A Historical Perspective on Salmonid Production from Pacific Rim Hatcheries
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A Historical Perspective on Salmonid Production
from Pacific Rim Hatcheries
Conrad Mahnkenl, Gregory Ruggerone2 , William Waknitzl, and Thomas Flagg l
lNorthwest Fisheries Science Center, 2725 Montlake Boulevard East
Seattle Washington, 98112-2097, U.S.A.
2Natural Resource Consultants, 4055 21st Avenue West
Seattle, Washington, 98199, U.S.A.
Mahnken, C., G. Ruggerone, W. Waknitz, and T. Flagg. 1998. A historical perspective on salmonid
production from Pacific rim hatcheries. N. Pac. Anadr. Fish Comm. Bull. No.1: 38-53
Annual hatchery production rates of chinook (Oncorhynchus tshawytscha), coho (0. kisutch) ,
sockeye (0. nerka) , pink (0. gorbuscha) , chum (0. keta), masu (0. masu} salmon, and steelhead trout
(0. mykiss} were obtained from published and unpublished sources and compiled as a computer
database. Pacific Rim hatchery production trends for the 40-year period from 1950-1992 were
analyzed for all species from four geographic areas: Pacific Northwest (Washington, Oregon, Idaho,
and California), Canada (British Columbia), Alaska, and Japan (Honshu and Hokkaido). Production
of chum, sockeye, and pink salmon has increased dramatically in Japan, Canada, and Alaska in the
past 20 years. Chinook, coho, steelhead, and masu have also experienced moderate increases in the
same time period; however, production of coho, chinook and steelhead has declined since 1985.
Trends in survival of hatchery fish over the period 1970-90 are demonstrated where data were
available. We noted that survival of coho salmon was greatest for releases into large estuaries, such
as southeast Alaska, Georgia Strait, and Puget Sound, than into drainages discharging directly into the
Eastern Pacific Ocean. A negative cline in survival of coho salmon was observed moving both north
and south from the center of the distribution of the species in British Columbia. Survival trends for fall
chinook released north of Puget Sound tended to be the opposite of those released to the south.
Survival of Japanese chum salmon released into the North Pacific Ocean has increased steadily from
the mid-1960's to the present.
INTRODUCTION Alaska, declining fish size and altered return timing
and age at maturity, have raised concerns over limits
Development of the North Pacific sahnonid on ocean carrying capacity.
hatchery system began in the late 19th century and has In the Pacific Northwest, recent Endangered
played a prominent role in enhancement of the Species Act listings of Redfish Lake sockeye in the
salmonid resource in Pacific Rim nations since the Stanley Basin of Idaho, Sacramento River winter
1950s. Until recently, the artificial propagation chinook in California, and fall, summer, and spring
approach to enhancement of fisheries has not been runs of chinook in the Snake River Basin of Idaho and
seriously questioned, but the recent alarming declines Oregon have focused attention not only on habitat loss
in wild spawning stocks have forced a re-evaluation of and fishery-related impacts on the wild stock" but on
industrial-scale hatchery production of north Pacific the genetic and demographic consequences of
sahnonids. Declines have been observed in chinook, uncontrolled expansion of hatcheries as well (Meffe
coho, and sockeye sahnon stocks in the Pacific 1992; Nehlsen et al. 1991). Proposed recovery plans
Northwest; high harvest rates of wild fish in fisheries for listed Snake River chinooks and sockeye call for a
targeted on the more abundant hatchery stock., have limit on annual releases from Columbia Basin
continued, and high production of hatchery chum hatcheries to 1994 levels (Schmitten et al. 1995).
sahnon in Japan and both pinks and chum sahnon in In Alaska, the hatchery successes that were hailed
38in the mid 1980s are being assailed in the 1990s. The and Oceans, 555 West Hastings Street, Vancouver,
return of record numbers of hatchery pink and chum B.C., Pers. commun., Oct. 1996). Japanese release
salmon and high abundance of natural fish in the information on chum and pink salmon was supplied by
North Pacific has led to record high catches and the Hokkaido Salmon Hatchery (Masahide Kaeriyama
record low revenues to fishermen, and has brought and Shigihiko Urawa, Hokkaido Salmon Hatchery, 2-
forward new criticism of hatchery management 2 Nakano shima , Toyohira-ku, Sapporo 062, Japan,
strategies. Concerns over decreasing fish size in the Pers. commun., Oct., 1996).
