8

1978

18-22 May

Abashiri Bay

1978

29 June - 2 July

Abashiri Bay

Larva netSpoon net with fish lamp
Larva net

1978

15-20 July

Abashiri Bay

1979

21-27 May

Abashiri Bay

6

1979

26 June - 2 July

Abashiri Bay

Gill netSpoon net with fish lamp
Larva net
Gill netSpoon net with fish lamp
Larva netSpoon net with fish lamp
Spoon net with fish lamp

7

1979

5- 10 July

Abashiri Bay

Spoon net with fish lamp

4

Purse seine
Purse seine1980

18-27 May

Abashiri Bay

Spoon net with fish lamp

1980

30 June - 6 July

Abashiri Bay

Spoon net with fish lamp

Purse seine

9

Purse seine

10

1980

8-12 July

II

1980

14-18 July

Abashiri Bay Off Etorofu Is.
Abashiri Bay

12

1981

2-15 June

Pacific Ocean

13

1981

6-19 July

Pacific Ocean

Spoon net with fish lamp
Spoon net with fish lamp
Purse seine
Larva netSpoon net with fish lamp
Larva netSpoon net with fish lamp

56

15
4
14
24
43
43

No. collected
O. ketaO. gorbuscha

6
2
41

4

166

36

2
149
225

75
52

143
5
III
I
79
202

32
2
160

19
3
77

69
8
I

Table 2.-Fork length distribution or juvenile chum and pink salmon collected in 1977-81.
Forklength
(em)

Year

1977

21-26
PeriodJuly

Oncorhynchus keta
2-3
3-4
4-5
5-6
6-7
7-8
8-9
9-10
10-11
11-12
12-13
13-14
Total

1978

1978

1979

1979

1979

1980

1980

1980

1980

1981

1981

18-22 29 June
May -2 July

15-20
July

21-27 26 June
May -2 July

5-10
July

18-27 30 June
May -6 July

8-12
July

14-18
July

2-15
June

6-19
July

1978

I

2
3

3
21
18
I

2

Oncorhynchus gorbuscha
3-4
4-5
5-6
6-7
7-8
8-9
9-10
Total

71
71
6
1

I

31
124
8
2

2

2
27
41
56
18
4

18
68
63
59
II

4

53
54
3
I

I
I

2
2
8
26
46
124
64
9

6
3
4
I

2
2

I

2
I
I

3
4
4
5
12
27
17
6
2

I

43

166

2

149

225

148

7
17
26
2

3
7
9
13
2

52

34

75
4
10
24
2

4

36

75

112
146
14

160

19

281

3
5
17
35
10
7
77

I
I
I

3

80

Total

I
J33
177
166
243
159
92
163
83
17
2
I
1.237

221
31
39
76
53
14
8
442

residence. They leave the coastal waters by the time the Soya
Warm Water becomes dominant in the area.
Compared with the Okhotsk Sea, the oceanographic conditionsin the parts of the Pacific Ocean where juvenile salmon are distributed are similar in temperature but lower in salinity. Comparing
water masses in the Pacific Ocean and the Okhotsk Sea shows aparallel phenomenon.

Neave 1966a, b). This suggests that the habitats of the two species
resemble each other closely at this stage of development.

DISTRIBUTION OF YOUNG SALMON ANDENVIRONMENTAL FACTORS
Oceanographic Conditions

Distribution of Zooplankton

Figures 3 and 4 show the distribution of juvenile salmon andthe surface water masses in Abashiri Bay. In mid and late May,
the coastal water mass is distributed along the coast, and the
Okhotsk Surface Water is spread further offshore. Juvenile
salmon were in the coastal water mass, near the shore.
In late June and early July, the coastal water mass is ordinarily
replaced by the Soya Warm Water, with the Okhotsk Surface
Water remaining offshore (Figs. 3,4).
Figure 5 shows juvenile salmon densities and water masses.
Juvenile salmon are found mainly in coastal water masses withsurface water temperatures from 10° to 13°C and salinity from33.00 to 33.700 / 00 . They are also found in low salinity areas,
below 33.8°1°°' even in the Soya Warm Water; some were in thearea of the Okhotsk Surface Water.
The Soya Warm Water is widely dispersed by late July and, as aresult, the number of juvenile salmon decreases sharply (Irie et aI.
1980, 1981 a, b). During this period, juvenile salmon were observed in the Okhotsk Surface Water off Etorofu Island (Irie et aI.
1982).
Figures 6 and 7 show the distribution of juvenile chum salmon
and water masses in the Pacific Ocean. From early June to midJuly, the coastal water mass was distributed near the Pacific coast;
the Oyashio Water was offshore. Juvenile chum salmon weremainly found in the coastal water mass with some in the lower
salinity area of the Oyashio Water (Irie 1982a).
This suggests that in Abashiri Bay, juvenile salmon live in contact with the coastal water mass throughout their coastal

Figure 8 shows the distribution of zooplankton and water
masses in Abashiri Bay and adjacent waters. In mid and late May,the density of zooplankton in the nearshore coastal water mass
was higher than in the offshore areas. In late June, it was higher inthe offshore areas, with the Okhotsk Cold Water, than in the nearshore areas. In early July, it was higher off Etorofu Island in the
Okhotsk Cold Water than in Abashiri Bay where the Soya Warm
Water occurred (Irie et al. 1982).
These results suggest that, through the intermediation of water
masses, there is a definite relationship between the distribution of
zooplankton and juvenile salmon.

FOOD FOR YOUNG SALMON
Juvenile chum salmon 3-5 cm FL collected near coasts fed on
small zooplankton, insects, and fish larvae. The main prey animals
were different at the different stations where samples were collected. Consequently, it has been suggested that young salmon do not
feed on specific animals but feed on the easiest prey available in aregion (Kobayashi et al. 1980).
Chum salmon of 5-11 cm and pink salmon of 5-8 cm FL
collected in Abashiri Bay were mainly feeding on larger zooplankton such as calanoida, amphipoda, fish larvae, andEuphausiacea larvae. They were feeding on especially Ca/anus
57

;

i

i

i

1979 May 21 - May 27
!!

}~

I

._.--....

o

.' \

.
I

\

j

)

\

i

,......,.....

..... -.

I

i

.i

\.,

.i

I

,I

\\.j'.

\',"•.J'....

o:: ....: ....-:;:~~....
.....,.
\

i ."\

.
i

i!

\.

i \

)

(I)i

! \ i
~

'.'
I
\"

!

,

1980 July \41979 July· 5 -- July 10

I
I

;

'.,

\

i

i

,

i

~

~

i

•
o •

(

\.

'- ' .

July 18

I

;

•

\

\)

o

i

14(1)

O.

i

j

\ I

i\ ,

0

July 6

I

i i

,
. i
\ 'i

,/

!
I

1980 June 30

1979 June 29 - iuly

!'

\)

\, .

j

i

i

\ i

j

...... j

,

j

i

.

/

\ ~
\ \

.

,

i \

J \ i
\""

Ma y 27

! i

)

i
i

,

1980 May 18

I

l
"

,-_.

..........

..... _·_·- .......·'·1

i
'-

34(7)

Figure 3.-Distribution of juvenile salmon and surface water masses in Abashir;
Bay from 21 May to 10 July 1979. Numerals indicate number of chum salmon
collected. Numerals in parentheses indicate number of pink salmon collected. No
number indicates zero. Dotted lines indicate the boundary of two water masses.
Solid circles indicate spoon net with fish lamp, open circles indicate larva net or
purse seine. 0: Okhotsk surface water, C: coastal water mass.

Figure 4.-Distribution of juvenile salmon and surface water masses in Abashiri
Bay from 18 May to 18 July 1980.0: Okhotsk surface water, C: coastal watermass, S: Soya warm water. (For further explanations, see Figure 3.)

specimens of about 4 cm FL and are present in all specimens over
5 cm. Simultaneously with the appearance of scales, the body
becomes more silvery, parr marks become obscure, and the tips ofthe dorsal and caudal fins begin to turn black (Irie 1982b).
Figure 9 shows gill raker number versus fork length in juvenile
chum salmon. Gill rakers reached the full number at about 5 cm
FL at the earliest and they were almost complete at a fork length
over II cm (Irie et al. 1980).
Figure 10 shows the development of body parts versus fork
length in juvenile chum salmon. Inflections in growth were observed in 11 body measurements: Head length, eye diameter, upper
jaw length, mouth width, pectoral fin length, caudal fin length,
dorsal fin height, anal fin height, body height, body width, andanal length. In eye diameter, mouth width, and pectoral fin length,
growth inflections were observed at a fork length of about 5 cm
and about 8 cm (Irie et al. 1981 b; Irie 1982b). These changes inplumchrus and Parathemisto japonica which are the most common
and abundant there (Irie et al. 1982).
Shershnev (1970) pointed out that prey size for juvenile salmon
was larger in May and June than in April. Okada and Taniguchi(1971) reported that the size of prey animals apparently changed
before and after 55 mm FL. Simenstad et al. (1980) clarified thatoutmigrating juvenile chum salmon exhibited a high degree of
selectivity in prey size, and they also discussed the mechanism of
prey selection in detail.

MORPHOLOGICAL CHANGES WITH
DEVELOPMENT
In juvenile chum salmon, parr marks persist on the body for atime after entering the sea from rivers. Scales first appear on

58

Similarly, specimens with 11-17 cm FL were caught in the: offshore areas of the Okhotsk Sea (Birman 1969).
Considering the sampling results and morphological changes(Irie et a!. 1981 a, b; Irie 1982b, unpub!. data), it may be concluded that juvenile pink salmon migrate offshore at smaller sizes
than juvenile chum salmon.
Physiologically, chum and pink salmon show a higher salinity
tolerance than other salmonid species in the early stages of development (Weisbarl 1968; Hoar 1976). According to McInerney(1964), the preference for salinity increases gradually and is temporally associated with seaward migration. Kashiwagi and Sato
(1969) and Kashiwagi and Iioka (1978) reported that in chumsalmon, salinity tolerance increases gradually as the fish becomesolder, and juveniles more than 90 d after hatching (6 cm, 2 g) all
survived in 100% seawater.
The results show that it takes time for juvenile chum salmon to
fully adapt physiologically to seawater, and changes in morphology, ecology, and physiology, the so-called "smoltification,"
occur from 5 to 8 cm FL. LeBrasseur and Parker (1964) suggested
that such changes occurred at about 6-8 cm FL in pink salmon.

1979 June 29- July 10

13 r-----j-----i-------t-::::::==:-:---------tHji:~

\l~

r",

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.w •.·····.,

0"llIi'"

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10 .•• (l--'.~- :.:":- _·······l5··:····

32 .00

33.00

34.00

1980 June 3D-July 18

I'i ....,.

15r-----,(;'-0'"'.~.---Q"'";-'o...",-.-.
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........ _-_... __ .... -

33.00

,

s

MIGRATION PATTERNS AND ROUTES OFYOUNG SALMON
Based on the results, the migration pattern for juvenile salmon
in relation to water masses is shown schematically in Figure 11.
Area B corresponds to estuaries, ports, and inlets. Area D corresponds to the boundary of two water masses or areas where they
are mixing.
In early marine life, juvenile salmon live first in the coastal
water mass which is influenced by freshwater. Thereafter. theliving area gradually expands along the coast. When development
is complete, they begin to migrate in schools to the offshore cold
water mass. As shown in Figures 5 and 7, there were no abruptchanges in temperature and salinity between the coastal water andthe offshore cold water. The migration occurs with an increase inswimming ability and changes in the animals preyed upon, as wellas with the movement of the water mass itself. The remaining
juvenile salmon migrate offshore responding to changes in environmental conditions such as the decline of the coastal watermass, the rise in water temperature and salinity, and changes infood conditions.
In conclusion, the migration route of juvenile salmon in earlymarine life coincides with the coastal water mass. Due to theoceanographic conditions in Abashiri Bay, the route was within
about 16 km of the shore along the coast. In the Pacific Ocean, theroute is more complex than in Abashiri Bay (Fig. 12). The routeshould be considered in relation to isothermal areas with surface
water temperatures ranging from 8 ° to 13°C, as shown in Figure
13.

34.00

SURFACE WATER SALINITY(9'oo)

Figure S.-Relation between surface water masses and number of juvenile chumand pink salmon observed. Surface water temperature and salinity were
measured at the same time as the juvenile sampling. 0: Okhotsk surface water,
C: coastal water mass, S: Soya warm water. Solid circles numerals indicate
number of juvenile salmon observed during a half hour period of lighting (29June-10 July 1979 and 8-18 July 1980). Open circles numerals indicate numberof juvenile salmon collected by purse seine (30 June-' July 1980). Circles withcrosses numerals indicate number of juvenile salmon collected by spoon net during a half hour period of lighting (30 June-' July 1980).

the slope of the relative-growth line indicate sudden changes inorganization (Martin 1949).

DISTINCTION OF DEVELOPMENTAL
STAGES
Morphological changes can be distinguished to correspond to
the above ecological changes in food habits, behavior, and extension of the living area away from the shore. In Table 3 the data arearranged in sequence, and four substages are distinguished in theearly marine development of the chum salmon: Stage A with afork length of 3 to 5 cm, just migrated seaward but not yet completely adapted to seawater; Stage B with a fork length of 5 to 8
cm, further adaptation to seawater and preparing for offshore
migration; Stage C with a fork length of 8 to 11 cm, completely
adapted to seawater and beginning ocean migration; Stage D witha fork length of 11 to 17 cm, ordinarily migrating offshore.
The end of stage D, 17 cm FL, is estimated from the size ofjuvenile chum salmon collected in coastal and offshore areas forour present investigation. The maximum fork length was reported
to be 18.6 cm with almost all below 17 cm (Mihara 1958;
Hayashi and Odate 1980; Hashiba and Yasui 1980; Ito 1980;
Mishima and Shimazaki 1980; Irie et a!. 1981 a; Irie 1982b).

TIMING OF YOUNG SALMON RELEASE
The most suitable time for release of juvenile salmon is when
the coastal water mass with lower salinity is spreading along thecoast. A temperature of 13 °C and a salinity of 33.8 0 / 00 in the surface water may be used as an upper limit for the release ofjuvenile salmon.
As shown in Figure 13, the release should be earlier in southernareas and later in northern areas of Japan. There are annual differences, however. The rise in temperature in 1981 was more than
10 d later than in 1978. In the coastal areas off the northeasternpart of Honshu, isothermal areas with a surface water temperature59

Nr------'-----,---r-----'-------'---------'----------=------,.--JL.,-,cc-r~,___'_---__,(

i1981 June 2 - June 15/ ..... ji./ ....... ,.,,-)HOKKAIDO
43

42

PACIFIC OCEAN

142

N

(

i

144

143

145

146

E

1981 July 6 - July 19

///'

./"

i
........... ,,-.)HOKKAIDO
43

o

42

0°

°0

0°

°0

° 0°
PACIFIC OCEAN
141

142

143

144

145

146

Figure 6.-Distribution of juvenile chum salmon and surface water masses in the Pacific Ocean orr Hokkaido from 2
June to 19 July 1981. Numerals indicate number of chum salmon collected by spoon net for a half hour period of lighting.
Numerals in parentheses indicate number of juvenile salmon escaped. C: coastal water mass, OY: Oyashio water. Solidcircles indicate station of oceanographic observation and plankton sampling; circled solid circles indicate sampling station by spoon net with fish lamp.

ranging from 8 ° to 13 °C are not generally found after late June
(Fig. 13). Juvenile chum salmon have not been observed offshoreof Tohoku, the northeastern part of Honshu, after late June
(Hayashi and Odate 1980; Hashiba and Yasui 1980). With further
data, it may become possible to determine the optimum time ofrelease for juvenile salmon in a particular sea area.
Providing that release in the later developmental stages reduces
natural mortality, it will be advantageous to rear juvenile chumsalmon artificially until they reach more than 5 cm FL. This is thecritical size for juveniles living in inlets or along shorelines.

As a next step, it may prove more effective to release juvenile
chum salmon at over 8 cm FL, when they have developed fully.
From results by Iioka, Urano, Takechi, Sato, Okawa, Hebiishi,
Terashima, and Minato (1980) and Iioka (1982), in experimental
releases of juvenile chum salmon in Yamada Bay, Iwate Prefecture, chum salmon showed various rates of return as adults depending on the size of juveniles released. Particularly high rates ofreturn were attributed to the juveniles having body weights of 1.3
and 8 g at the time of release. Changing body weight to fork
length, 1.3 g in body weight corresponds to about 5 cm FL, and 8 g60

,'c r - - - - ' I---~----,---~----;,/ 1980 May 18 - May 22

1981 June 2 - June 15;

15f------+-----+-----+--------,-----,
I,:.-': t .
~..... ·:'1:·~-7------_.

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15

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44

Oy
3390

,-

145

,--_ _---,N '"g/lOOOm 3

30

oOc{J

H -'--_-:-'----:.-------1:, 1979 June 26 - June 29
,,
,

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,

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July 19

1981 July 6

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44o"---~~-I~31.00

32.00

145

144

33.00

E

N

SURFACE WATER SALI;\ITY(°'OO)

1980 July 1 - July 10oFigure 7.-Relation between surface water masses and number of juvenile chumsalmon observed during a half hour period of lighting in the Pacinc Ocean off
Hokkaido from 2 June to 19 July 1981. No number indicates zero. M: many. C:
coastal water mass, OY: Oyashio water.

145

25

""'!;2

E.II 1I t' I.' I.' I 1+ I \+t t +

21
en
cc

147

Figure 80-Distribution of zooplankton and water masses in Abashiri Bay. Density of zooplankton was estimated by a vertical haul of NORPAC net. Dottedlines indicate the boundary of two water masses. 0: Okhotsk surface water, C:
coastal water mass, S: Soya warm water.

23

u.J

146

19
17
15

I'

==

;OJ

--'

--'

co
u.

25

~

23

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z

21

0

co
-

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..... lfo,-'''.

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15

,

I

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3

COLK LFNGTf, (V)1112

Figure 9.-Number of gill rakers with development in juvenile chum salmon.
Circles with vertical rules indicate average number and range in each 5 mm offork length. Vertical bar in lower figure indicates range of gill raker number in
adults.

61

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:r:
f-

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Z

n=296

A

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g
<3

L~--,------;~,--r~--l---t---j--------I--l_._I
1,00

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I __. I ._1.60+-----------t---l--l--+---l--+----+----<~_<__,___-+-+--I-----+---+.~
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le.GO

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5.20-I--+----+--l--~I--t---+_0.90
7.60:1.4(,

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1": . .;013,20

14-. CO

<C

0::

n=296

.

~,

l!.<:O

FOR K

13.20

14.00

LEN G T H eM)

Figure to.-Development of each body part against fork length in juvenile chum salmon. A: pectoral fin length, B: mouth width, C: eye diameter.

Table 3.-Substages in the development of juvenile chum salmon.

Stage

Range offork length
(em)

A

3-5

DiSiribution
area
Coastal within
1.6 kmPorts, inlets

B

5-8

Coastal withinseveral kilometers

C

8-11

Coastal within
16 km"-' offshore

D

11-17

Offshore

Characters inmorphology

Habitat

Prey animals

Behavior

Parr marks present.
Scales incomplete.
Eye diameter, mouth
width and pectoral fin
length is large against
fork length.
Gill rakers incomplete.
Parr marks become
obscure.
Scales formed.
Silvering advanced.
Tips of dorsal and caudal
fins become blackish.
Rate of each body part
fixed.