hatchery-based fishery for chum salmon in northern Until recently, a consolidated data set for hatchery
Japan has led to a decision by the Japanese production has been unavailable for the western
government to reduce hatchery releases. Similar United States (Wahle and Smith 1979; Malmken et al.
concerns for declining size and increasing age at 1983; Isaksson 1988). We compiled a comprehensive
maturity observed in North Pacific stocks of five historical data set from previously unreported raw data
salmon species suggests that large-scale hatchery forms archived by fishery agencies, annual reports of
production is resulting in density-dependant growth hatcheries, and electronic databases. We obtained
reduction (Kaeriyama and Urawa 1992; Bigler et al. earlier salmon release records from Oregon and Idaho
1996). and steelhead from Washington which were previously
This report provides managers with an historical not available.
data set of hatchery releases from Pacific Rim nations,
excluding Russia, for the six Pacific salmon species Survival Data
and steelhead through 1992. In addition, an analysis
of survival trends for hatchery coho and fall chinook Survival information for coho and chinook salmon
from the eastern Pacific and chum from Japan are was obtained from coded wire tag (CWT) data bases
presented. maintained by the Pacific States Marine Fisheries
Commission. The historical CWT data set was
METHODS assembled by Maria Claribel Coronado-Hernandez
(1995) and is contained in her doctoral dissertation.
Release Data This seminal work synthesizes and analyzes, for the
first time, spatial and temporal factors affecting
Annual production rates from Pacific Rim survival of hatchery-reared chinook and coho salmon
hatcheries were obtained for six species of Pacific and steelhead in western North America over the time
salmon: chinook (Oncorhynchus tshawytscha), coho period for which coded wire tag recoveries are
(0. ldsutch) , sockeye, (0. nerka) , pink (0. available (1971-1989). Release-recovery information
gorbuscha) , chum (0. keta) , masu (0. masu), and is presented in the form of expanded CWT recoveries
steelhead trout (0. myldss). We compiled this using only non-experimental production groups.
information from published and unpublished sources Recoveries were standardized to the most common age
and organized it in a computer database. Production at return using virtual population analysis (Coronado-
trends for the 40-year period from 1950-1990 were Hernandez 1995).
analyzed for all species from four geographic areas: We computed mean survival rates from this data
Pacific Northwest (Washington, Oregon, Idaho, and set and used two-way analysis of variance to make
California), Canada (British Columbia), Alaska, and statistical comparisons of mean survival values over
Japan (Honshu and Hokkaido). Data from Russia and time. We chose coho and fall chinook salmon for
Korea were unavailable as a continuous historical analysis of temporal and geographic variatIOn because
series, however discontinuous data were available of the large data sets available for these species.
from three sources and were used to estimate total Pairwise comparisons between sampling dates were
present Pacific Rim output (Heard 1995; Malmken et made using the Fishers PLSD test. All statements
al. 1983; Konovalov 1980). about statistical comparisons are based on the P
Release data from Alaska for chum, pink, coho, < 0.05 significance level.
sockeye, and chinook salmon were obtained through Survival data for Japanese chum salmon was
Alaska Department of Fish and Game annual reports provided by the Hokkaido Salmon Hatchery
(McNair 1996). Alaska steelhead releases were (Masahide Kaeriyama and Shigihiko Urawa, Hokkaido
supplied by Alaska Department of Fish and Game Salmon Hatchery, 2-2 Nakanoshima, Toyohira-ku,
(Marianne McNair, Alaska Department of Fish and Sapporo 062, Japan, Pers. commun., Oct., 1996).
Game, P.O. Box 25526 Juneau Alaska, Pers. These data were compiled through records of fishery
commun., Oct., 1996). Release data for all species catch and hatchery escapement to the Japanese coastal
from British Columbia were provided by Canadian net fishery and to Hokkaido and Honshu hatcheries,
Fisheries and Oceans (Ted Perry, Canadian Fisheries respectively.
39NPAFC Bulletin No.1 Mahnken et al. (1998)
RESULTS - HISTORICAL PRODUCTION OF decline can be attributed to various factors: Survival
PACIFIC SALMON AT PACIFIC RIM of adult hatchery fish declined following the oceanic
HATCHERIES regime shift in 1976 and a series of EI Nmos events in
the late 1970s and early 1980s. These conditions
Coho Salmon resulted in reduced escapement, and hatcheries were
unable to meet egg needs for full production. More
Coho salmon are among the most successful of restrictive inter-basin egg transfer policies were
hatchery-cultivated species in the Pacific Northwest introduced to protect remaining wild populations, and
and Canada. Coho salmon hatcheries were highly reduced operating budgets at some hatcheries further
successful in returning adults to the fisheries in the reduced coho salmon production.