Coastal waterInsects
Small zooplankton;
calanoida, fish eggs andlarvae, Polychaeta

Schooling behavior.
Swim near surface water.
Phototaxis observed.

Coastal water

Large zooplankton;
calanoida, amphipoda,
fish larvae,
Euphausiacea

Schooling and migration
behavior strong.
PholOtaxis observed.

Coastal water, lower
salinity part of cold
and warm current
water

Large zooplankton;
calanoida, amphipoda,
fish larvae,
Euphausiacea

Gill rakers completed.

Offshore cold water

Large zooplankton;
calanoida, amphipoda,
fish larvae,
Euphausiacea

Schooling and migration
behavior strong.
Phototaxis observed.
Swim just below surface
water.
Schooling and migration
behavIOr slrong.
Phototaxis observed.
Swim just below surface
water.

ACKNOWLEDGMENTS

in body weight corresponds to about 9-10 em FL. The results
agree well with our results from the developmental stages ofjuvenile chum salmon. In applications to release of juvenile
salmon, it is necessary to consider both the size of the juveniles
and the environmental conditions in the sea.

1 am particularly indebted to Masanao Osako and Tokimasa
Kobayashi for their many helpful discussions during the develop-

62

~

)

,,

,
,,

C

0

E

.-

F

E

4t

,

---

-

':-'.

,
:-

145

N

~:-------

A

\

O

lAO

~

OKHOTSK SEA

-

JAPAN

- p ......

Figure ll.-A schema of the seaward migration pattern against water masses inyoung salmon. A: freshwater, B: brackish water, C: coastal water, 0: lower
salinity part of the cold water or that of the warm water, E: offshore cold water,
F: subarctic water. Arrows indicate migration course.

ment of this study. I wish to thank Soichiro Shirahata for criticallyreading the manuscript.

LITERATURE CITEDBALON, E. K.
1975. Terminology of intervals in fish development. J. Fish. Res. Board
Can. 32:1663-1670.
BIRMAN, I. B.
1969. Distribution and growth of young Pacific salmon of the genus Oncorhynchus in the sea. Vopr. Ikhtiol. T. 9, Vyp. 5(58):859-877. [In Russ.) (lpn.
transl., Soren Hokuyo, Gyogyo Kankei Bunken Shu. 89:33-64.)
GlLHOUSEN, P.
1962. Marine factors affecting the survival of Fraser River pink salmon. In
N. J. Wilimovski (editor), Symposium on pink salmon, p. 105-111. H. R.
MacMillan Lectures in Fisheries, Inst. Fish. Univ. British Columbia.
HASHIBA, T., K. KOTAKI, and T. YASUI.
1982. Distribution ecology of juvenile chum salmon off the northern part ofSanriku district. In Offshore investigation on ecology during young and adultstages, p. 23-29. [In Jpn.] Final report, Far Seas Fish. Res. Lab.
HASHIBA, T., and T. YASUI.
1980. Results of the investigation on the distribution ecology in the coastaland offshore waters of Iwate and Aomori Prefecture in 1978. In Offshore
investigation on ecology during young and adult stages, p. 33-48. [In Jpn.]
Progress report of 1977 and 1978. Far Seas Fish. Res. Lab.
HAYASHI, K., and S. ODATE.
1980. Distribution, migration, growth, and food habits of juvenile chumsalmon in the coast of Tohoku district. In Offshore investigation on ecology
during young and adult stages, p. 28-32. [In Jpn.] Progress report of 1977
and 1978, Far Seas Fish. Res. Lab.
HEALEY, M. C.
1980. The ecology of juvenile salmon in Georgia Strait, British Columbia. In
W.1. MacNeil (editor), Salmonid ecosystems of the North Pacific, p. 203229. Oregon Univ. Press, Eugene.
HOAR, W. S,
1976. Smolt transformation: evolution, behavior, and physiology. J, Fish.
Res. Board Can, 33:1234-1252.
HOSHIAI, S., K. TAKAHASH[, A. IIZUKA, and Y, SATO.
1981. Migration and growth of juvenile chum salmon by the results of markrecapture in the coastal waters of Miyagi Prefecture, In Minimization ofmortality in the juvenile salmon by means of sea-pen culture release system.
p, 21-28, [In Jpn.] Report of 1980, Tohoku Reg. Fish. Res. Lab,IBANKOV, B. N., and A, P. SHERSHNEV.
1968, Biology of young pink and chum salmon in sea. Rib. Xoz. 4:16-17.
[In Russ.] (Jpn. transl., Soren Hokuyo Gyogyo Kankei Bunken Shu. 83:101104.)
IIOKA,C.
1982. Homing run specificity in chum salmon released by sea-pen culture
technique, In Minimization of mortality in the juvenile salmon by means of
sea-pen culture release system. p. 35-46. [In Jpn.) Report of 1981, Tohoku
Reg, Fish. Res. Lab,IIOKA, c., M. TAKECH[, S. SATO, and Y. MINATO,1980. Ecological investigations of released juvenile chum salmon during
coastal residence, In Minimization of mortality in the juvenile salmon bymeans of sea-pen culture release system, p. 20-32, [In Jpn,] Report of1978, Tohoku Reg. Fish. Res. Lab.
IIOKA, c., K. URANO, M. TAKECHI, S. SATO, Z. OKAWA, K. HEBIISH[, J.
TERASH[MA. and Y. MINATO.
1980. Report on the technical development of fry culture and release in chum

PACIFIC OCEAN

Figure 12.-Estimated migration route and distribution area of young salmon in
their early marine life. Arrows indicate migration route; hatch lines indicate
distribution area. (Data, partiy modified: Iioka, Takechi, Sato, and Minato
1980; Irle et al. 1981a,b; Hoshiai et al. 1981; Irie 1982a, unpubl. data; Hashiba
et al. 1982; Ito 1982; Kato 1982; Mishima, Shimazaki, Yamamoto, Ishii, Sasaki,
and Meguro 1982.)

salmon with special reference to rate of adult return-roark-recapture investigation. [wate Pref, Fish. Exp, Stn, In Minimization of mortality in thejuvenile salmon by means of sea-pen culture release system, p, 137-164, [InJpn.) Final report of 1974-1977, Tohoku Reg, Fish. Res, Lab.
IRIE, T.
1982a. Ecological studies on juvenile chum and pink salmon in the outmigrating period: Distribution of young salmon in the Pacific Ocean off Hokkaido,
In Offshore investigation on ecology during young and adult stages. p, 13-20.
[In Jpn.) Progress report of 1981, Far Seas Fish. Res. Lab.
1982b. On the morphological changes with development of juvenile chumand pink salmon in their early marine life. In Summary of 1982's spring
meeting of Ihe Japanese Society of Scientific Fisheries, p. 65. [In Jpn,] Jpn,
Sci. Fish.
IRIE, T,. T, KOBAYASHI, and M. OSAKO.
1980, Ecological studies on juvenile chum and pink salmon in the oUlmigrating period: Changes in distribution, migration, growth, and food habits with
development. In Offshore investigation on ecology during young and adultslages, p, 1-7. [In Jpn.) Progress report of 1979, Far Seas Fish. Res. Lab.
1981 a. Ecological studies on juveniles of chum and pink salmon during earlyocean residence-I. Distribution and behavior of the juveniles in Abashiri
Bay and the adjacent waters. [In Jpn., Engl. abstr.] Bull. Hokkaido Reg.
Fish, Res, Lab, 46:15-36.
1981 b. Ecological studies on juvenile chum and pink salmon in the outmigrating period: Changes in distribution, migration, growth, and food habits with
development. In Offshore investigation on ecology during young and adultstages. p. 1-15. [In Jpn.] Progress report of 1980, Far Seas Fish. Res. Lab.
1982, Ecological studies on juvenile chum and pink salmon in the outmigrating period: Prey animals of the juveniles and zooplankton distribution. In
Offshore investigation on ecology during young and adult stages, p, I ·11. [InJpn.] Progress report of 1981, Far Seas Fish, Res. Lab,

63

1978

1979

N

~~

I·

'cv'1'!1

40

I""

35 W-H+f+H-++++-Hi-+++++--+-l

-8)

1980

1981

Mid-July

Mid-July-

Early-June _N

40

Early-July
35f'l1.LJ-H+I-+-H;+H+I-+-H+-f+,

Early-July

Mid-July

Mid-July-lJ~

Nb!/ 'J~I'if...., ,

~

0

Ij

3

140

145

150

155

Late-July

Late-July

Late-July

-8;

J1.

E

145

150

140

155

E

140

,,
R Late-July
145

150

155

E

Figure B.-Periodical and annual differences of the water zone with surface water temperature from 8° to BOC in the northwestern part of the Pacific Ocean. (Data: A
hrief report of fisheries and oceanographic conditions, Fisheries Information Service Center, 1978.81.)

64

MISHIMA, S., and K. SHIMAZAKI.
1980. On the distribution and ecology of juvenile salmon in the outmigrating
period: Report on the survey of Hokusei-maru in 1979.ln Offshore investigation on ecology during young and adult stages, p. 27-36. [In Jpn.) Progress
report of 1979, Far Seas Fish. Res. Lab.
MISHIMA, S., K. SHIMAZAKI, S. YAMAMOTO, K. ISHII, S. SASAKI, and T.
MEGURO.
1982. Studies on the distribution and ecology of juvenile salmon ids in theiroutmigrating period. In Offshore investigation on ecology during young
and adult stages, p. 33-47. [In Jpn.] Final report, Far Seas Fish. Res. Lab.
MISHIMA, S., S. YAMAMOTO, and K. SHIMAZAKI.
1982. Investigation of young salmon using the small purse seine and gill net
in the northern Japan Sea and in Abashiri Bay area. In Offshore investigation
on ecology during young and adult stages, p. 35-42. [In Jpn.) Progress
report of 198 I, Far Seas Fish. Res. Lab.
NEAVE, F.
1966a. Salmon of the North Pacific Ocean-Part 111. A review of the life
history of North Pacific salmon. 5. Pink salmon in British Columbia. Int.
North Pac. Fish. Comm. Bull. 18:71-79.
1966b. Salmon of the North Pacific Ocean-Part 111. A review of the life
history of North Pacific salmon. 6. Chum salmon in British Columbia. Int.
North Pac. Fish. Comm. Bull. 18:81-85.
NIKOLSKY, G. V.

ITO, J.
1980. Studies on ecology of young salmon in outmigrating period: Changes
in distribution, migration, growth, and food habits with development. In Offshore investigation on ecology during young and adult stages, p. 1-22. [InJpn.] Progress report of 1977 and 1978, Far Seas Fish. Res. Lab.
1982. A brief consideration about migration, growth, and mortality ofjuvenile salmon in coastal waters by means of fin-clip mark~recapture. In
Offshore investigation on ecology during young and adult stages, p. 49-65.
[In Jpn.) Final report, Far Seas Fish. Res. Lab.
KASHIW AGI, M., and C. 1I0KA.
1978. On the salinity tolerance in juvenile salmon. In Report on the technicaldevelopment and pilot experiment on salmon culture, p. 23-25. [In Jpn.)
Final report of 1970-1972, Fish. Age. Res. Dep. Res. Sec. and Tohoku Reg.
Fish. Res. Lab.
KASHIWAGI, M., and R. SATO.
1969. Studies on the osmoregulation of the chum salmon, Oncorhynchus keta
(Walbaum). I. The tolerance of eyed period eggs, alevins and fry of the chumsalmon to sea water. Tohoku J. Agric. Res. 20:41-47.
KATO, M.
1982. On the juvenile chum salmon of Europium tagged and released fromthe Chitose River, a water system of the Ishikari River. In Offshore investigation on ecology during young and adult stages, p. 67-77. [In Jpn.] Finalreport, Far Seas Fish. Res. Lab.
KOBA YASHI, T.
1977. Ecology of young salmon during coastal residence. [In Jpn.) Bull. Jpn.
Soc. Fish. Oceanogr. 31 :39-44.
KOBA YASHI, T., and S. ABE.
1977. Studies on the Pacific salmon in the Yurappu River and Volcano Bay.
2. On the migration and growth of the fry during seaward migration and thereturn of marked adults. [In Jpn., Engl. abstr.] Sci. Rep. Hokkaido Salmon
Hatchery 31: I-II.

1963. The ecology of fishes. Acad Press, N.Y., 352 p. (Transl. from Russian
by L. Birkett.)
OKADA, S., and T. NISHIYAMA.
1970. Notes on morphological differences between the juveniles of chum andpink salmon in shore waters. Bull. Fac. Fish., Hokkaido Univ. 20:277-285.
OKADA, S., and A. TANIGUCHI.
1971. Size relationship between salmon juveniles in shore waters and theirprey animals. Bull. Fac. Fish., Hokkaido Univ. 22:30-36.
SANO, S., and T. KOBAYASHI.
1952. An ecological study on the salmon fry, Oncorhynchus keta (I). [In Jpn.,
Engl. abstr.] Sci. Rep. Hokkaido Fish. Hatchery 7:1-10.
1953
An ecological study on the salmon fry, Oncorhynchus keta (2). The
migration and growth of the fry in the marking experiment. [In Jpn., Engl.
abstr.] Sci. Rep. Hokkaido Fish. Hatchery 8:71-79.
SHERSHNEV, A. P.

KOBA YASHI, T., T. IRIE, and M. OSAKO.
1980. Ecological studies on juvenile chum and pink salmon in the outmigrating period: Changes in distribution, migration, growth, and food habits with
development. In Offshore investigation on ecology during young and adultstages, p. 23-27. [In Jpn.) Progress report of 1977 and 1978, Far Seas Fish.
Res. Lab.
LeBRASSEUR, R. J., and R. R. PARKER.
1964. Growth rate of Central British Columbia pink salmon (Oncorhynchus
florbuscha). J. Fish Res. Board Can. 21:1101-1128.

1970.

Biological character of chum fry in coastal waters of south-eastern pariof Tatar Strait. [In Russ.] Izv. TlNRO T. 74:101-111. (Jpn. transl.. Soren
Hokuyo Gyogyo Kankei Bunken Snu. 95:74-92.)

MANZER, J. I
1956. Distribution and movement of young Pacific salmon during early ocean
residence. Fish. Res. Board Can., Prog. Rep. Pac. Coast Stn. 106:24-28.
MARTIN, W R.
1949. The met:hanics of environmental control of body form in fishes.
Univ. Toronto Stud., BioI. Ser. 58:1-72.
MciNERNEY, J. E.

SIMENSTAD, C. A., W. 1. KINNEY, S. S. PARKER, E. O. SALO, J. R. CORDELL.
and H. BUECHNER.
1980. Prey community structure and tropnic ecology of outmigrating juvenile
chum and pink salmon in Hood Canal, Washington: A synthesis of three
years' studies, 1977-1979. Fish. Res. lnst., Coli. Fish .. Univ. Wash., Seattle,
FRI-UW-8026, 112 p.
llDA, M.

1964. Salinity preference: an orientation mechanism in salmon migration.
J. Fish. Res. Board Can. 21:995-1018.
MIHARA, T.
1958. An ecological study of chum salmon fry, Oncorhynchus keta, in the
coastal waters of Hokkaido. [In Jpn.] Sci. Rep. Hokkaido Fish. Hatchery
13:1-14.

The results of simultaneolls oc~all()graphicai investigation in the northPacific Ocean adjacent to Japan made in .\ugust. 1933. [In Jpn., Eng!. abstr.]J. Imp. Fish. Exp. Stn. 6: 1-130.
WEISBART, M.
1935.

1968. Osmotic and ionic regulation in embryos, alevins, and fry of the fivespecies of Pacific salmon. Can. J. Zoo!. 46:385-397.

65

Recent Information on Europium Marking Techniques
for Chum Salmon
MAMORU KATOIABSTRACT
A marking experiment using an activable tracer method was conducted with 4 million chum salmon fry
which originated in the Ishikari River System in 1979. Europium was detected in young chum salmon whichwere collected in the river and coastal waters along Hokkaido. Scales and livers were used as the detection
organs for europium. Europium could be detected most etTectively from scales. Forty-three europium marked
fry, 13.4% of the total, were caught in the Chitose River. Seventy-two europium marked juveniles, 7.7% of thetotal, were recovered in coastal waters, consisting of 59 fish, 14.7% from the Japan Sea coast and 13 fish, 2.4%
from the Okhotsk Sea coast. Chum salmon juveniles from the Ishikari River System were distributed close to theshore along the Japan Sea coast and further from the shore along the Okhotsk Sea coast. They still depended oncoastal waters even though they spent more than 2 months in seawater. Considering the relationship between
fish size and area of distribution, ditTerences in fish size among areas in the same period exceeded that among
periods in the same area. Europium was clearly detected from 2-year-old adult chum salmon that returned to lhe
Ishikari River System. This indicates that europium was still present in the fish body for 580 days after being
released.

INTRODUCTION

MATERIALS AND METHODS

Activable tracer is a marking method based on neutron activation analysis. The method has the following advantages when applied to fish: I) Marking can be u;ed for very sIr.all fish, including
fry and juveniles. 2) Marking can be used for a large number offish (unit of million). 3) The fish body is not inj,lred in the marking process. 4) There are no radioactive contaminations to the fish
and the environment.
In the activable tracer method, a nonradioactive element isadministered to fish fry with their feed. After they have beenreleased, they gradually emit the element. Some of the element,
however, accumulates in the fish organs and tissues over an extended period of time. The element, of course, must be harmless toboth fish and humans.
Europium, one of the rare earth elements, exists in the earth invery small quantities, has a large cross section to thermal neutrons,
has a long half-life after being activated, and remains for a kmg
time within fish organs. For these reasons, europium IS one of themost effective activable tracer elements.
Marking is an important means for studying fish resources andevaluating the artificial enhancement of fish. Applying the activable tracer method to young (hum salmon, the author tried to obtain more information and knowledge on their migration andgrowth.
The Hokkaido Salmon Hatchery released 27 million chumsalmon fry from the Chitose Hatchery in April 1979. Amongthem, 4 million fish were marked by europium. Four organizations collected chum salmon fry and juveniles in the river andcoastal waters from April to June in 1979 and adult fish which
returned to the Chitose River from October to November in 1980.
Europium marked fish were recoveree among them by activation
analysis.

Twenty-seven million churn salmon fry were released from the
Chitose Hatchery, a branch of the Hokkaido Salmon Hatchery, to
the Chitose River, a tributary of the lshikari River System, from
Mar:h to May 1979 Among them, 4 million chum salmon fry,
14.1>% of the total, were fed europium-containing food for 40 dfrom 13 February to 23 March and then reieased there between 26
Man;h and 5 April. Europium chloride (EuCI)' 6H 20) was mixed
into pellet-type food at a mean europium content of 817 ppm (SD85 ppm). A total of 920 kg europium-containing food was fed (23kg/d). Daily food supply increased from 4 kg on the first day to 30
kg on the last day. Of fry marked by europium, 1,200,000 fish
were also marked by fin-clipping the adipose fin. All theeuropium-marked fry were released during the peak period of
releasing.
Sampling of fry was conducted in rivers and on the coasts using
various gears by four organizatiom-Hokkaido Salmon Hatchery,
Far Seas Fisheries Research Laboratory, University of Hokkaido,
and Wakkanai Experimenta! Station. Hokkaido Salmon Hc.tcheryalso caught adult chum salmon in the Chitose River.

River
The Hokkaido Salmon Hatchery collected chum salmon fry
before being released to the Chitose River in April at the Chitose
Hatchery and also caught them with trap-nets set at the middle
section of the river near Ebetsu during the period of 6 April to 18
May 1979 (Fig. 1).
The hatchery also cwght adult chum salmon (age .1 fish) in the
Chitose River on 31 October and 6 November 1980.

Coastal Areas and Offshore Waters
The Hokkaido Salmon Hatchery captured chum salmon
ju'/cniles with a purse seine in the coastal zone of the Ishikari Bay
and also caught them with stationary nets in Mashike and Shosan-

IFar Seas Fisheries Reseacch Laboratory, 5-7-1 Grino, 424 Shimizu, hpan.

67

work to di:;rupt finding the tracer element in activation analysis.
Scales consist of a large amount of calcium carbonate (CaC0 3 )and calcium phosphate (Ca 3 (P0.h). In addition, scales takenfrom fish in seawater are covered with sodium chloride (NaC!) on
the surface. These elements Ca, P, and Na are converted to radioisotopes of .5Ca (half life: J 65 d), 32p (14 d), and 24Na (14 h) by
neutron radiation.
The photo-peaks of 152Eu come out in the vicinity of 122, 345,
779,965,1,087,1,113, and 1,408 KeV of gamma-ray energy.
The author used three photo-peaks-122, 345, and 1,408 KeVfor detection of 152Eu. These photo-peaks, however, especiallycoming out in lower energy channels as 122 and 345 KeV, areoften disturbed by the Compton effect caused by a large numberof gamma-rays radiated from other elements, when the analysis isconducted a short time after neutron radiation. 152Eu, however,has a very long half life, 12.7 yr, when the analysis is carried out
after a long cooling time; photo-peaks, even in lower energy channels, can be clearly found.
In the experiment, the author used a cooling time of about 6 mo,
which is longer than the half life of 45Ca, obtaining clear photopeaks of 152Eu.

RESULTS AND DISCUSSION
Detection of Europium From Fry in Freshwater
Activation analysis was conducted for 47 fry (mean fork length:
38 mm, mean body weight: 0.5 g) collected in the Chitose Hatchery on 2 April,just before being relea~ed to the Chitose River and
30 fry (mean fork length: 37 mm, mean body weight: 0.4 g)caught in the Chitose River as background samples on 19 March.
Muscles, vertebrae, and livers of these fry were taken for activation analysis. Two photo-peaks of 152Eu in the vicinity of 122 and345 KeV were clearly recognized in the gamma-ray spectrogramsof europium-marked fry. On the otht:r hand, there was no clear
photo-peak in the unmarked fry (Fig. 2). The highest europium
absorption was observed in the liver among the three organs andtissues. Detection rate was 100% in livers, whereas it was 16.7%
in muscles and vertebrae (Table 1). Europium contents of hvers
ranged between 0.18 and 3.50 ppm, averaging 1.15 ppm, that ofvertebrae ranged from 0.01 to 2.94 ppm, averaging 0.32 ppm, andthat of muscles ranged between 0.02 and 0.27 ppm, averaging
0.14 ppm. The europium content in liver varied significantly
among individuals and in some cases the content in one individual
was 20 times as much as that of the other individual. The variation is considered to be mainly caused by the different amount offeed for the fry during rearing.
The Hokkaido Salmon Hatchery caught 365 chum fry with a
trap-net set near Ebetsu from 6 April to 18 May. Europium was
detected from their liver samples. Europium was detected from 49
fish, which was 13.4% of the total (Table 2). The rate of europium
detection on each day was 8.6% on 6 April, 38.9% on 9 April.
29.5% on 12 April, 22.5% on 14 April, 7.7% on 17 April, 2.2%
on 20 April, 0% on 3 and 7 May, 8.3% on 11 May, arId 7.7% on
18 May. A peak number of europium-marked f~y passed throughEbetsu from 9 to 12 April, and none was found from late April toearly May. Then they again appeared there in mid-May. This indicates that most europium-marked fry migrated seaward 10 to 15
d after being released, however, a portion of the migrating fry remained for about 2 mo in the upper stream of the river. Sano andKobayashi (1953) and Mayama et al. (1982) reported two typesof fin-clipped chum salmon fry in seaward migration in the
Chitose River-one migrated in a short period of about 10 d;

Figure I.-The sampling stations of chum salmon fry in the Ishil<ari Hiver
System.

betsu, along the northern Japan Sea coast from March to June, andin Soya Toyoiwa, along the Okhotsk Sea coast, in June 1979.
Using the Hokusei-maru, a research vessel of the University of
Hokkaido, and a purse seine, small mesh gill nets, and larval nets
with wings, the University of Hokkaido and the Far Seas Fisheries
Research Laboratory collected chum salmon juveniles in offshore
waters of the Japan Sea coast from Ishikari Bay to Shosanbetsu
and on the Okhotsk Sea coast from Abashiri Bay to the Shiretoko
Peninsula on 3-27 June 1979.
The Wakkanai Fisheries Experimental Station caught chumsalmon juveniles with stationary nets set along the coast from
Shosanbetsu to Soya from May to June 1979.
Scales, livers, muscles, and vertebrae from fry and juveniles
were used as samples for activation analysis. Scale samples were 4
to 37 mg, liver samples (whole organ) were 6 to 115 mg, muscle
samples 17 to 48 mg, and vertebra samples were 1 to 5 mg in dry
weight.
Scale samples taken from adult fish weighed from 68 to 240
mg.
Activation analysis for europium detection was conductedusing the JRR-2 atomic reactor of Japan Atomic Energy ResearchInstitute. Samples were bombarded with thermal neutrons (thermal neutron flux: 8 xl 0 13 n/cm 2s) for 20 min in the reactor. The
radioactivity of 152Eu (half life: 12.7 yr) in the samples were
measured with a Ge(Li) gamma-ray spectrometer and multichannel analyzer (4,096 channels) after about 6 mo of coolingfollowing the activation.

Cooling Time
When an activable tracer element is included in the fish organs
in a very small amount, other elements forming the organs often
68Europium marked fish collected in the
Chitose Hatchery, April 2 in 1979200

while the other stayed for more than I mo in the upper section of
the river. The results obtained by europium marking on seaward
migration of fry agree with those of their reports.

Detection of Europium Marked Juveniles
In Coastal Waters
From May to June, 1,990 juveniles were caught in the coastal
waters around northern Hokkaido. In order to detect europium,scales and livers were taken. Fork length and body weight of thejuveniles ranged from 40 to 170 mm and 0.5 to 42 g, respectively.
Scale samples weighed 8.1 mg on the average, ranging from 1 to
37 mg, and that of dried liver samples weighed 30 mg on the
average, ranging from 5 to 14 mg.

100
>,

~,

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~
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E

....

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o

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.............
,...............
i
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Detection of europium from scales.-According to Shibuya(1979), europium in scales is eliminated from the fish body by themetabolism of organs and tissues. However, a ceftain level remains in the body throughout the life of the chum salmon. Thus,
scales were the most suitable organs for the detection of europium.
Activation analysis was conducted for scales of 208 fish andeuropium was detected from 33 fish, 15.8% of the total. The rateof europium detection and the europium content in coastal waters
along northern Hokkaido are shown in Table 3.
Mean values and ranges of europium contents by area were0.50 and 0.13 to 1.32 ppm in Ishikari Bay, 0.33 and 0.15 to 0.59
ppm in Ofuyu, 0.38 and 0.19 to 0.74 ppm in Mashike, 0.29 and0.15 to 0.43 ppm in Shosanbt:tsu, and 0.09 and 0.07 to 0.10 ppm
from Abashiri Bay to the Shiretiko Peninsula, respectively. The
farther an area was from Ishikari Bay, the lower the europium
content. Europium-marked fish were recovered within a comparatively short time period (24 d). These facts show that a decrease ineuropium content depend, not on a decrease in the total amount ofeuropium by fish metabolism but on scale growth. Europium content in scales was calculated as follows:.",

Non-europium mar~ed fish collected inthe
Chitose river, March 19 in 1979

40

20

o
100

120

140

320

340

360

Gamma-ray Energy (MeV)

Figure 2.-Europium detection in liver samples of chum salmon fry.

Table I.-Europium contents in organs of chum salmon fry caught in tht
Chitose Hatchery.
Europium contents

Number offish analyzed

Number of fishwith europium

B/A

Organ

(A)

(B)

(%)

Mean

Range
(ppm)

Muscle

30
30
47

5
5
47

16.7
16.'1
100.0

0.14
0.32
1.15

0.02-0.27
0.61-2.94
0.18-3.50

Vertebra

Liver

Eu content in scales = Eu w.eight in scales x 1 000.
'
Weight of scales
Mean body weight of europium-marked juveniles was 2.9 g in
Ishikari Bay, 3.1 gin Ofuyu, 3.0 gin Mashike, 4.7 g in Shosanbetsu, and 32.1 g from Abashiri Bay to the Shiretoko Peninsula,respectively. Thus, the body weight in Abashiri Bay-Shiretoko
Peninsula was 10 times as much as that in Ishikari Bay. Considering that scales grow in proportion to body growth, even if theweight of europium in the scales is constant during this period, theeuropium content decreased rapidly with scale growth.

Table 2.-Europium-marked chum salmon fry caught in the Chilose River by
trap-net near Ebetsu detected by liver samples.
Fish with europium

Dale
April
6
9
12
14
17
20
May
3
7
II

18
Total

Numberof fishanalyzed

Rate of
Numberof fishEuropium contents

(%)

35
36
44
40
39
31

3
14
13
9
3
1

8.6
38.9
29.5
22.5
77
3.2

34
31
36
39
365

0
0
3
3
49

0
0
8.3
7.7
13.4

Table 3.-Europium-marked chum salmon juveniles detected by their scales.

(10-' mg)detection

Mean

Fish with europium

Range

8.40
5.64
6.44
7.44
3.82
14.33

6.70-10.21
2.41- 6.77
2.62-13.25
3.69-12.91
2.35- 4.99

8.94
10.10

616-14.13
8./4-11.67

Area
Japan Sea
Ishikari Bay
Ofuyu
MashikeShosanbetsu
Abashiri Bay Shiretoko Pen.
Coast
Offshore
Total

69

Europium contents

Numberof fishanalyzed

Numberof fishdetection
(%)

Mean

Range
(ppm)

52
46
28
57

8
II
3
8

15.4
23.9
10.7
14.0

0.50
0.33
0.38
0.29

0.13-1.32
0.24-0.59
o 15-0.56
0.15-0.74

5
21
209

0
3
33

0
14.3
15.8

0
0.09
0.34

0.08-0.10
0.08-1.32

Rate ofActivable tracer elements can be detected most effectively fromscales for the following reasons: I) Samples can be taken easily
from the fish body. 2) It is easy to treat samples (not necessary for
Formalin z fixation and desiccation). 3) Higher element contents
and longer retention.

water. Some of the 15 fish from which europium was detected intheir livers overlapped with some of the 33 fish from which
europiun; was detected in scales. As a result of europium detection
from both organs, europium was detected from 41 or 4.4% of 284
juveniles.
2) Wakkanai Fisheries Experimental Station collected liver
samples from 413 chum salmon juveniles from 18 May to 18
June. In activation analysis of these samples, europium was
detected from only one fish among eight juveniles caught inHahow along the Japan Sea coast on 23 May. The weight ofeuropium of the sample was 4.62 x 10- 3 mg. This was the first fishwith europium marking in coastal waters.
3) Hokkaido Salmon Hatchery took liver samples from 243
chum salmon juveniles caught from I to 16 June. In activation
analysis, europium was detected from 30 fish, 12.4% of whichwere caught off the coast of Morai, Gokibiru, Mashike, Shosanbetsu, and Soya Toyoiwa. The rate of europium detection and themean europium weight by area were 20.0% and 7.25 x 10- 3 mg in
Morai, 17.9% and 8.11xlO- 3 mg in Gokibiru, 8.9% a:Jd
5.56x 10- 3 mg in Mashike, 16.7% and 2.67x 10- 3 mg in
Shosanhetsll, and 11.0% and 5.56x 10- 3 mg In Soya ToyoiwJ,
respectively.

Detection of europium from livers.-When europium isabsorbed by the body of chum salmon fry, no scales are yet forn;ed. Therefore, europium retained in the scales is thought to shift
from other organs and tissues. As mentioned earlier, europium
contents in the liver were higher than those in other organs. Judging from this, the liver is also an organ from which europium canbe detected effectively.
Europium was detected from livers of chum salmon juveniles asfollows:I) Liver samples were taken from 155 juveniles caught by the
Hokusei-maru from 3 to 27 June. In activation analysIs of thesesamples, europium was detected from 15 fish, 9.7% of the tOla!.
The rates of europium detection and mean europium weight byarea were 11.4% and 2.57 x 10- 3 mg in Ishikari Bay, 19.5% and1.71 x 10- 3 mg in Ofuyu, and 10.3% and 1.36 x 10- 3 mg in the
Shiretoko Peninsula, respectively. No europium-marked fish were
found in the area between Mashike and Shosaabetsu. The rate ofdetection was lower in livers than in scales, indicating that theliver is less fit for the detection of europium in fish living in sea-

As described above. europium was detected from Evers of 46
bh, which was 5.7% of 812 chum saltnor. juveniles caught from
Ishikari Bay to the Shiretoko Peninsula. The mean europium
weight of the sample; was 4.89x 10- 3 mg and the mean europium
content was 0.13 ppm (Table 4).
Table 5 shows europium weights and contents of liver samples
collected in the whole area, including the rivers. The europium

2Reference to trade names does not imply endorsement by the National Marine

Fisheries Service, NOAA.

Table 4.-Europium-marked chum salmon juveniles detected by their livers.
Fish with europium

Area

Rate ofEuropium contents

Number offish analyzed

Numberof fishdetection
(%)

Mean

Range
(ppm)

35
61
41
124
17

4
11
8
9
2

11.4
18.0
19.5
7.3
11.8

0.13
0.21
0.08
0.16
0.14

0.02-0.27
0.07-0.54
0.01-0.14
0.04-0.26
0.06-0.23

222
123
75
60

0
0
9
0

0
0
12.0
0

0
0
0.09
0

29
25
812

3
0
46

10.3
0
5.7

0.04
0
0.13

Japan Sea
Ishikari Bay (offshore)
Ishikari Bay (coast)
Ofuyu
MashikeShosanbetsu
Okhotsk Sea
Soya Koetoi
Soya Mineoka
Soya Toyoiwa
Esashi Menashidomari
Abashiri Bay Shiretoko Pen. (offshore)
Shiretoko Pen. (coast)
Total

0.02-0.15

0.01-0.05
0.01-0.54

Table S.-Change of europium weight and contents of liver in chum salmon juveniles from April to
June.
Europium weight
Area

Date

Numberof fish(A) Chitose Hatchery(B) Chitose River(C) Coastal waters

2 April
6-20 April
1-25 June

47
43
45

Mean

15.88
6.53
4.95
(41.1%)(31.1 %)

(B/A)
(CIA)

70

Range
(10-' mg)
4.12-58.82
2.41-14.23
0.78-21.47

Europium contents
Mean
1.15
0.69
0.13
(60.0%)(11.4%)

Range
(ppm)
0.18-3.50
0.21-1.56
0.02-0.54

than that in tbe hatchery. This indicates that chum salmon
juveniles on the Okhotsk Sea coast originated in the various
rivers, including the Ishikari River System.

weight decreased to 41 % within about 20 d and 31 % within about
3 mo after the fry were released from the Chitose Hatchery.
Using samarium, one of the rare earth elements, as an activable
tracer for medaka and gold fish, Machibata and Hori (1981) andMachibata (1981) also reported that samarium deposited in the
sca les and gills did not result from absorption through the gastrointestinal tract but from direct absorption from water, where theelement was dissolved in feed or fish excrement; while Shibuya(1979) reported that europium was deposited mainly in scales
after it was absorbed through the digestive organs. As mentioned
above, no scales were formed when europium-containing feed wasgiven to fry in the hatchery. However, europium was deposited in
the scales of juveniles caught in coastal waters. On the other hand,the amount of europium in livers gradually decreased as time
passed. These facts indicate that europium is absorbed by thedigestive organs, goes outside the fish body, and at last some isdeposited in the scales. Europium is thought to be absorbed fromthe digestive organs and then brought to the liver.
Seventy-two europium marked fish, 7.7% of the total, wererecovered in coastal waters. Fifty-nine fish (14.7%) were recovered on the Japan Sea coast and the remaining (2.4%) on the Okhotsk Sea coast. The rate of europium detection on the Japan Sea
coast was 14.7%, which was very similar to 14.8% in the Chitose
Hatchery. This indicates that most of the chum salmon juveniles
on the Japan Sea coast originated in the Ishikari River System. On
the other hand, the rate on the Okhotsk Sea coast is much lower

Migration Route of Chum Salmon Juveniles
Originating in the Ishikari River System
Estimated by Europium-Marked Fish
Migration route of chum salmon juveniles originating in the
Ishikari River System could be estimated by tracing europiummarked fish.
Figure 3 shows the points where europium-marked fish werecaught in coastal waters along northern Hokkaido and the estimated migration route of the juveniles.
After leaving the mouth of the Ishikari River, most juveniles
migrated northward along the Japan Sea coast. Some of them,
however, migrated southeastward. The migration in the opposite
direction of the ordinary route is thought to be related to the direction of the current from the Ishikari River from May to June. The
current flows most strongly during this period due to water frommelted snow.
Europium-marked fish were continuously found in areas along
the Japan Sea coast from Ishikari Bay to Shosanbetsu. The marked fish were not found between Shosanbetsu and Cape Soya. They
appeared again in Toyoiwa, the eastern coast of Cape Soya facing
the Okhotsk Sea. They were caught in an area shallower than 10

46.~iii40~·~E="""~3EO'===,",'4..1",·,::E="",,~';;,O·===1;,;4:.i2,,,·",E==~,o""==""",'",4""3,,,,':;:E==~,o",' ==E'",4E
4'""E3==='io",'""""""'''''''''34t,S'",E"""==ii'o,,,,'"",,=~1'li4i6;:. N

30'

30'

~:

()
45"N

Menashidomari
THE OKHOTSK SEA

30'

THE SEA OF JAPAN

44'N,

30'

Figure 3.-The sampling stations of chum salmon juveniles (shown hy open and closed circles), 1979, Closed circles mean europium-marked fish were ohtained. Arrows
indicate estimated migration route of chum salmon juveniles originating from the Ishikari River System,71

m deep, indicating that they were distributed very close to thecoast. No marked fish were found in the areas between Soya
Toyoiwa and Abashiri Bay. Marked fish were again collected in
offshore waters 8 to 16 km from the coast, from Abashiri Bay to
the Shiretoko Peninsula.
The migration route of the marked juveniles is very similar to
the route of the Tsushima and Soya current running along thenorthern part of Hokkaido. Chum salmon juveniles originating in
the Ishikari River System seem to migrate through waters between
the warm current and colder coastal waters. This indicates thatthey still depend on the coastal waters although they spend morethan 2 mo in seawater.