1970s, when record smolt-to-adult survivals were
recorded in the British Columbia and Puget Sound Chinook salmon
regions.
Coho salmon production in western North Like coho salmon, chinook salmon are released
America grew slowly from its inception at the tum of either as fry or as yearling smolts. Chinook salmon
the century, and before 1940 the output from were the first salmon species to be artificially
hatcheries never exceeded about 25 million fish propagated in western north America and are
annually (Fig. lA). The slow rate of growth can be artificially propagated in hatcheries along the eastern
attributed to failure of hatcheries to contribute to Pacific seaboard from California to Alaska. More
expansion of the fishery (McNeil and Bailey 1975). chinook salmon have been produced from hatcheries
Following a period of reduced production during than any other species in the Pacific Northwest. The
World War II, coho salmon hatcheries entered an first effort to artificially propagate chinook salmon in
industrial phase of expansion that lasted through the North America was at the Baird Fish Hatchery on the
1970s. McCloud River in California in 1872. This hatchery
In the 1950s and 1960s, advances in the was established to obtain chinook salmon eggs for
knowledge of feeds, diseases, and the early life history transport to Atlantic Ocean tributaries to replace
culture requirements of coho salmon led to improved depleted Atlantic salmon (Salmo salar) runs. Today,
post-release survival of hatchery fish (Lichatowich and the center of hatchery production is the Columbia
McIntyre 1987). Coho salmon are released either as River Basin where approximately 27 % of world
fry or as yearling smolts (25-30 g) and size at release chinook salmon is produced.
had also been increased over the years and contributed Fall chinook are the most commonly cultured life
to improved adult survival (Wahle and Smith 1979). history type in both British Columbia and the Pacific
These achievements were even more important in that Northwest. Also known as "ocean-type" (Healey
they coincided with a period of rapid deterioration of 1991), fall chinook salmon most frequently inhabit
freshwater habitat and blockage of major migratory coastal rivers, although ocean-type fish are cultured in
pathways by hydroelectric dams. Given these the Columbia River as far upstream as the Methow
successes, fishery managers came to believe that River. Fall chinook salmon are sometimes released as
hatcheries were a means by which the Pacific fry but are more commonly reared for three months
Northwest could continue to develop its water and released at hatcheries in the spring at
resources for power, irrigation, and industrial or approximately 7-10 g. To improve survival, some
domestic use and at the same time, maintain fisheries hatchery populations of fall chinook are reared to
at historic levels (Lichatowich and McIntyre 1987). yearling size and generally released in the spring at
Increased reliance on hatchery coho salmon led to the 25-30 g as age-l smolts (Wahle and Smith 1979).
rapid expansion of production through the 1970s. In Spring and summer chinook salmon, or "stream-
the late 1970s and early 1980s, private sea ranches type" life history stocks (Healey 1991), are produced
added 9.3 million smolts per year to Oregon coastal at hatcheries located primarily on large river systems
production (Fig. lA) and helped lead to a record of the Pacific Northwest, British Columbia, and
production of 198 million hatchery coho salmon in Alaska. Spring chinook salmon are the predominant
1981. In the years that followed however, coho stocks produced in Alaskan hatcheries. Spring and
salmon production in the Pacific Northwest stabilized summer stocks of chinook salmon are seldom released
and began to decline (Fig. lA). as underyearlings and are grown in hatcheries to the
Begmning in 1989, a period of declining largest size, often over 100 g average, of any of the
production began in most sectors of the coho salmon Pacific salmon species (NRC, 1995). Underyearling
hatchery system. The decline in overall production releases have been attempted at hatcheries where high
from the contiguous western United States was rearing water temperatures result in accelerated
partially offset by the added production of 40 million growth, but survival to adult from releases of these
hatchery fish from Alaska and British Columbia. This intermediate sized fish is generally lower than those of
40larger yearling fish (Zaugg et al. 1985, Coulee dam and other mid-Columbia hydroelectric
1986). projects. Between 1960 and 1976, 30 hatcheries and
Hatchery production of chinook sahnon began in 12 rearing ponds raised anadromous sahnonids in this
Washington State in 1895 at the Kalama hatchery on region (Wahle and Smith 1979). Another surge in
the Columbia River, and production grew slowly to production occurred in Puget Sound hatcheries in
around 50 million fish released until the late 1930's Washington State during the 1960s. New lower
(Fig. lB). Production dropped slightly during World Columbia River hatcheries and growing production in
War II, then accelerated following improvements in other sectors of the Pacific Northwest drove annual
culture technology and construction of new hatcheries. releases to more than 300 million chinook salmon
The decade of 1950-1960 began the industrial phase of smolts by the early 1980s. Production increases from
chinook sahnon hatchery production, as development British Columbia and Alaska hatcheries in the 1980s
in the Pacific Northwest resulted in loss of freshwater added another 100 million fish annually. By 1988,
habitat. Growth of the fisheries also added pressure when production peaked, more than 420 million fry,
to the hatchery system to increase production. New fingerling, and smolts were being released from
hatcheries on the middle Columbia River were eastern Pacific hatcheries, a seven-fold increase from
constructed to mitigate for lost habitat above Grand the base level of 59 million fish released in 1949.