Considering the relation between fork length and area of distribution, juveniles whose average length was 8 cm were mainly
distributed along the Japan Sea coast and when they grew to morethan 10 cm they appeared in the Okhotsk Sea. In conclusion, difference in fish size among areas in the same period exceeded thatamong periods in the same area. This indicates that juveniles
change their area of distribution according to their body sizes.

Europium Detection From Two-Year-Old
Adult Chum Salmon
Chum salmon fry were released to the Ishikari River System inspring 1979 and then they migrated to the Pacific Ocean throughcoastal waters along northern Hokkaido.
Some of them returned to the Chitose River as two year (age I)
adult fish in fall 1980. Seven male fish (mean fork length: 46 em,mean body weight: 1.1 kg) were collected on 31 October and 6
November. Activation analysis was conducted on their scale
samples.
Europium was dearly detected (Fig. 4), thol!gh their scales weresevelely eroded except for the central parts. Europium contents
were 0.04 and 0.05 mg, respectively. This indicates that europium
per~is:ed in the scales for 580 d since being released. Scales takenfrom 3-yr-old (age 2) adult fish returning in 1981 are now underanalysis. The author expects that europium in chum salmon can betraced for a longer period of time than 2 yr.

Growth of Chum Salmon Juveniles of the Ishikari River
System Indicated by Europium-Marked Fish
Growth of chum salmon juveniles originating in the Ishikari
River System was traced using europium-marked fish in river andcoastal waters. Mean fork length and mean body weight by areaand by 10-d periods are shown in Table 6.
In the river, mean fork length and weight were 37 mm and 0.4 g
in early April, 41 mm and 0.6 g in mid-April, and 47 mm and 1.0
g in mid-May, respectively. These values indicated a very low
growth rate of fish during the freshwater phase.
In the coastal areas of Ishikari Bay, mean fork length and bodyweight were 43 mm and 0.6 g in early April which is a little larger
than those in the river. They grew to 64 mm and 2.1 g in earlyMay. Even in June, however, mean length and weight were 66
mm and 2.9 g, indicating almost the same values as those in earlyMay.
Along the Japan Sea coast in early June, mean length andweight were 69 mm and 3.1 g in Ofuyu, 73 mm and 3.4 g in
Mashike, and 73 mm and 4.0 g in Shosanbetsu, respectively,
showing that fish were bigger in the north.
On the western coast of Cape Soya, mean length and weight offin-clipped juveniles originating in the Ishikari River System were70-75 mm and 3.6-4.4 g in mid and late May (Suzuki et al. 1980).
Europium-marked fish were 87 mm in mean length and 5.7 g inmean weight in Soya Toyoiwa in mid-June. Juveniles around
Cape Soya were much larger than those in the Japan Sea coastal
areas during the same period.
Mean fork length and body weight were greatest, 126 mm and26.4 g, in the areas between Abashiri Bay and the Shiretoko
Peninsula in late June.

LITERATURE CITED
MACHIBATA, H.
J 98 I. Labeling fish with an aClivable element through diet. Can. J. Fish.
Aquat. Sci. 38: 1281-1282.
MACHIBATA, H., and R. HORI.
1981. Labeling fish with an activable element. Can. J. Fish. Aquat. Sci. 38:
133-136
MAYAMA, H., M. KATO, J. SEKI, and I. SHIMIZU.
1982. Studies on Ihe chum salmon roleased in the Ishikari River System-I. On
the seaward migration and inshore distribution of liberated fry in 1979. lIn
Jpn.] Sci. Rep. Hokkaido Salmon Hatchery 36: 1-17.
SAND, S., and T. KOBAYASHI.
1953. An ecology study on lhe salmon fry, Oncorhynchus kew (2). The migration and growth of the fry in the marking experiment. [In Jpn.] Sci. Rep.
Hokkaido Salmon Hatchery 8(1-2):71-79.
SHIBUYA, M.
1979 Non-destructive activation analysis for Eu in fish materials. [In Jpn.]
Radioisotopes 28:64-68.

Table 6.-Mean fork length and body weight of europium.marked juveniles originating from the Ishikari River System by
fO·d periods.
Mean fork length (mm)
April
Area
River
EbetsuCoastal waters
Ishikari Bay
Ofuyu
MashikeShosanbelsu
Soya Toyoi wa
Abashiri BayShireloko Pen.

E

M

37

41

'43

Mean body weight (g)
June

May
L

E

M

L

E

M

April
L

M

May
L

E

0.4 0.6

47
'64

71
'75

E

66
69
73
73

'0.6

M

June
L

E

4.0

2.9
3.1
3.4
4.3

'2.1

'3.6
128

IFin-c1ipped fish (Mayama et al. 1982).
'Fin-clipped fish (Suzuki et al. 1980).

72

L

1.0

75
87

M

3.5
5.7
26.4

300

152

Eu

N-4,

2,000sec.

200

100

:. ~.'.........
. . -, .. .... .-. ,. .,...

.

,.~

."

..'" ... .....""..
. -- .
"e.__
,

.:.
,. ,

100

120

140

.

340

160

360

380

1S.2 Euf"'*:~' ..., .,t.
1,380

I ,400I ,42015;EU
Eu Standard 2p9. 20sec.

1,000

500

100

120

140

152
Eu
.,.._"",A_

.e.

'*><;
340

160

r-__
360

380

1,380

1,400

1 ,420Garrma_ray Energy (KeV)

Figure 4.-Europium detection from scales of age 1 adult chum salmon which returned to the Chitose River on 11
November 1980. N·4: Male fish of 48 cm FL and 1.2 kg in body weight.

SUZUKI, U., H. KONDO, Y. ONO, T. KITAGUCHI, and M. SANa.
1980. Comprehension and analyses on conditions of physical environments
around the coastal areas of Soya (1979). In The progress report on chumsalmon enhancement in hatcheries of Hokkaido, p. 55-70. [In Jpn.)
kaido Reg. Fish. Res. Lab.

73

Hok-

Development of Seawater Net-Cage Culture andRelease of Chum Salmon
AKIMITSU KOGANEZAWA and MINORU SASAKPINTRODUCTION

predation which is very common in rivers, estuaries, and seaside
areas,
This study was carried out in cooperation with the research
institutes of the Aomori Prefectural Aquaculture Center, Miyako
branch of the Iwate Prefecture Farming Center, Iwate Prefectural
Fisheries Experiment Station, Miyagi Prefectural Fisheries Experimental Station, Miyagi Prefectural Fish Farming Center,
Tohoku Regional Fisheries Laboratory, Faculty of Science ofTokyo University, Nikko branch of the National Research Institute of Aquaculture, and National Research Institute of Fisheries.

Until the latter half of the 1960's, production of chum salmon
on the Pacific coast of the Tohoku District of Japan declined toslightly less than 1,000 tons (return rate: below 1.0%) The salmon
propagation area was centered around 50 hatchery stations in the
Tohoku District (Fig. 1). Starting 10 1967, the technology ofsalmon hatchery development increased in Hokkaido. Therefore,knowledge of feeding of reared fry and timing of release produced
favorable results. In 1971, feeding and releasing techniques wereintroduced to the northeastern district of Japan. Starting in 1975,
the development and study of underwater rearing in cages was
begun and releasing technology was introduced. This resulted in
the development of a new technology in the local industry.
The development and study of underwater rearing in cages andreleasing technology of salmon originated in an effort to produce
salmon on a commercial basis for mass rearing and large fish
cultivation in rhe sea utilizing artificial feed for chum salmon fry.
This study started at the Miyagi Fisheries Experimental Station in
the mid-1960's.
Koganezawa (1970) tested the seawater adaptability of salmon
and trout (Genus Oncorhynchus, Genus Salmo, Genus Salvelinus)
which were cultured in a t'reshwater area accessible to seawater.
Consequently, the upper limit of the rearing temperature wasovercome by the relationship between the size of chum salmon
and salinity, although the critical period for the cultured salmon
occurred during summer, when the seawater temperature increased considerably.
Afterward, a large-scale releasing experiment was conducted at
the Iwate Prefectural Fisheries Experimental Station from 1973 to
1976. This was followed by studies of loss control and eliminationof fry in underwater rearing and releasing. These studies were carried out mainly at the Tohoku Regional Fisheries Laboratory from1977 to 1981 (Tohoku Regional Fisheries Laboratory 1977-81).
In these studies, the setting of three different releasing points wasmade in geographical and topographical conditions to examine
the returning conditions of chum salmon.
In this way. underwater rearing and releasing technology forchum salmon fry was conducted directly in seawater, without
releasing the fry from hatcheries to rivers in the conventional
method. The method is described as follows: The fry (above 0.6 g)
are held in a net-cage set on the sea surface and fed until they haveadapted to a seawater temperature of l3°C. The releasing method
is designed to prevent the salmon fry from mortality caused by

2S

20

I

~ '5~

CJ TOTAL CATCHEIJ RIVER CATCH

U

-J

<

I-

oI10

S

1967 '68 '69 '70 '71'72 '73 '74 '75 '76 '77 '78 '79 '80

'81

YEAR

Figure I.-Fluctuation of catches of chum salmon on the Pacific coast of the
Tohoku district of Japan (Aomori Prefecture to Ibaragi Prefecture).

'Tohoku Regional Fisheries Research Lat-oratory, The Mimstry of Agriculture andForestry, Fisheries Agency. Shiogama. Miyagi 985, Japan.

75

METHODS AND RESULTS

release in the river, this method provides an extremely high returnrate. A close relationship between the size of fry when released
and the return rate was confirmed by this releasing experiment asshown in Figure 4.
The 1973 and 1976 brood years showed extremely high return
rates. Both brood years, however, were in e1(cess of the 8.0 g
releasing size. This resulted in a 6% or more return rate for 1973
and 1976. At this size, the fry move towards the outside of the bay
within 7 d after release, and begin offshore migration. It is therefore presumed that the fry have a strong resistance to environmental conditions upon reaching 8.0 g in body weight. Great mortality has occurred during early release from the river to theUnderwater Rearing and Releasing Research From1973 to 1976
Figure 2 shows the positions of fry-holding cages and releasingsites and Table I gives the test results of releasing in Iwate Prefecture from 1972 to 1976. Figure 3 shows the construction of underwater cages set in Yamada Bay. Yamada Bay in Iwate Prefecturelies near the middle of Sanriku area coast with an inlet of average
depth of 30 m. This bay has a 6° to 14°C water temperature during April to June. Experimental fry were reared as marked and unmarked fish in large underwater cages, and were released after adefinite time period of feeding. As shown in Table I, the returnresults vary each year. Delay in release time of small fry is responsible for the low return rate (1.84%) of the 1972 brood year, as
compared with other released fry. The return rates from 1973 to
1975 were 7.58, 3.96, and 4.93%, respectively. In 1976 the return
rate was 11.46%, which was the highest return during the periodof study. Taking into account the fact that the return rate ofsalmon on the Pacific coast of the Tohoku District of Japan isslightly below 1.0% according to the conventional method of

~

----~

fish net

12 ¢Figure 3.-Sectional drawing of underwater preserves in Yamada Bay of (watePrefecture.

i~Att'":tf4::
:r

I

I

10

I

......

;.'::::::.;.:=1

I
I
I

cfi
.....
(j)

I
I
-II

ell

0:
c: 5

...

-

Bay

::l

6

o

( j)

0:

:::-'

L--

.~;;>;

.'

I

I

I
I
I

e

.4t~

I

I
I
I

\0

5
20

Body Weight (g)Figure 4.-Relationship between releasing size and return rate.

Figure 2.-Underwater rearing experimental stations in (wate Prefecture.

Table I.-Return results of marked fish released in Iwate Prefecture.
Number of adult returns
Brood
year

ReleasestationNumber of fry
released

1972

YamadaBay
YamadaBay
YamadaBay
YamadaBay
YamadaBay

103,535

1974
1975
1976

15

km

:,:,:,:+::,:.::"':::::::1t~-------

1973

e'972
4 1973
01974
61975
.1976

I.
I

-

::::~

Buoy

2 ton concrete block:::::::::.,.;.:.:.:.:.....

- - SSm

Rate ofin each year class

Total number ofadult returns

return

3

4

6

474

1,233

189

1.907

1.84

114.611

360

4,218

3.848

262

8,688

7.58

118.365

256

t,646

2.563

227

4.692

3.96

135,510

35

1,473

4,435

729

6,675

4.93

83,047

576

4,799

3,731

412

9,518

11.46

2

76

6

3

(%)

Table 2.-Number of fish released and number of fish
marked for each experimental station in 1977 to 1981.

estuary and until coastal waters are reached. Loss in the early days
which was caused by direct release in the river can be improvedby rearing the fry to 8.0 g or more in underwater cages. Thismethod minimized predation during outward migration by direct
release into the sea. The results of this study showed that if theriver, estuary, and coastal movement of the fry can be substituted
as in the conventional method, the return rate (1.0%) can be improved to 10% or more, as during the brood year 1976.

Year
released
1977

1978

Underwater Rearing From 1977 to 1981
1979

On the basis of the data obtained from research from 1973 to
1976, experiments were conducted on the Pacific coast of the
Tohoku District of Japan at Moura in Aomori Prefecture, Yamada
Bay in Iwate Prefecture, and Samenoura in Miyagi Prefecture(Fig. 5). Underwater rearing and release were carried out to examine the condition of salmon upon return during that period.
With the chum salmon fry used in experimental release, seedlings of the Tokachi River brood at the Hokkaido Salmon Hatcheries were used in three areas. About 20% of the fry released fromthree stations were marked on the adipose fin and by ventral fin
cutting. Table 2 gives the number of fry released from the experimental stations over a period of 5 yr from 1977 to 1981. The purpose of this study was: I) To check the effects of the geographical

1980

1981

Miyagi

tlD
tlD
1IJ
C

o

E

co
(/)

Hokkaido Salmon Hatchery(~~l-~~~~p~VV
~

)
~
C

1IJ

E

.~

0X

W

IS'
E"perlmenta !atlonof Aomori Prefecture~\'--------7--- - - - - - 3 --,5/"-

Number ofmarked fish(x 10')

0
2,712
1,930
2,086
2 899
3,000
1,742
1,983
2 510
1,903
1 390
2,170
1,420
3,000
2 500

0
159
152
204
300
312
207
127
208
207
107
366
165
236
300

0

0

0

0

conditions of three different experimental stations on releasing
techniques of fry in the sea, and 2) to apply the fry releasing
techniques which were developed during the period of study at
different representative geographical locations. This will finallyprovide a more precise technology of fry releasing techniques
based on geographical conditions within the Tohoku area. Fromphysiological and ecological points of view, the following information provided data in the establishment of the underwater rearing techniques: I) The size of fry during transfer from freshwaterto seawater; 2) releasing time in the coastal area. The assumption
was made, based on experiments, that fry more than 0.6 g weremore adapted to seawater. Seawater temperatures could bemonitored where cages were set in bays in the Sanriku area. Thesephenomena were the basis for the development of a releasing
technique which would eliminate loss. Therefore, the natural
movement of the fry upon release would be affected by coastal
water temperatures of \20 to 13°C (toward the middle or end ofMay) which coincides with the time the salmon leave the coast to
migrate offshore.
The construction of underwater rearing cages used at three stations was divided into inland bay type and the float-type suitable
for the open bay (Fig. 6). The methods and results of the releasing
experiments for each area are given below.

(C:~
(f)

Aomori[wale
Miyagi
Aomori
Iwale
Miyagi
Aomori
Iwale
Miyagi
Aomori
Iwale
Miyagi
Aomori
[wale

I--~

,-.J

StationNumber of
released fish(x 10')

E""im,"'" S,,,,,"

Experimental sites in Iwate Prefecture.-The releasing sites
in Iwate Prefecture are in Yamada Bay and Miyako Bay. Table 3
gives the number of fry reared and released and the number ofmarked fry released. Table 4 gives the return rates of the marked
fish experiment, which was carried out at different stations
centered around eight fish markets and river fisheries in Iwate
Prefecture. For the brood year 1977, the return rate of 4-yr-old
fish was 1.42%. The brood year 1978 produced a return rate of
3-yr-old fish of only 0.92%. However, the return rate increased in,~omparison with 3-yr-old fish of the brood year 1977. This result
will be confirmed by the return of 4-yr-old fish in the autumn of1982. The estimated coastal return rate of fry reared underwaterand released brood fish, including unmarked brood fish, is shownin Table 5 as the return rate of marked fish. In this experiment, theearly return brood in Hokkaido was used. It was expected that thereturning brood from this experiment would have a silver color.
Normally, fish caught on this coast take on nuptial colorations;
therefore. the distinction could be made clearly. In the analysis of-Sof . Iwate Prefecture

Experimental Stationof Miyagi Prefecture

Tohoku Regional

Fisheries Researc:h Laboratory)
Figure So-Underwater rearing and releasing experimental stations in Tohoku
district in Japan.

77

floatr-1Omi

1

r

10m

j
I

20m

/

20m

~

J

1

-9.12mL-

o

~

N

E

-N

I

1m

L[

f,. ame of underwater net pen'"iI

styrofoam
canvas --~"

styrofoam/I

31.36m/./i=:=J1'----_M~~"/
L ~ JIII _ I ~"
9.12m

:/
I

I

I~

fish net

I

I
I
I

Side view of float

I

Inland Bay type(raft type)

Cross recline of float
Off Bay type (float type )Figure 6.-Structural drawing of underwater preserves.

Table 3.-Number of fish released and number of fish marked at eachexperimental station in (wale Prefecture.
Number of
released fish

Brood
year

Date
released

Station

1977
1978
1979

1978.5.17
1979.5.14
1980.3.27
1980.4.17
1981.5. 6
1981.5. 7

Yamada Bay
Yamada Bay
Yamada Bay
Miyako Bay
Miyako Bay
Yamada Bay

1980

Table S.-Estimated migrations of salmon to the coast in Iwate Prefecture
experimental area.

Brood

Number of released fish
lit underwater preserve

Return rate ofmarked fish(x 10')

Number ofmarked fish

year

~xperiment(%)

Estimated migrations
to experimental area

7..712
2.899
930
1,053
322
1.068

121.685248.273
93.64198.53984.41890.8671977
1978

2,712,000
2,899,000

1.072
0.924

29,00027.000Experimental sites in Miyagi and Aomori Prefectures.-The
experimental releasing sites in Miyagi and Aomori Prefecturessituated at Yagawa of Samenoura Bay, Moura and Noheji of Mutsu Bay, are shown in Figures 8 and 9, respectively. At theseexperimental sites, there is no river where the salmon can escapefrom the areas near the underwater rearing facilities. For example,
Ushirogawa River is a small river at Samenoura about 2 m wideand 4 km long, and has a small quantity of water; it has little influence on the water from the coastal area. Therefore, it is possiblethat in these places the fish will return to the sea area which would
be an underwater rearing site, as compared with the Iwate Prefectural experimental sites where the released fish return to the river.
Tables 6 and 7 show the number of underwater reared andreleased fry and that of marked fry released at these experimentalsites. The return results of two experimental sites are as follows:
The fishery for salmon where the releasing was performed atSamenoura Bay at the Miyagi Prefectural experimental site produced only about 40 to 50 fish annually prior to 1976. Thereafter,
underwater rearing and releasing experiments started in 1977,-----Table 4.-Return results of marked fish in Iwate Prefecture.
Number of returns
at each age

Brood
year

Number ofmarked fish

2

1977
1978
1979

121.685
248,273
98,539

20
26
1

408
2,296

4

Total

1.072

1,500
2,322
I

recapture conditions (classified by year and day) of marked fishcaught in three fish market catches in Iwate Prefecture, it can beassumed that the increase in the fish market catch at Yamada Bay
early in September and October of 1977 to 1978 can be attributed
to the experimental brood of underwater rearing and releasing
techniques and the resulting catch in the fishery (Fig. 7).
78

MIYAKOKUJI

YAMADA-='L-,~~.LL=_"_"'_B__'RllO_00__l.UY.l'EA'_R"___I9_76___"_"___.rJ"JL [!(J, N 0

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__

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::1

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I:iROOD YEAR 1979~~','['---------------------':L---','Lr
15202530
SEP.

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10

152025

OCT.

31

5

10

NOV

15

20

25

30

152025
DEL;.

~P

30

5

10

15

20

25

31

5

10

15

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_

BROOD YEAR 1979

20

;5

30

___'N'__"_~.,.,'5~2c:'~25~3~'~,---:'-:"'-c:'5-c:,::"~25~';':3'~5~'~'--;;"~;::"~;5~

DEC. SEP.

OCT

NOV

DEC.

Figure 7.-Fluctuation of seasonal catches of chum salmon near the main fish market in fwate Prefecture.

I",,~fbi0v.

:],j0:.i'-::.".\SAMENOURA B O Y ' : '~\Figure 9.-Underwater rearing experimental station in Aomori Prefecture.

I km

Table 6.-Number of fish released and number of fish marked in
Miyagi Prefecture.
Figure S.-Underwater rearing experimental station in Miyagi Prefecture.

resulted in a gradually increasing fishery production from year toyear. Set nets were constructed at nine points in this bay and a fish
trap was set in a small river at Ushirogawa that flows into the bay.
The number of chum salmon captured by the set nets and thenumber of fish that escaped in the rIver of Ushirogawa are given
in Figures 10 and II. The catch by set nets at nine locations was

Brood
year

Date
released

1977
1978
1979

1978.5.29
1979.5. 7
1980.4.18
1980.5.21
1981.6. 2
1981.6. 2
1982.5. 7

1980
1981

79

StationNumber of
released fish(x 103 )YagawaYagawaYagawaYagawa

1,930
3,000
1,160
1,350

Yagawa2,170

Yagawa1,800

Number ofmarked fish
152,630
312,000
58,000150,000
52.947
314,596
300,000

Table 7.-Number of fish released and number of fish marked in
Aomori Prefecture.

Brood
year

1979
1980
1981

Date
released

Station1980.5. 91980.5.19
1981.5.16
1981.5.21
1982.5.16
1982.5.29

Moura
Nohegi
Moura
Nohegi
Moura
NohegiNumber of
released fish(x 10 3 )were recovered. Sixty of the marked 3-yr-old fish released from
Samenoura Bay were recovered along the coast of Iwate Prefecture in 1981. Recapture of marked fish released from Moura and!'<oheji of Mutsu Bay in Aomori Prefectural experimental sites has
not yet been confirmed. As a result of the research in 1981
centered at the Moura experimental releasing area, 1,236 chumsalmon were captured between the middle of November and theend of December and the peak at the beginning of December. In
comparison with the ages of the returned fish, the ratio of 3-yr-old
fish is extremely high as compared with that of 4-yr-old fish (theratio for 3-yr-old fish is 95.7% and 4-yr-old fish is only 3.8%). So
far, the annual fishery catch of chum salmon in this district is only
10 fish. It can be assumed that the brood released in 1979 returned as 3-yr-old fish as shown in Table 8. It shows the number ofchum salmon recovered at Moura. The Moura District in Mutsu
Bay has no river where the salmon can escape, and the broodreleased by underwater rearing and releasing techniques was captured on the coast near the releasing site. It may be conduded,
therefore, that when the underwater rearing and releasing area has
no large accessible river, such as at Samenoura Bay in Miyagi

Number ofmarked fish

1.905
180
152,000
53.000101,000
106,000

853
987
962

---2,000 fish or more in 1980. These salmon were the 1977 broodfish and therefore returned as 3-yr-old fish. The increase inescapement in the river of Ushirogawa is correlated with the increase in fish caught by set nets. However, in 1981, when the fish
released in 1977 returned as 4-yr-old fish the return rates in boththe set nets and river escapement was very low. It was also difficult to find the marked fish and only four of the 3-yr-old fish

v~ II

1

SAMENOURA Bay•

before December

0

600

(J')

No.

,

after December

No.

2

No.

3

No.

4

No.

S

No.

6

No.

7

No.

8

No.

9

500

W

J:

0

I-

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0

u.

0

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W

al

::E
~

Z

200

100

'76'77'78'79'80'81 '76'77'78'79'80'81 '76'77'78'79'80'81 '76'77'78'79'80'81 '76'77'78'79'80'81 '76'77'78'79'80'81 '76'77'78'79'80'81 '76'77'78'79'80'81 '76'77'78'79'80'81

YEAR
Figure IO.-Annual nucluation of catches of chum salmon put in the set net of Samenoura Bay in Miyagi Prefecture.

802) The size of fry has been examined for effective experimental
release. This has resulted in a remarkable improvement in return
rate with a releasing size of 8.0 g or more. For example, the underwater rearing and releasing experiment which was carried out in
Iwate Prefecture resulted in a return rate of marked fish of up to
11.5%.
3) At a releasing area where there is a very small river, such asat the experimental location in Miyagi Prefecture, the high fish
catch was accomplished by a set net near the underwater rearing
site. In an area having no salmon returning to the river, as in theexperimental site in Aomori Prefecture, the fishery for salmon
occurred near the underwater rearing cages. This phenomenon
poses the question whether the salmon remember the sea as wellas the river. An important phenomenon for underwater rearing
and releasing techniques is the delay in river return caused temporarily by loss of the homing instinct by the salmon. Whenreleased in the rivers, imprinting of the homing instinct is madecontinuously under natural conditions. Fry which are taken tounderwater rearing cages are artificially moved a distance of a few
hundred meters or a few kilometers from the hatcheries to sea surface cages. Therefore, conditions for natural imprinting are temporarily removed. It can, therefore, be presumed that the fryreared in cages imprint on the sea conditions of their release.
Hereafter, applicable research is required to determine the returning capacity of the river of release by underwater rearing andrelease and the relationship between the releasing site and temporary loss of imprinting of homing instinct.
4) In an area centered around the rivers in the northeastern
district of Japan, propagation and research on these salmon was
carried out. The theme of this research, the introduction of underwater rearing techniques for salmon, has enabled a remarkable increase in releasing quantity. Instead of releasing small fry in therivers, it enabled the release of a large number of fry. Therefore,
the loss caused by predatory fish in the rivers, in the estuary, andon the coast and the loss caused by capture among various fisheries has been reduced. The introduction of this underwater rearing technique and the timing of release increased production from
1,000 tons in 1960 to 25,500 tons in 1981. In the future, we expect that these techniques will be closely linked to effective
utilization of inland bay areas in the northeastern district of Japanand further provide guidelines for fishery administration by overall utilization of inland areas and seawater for salmon production.

1000 f-en
~

z

UJ

:::E
UJ

Q.

«
()

en
UJ

Cl

~
Z

;: 500

«

Q.

en
u.

o

0::
UJ

I---

co

:::E
='

z

1976 '77

'78

'79

'80

'8 I

YEAR
Figure H.-Annual fluctuation of anadromous chum salmon
at the Ushirogawa River of Samenoura Bay in Miyagi
Prefecture.

Table 8.-Recaptures at Moura in Aomori Prefecture.
Number of recaptures
Recaptures

Period of recaptures

9

6

Unknown

Total

Fish farming center
Fishermen

1981.11.1 0-12.22
1981.11. 3-12.29

36
304

132
756

0
8

168
1,068

Prefecture and at Moura in Aomori Prefecture where underwater
rearing was conducted, the fish return to their releasing points.

CONCLUSIONSThe Pacific coastal area in the Tohoku District of Japan has
only small and medium-sized rivers where the propagation of
salmon is limited due to low productivity of the rivers. Theserivers are not fully supplied with the natural food necessary fornourishment of the released fry. Furthermore, it is not economical
to rear and release a large quantity of fry (1.0 g or more) by
feeding the fry during rearing at the hatcheries. The low productivity of the rivers and the economical limit at the hatcheries are
overcome by using underwater rearing and releasing techniques.
In addition, these new techniques increase the amount of fry
released and eliminate the initial loss in the river and on the coastby rearing the fry in cages before releasing them. In the process of
this technological development, points clarified and points yet tobe solved are as follows:

LITERATURE CITED
KOGANEZA w A. A.
1970. Sea water culture and its points of two or three genus Oncorhynchus.
[In Jpn.) Fish. Oceanogr. Res. Bull. 17:95-101.
TOHOKU REGIONAL FISHERIES LABORATORY.
1977. Overall research on the development of mass culture technology of searun salmon/trout. Control of fry loss by using underwater rearing and releasing technology. [In Jpn.] Sci. Rep., p. 1-108.
1978. Overall research on the development of mass culture technology of searun salmon/trout. Control of fry loss by using underwater rearing and releasing technology. [In Jpn.) Sci. Rep., p. 1-113.
1979. Overall research on the development of mass culture technology of searun salmon/trout. Control of fry loss by using underwater rearing and releasing technology. [In Jpn.) Sci. Rep., p. 1-164.
1980. Overall research on the development of mass culture technology of searun salmon/trout. Control of fry loss by using underwater rearing and releasing technology. [In Jpn.] Sci. Rep., p. 1-149.
198 I. Overall research on the development of mass culture technology of searun salmon/trout. Control of fry loss by using underwater rearing and releasing technology. [In Jpn.) Sci. Rep., p. 1-126.

I) It is possible for the fry (0.6 g or more) to acclimate to seawater. Concerning a suitable release time, loss in the river or along
the coast can be eliminated by release at the proper time whencoastal water temperatures are 12° to BOC.
81

Technical Innovations in Chum Salmon Enhancement With
Special Reference to Fry Condition andTiming of Release
HIROSHI MAYAMA 1
INTRODUCTION
20

A recent upward trend in the survival rate of chum salmon,
namely the increase in the rate of adult returns, has followed anincrease in the number of fry released after short-term feeding.
The higher survival rate is thought to have been achieved by therelease of larger fish at the proper time. Chum salmon fry are firstreleased when coastal water temperatures in Hokkaido rise above
5°C. At the latest, the release of fry must be completed prior to 50
d before the average surface temperature of coastal waters reaches
15°C. During this period, it is important to adjust the number offry released so they can be effectively produced in the river andalong the coast.
This report deals with the proper releasing time and the condition of fry at the time of release based on experimental data fromthe chum salmon enhancement project in Hokkaido.

--

SUTTSU COAST-0-MONBETSU COAST : OKHOTSK SEA: JAPAN SEA--e--

AKKESHI COAST-'jl'-

u
15
0

,,

,-.'
.'--

UJ

a:

::>

~ 10

/,,--'- - - - - - - - -

a:
~

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/

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; PACIFIC

5

~

/

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,JII'

,.',~---------------

,JII'

,,It'

RELEASE OF FRY IN PREVIOUS YEARS

0

The artificial propagation of chum salmon began in Japan in
the late 1880's. Until the early 1960's, fry migrated from hatcheryponds to streams and other natural waters, as soon as the yolk sac
was absorbed. Therefore, timing of release was determined by the
cumulative water temperature required for fry development andincubation.
Eggs and fry are reared in ground water (spring water), which isusually kept about 8°C in Hokkaido. The time period between
fertilization and emergence is 110-120 d. F~r example, fry hatched out from eggs taken in mid-October are released in early to
mid-February of the following year. Fry which have just hatchedout are very small, around 0.3 g, and have limited swimming
capability. They are reared in incubation ponds with a gentle current at a temperature of 8°C, but are released directly into streams
with a rapid current and a temperature of OOC. At this time, thesurface of the streams in Hokkaido is usually covered with ice
because of low ambient temperatures and a decrease in waterlevel; the surface ice begins to melt in late March.
Fry which are released in cold streams have limited swimming
capability and normal behavior is affected by this rapid change inenvironmental conditions. Most of the fry are brought to the sea
drifting with the river current. However, in Hokkaido the coastal
water temperature in February and March, when the fry migrate
to sea, is the lowest of any coastal area (Fig. I). For instance,water temperature is 3 °_5 °C at the Japan Sea coast, OOC at the
Pacific coast, and at the coast of the Okhotsk Sea drifting ice
comes close to shore. Moreover, this is a difficult season with continual strong northwest winds. It is easy to understand that the sur-._-........--.-

JII'------~~'------------------------

FEB.

JUL.

Figure I.-Seasonal changes in average decade water temperature of three typesof coast in Hokkaido, Each value is the mean of 10 yr, 1972-81.

vival rate of fry which migrated to sea at this time was remarkably
low.

Delayed Release After Feeding
To reduce the effects of these harsh environmental conditions,
it is necessary to delay the release of fry. It is best to keep the fry
in hatchery ponds until the proper release time.
In 1962, a project was undertaken to yield twice as many as the
300 million fry which were being released at that time. In thisproject, fry were grown on a proper diet and were released aslarge, healthy fry at the optimum time.
Figure 2 shows the number of unfed and fed chum salmon fry
released from 1955 to 1976, and the rate of return of adults of thebrood year stocks. The release of fed fry began in 1962. In theprevious 4 yr, improvements in methods included improved diets,
amounts of food used, and duration of rearing in the hatchery.
Based on these experiments, feeding fry with dry diet was begunin the 1966 brood year to try to produce fry twice as heavy inabout a month. In this year, over 50% of the total number of fryliberated were fed the dry diet. Since then 80 to 90% of the total
releases (400-500 million fry) were fed. The remaining 10-20%
delayed swimming up because of the low temperature of thehatchery water. The eggs were collected late in the spawning

IHokkaido Salmon Hatchery, Fisheries Agency, 2-2, Nakanoshima, Toyohiraku,
Sapporo, Hokkaido, Japan 062.

83

o

30

•

..Q

o

">-20

x
10~

o

If
\5

Cl
UJ
(J)

«
UJ

;-- .....

...

It:

,,

~IO

~
>-

,6
,,

5~

lL.

a::

O'-<l:........,-............'ro:lJe--.--....__....-lHl"'r-~,....,Mc:a:>-;

UJ
lD
~

o
60

65

70

0

0"

o

1955

,

,,
,,

III

....J

•

MAR.

=>.
z

Figure 3.-Seasonal variations in the densities of chum salmon fry
captured at the beach (open circles, mean value for each day) and
offshore (solid circles, each value at every station) in Ishikari coast,
1977-81.

75
BROOD YEAR

Figure 2.-Numbers of chum salmon fry released in Hokkaido, 1955.76, andrates of return of these brood year stocks.

spread; however, most fry disappeared by late May. Most of the
fry in this area were < 4 cm in fork length (FL) and even in May,
small fry of this size stayed there. On the other hand, from results
obtained using a purse seine at depths of 5-25 m, and from up to 5
km offshore, the numbers of fry were low in April, increased
rapidly from late May to early June and disappeared by mid-June.
The rapid decrease of large fry was found at the same time every
year. This may indicate that the environment became inadequate
causing the fry to migrate offshore. The fry were 6-8 cm FL and2.5-4.0 g in body weight just before they disappeared from coastal
waters adjacent to the mother river. Marked chum salmon fry produced in the lshikari River were recaptured along the coast about
80 km north in early and mid-June. They averaged 7.4 cm FL(range 6.6-8.0 cm) and 3.5 g in body weight (range 2.7 -4.5 g).
Based on these results, a body size of about 7 cm FL and 3 g bodyweight was considered to be necessary for offshore migration. The
growth of fry migrating a greater distance was better than that ofmarked fry recaptured at the same time. Therefore, it was suggested that offshore migration from the native coastal area near themouth of the mother river occurred when fry grew to a certain size
(Mayama et al. 1982).
The mechanism by which fry disappear from coastal areas adjacent to the natal river is not understood. However, offshore migration may be induced as changes in the marine environment occurring at this time produce inadequate conditions for growth.
Salinity and temperature of Ishikari coastal waters during thesampling of the fry are shown in, Figure 4. The temperature at a
depth of 5 m shows a linear increase and reached II °-12 °C inlate May to early June, when the numbers of fry had decreased.
Salinity decreased in April and Mayas a result of the influence ofan increasing amount of water from the river, and then increased
rapidly in late May. At this time, the effect of the Tsushima Warm
Current increased, raising the water temperature and salinity, andseemed to produce some physiological effects that induced offshore migration. This is considered to be one of the factors
responsible for migration. Also at this time, the amount of marine
food for fry decreased due to a change in species composition ofcrustacean zooplankton from oceanic cold-water zooplankton
species to coastal warm-water species. As the water temperature
increased, the growth rate of fry increased rapidly and the amountof food they required increased. The decrease in amount of food atseason, in December and January, and it was not necessary to feedthem an artificial diet.
In the 1950-60 brood years, the average rate of return of thosereleased from unfed rearing was 1.19%. In the 1966-76 broodyears, the average rate of return was twice as high (2.31 %) as inprevious years and the variability between years was small.
Therefore, stable reproduction of chum salmon was obtained.
The increased rates of return resulting from the liberation of fed
fry were the result of decreased mortality of the fry released. Thatis, releasing larger fry (0.6 to 1.0 g) by feeding and delaying thetime of release by a month was effective in increasing survival of
the fry.

Limit of Time of Release
The problems of an early release time, as described above, were
alleviated by means of delaying the release time. The problems ofa late release time have not yet been considered. In some hatcheries, release of fry was delayed every year by the low watertemperature for incubation and the small size of fry; therefore, therate of return was low. Even in these hatcheries, a change to thehigher temperatures of spring water increased the rate of return.
From these results, the latest limit of the time of release could be
estimated. In the case of reared releases, it is necessary to clarify
the time limit to determine the duration of feeding. Based on
research with trap nets on the coast, it is known that chum salmon
fry disappear from coastal areas at a certain time every year.
Since the beginning of fry feeding, ecological research on chumsalmon fry in coastal areas was undertaken to determine the proper time of release. Ecological research on the distribution andmigration of chum salmon fry produced in the Chitose River, atributary of the Ishikari River, was carried out on the Ishikari
coast of the Japan Sea for 5 yr, from 1977 to 1981.
Figure 3 shows the density and distribution of churn salmon fry
along the Ishikari coast, adjacent to the mother river, as a functionof time. Fry appeared in the near shore, at approximately I m
depth, beginning in late March when the water temperature roseto 3 °_4 °C. Beginning in mid-April, the distribution was wide84

decreased swimming capability and cannot stay in rivers with afast current. Thus, they move quickly to coastal waters whereserious problems can develop; fry suffering from the disease fail toadapt to seawater. Because it is difficult to culture the bacteriumthat causes gill disease, experiments involving adaptation of fry
suffering from this disease have not yet been done. According topreliminary experiments, fry are thought to have little resistanceto the stress of moving to seawater. It is known that rearing fry ata high density leads to decreased swimming capability. Anotherimportant goal is to develop a technique to produce healthy fry
with a high survival rate after release. From experimental results(Kobayashi 1982 2 ), it is clear that training in a current and adjusting loading densities of the rearing pond are required in order toproduce strong fry.