Fig. 1 Hatchery production of (A) coho salmon and (B) chinook salmon juveniles from Pacific Northwest, British
Columbia, and Alaska hatcheries, 1990-1992.
200~--------------------------------~--~
A COHO SALMON
150
.. PACIFIC NORTHWEST
G
U 100NPAFe Bulletin No.1 Mahnken et al. (1998)
Chinook salmon hatchery production began to decline Japan. Another interesting feature of the Japanese
in the late 1980s for the same reasons that coho hatchery system is that it has reduced reliance on high-
salmon production is now falling. seas fisheries. The imposition of foreign EEZs has
restricted the Japanese high-seas fishery on chum
Chum salmon salmon destined for Russia and North America, but
the loss to the national fishery has been more than
From the late 1880s until the recent expansion of replaced by hatcheries.
chum salmon ranching in Japan, hatcheries released In North America, enhancement efforts for chum
fry from rearing ponds to the stream soon after yolk salmon also accelerated in the 1970s, primarily in
sac absorption. Egg and fry development was Alaska and British Columbia (Fig. 2A), adding an
accelerated in Hokkaido through the use of constant, additional 850 million fry to the already impressive
8°C ground water. These condition favored releases releases by Japan for a total Pacific Rim production of
from early to mid-February when fry were sometimes nearly three billion chum salmon fry (exclusive of
subjected to severe conditions in the streams and Russian hatchery releases).
coastal marine waters. With temperatures as low as 0-
SoC during February and March, survival was Pink salmon
minimal. In 1962, production-scale hatchery
experiments were undertaken to delay release to a Pink salmon are second to chum salmon in the
time of more favorable sea temperatures. These numbers of juveniles released into the North Pacific
experiments involved feeding up to 300 million fry for Ocean; accounting for 29% of the total reported in
short periods (Mayama 1985) and demonstrated that 1992 (Heard 1995). Pink salmon are released from
dry diets could increase body weight from 0.6 to 1.0 most hatcheries at 0.5-2.0 g size (Isaksson 1988).
g in about one month. Fry fed on these diets could be Alaska is the largest producer of pink salmon and
released from Hokkaido hatcheries in May, when released more than 800 million juveniles in 1992
coastal water temperatures exceeded 10°C. These fry (Heard 1995; McNair 1996). Heard (1995) also notes
are usually released 50 d before average sea surface that Russia is the second largest producer of hatchery
temperature reaches 15°C. Larger fish of 2-3 g pinks; with 584 million juveniles released in 1992.
average weight released .to coastal waters during Pink salmon releases remained low (less than 100
spring periods of high primary and secondary million) until the early 1980s, when an
productivity survived at a much higher rate than industrialization period began in Alaska, and numbers
smaller ones. Adult returns from unfed fry released of released fish from North America increased tenfold
in 1950-60 averaged 1.2%; returns improved to 2.3% to a total of 1.006 billion in 1992 (Fig. 2B). When
after 1966 as the percentage of fed fish increased added to Russian production, total world production
(Isaksson 1988). of pink salmon was 1.590 billion produced in 1992.
Japanese chum salmon catch was high prior to Pink salmon is the most recent of the Pacific salmon
World War II, but dropped during the war years. species to be industrially produced.
Following the war, catch increased for a few years, Sockeye salmon
then decreased as stocks were overexploited.