L........,----,r---r--r---,---,-----,----.-r----.--....---l 0
MAR.

MAY

Future Technical Problems

JUL.

Artificial techniques can change the behavior of chum salmon,
benefitting fish production. In the United States, active researchon the effects of delayed release time on migration patterns in thesea have been carried out with coho and chinook salmon (Novotny 1980). However, in Japan, chum salmon fry are released
within a restricted period because of the rapid increase in coastal
water temperatures in spring. The migration route of fry depends
on sea conditions, so it may not be possible to carry out the release
operation needed to give the desired migration pattern.
The effects of a given age and body size of fry on returns has
been discussed in combination with release timing in North
America (Bilton 1978, 1980). In different species of salmon
released after long-term rearing, body size is adjusted based on
differences among rearing methods. However, in chum salmon fry
liberated after short-term feeding, clear differences in body size ofthe adult upon return have not been recognized. Body size at thetime of release was increased by fry-feeding; however, age composition, determined by 5-yr averages since 1951 (Table I),
showed no differences as a result of feeding.

Figure 4.-Seasonal changes in average salinity (open circles) and watertemperature (solid circles) of 5 m depth at Ishikari coast, 1977-81. Vertical bars
show the ranges.

this time made the environment relatively worse. For thesereasons, the fry may have been obliged to migrate from this area.
It is clear that fry growing to about 7 cm FL and 3 g in bodyweight, are able to migrate northward and their survival rate ishigh, until the surface temperature of the coastal water reaches
12°·13°C.
Since spring water is used in incubation and rearing in many
chum salmon hatcheries, the release of fry can be completed after
about a month. However, when stream water is used in the hatchery, development is delayed by low temperature. Even at the latest
time of release, only a few fry with adequate growth can survive.
For this reason, the rate of return is very low. The occasionalabsence of any returns indicates high mortality as a result of laterelease.

Table I.-Average age composition of chum salmon in Hokkaido.

Problems During Feeding

Percentage of return by age

Increasing the survival rate after liberation by adjusting therelease time with fry feeding and producing larger fry by feeding
was evaluated on the basis of the increase in the rate of return andnumbers returned. In order to rear a large number of fry, a rearing
pond and water are needed.
Reconstruction of the facilities began in the late 1960's. A new
problem-diseases-arose as a result of the increase in thenumber of fry reared. This was not a problem in unfed reared fry.
Even in a short time-I to 2 mo-rearing large numbers of fry ina limited amount of water caused the water quality in the rearing
pond to decline as the fry grew, and diseases occurred. Bacterial
gill disease occurred frequently and became a serious problem.
Because this disease is acute, it caused a high death rate. Bathtreatment is effective, but under high rearing densities, it was difficult to apply. When this disease occurs, rearing densities must be
decreased. Therefore, fry must be released that have not fully
recovered, and are released at an improper time. Thus, inactive
behavior and cessation of feeding by fry suffering from thisdisease make it difficult for them to adapt to the natural environment after release. Therefore, this causes a significant reduction in
their numbers. Since chum salmon are liberated at the fry stage,
recovery from the disease must be rapid if they are to be released
at the proper time. Fry suffering from bacterial gill disease have4

Brood year
1951-55
1956-60
1961-65
1966-70
1971-75

1.5
1.3
1.8
1.6
0.5

37.3
32.4
34.5
33.2
28.2

54.3
54.7
56.3
57.8
60.8

6.8
11.5
7.5
7.5
10.5

Percentage of fry
fed before release
0
0
18.1
67.4
74.1

CONCLUSIONSIn order to delay the time of release and produce larger fry, theliberation of chum salmon fry after feeding was begun in the
1960's. This resulted in an increase and stability in the number ofreturns. Japan is located at the southern limit of the distribution ofchum salmon. Along the coast, the effects of the warm current are
pronounced during spring and summer. Therefore, chum salmon
fry must migrate offshore until seasonal conditions are appropriate. Recently, about I billion chum fry were liberated from theisland of Hokkaido, which has a 2,734 km coastline. It is important to adjust the number of fry released to increase future coastal'Kobayashi, T. 1982. Technical development to produce healthy and strong chumsalmon fry for liberation. [In Jpn.] Unpubl. manuscr. Hokkaido Salmon Hatchery.

85

productivity. Moreover, it has been explained that fry in poor condition cannot adapt to natural environments. Therefore, production of healthy fry and the development of techniques for the production of strong fry are urgent problems for future churn salmon
research. These technical innovations should lead to an increase in
the survival rate.

release of juveniles.

Can. Fish. Mar. Serv.• Tech. Rep. 832, 73 p.

1980. Returns of adult coho salmon in relation to mean size and time atrelease of juveniles to the catch in the escapement. Can. Tech. Rep. Fish.

Aqua!. Sci. 941. 41 p.
MAYAMA, H., M. KATO, J. SEKI, and I. SHIMIZU.
1982. Studies on the chum salmon released in the Ishikari River System - I.
On the seaward migration and inshore distributions of liberated fry in 1979.
[In Jpn., Eng!. summ.) Sci. Rep. Hokkaido Salmon Hatchery 36: 1-17.
NOVOTNY, A. J.
1980. Delayed release of salmon. In J. E. Thorpe (editor), Salmon ranching,p. 325-369. Acad. Press, Lond.

LITERATURE CITED
BILTON, H. T.
1978. Returns of adult coho salmon in relation to mean size and time at86

Nutritional Studies for the Development of
Formulated Diet for Salmon Fry
TAKESHI MURAl, TOSHIO AKIYAMA, and TAKESHI NOSE!

INTRODUCTION-.,'" .

/ .~.=-

9.4°C

Chum salmon, Oncorhynchus keta, is one of the most importantfishes in salmon enhancement operations in Japan. The rate of
return to coastal areas or rivers of northern Japan has shownsteady improvement as a result of technical progress in artificial
propagation and feeding before their release. In most cases,
fingerlings are released at < 0.8 g in March through June. According to the report by Okada and Taniguchi (1971), natural foodorganisms are abundant in coastal waters from May to June, but
are too large to be consumed by fingerlings < I to 2 g. Akiyama
and Nose (1980) reported that the larger fish could sustain theirlife longer under adverse conditions, because the larger the size ofthe fish, the higher the level of deposited energy sources and thelower the basal metabolic rate. Thus, release of fingerlings> 1 gseems to be more advantageous for their survival.
In order to achieve this goal, a high quality feed for chumsalmon fry, especially for swim-up fry, is essential. However,there has been almost no information on the nutrient requirementsof chum salmon and various commercial feeds for rainbow trout
have been used. Under the special project entitled "Technicaldevelopment of the large scale farming of anadromous salmons"sponsored by the Agriculture, Forestry and Fisheries ResearchCouncil, we have conducted several nutritional studies over the
past 5 yr to develop a good formulated diet for chum salmon fry.
The results of these studies will be presented, focusing mainly on
growth and feed efficiency data.

5!}

0.4

• Dietary fat level

Y

c:

-..

'01"
c:

ClJ

..

'0
0..

0.3

•

..

..7

./.

0.7

./

c:

..

.~

,,-

/'

'0"1
a

.

,/

16.3°C

01

~

5%

•

0.8

c:

14%
10%

0.6

,/'

.

0..

0.5

•
25

30

35

40

45

50

Dietary protein level (%)

Figure I.-Effect of dietary protein and fat levels on protein gain in fingerlingchum salmon (7.wk feeding). Initial mean weight was 0.9 g (100 fish/tank) and
0.65 g (70 fish/tank) for 9.4° and 16.3°C studies, respectively. (Akiyama et at.
1981.)OPTIMUM LEVELS OF DIETARY PROTEIN
AND FAT
Two feeding experiments were conducted In a freshwater
environment for 6 wk to determine optimum levels of dietary protein and fat at 9.4° and 16.3°C, because DeLong et al. (1958)
reported that protein requirements of chinook salmon are remarkably higher at 14.4 °C than at 8.8 0c. Graded levels of dietary protein and fat were prepared using fish meal and pollock viscera oil
as the sole protein and fat sources, respectively. Initial mean
weight of the fish was 0.90 g for both 9.4° and 16.3°C studies.
Since the moisture and fat contents in the carcasses changed as thefish grew, body protein gain instead of weight gain was used as acriterion, as suggested by Ogino and Saito (1970).
As shown in Figure 1, when the dietary fat level was 5%, bodyprotein gain increased linearly as the dietary protein level increased up to 43% at both 9.4° and 16.3°C. Again at both watertemperatures, body protein gain increased linearly to the protein
level of 38% with the supplemental fat level of 10%. From theseresults, protein requirements of chum salmon fry were estimatedto be 43% with 5% fat and 38% with 10% fat at watertemperatures of both 9.4° and 16.3°C.

DIETARY CARBOHYDRATE SOURCE
Carbohydrate is the least expensive energy source and moreincorporation of carbohydrate in fish feed is necessary for the formulation of an inexpensive feed. However, utilization of carbohydrate in fishes is still a subject of controversy. Buhler andHalver (1961) reported that chinook salmon can utilize carbohydrates with smaller molecular weight more efficiently, but the
opposite results have been shown in channel catfish (Simco andCross 1966) and carp (Furuichi and Yone 1982). This experiment
was conducted to determine the best carbohydrate source forchum salmon. Fish with a mean body weight of 2.5 g were fed
diets containing 20% of either glucose, fructose, galactose,
sucrose, maltose, lactose, dextrin, gelantinized potato starch, or
cellulose (as a control) as a carbohydrate source. This feeding
study was conducted for 4 wk.

'National Research Institute of Aquaculture, Fisheries Agency, 224-1 Hirota,
Tamaki-cho, Watarai-gun. Mie 519-04, Japan.

87

As shown in Table I, the substitution of cellulose with any typeof carbohydrate resulted in reduced feed consumption. Supplements of fructose, galactose, or lactose in lieu of cellulose depressed the growth slightly, but supplements of glucose, sucrose,
maltose, dextrin, or starch slightly improved growth over that of
the control group. Data on feed efficiency reflected weight gains.
Among all dietary groups, fish fed the diet supplemented withstarch showed the best growth rate and feed efficiency. These
results indicate that chum salmon cannot utilize carbohydrate very
efficiently at a 20% supplemental level, but gelatinized potato
starch might be the best choice as a dietary carbohydrate.

400
';'0

c
III

...:;:<t:.!!!

Carbohydrate

u..

....

GlucoseFructose
Galactose
SucroseMaltoseLactoseDextrinStarchCellulose

3.50
3.59
3.47
3.59
3.41
3.68
3.66
3.44
3.94

213
184
165
215
213
184
21Q
219
203

106
96
92
104
108
93
102
110
95

120

Qj

110

"0

Qj
Qj

source

130

u

;;:

Feed efficiency(%)

100
at 16.SoC

Table I.-Effect of dietary carbohydrate sources on reed consumption, growth,and reed emciency or fingerling chum salmon (4-wk reeding). Initial mean
weight was 2.5 g (40 fish/tank). (Akiyama et al. 1982.)
Avg. wt. gain
(%)

200

dl

>

dP
>u
c

Feed consumption(%/day)

300

C1

100

o

2

6

4

8

10

Supplemental mineral mix(%)
Figure 2.-Errect of dietary mineral on growth and reed emciency in fingerling chum salmon (6-wk reeding). Initial mean weight was 2.1 g (40fish/tank). (Akiyama et al. 1979.)

d,O

140

c
III

C1

;:

ci1

>
<t:

OPTIMUM LEVEL OF SUPPLEMENTALMINERAL MIX

120
100
80
at 8. SoC

Optimum supplemental level of salt mixture (U.S.P. XII salt
mixture No.2 with trace elements, Halver 1957) for chum salmon
fingerlings was determined as a preliminary step because essentially no information on mineral requirements for chum salmon isavailable at present. Two feeding studies were carried out for 6 wk
at 16.5° and 8.5°C using purified diets. When water temperature
was 16.5°C, both average weight gain and feed efficiency reachedplateaus at 2% of the supplemental level (Fig. 2). At 8.5°C,
similar results were obtained (Fig. 3). From these results, we concluded that the optimum level of supplemental mineral mix for thediet of fingerling chum salmon was about 2%.

100
0\0

>-

u

c

Qj

90

u
;;:

....
Qj

"0

80

Qj
Qj

u..

o

2

3

4

Supplemental mineral mix (%)

ESSENTIAL FATTY ACIDS

Figure 3.-Effect of dietary mineral on growth and feed emciency infingerling chum salmon (6-wk feeding). Initial mean weight was 1.2 g (SOfish/tank). (Akiyama et al. 1979.)

Essential fatty acids for chum salmon fingerlings were examined by feeding diets containing different levels of methyl ester:
18:2w6, 18:3w3, 20:5w3, and a mixture of 20:5w3 and 22:6w3(w3 HUFA), and their optimum levels were determined. A
feeding study using purified diets was conducted for 7 wk. The
substitution of lauric acid with either 1% 18:2w6, 0.5% or 1%
18:3w3, 0.5% 20:5w3, or 0.5% w3 HUFA improved growth.
However, growth and feed efficiency were improved further by
substituting lauric acid with either a mixture of 1% 18 :2w6 and
1% 18:3w3 or 1% w3 HUFA. These results indicate that w3
HUFA or 20:5w3 may be more effective than 18:2w6 or 18:3w3
as the essential fatty acids for chum salmon. The optimum level
was concluded to be a combination of 1% 18:2w6 and 1% 18:3w3
or 1% w3 HUFA (Table 2).

FEED ATTRACTANT
In order to stimulate feed consumption of swim-up fry, various
meals which we considered to be potential feed attractants such as
silkworm, beef liver, krill, and earthworm meal were supplemented to practical type diets at a level of 5% in lieu of fish meal.
The protein source other than these meals was fish meal and the
major fat source was pollock viscera oil. Swim-up fry with mean
body weight of 0.21 g were fed the diets for 6 wk.
88

Table 2.-Effect of dietary lipids on growth and feed efficiency offingerling chum salmon f7-wk feeding). Initial mean weight was 1.3 g.
(Takeuchi et al. 1979.)

sao
dP
c

Avg. wI. gain(%)

Feed efficiency(%)

5.0% 12:0
4.0% 12:0 + 1.0% 18:2w6
4.5% 12:0 + 0.5% 18:3w3
4.0% 12:0 + 1.0% 18:3w3
1.0% 18:2w6
3.0% 12:0 + 1.0% 18:3w3

52
276
206
320

69
90
66
86

402

101

4.5% 12:0 + 0.5% 20:5w3
4.5% 12:0 + 0.5% w3HUFA
4.0% 12:0 + 1.0% w3HUFA

340
325
377

92
91
106

Lipid source...;:

rn 300>«115>cQ) 110

0\0

u

u
;;:

..... 105

As shown in Table 3, none of the supplemented meals stimulated feed consumption of fry. However, fish fed the diets withany kind of meals showed at least 10% higher feed efficiency thanthat of the control group. Among the meals tested, supplement of
only krill or earthworm meal substantially improved weight gain.
The dietary group with earthworm meal showed almost 40%
higher weight gain over that of the control group. These dataclearly indicate that these meals were not a feed attractant forchum salmon, but supplement of either krill or earthworm meal
could facilitate growth of chum salmon fry.

<lJ

"0
Q)
Q)

u-

supplemented
Silkworm
Beef liver

Krill
Earthworm

Control

Feed consumption(%/day)Feed efficiency(%)

Avg. wI. gain
(%)

4.12
3.95
4.08
4.07
4.60

89.2
88.2
89.9
107.6

439
427
500
587
429

77.1

/

100

a

4

8

6

Supplemental vitamin mix (%)
Figure 4.-Effect of supplemental vitamin premix on growth and feed
efficiency in fingerling chum salmon (4-wk feeding). Initial mean weightwas 0.58 g (50 fish/tank). (Murai et al. 1981.)

Table 3.-Effect of supplemental attractants on feed consumption, growth, andfeed effidency of fingerling chum salmon (6-wk feeding). Initial mean weightwas 0.21 g (200 fish/lank). (Akiyama el al. 1980.)
Attractant

400

C1l

0>

FORMULATION OF A PRODUCTION DIET
Based on the information obtained from the studies we havedone, five types of production diets were formulated as shown in
Table 4. In all diets, fish meal was used as a major protein source
and 5% brewer's yeast was supplemented. In diets 3 and 4, fishmeal was isonitrogenously substituted with 5% earthworm meal.
In diet 5, krill meal was used instead of earthworm meal. About
5% pollock viscera oil can provide adequate quantities of w3 fatty
acids required by chum salmon (Takeuchi et al. 1979) and Yu andSinnhuber (1981) reported that better growth performance is obtained by using a combination of tallow and salmon oil than use of
salmon oil alone. Therefore, pollock viscera oil in diets 2, 4, and 5
was substituted with 5% beef tallow on an isocaloric basis.
Gelatinized potato starch, which was found to be the best carbohydrate source (Akiyama et al. 1982), was used to adjust the total
amount. Both vitamin and mineral mixtures were supplemented at
a level of 2%. As a cOl!lparison, a salmon feed made by a commercial company exclusively for Hokkaido Salmon Hatchery (diet 6)
and a commercial feed for salmon made by a commercial company in Europe (diet 7) were also tested.

OPTIMUM LEVEL OF SUPPLEMENTAL
VITAMIN PREMIX
As with mineral requirements, no information on individual
vitamin requirements of chum salmon was available. It is still
true, therefore, that Halver's premix for the purified diet (Halver
1957) has been used even for a practical type diet. Since hypervitaminosis of some water soluble vitamins such as pyridoxine(Andrews and Murai 1979) has been shown, the supplementationof a high level of vitamin mix to a diet without knowledge may
not only be economically wasteful but also dangerous. As apreliminary step, the optimum supplemental level for chumsalmon fry was studied using Halver's premix. Fish with mean
body weight of 0.58 g were fed practical type diets supplemented
with five levels (0, 2, 4, 6, and 8%) of the vitamin premix for 4
wk. The protein sources were 61 % fish meal, 5% brewer's yeast,and 5% earthworm meal; and 9% pollock viscera oil was used as
the fat source. At a supplemental level of 8%, Halver's recommended level for the purified diet was attained.
As shown in Figure 4, both average weight gain and feed efficiency reached maximum levels at 2% of the supplemental leveland declined thereafter. From these data, we concluded that the
optimum level of supplemental vitamin premix to the practical
diet for chum salmon fry was about 2%.

---_.

Table 4.-Composition of the experimental diets.

Diet no.
IngredientWhite fish meal
Brewer's yeast

Earthworm IT.eal
Krill meal
Pollock viscera oil
Beef tallow
Gelatinized starch
Vitamin mix
Mineral mix
CMC

89

4
66.62
5.00

9.96
9.42
2.00
2.00
5.00

66.62
5.00

4.96
5.00
9.42
2.00
2.00
5.00

62.37
5.00
5.00
9.82
8.81
2.00
2.00
5.00

62.37
5.00
5.00
4.82
5.00
8.81
2.00
2.00
5.00

6
61.34
5.00

Feed made by acommercial

5.00
5.10
5.00
9.56
2.00
2.00
5.00

companyABAs shown in Table 5, the experimental diets (1-5) prepared byus had similar nutrient contents, but crude fat content of diet 6
was about 7% and crude protein content of diet 7 was about 50%.
A feeding study was conducted for 4 wk using swim-up fry with amean body weight of 0.26 g.

can be raised up to 1.5 g in body weight within 4 wk, which is thedesirable size for release.

LITERATURE CITED
AK[YAMA. T, T. MURA[, Y. H[RASAWA, and T. NOSE.
[980. Studies on improvement of feed for fingerling chum salmon-VlIl.
improvement of feed for fingerling chum salmon by supplement of feed
attractant. Interim reports of research group for salmon propagation in
1979, published at Hokkaido Reg. Res. Lab .• p. [59-162.
AKIYAMA, T., T. MURAl, and T. NOSE.
1982. Effects of various dietary carbohydrates on growth, feed efficiency, andbody composition of chum salmon fry. Bull. Natl. Res. Inst. Aquaculture
3:75-80.
AK[Y AM A, T., and T. NOSE.
1980. Changes in body weight, condition factor and body composition of
fingerling chum salmon with various sizes during starvation. Bull. Natl.
Res. Inst. Aquaculture 1:71-78.
AKIYAMA, T., I. YAGlSAWA, and T NOSE.
1979. Studies on improvement of feed for fingerling chum salmon-V, optimum level of supplemental mineral mix in a purified and practical diets forchum salmon fingerling. Interim reports of research group for salmon
propagation in 1979, published at Hokkaido Reg. Res. Lab., p. 127-131.
1981. Optimum levels of dietary crude protein and fat for fingerling chumsalmon. Bull. Natl. Res. Inst. Aquaculture 2:35-42.
ANDREWS, J. W., and T. MURAl.
1979. Pyridoxine requirements of channel catfish. J. Nutr. 109:533-537.
BUHLER, D. R., and 1. E. HALVER.
1961. Nutrition of salmonoid fishes IX. Carbohydrate requirements orchinook salmon. J. Nutr. 74:307-318.
DeLONG, D. c., J. E. HALVER, and E. T. MERTZ.
1958. Nutrition of salmonoid fishes VI. Protein requirements of chinook
salmon at two water temperatures. J. Nutr. 65:589-599.
FURUICHI, M., and Y. YONE.
1982. Availability of carbohydrate in nutrition of carp and red sea bream.
Bull. Jpn. Soc. Sci. Fish. 48:945-948.
HALVER, J. E.
1957. Nutrition of salmonoid fishes III. Water-soluble vitamin requirementsof chinook salmon. J. Nutr. 62:225-243.
MURAl, T., Y. H[RASAWA, and T. NOSE.
1981. Optimum supplemental level of vitamin premix in a practical diet for
fingerling chum salmon, Oncorhynchus ~eta. Bull. Natl. Res. [nst. Aquacul·
ture 2:43-47.
OGINO, C., and K. SAITO.
1970. Protein nutrition in fish-I. the utilization of dietary protein by young
carp. Bull. Jpn. Soc. Sci. Fish. 36:250-254.
OKADA, S., and A. TANIGUCHI.
1971. Size relationship between salmon juvenile in shore water and their preyanimals. Bull. Fac. Fish. Hokkaido Univ. 22:30-36.
SIMCO, B. A., and F. B. CROSS.
1966. Factors affecting the growth and production of channel catfish, fctalurus puncta/us. Univ. Kansas Mus. Nat. Hist. 17:191-256.
TAKEUCHI, T., T WATANABE, and T. NOSE.
1979. Requirement for essential fatty acids of chum salmon (Oncorhynchus
ketal in freshwater environment. Bull. Jpn. Soc. Sci. Fish. 45:1319-1324.
YU, T. c., and R. O. SINNHUBER.
198 I. Use of beef tallow as an energy source in coho salmon (Oncorhynchus
kisulch) rations. Can. J. Fish. Aquat. Sci. 38:367-370.

Table s.-Proximate analysis of the experimental diets.
Diet no.

2

Nutrient

Crude protein
Crude fat
Ash
Moisture

45.3
13.4
13.3
8.1

4

45.9
13.6
13.5
7.3

46.3
13.0
13.0
6.6

46.5
12.5
13.0
8.0

44.9
13.1
13.0
9.2

6

7

46.8
7.3
10.2
8.5

49.9
13.5
10.6
7.2

Results from the feeding study are summarized in Table 6. Feed
consumption of fish fed the feed made by the European company
Table 6.-Feed consumption, feed efficiency, and growth of chum salmon fry
fed the experimental diets for 4 wk. Initial mean weight was 0.26 g (ISOfish/tank).
Feed
Diet

(%/day)Feedefficiency(%)

Control+ tallow
Earthworm+ E and T+ Krill and T
A
B

3.45
J.48
3.40
3.52
3.60
3.47
3.15

137
135
145
138
137
138
141

consumption

Avg. wt. gain

Final mean wt.

(%)

(g)

396

1.3
U
1.5
1.4
1.5
1.3
1.2

3~3

443
432
453
412
342

was substantially lower than the remaining groups, possibly due tothe high protein and high calorie content of this diet. However,there was no clear difference in feed efficiency among all dietarygroups. The substitution of beef tallow for pollock viscera oil failed to facilitate growth of chum salmon (diet 1 vs. 2 and diet 3 vs.
4), but showed at least a comparable weight gain in each dietary
treatment. The substitution of either earthworm or krill meal forfish meal with or without tallow resulted in a substantially higher
average weight gain than that of the corresponding dietary treatment. Average weight gain of these three groups was more than
430%, which was higher than that of fish fed the feed made by theJapanese commercial company. Average weight gain of 430% in
4 wk was almost twice as much as those of fish fed diets with fishmeal as the sole protein source or the casein diets used in theprevious studies described earlier. Thus, if water temperature isabout 15°C, by feeding only one of these three diets, swim-up fry

90

Strategies in Salmon Farming in Japan
SOICHIRO SHIRAHATAIINTRODUCTION30
The present status of salmon propagation in Japan and the 5-yr
program of salmon enhancement being conducted under the
auspices of the Fisheries Agency will be discussed in this report.
Strategies and related problems will be reviewed from a research
point of view.

c

~

E

--Total......•... HOKKAIDD_._.- HONSHU

25
20

c

';

~

15

"3

SALMON PROPAGATION: PRESENTSTATUS AND TARGET

"
0

'0
0

10

z

/

Figure I shows the variation in total catch of Pacific salmon in
Japan for the past 25 yr. Recent catches fluctuate at a level of..... - .....

1954
~

j
c'

140

~

~

~

'0

!

~

100

Iif?

60

.~

f- 20
1957

6\

...

i

80

40

Ii

~
E

"

J;.;
65

69

73

))

73

77

81

ly after 1975. Honshu, at present, takes 30% of the returns ofchum salmon in Japan.
The Salmon Enhancement Program, now in operation under the
Fisheries Agency, is a 5-yr program which began in the broodyear 1979. Table 1 shows the progress and the final target forchum salmon. According to the Fisheries Agency, the return of
38.6 million fish, or 140,900 tons out of the release of 2,150
million fry in the brood year 1983, is set as a target figure to beachieved by the program. Judging from the numbers of fry released and adult returns in 1981, both being equal to about 80% of thetarget, the program appears to be successful.
To establish this program with success, it is necessary to 1) set
up and/or improve hatchery facilities; 2) secure a desirable
number of brood stocks; 3) enhance the rate of return; 4) transplant fry to barren rivers, especially in the Honshu area; and 5)
rehabilitate salmon stocks in large river systems. As for the
research operation on salmon enhancement, a large project(1977 -81) was carried out by 27 institutions with a working
budget of 830 million yen or 3.3 million U.S. dollars, in total.
Results obtained for the 5 yr are currently being drafted.

20

h.

69

g
60

,5

Ii

65

61

Figure 2.-Annual numbers of ehum salmon adult returns (coastal catch plus
escapements) from 1954 to 1981.

180

S

57

.'

/
.~.

81

Figure I.-Total catch of Pacific salmon and chum salmon as percent of total
catch.

110,000-150,000 tons; from FAO statistics, this means 25% of alllandings of salmon on the North Pacific coasts. In addition, in
1981 Japan imported salmon and their products amounting to
83,000 tons or 457 million U.S. dollars, equivalent to 12% ofJapan's total import of marine products. In this figure, note the increase in chum salmon returns. Annual returns began to increase
from around 1970, with great strides since 1975. In 1981, chumsalmon returns reached 30 million fish, accounting for 70% of thetotal catch of Pacific salmon in Japan. This drastic increase inreturns of chum salmon may have resulted from recent advancesin artificial hatching and release operations.
In Figure 2, chum salmon returns are explained in more detail.
From 1954 through 1970, annual returns crept up to near 5
million fish. Returns broke the 10 million record in 1974,20
million in 1979, and 30 million in 1981. A breakthrough at the 10
million level in 1974 is especially noteworthy as this was thehighest level under entirely natural spawning since the 1880's,
100 yr ago (Kobayashi 1979). Furthermore, in this figure note theincrease in returns of chum salmon in mainland Honshu, especial-

Table I.-Chum salmon enhancement program (1979-83).

'Hokkaido Regional Fisheries Research Laboratory, Fisheries Agency of Japan,
116 Katsura-koi, Kushiro, Japan 085.

Brood
year

1979
No. of fry
released(millions)

1981
No. of fry
released(millions)!

1983
No. of fry
released(millions)millions

1,000 tons

Hokkaido
Honshu
Total

871
576
1,447

1,080
738
1,818

1,150
1,000
2,150

27.6
11.0
38.6

100.7
40.2
140.9

Expected return ofadults from 1983 fry'Number of adult returns in 1981: 21.89 (Hokkaido) and 7.59 (Honshu) inmillions.

91

STRATEGIES: MANIPULATION OF THE
RATE OF RETURN OF SALMON AND
THEIR MIGRATIONThe brood year 1966 is a memorable one III the history of
salmon propagation in Japan. It was not until 1966 that dry formula feed was used with over 50% of the fry released in Hokkaido. The staff of the Hokkaido Salmon Hatchery initiatedfeeding trials from the brood year 1961 with the hope of obtaining
more robust fry. They fed them with cod roe and bound diet having a high moisture content for a couple of years, followed bycommercially formulated dry pellets. Of the roughly 100 yr ofexperience with the artificial release of salmon in Japan, the ideaof raising fry for a longer period and thus releasing larger, morerobust fry is relatively new-within the past 20 yr.
. Figure 3 shows that the higher the feeding rate, the higher therate of return. This relationship was originally introduced by
Kobayashi in a paper presented at the FAO meeting in Kyoto in
1976. New plots were added to his figure with open circles
representing the rate of return for non fed fry before the brood year
1966, and solid circles for fed fry thereafter up to the brood year
1977. These salmon returned mainly in 1980 and 1981.
As a result of artificial feeding, the size of fisl·; increased from
0.3 g for swim-up fry to 0.5 g at the time of release. It is importan,
to note the size of fry, as well as the number of fry released, that is,the biomass. Figure 4 shows the remarkable increase in aduli
returns when the biomass of chum salmon fry at release surpassed
200 tons. Twenty years ago, in the 1960's, the release of 300
million fry or 100 tons of biomass was thought to be the limit
based on reproduction curves for chum salmon in Hokkaido. As
seen in this figure, it will be a long time before the number ofreturns decreases.
The problem of the appropriate size of fry at release will now
be discussed. Figure 5 shows the relationship between the rate of
return and size of fry. Data on cherry, coho, chinook, and sockeye
salmon smoits were added to this figure for reference. Body
weights of chum salmon used here range from 0.3 to 10.5 g. The

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Figure 4.-Numbers of adult returns and biomass of fry released (no. x bw) inchum salmon of Hokkaido in the brood years 1950·77.

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Numbers of fed fry released, %Figure S.-Increase in rate of return as a function of size at release. Ct: Cultus
sockeye from Foerster (1954), Gc: Great Central sockeye from LeBrasseur et al.
(1978) and Manzer (1976), KI: Karluk sockeye from RounsefeU (1958), Kr:
Kurile sockeye from Kroglus (1%1), Rw: RosewaU coho from Bilton (1978), Sb:
Shlribetsu cherry from Hokkaido Salmon Hatchery, Sm: Sacramento chinookfrom Reisenbichler et al. (1982).

Figure 3.-Rate of adult return and percentage of fed fry released in chum1957.65, solid circles
1%6-77 (supsalmon in Hokkaldo. Open circles
plemented to Kobayashi 1979).

=

=

92

longer bar on the lower side of the figure represents the rate of
return when nonfed fry were released at 0.3 g, giving 1%; whereas
the second bar represents the increased rate of return of 2.4%
when fed fry were released at 0.5 g; both are averages for Hokkaido in total. The highest rate of return for chum salmon was
11.5% and was attributable to fin-clipped fry released at 8.3 gfrom a sea pen in Iwate Prefecture (Iioka 1982). The shaded
curved line is a possible maximal rate of return in Pacific salmon.
In this figure, note the dotted portion where comparatively higher
values of return ranging from 3.4 to 9.7% are plotted against bodyweights of 0.9-2 g. Fry of 0.9-2 g appear as smolts, showing active
swimming.
The larger the fry become, the sooner they migrate offshore.
They were often found in big shoals mingling with other fish, suchas young Atka mackerel. This migratory manner would enhance
the possibilities for survival (Ito 1980). Further research must be
directed to the behavior and physiology of young chum salmon in
the transient phases of migration, and also to the changing patternin their migration.
Having no experience in Japan with chum salmon fry of morethan 109 in body weight, except once in Iwate, we released larger
fry of 18, 300, and 1,000 g in a transplant project in Chile, SouthAmerica,2 and are presently awaiting the results. In the next trial,
we will devote our attention to what level the size at release can be
decreased.
The rate of return in itself might be a result of many difficulties
such as loss in river, estuarine, coastal, and ocean migration. We
assumed that the greater part of natural mortality occurs in fry
during coastal migration. Survival from fertilization to time ofrelease, at present, is 80%. In Hokkaido, survival during downstream migration is 25-40% in nonfed fry, while much higher,
50-70%, in fed fry (Kobayashi 1976). In a radiotracer experimentwith chum salmon fry in a small stream in Honshu, Hiyama et al.
(1972) reported survival rates of more than 90% for larger fry (1.3g) and 60% for smaller fry (0.4 g).
On the other hand, ocean mortality is considered to be relatively constant (Parker 1962). Hence, the first measure to be undertaken should be enhancement of survival during coastal fry migration after release. Figure 6 shows the relationship of the rate of
return to coastal fry survival under various levels of ocean survival. In this figure, dotted lines shown the case in British Columbia for naturally wild chum salmon by Parker (1962). He provides
estimates of survival for various phases from egg to adult. The
final rate of return in B.c. chum salmon was estimated to be
0.08% of the number of eggs spawned. This rate of return corresponds to about I % of the number of emerged fry.
As shown in Figure 3, the rate of return in Hokkaido wasaround 1% when fry were released without supplemental feeding.
Assuming that ocean survival is in the range of 30-50%, coastal
survival is estimated to be only 2-3%. In recent years in Hokkaido, coastal survival of fry released after feeding can be expected to be at a much higher level, as high as 6-10%, because
their rate of return was nearly 3%. Furthermore, the highest rate of
return was in Iwate Prefecture, northeast Honshu, when: fry of 1.8
g in body weight at the time of release from the hatchery returned
as adults at a rate of 9.7% (Iioka 1982). Again, assuming that
ocean survival will be 30-50%, coastal survival can be estimatedto be 20-35%.

60
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Figure 6.-Rate of adult returns and coastal survival rate of fry. Numbers infigure are survival rates during pelagic-coastal migration. Modified from
Kobayashi, unpubl.

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Figure 7.-Distribution of rivers of chum salmon return in 1981.

93

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Past and present levels of survival of fry during early life incoastal waters has been estimated. The next question is where,
how, and to what extent are they damaged. This is a very difficult,complicated problem. In Japan, we try to release robust fry at theappropriate time depending on local conditions of the river andcoastal waters. Fry are usually released in Hokkaido timed to therise in the rivers due to snow melt. Large quantities of turbid
waters from rivers could provide increased chances of survival
through reduction of predation, as well as through the supply ofnutrients to coastal waters.
Seemingly, coastal survival is liable to be influenced by the
localities where fry are released. Figure 7 shows the distribution ofrivers to which statistically significant numbers of adults returned
last year. In total there were 262 rivers; 149 in Hokkaido and 113
in Honshu, 1.6 times more than 10 yr ago. Eastern Hokkaido and
Iwate Prefecture have many rivers with high rates of returns.
Other remote localities such as Chiba, Sadogashima, Ishikawa,
Fukui, Kyoto, Hyogo, and Tottori have very small returns but are
steadily increasing. In this figure, it can be seen that chum salmon
fry released from the Honshu area are forced to spend a longer
period of time along the coast to get to eastern Hokkaido before
starting offshore migration. This implies that they are more liable
to be damaged.
High rates of return of more than 4% have been reported insome rivers feeding into the seas surrounding Shiretoko Peninsula,
Hokkaido (Kobayashi 1979). Fry from these rivers need only
travel < 100 km to reach the tip of the peninsula, while fry fromFebruary

the Yura River, Kyoto, must travel> 2,000 km. In Honshu, toovercome this topographic handicap it would be necessary torelease much larger, more robust fry. There is one more problem
different from that in Hokkaido-the temperature conditions of
the seawater. Figure 8 shows the distribution of surface watertemperatures around the Island of Japan during the season of fry
release. Due to the northward movement of warm water currents
in springtime, fry release must be completed by the end of April,especially in the western part of Honshu.
As outlined previously, the main manipulations at present forenhancement of salmon can be summarized as follows: Releasinga fairly large biomass of robust fry composed of the appropriate
size, coupled with the suitable timing of release to environmental
conditions.
Hatchery water supply places limitations on fry rearing.
Presently, more than 260 hatcheries, in total, use water for
incubation and fry rearing at a rate of 700 tons/min. This amountof water is sufficient to accommodate 4,400 million swim-up fry
or 1,200 million 0.6 g fry at 8°C. This is a problem because ourtarget for the number of fry to be released in the brood year 1983
is over 2,000 million. Since we cannot expect additional new
water resources in the future, we should consider actively the effective use of fry produced resulting in a high rate of return, therotation of fry production, re-use of water, and the use of
seawater.
The recent increase in salmon resources in Japan could only berealized through the enormous input of energy, directly and in-

Apri I

June

Figure S.-Distribution of surface-water isotherms in the seas of Japan during fry migration. Redrawn from data supplied by the Japan Oceanographic Data Center.

94

directly, into the system of artificial fry release. As we enter theera of energy conservation, we must consider costs associated withwater usage, human labor, and so forth, in relation to the production of healthy fry. Cost effective returns of quality salmon must
become an important consideration.

ITO. J.
1980. Investigation on the ecology of young chum salmon in transient stagesof offshore migration. Presented at annual meeting on the Salmon Enhancement Research Project. Tokyo. 4 p.
KOBA YASHI. T.
1976. Problems in the direction of technical development in salmon farming.
Presented at the 2d meeting of working group on the Anadromous Salmon
Enhancement. Tokyo. lOp.
1979. Salmon propagation in lapan.ln T. V. R. Pillay and W. A Dill (editors),
Advances in aquaculture. p. 554-560. FAO. Fish. News Books Ltd., Farnham. Engl.
KROGIUS. F. V.
196 I. On the relation between rate of growth and populalion density insalmon. Fish. Res. Board Can .• Transl. Sel. 4 I I. 16 p.

ACKNOWLEDGMENTS
I am particularly indebted to my colleagues, Tetsuo Kobayashi.
Hokkaido Salmon Hatchery; Jun Ito, Far Seas Fisheries ResearchLaboratory; and Takahiko Irie, Hokkaido Regional Fisheries
Research Laboratory, who suggested valuable information andcomments. I would like to extend my personal thanks to Byron
Sigel, Hiroshima University, for reading the manuscript.

LeBRASSEUR. R. J.• C. D. McALLISTER, W. E. BARRACLOUGH. O. D.
KENNEDY, J. MANZER, D. ROBINSON, and K. STEVENS.
1978. Enhancement of sockeye salmon (Oncorhynchus nerka) by lake fertilization in Great Central Lake: Summary report. J. Fish. Res. Board Can. 35:
1580- I 596.

LITERATURE CITED

MANZER, J. I.
1976. Preliminary results of studies on the effects of fertilization of anoligotrophic lake on adult sockeye salmon (Oncorhynchus nerka) production.
Can. Fish. Mar. Serv., Tech. Rep. 678, 25 p.

BILTON. H. T.
1978.

Returns of adult coho salmon in relation to mean size and time atrelease of juveniles. Can. Fish. Mar. Serv., Tech. Rep. 832, 73 p.
FOERSTER. R. E.
1954. On the relation of adult sockeye salmon (Oncorhynchus nerka) returns
to known smolt seaward migrations. l. Fish. Res. Board Can. I 1:339-350.
HIYAMA. Y., Y. NOSE. M. SHIMIZU. T. ISHIHARA. H. ABE, R. SATO, and T.
MAIWA.
1972. Predation of chum salmon fry during the course of its seaward migration. I. Otsuchi River investigation 196 I - I 963. Bull. lpn. Soc. Sci. Fish.
38:211-221
IJOKA,C.
1982. Characteristics of coastal homing of chum salmon from thc releases ofseapen-reared fingerlings. Presented at annual meeting on the Salmon
Enhancement Research Project, Tokyo. 3 p.

PARKER. R. R.
1962. A concept of the dynamics of pink salmon populations. In N. J. Wilimovsky (editor), Symposium on pink salmon. p. 203-2 I I. H. R. MacMillan
Leciures in Fisheries. Ins!. Fish. Univ. British Columbia.
REISENBICHLER. R. R.• J. D. MciNTYRE, and R. J. HALLOCK.
1982. Relation between size of chinook salmon. Oncorhynchus tshawy/scha.
released at hatcheries and returns to hatcheries and ocean fisheries. Calif.
Fish Game 68:57-59.
ROUNSEFELL, G. A.
1958. Factors causing decline in sockeye salmon of Karluk River, Alaska.
U.S. Fish Wildl. Serv., Fish. Bull. 58:83- 169.

95

An Electrophysiological Approach to the Olfactory
Recognition of Homestream Waters in Chum Salmon
KAzva VEDA'INTRODUCTION

Water samples tested were collected on the day of use from fiverivers, just upstream of the fish barriers, i.e., the Tsugaruishi
River, Origasa River, Otsuchi River, Kotsuchi River, andVnosumai River, and were kept at about 5°C until used. Water
samples and rinsing water (redistilled water), both of which were
kept at room temperature (17.5°-19.0°C), were infused alternately into the nasal cavity for 20 s at regular 30 s intervals at a flowrate of 0.6 mils. L-serine, reported to be an active component of
the repellent in mammalian skin extract for adult migrating
Pacific salmon (Brett and MacKinnon 1954; Idler et al. 1956),
was also used as a test solution.
Electrical activities were recorded through Ag-AgCI bipolarelectrodes (0.2 mm in diameter, 0.8 mm apart) from the olfaclory
bulb or telencephalon, ipsilateral to the stimulated naris; electricalresponses were recorded on an FM tape recorder through a
preamplifier for subsequent frequency analysis by a series of active band-pass filters (1/3 octave steps with attenuation rates of
65 dB/octave, see Kudo et al. 1972).

Behavioral studies have shown that salmon in the final freshwater stage of spawning migration can discriminate among stream
waters by utilizing an olfactory sense (see reviews by Hara 1971;
Hasler et al. 1978; Cooper and Hirsch 1982). Several attempts
have been made to find neurophysiological correlates in salmon
olfactory responses that are more or less characteristic of thequality of the odorants in the various stream waters (Hara et al.
1965; Veda et al. 1967; Oshima et al. 1969; Cooper and Hasler
1974; Dizon et al. 1973; Bodznick 1975). In these earlier studies
the amplitude of the response usually has been the exclusive
parameter studied. However, the amplitude of the response may
be of limited importance for studying the mechanism for discrimination of the quality of the stimulus since it varies greatly withthe changing intensities of the same stimulus. The analytical procedures using the magnitude of the olfactory responses as an index
have been criticized by Veda et al. (1971) and Veda (1982).
Recently, frequency analysis, a familiar technique in EEG dataprocessing, has been applied to characterization of the olfactorybulbar responses in fish as a function of frequency by using aseries of active band-pass filters (Veda et al. 1971; Kudo et al.
1972), by a Heterodyne-Wave-Analyzer (Satou and Veda 1975),
and by a Fourier transform on a digital computer (Kudo et al.
1972; Hara et aJ. 1973; Veda 1973; Kaji et aJ. 1975). These
reports have suggested that specific odor quality may be
associated with a characteristic response frequency spectrum.
In this paper I report a frequency analysis of the olfactory
responses of adult spawning salmon. In this study the band-passfilters were used in an attempt to decide whether it is possible torecognize a neural coding mechanism for olfactory discriminationof stream waters in terms of the frequency components of the
response.

MiyakoHeii River

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MATERIALS AND METHODS
Adult male chum salmon, Oncorhynchus keta, were taken fromthe Tsugaruishi River and the Otsuchi River (Tohoku district,Japan) in the early phase of their upstream migration. Seawater
chum salmon captured by set nets in Otsuchi Bay were also used.
They were transported in a 220 I oxygenated tank to the Otsuchi
Salmon and Trout Hatchery, where the experiments were performed (Fig. 1). No more than six fish were carried at one time.
They were kept in a large tank with a constant flow (450 mlls) of
well water for 12-48 h before use. The techniques for the operation and recording of electrical activity were essentially the sameas those described previously (Veda et aJ. 1971).

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where the rlShes (solid circles) and test water samptes (open circles) werecollected.

'Zoologicallnstitule, Faculty of Science, University of Tokyo. Tokyo. Japan.

97

RESULTS

the characteristic chemical features can be discriminated bysalmon among the different stream waters tested.

Spectral Analysis of Olfactory Responses
Recognition of homestream water.-In Figures 2 and 3 (seealso Figs. 5, 6), it is clear that lower frequency components(3.15-5.0 Hz, mainly 4-5 Hz) appeared only when stimulated withhome water. This finding suggests that activity of the frequency
component in this range shows a part of information reflecting thehome water memory (called, tentatively, memory wave) by whicha given stream water is recognized as the homestream water.
Figure 4 shows the typical responses of "seawater salmon" captured in the Otsuchi Bay, into which three rivers (Otsuchi, Kotsuchi, and Unosumai Rivers) are flowing (Fig. I). At this moment,
no one knows the home river, or natal stream to which he should
return. The spectral patterns of Figure 4, indicating the memory
wave in response to Otsuchi River, are fundamentally similar to
those of Figure 3 ("Otsuchi salmon"). Therefore, one may conclude that his homestream is Otsuchi River. The present method,
based on memory wave, can be used to guess the home river prior
to upstream migration.

Discrimination among stream waters.-Time-frequency
features "spectral patterns" of the responses to different waters
are shown in Figures 2-4.
Figure 2 shows the typical responses of the "Tsugaruishi
salmon," respectively to water samples from Tsugaruishi River(homestream water) (A), Origasa River (B), Otsuchi River (C),Kotsuchi River (0), Unosumai River (E), and to L-serine (F). The
frequency analysis indicated that there are recognizable different
spectral patterns for different stream waters and L-serine.
Figure 3 shows the typical responses of "Otsuchi salmon."Magnitudes of unprocessed responses to stream waters except
Otsuchi River (home water) were small. However, different spectral patterns were also observed, after the spectral analysis, in the
responses to different streams.
Since there are recognizable qualitative differences in the electrical responses of the brain to natural waters, this suggests that

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trace of each column shows the originat olfactory response to be frequency.analyzed. A, B, C, D, E, and F are the responses
to Tsugarulshi River (homestream water), Orlgssa River, Otsuchl River, Kotsuchi River, Unosumai River, and 0.02% sotu·
tion of L-serine. Traces from a to i show the frequency components within each response. The arrows indicate the onset ofstimulation. Electrode position, surface to the anterior telencephalon; calibration,S s and l~V. The ampliludes of Iraces athrough I are enlarged twice.

98

The data presented here may prove that there is a memorybased brain mechanism for the recognition of homestream water.

homestream odor is absorbed on activated carbon. When thehomestream water was passed through a mixed bed of ionexchange resin (IR 120B and IRA 402, by a ratio of 2 to I), thefish no longer responded to it.
When the homestream water was fractionated by vacuum
distillation at a low temperature (28 °_32 0q, the salmon consistently responded to the concentrate (nonvolatile fraction, adjusted to the original volume with redistilled water), but not to the
distillate (volatile fraction). Even if the distillation was carried out
with heating up about 80°C, the fish responded in the same way
to the concentrate (Fig. 6). Figure 6 shows that the spectral patterns of the bulbar responses to the homestream water (A) and to
its nonvolatile fraction (B) are very similar. The results indicatethat the homestream stimulant is a nonvolatile and heat-stable
substance. Successive experiments disclosed further that thehomestream stimulant(s) is insoluble in petroleum-ether and isdialyzable.
Using behavioral assays with adult sockeye salmon, Idler et al.
(1961) reported that the homestream stimulant(s) was volatile,
heat-labile, neutral, and dialyzable (see also Hasler 1971).
However, in further experiments with juvenile (Bodznick 1978)
and adult sockeye salmon (Fagerlund et al. 1963), it became clear

Stimulants in Homestream Water
Hasler and Wisby (1951) suggested that young salmon are "imprinted" by a distinctive odor in the homestream water; throughdiscrimination and memory, this serves later as a guide to theadult fish in orienting toward and reaching the homestream. So
the experiments were designed to develop a laboratory bioassay,
based on the spectral pattern, to facilitate the isolation and identification of the homestream odor(s).
Test water (homestream waters or their fractions) and rinse
water (distilled water) were infused alternately into the nasal cavity for 20 s at regular 30 s intervals. The electrical activity was
frequency-analyzed by means of a series of active band-passfilters. The experimental results obtained were the very same forall of the fish used (four Tsugaruishi and eight Otsuchi salmon). A
preliminary study was reported elsewhere (Ueda et al. 1979).
Figure 5 shows the spectral patterns of responses to homestream water before (A) or after (B) a treatment with activatedcarbon. Memory wave disappeared in (B). This indicates the

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Figure 3.-Spectral patterns of the olfactory responses. This specimen had homed to the Otsuchi River.
C is the response to homestream water (Otsuchi River). Electrode position, between the olfactory bulb
and the telencephalon; calibration, 5 s and 50 I'V. See Figure 2 for the other legends.

99

A~~~B~C~~'Tsu!:;aruishi River

IOrigasa River............ '" flO

•

tt

b
c

1.1t.

,.

d~
e

II"

I

11

r....,......

''''''" •• '1. . . . II

, ......

I.

I

II

_ •••••,++ ••.••••••

••

~ ••

to

'l

..

~

,

..............

.

Otsuchi RiverI•• "' •• "'.

II • • • • • t

III,

I . t ••II'"

II II.' •• t ..... " • ....

Illiia...

••'I '1. I.... " ..
It••... ... •• 1'1'" ..... I"i ••• g

• I

I'

I

I I

. . . . . .,-••_ ....I~I..I..._'_...I~.__,..'.I._•••........._11......._ ...._ _,..._ _'.....
, ..
,.

O~~E_

.,..IIl,I Kotsuchib'"
Figure 4.-Spectral patterns of the olfactory responses.
This specimen was captured in the Otsuchi Bay; transferred
directly to freshwater (well w2ter), and adapted in it for 24 h
before testin~. Electrode position, surface of the posterior
telencephalon; calibration,S s and 2~V. See Figure 2 forthe other legends.

,

River

_ . . . . . . . ••ct

dUll'.

..,,. 3.15-4.0'.11" 4.0-5.0"'1'.' ......"................
' -JlIIe •• ,r...", t-~+I
. . . '11 . . . . . ,. . . . . .

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,.

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i •••

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.

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I

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6 . 3 - 80

"I.

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(Hz)

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,

gill

t Unosumai River

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I'

III

'.4

II

10.0-12.5
12.5-16.0'1. .• 16.0-20.0

B

A

r

1

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...-

Hz

-----_--- _ _..--.

"'....... ...._ - .._-_ -.. _ ........_.......

• ....~-...•• _ _........- .._>--·~~~I....' ..

9 ._.--.-.~+-4hI'••. I..................-~~-¥ ••~- - -.., ~--_,~_"_"I"~

,

-,

'I" ,
,-

, . ,.

."........-

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-

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-.

II

...

'....

•......

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...
, .....,....._I- ,..I~...~>4. ......,. ....-... ••••

J. 1 5 .. 4

4 - 5

5 - 6.J

e...... . . . .. . . . .--_.---+t, •..

eJ. I 52.5 -••- I..~_-...................

• ..........-+.-4. ...,...,.....,...,. ..
, - -.....-.......-......-

6. J - 8
8 - 10
10 -

12.5

12. 5

-

16

16 .. 20

Figure 5.-Typical spectral pallerns of the olfactory responses to homestream water (Otsuchi River) before (A) and after (B) a treatment withactivated carhon. This specimen had homed to Otsuchi River. Electrode position, between the olfactory bu.lb and the telencephalon; calibration, 10s and 5~ V. See Figure 2 for the other legends.

100

A

c

B
-::11

~'X~~~~,ij»_WWJ;~M~~ ~i-~l~~~~~,~~II

1
J. . . . . ~, ..-';\\\.". -........ AA~~.Jv-NIN..-~b ~l\'-- 'IN$ 'W!1'

#til

'r

.vv.

_______..
""......,.......__- - - - ~.5-3.15

II IN:".......~ .
e~q...... '••• If~~'"'1 I••••

g~~

, •••

h~~..-.ct ...

I. I • • • •i~~O"""'1. . -+.,..•

~

,
I

o.~.~

l

-... •. till."" .... • ••. ..-t--5
II'.' •••• '.. •.•.
• ••. . . . . I" I_____I I' .... '.. . • t,~ • • 1.

I . . . . . . I ••

0 I

• ••

I"

5-6.3

'1 .. ~6.3-8.e•118-10•.....--....-._..-.- - - - - -....- - 10--12.5••••--,.., · · - - - - - - · - '..·12.5-16

Figure 6.-Typical spectral patterns of the olfactory responses to homestream water and its fractions. This specimen had homed to
Tsugaruishi River. A, B, and C are the responses to homestream water (Tsugarulshl River), its nonvolatile fraction, and volatile fraction,
respectively. Homestream water was fractionated at7S·C. Electrode position, 0.86 mm below the surface ofthe posterior olfactory bulb;
calibration, 10 sand loo,..V. See Figure 2 for the other legends.

Further studies are needed to characterize the homestream
stimulant(s).

that the nonvolatile fraction was also important. Moreover,
Cooper et al. (1974) have indicated, based on the amplitude ofolfactory bulbar EEG of spawning coho salmon, that the stimulatory portion of the homestream water is nonvolatile.
Some inconsistency of the results between our electrophysiological assay and behavioral ones may be either because the active
stimulant(s) is characteristic for each species or because of thedifferences in the bioassay method. The method used by Fagerlund et al. (1963) and Idler et al. (1961) seems to have serious
defects; for instance, it was found that the behavioral response tohomestream water, adopted as an indicator, was indistinguishable
from that elicited by temperature changes of the test water.
Nordeng (1971), Solomon (1973), and Dl2lving et al. (1974)
have suggested that pheromones are used for homing. In the present experiment, however, the water samples tested were all collected upstream of the fish barrier where there were no adultspawning salmon. No young fish of the same species are known toremain in the river at this time of the year, since fingerlings
released in the spring migrate immediately toward the sea. Therefore, it seems likely that the stream water samples used in thepresent experiments contained olfactory stimulants other than theputative conspecific pheromones suggested by Dl2lving et al.
(1974). However, it is not yet possible to rule out heterospecificfish pheromones as possible olfactory cues.
Hasler and his colleague have reported that coho salmon may
imprint to morpholine in the same way as they do to naturally
occurring homestream odors (see reviews by Hasler et al. 1978;
Cooper and Hirsch 1982). By contrast, Hara (1974) and Hara andMacdonald (1975) have concluded, based on characteristic differences between olfactory bulbar responses induced by morpholine
and natural olfactory stimulants, that the morpholine effect is probably caused by a mechanism not directly associated with normal
olfactory function. In fact, morpholine is an irritant and corrosive
to mucous membranes such as olfactory epithelium.

SUMMARY
1) The electrical responses of the olfactory center of spawning
chum salmon, Onchorhynchus keta, induced by the nasal infusionof various stream waters were frequency-analyzed by a series ofactive band-pass filters to investigate whether there is any neurophysiological coding in the discrimination of stream waters.
2) Temporal changes in each frequency component "spectral
patterns" seemed to characterize a quality of the stream waters.
3) Lower frequency components (3.\5-5.0 Hz) appeared only
when stimulated with homestream water. They may indicate apart of the brain information by which the salmon can recognize,or identify one of the stream waters as their homestream water
through "memory" imprinted at the young freshwater stage andretained until the spawning migration.
4) The analyses suggest that olfactory function in migrating
chum salmon is useful in discriminating among various stream
wate~s and in recognizing the homestream water.
5) A bioassay based on the spectral pattern was performed todetermine the homestream stimulant(s). The stimulant(s) is absorbed on activated carbon and ion-exchange resin, insoluble inpetroleum-ether, dialyzable, nonvolatile, and heat-stable.

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101

BRETT, J. R., and D. MacKINNON.
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102'GPO 593-081 1985