Beginning in the 1970s, catch of Asian chum salmon Sockeye salmon were propagated in Alaska before
rose again, primarily as a result of massive Japanese the tum of the century to enhance existing runs, and
hatchery releases. From 1950 until 1970 Japanese millions of eggs were sent to the Atlantic coast in an
hatchery production rose from 260 million fish attempt to establish runs there (Roppel 1982).
released to around 580 million (Fig. 2A). Following However, initial culture efforts in Alaska were
improvements in adult contribution through the release unsuccessful, and sockeye salmon programs were
of fed fry, and the loss of foreign fishing grounds to discontinued early in the 20th century (Allee 1990).
exclusive economic zones (EEZs), the Japanese chum Similarly, 11 sockeye salmon hatcheries built in
salmon hatchery system entered a phase of rapid British Columbia before 1917 produced no consistent
industrialization. Production rose from 260 million benefits, and production ceased soon thereafter
fry released in 1970 to 2 billion released in 1981. (Foerster 1968). In Washington, artificial propagation
After the early 1980s, Japanese production of chum of sockeye salmon began in 1896 at the Baker Lake
salmon leveled off. Station in the Skagit River basin and continued until
The Japanese hatchery system is the largest in the this facility was closed in 1933. In addition to
world in terms of fish released and returned 78 million supplementing the run of sockeye salmon to Baker
adult fish to the Japanese coastal fisheries in 1995 Lake, this facility was the source for the sockeye
(H. Urawa, pers. commun.). The Japanese land- salmon introduced into Lake Washington where a
based fishery is almost entirely hatchery-dependant; strong run was eventually established (Kemmerich
wild stocks are virtually non-existent in northern 1945).
42Fig. 2 Hatchery production of (A) chum salmon and (B) pink salmon juveniles from Pacific Northwest, British
Columbia, Alaska, and Japanese hatcheries, 1950-1993.
3000~------------------------------------~
2500 A CHUM SALMON
2000
PACIFIC NORTHWEST
v(!) 1500 D BRITISH COLUMBIA
V') ALASKA
o(!) 1000 I2l JAPAN
(!) 500
0::::
..c
.-
V')
UL 1250~--------------------------------------~
"+-
o
C 1000 B PINK SALMON
o
750
500 o PACIFIC NORTHWEST
o BRITISH COLUMBIA
[] ALASKA
250 fa JAPAN
IJ')
IJ')
o IJ')
CO CO
0-. 0-. 0-.
Release Year
Sockeye salmon culture began in the Columbia programs for any species in the PacIfic Northwest.
River in the 1940s at the Leavenworth Hatchery in Recent attempts to reinvigorate sockeye salmon
eastern Washington state. This production effort culture program in the Pacific Northwest include a
attempted to mitigate for losses of sockeye due to combined hatchery and net-pen culture system
construction of hydroelectric dams on the middle operated by the State of Washington in Lake
Columbia River (Mullan 1986). Smolts were Wenatchee and a recovery program for the
for a period of about 20 years, but disease endangered Redfish Lake sockeye salmon in Idaho's
and low returns forced abandonment of the program Stanley Basin (Flagg et al. 1991, 1995).
the 1960s. Small smolt and fry-release programs British Columbia is now by far the largest
still exist for sockeye in Puget Sound and on the producer of artificially propagated sockeye salmon,
Washington coast, but by and large, sockeye salmon producing more than 290 million fry in 1993 (Fig.
culture in the Pacific Northwest is insignificant. 3A). Fry are produced ill spawning channels
Along with pink salmon, sockeye salmon production containing gravel substrates, where returning adults
constitutes one of the smallest artificial propagation spawn naturally. Fry are allowed to migrate
43NPAFCBulletinNo.l Mahnken et al. (1998)
volitionally out of the channels upon swimup, usually 75 million smolts in 1994, or 21 % of total North
into a lake. Spawning-channel culture of sockeye American production (Fig. 3A). Alaska also releases
salmon in British Columbia constitutes the least age-O sockeye after brief holding in sea-pens.
invasive culture technique used to mass culture Pacific
salmon. These extensive artificial propagation Steelhead and masu salmon
techniques require no feed, use natural spawning
substrates, and require no handling of either juveniles Hatchery steelhead are produced entirely in North
or adults during rearing. Although spawning-channel America (Fig. 3B), while masu salmon are only
culture of sockeye was initiated prior to the 1950s, the produced in significant numbers in Japan (Fig. 4). In
pro gram did not accelerate until the 1960s when terms of total production, steelhead and masu salmon
output increased from 2 million fry in 1960 to 258 are minor species, but in terms of their contribution to
million in 1980 (Fig. 3A). regional fisheries, steelhead programs are important
The Alaskan hatchery system is now the major and produced an estimated 738,000 adults annually
producer of sockeye smolts in North America, and from 1978 to 1987 (Light 1989). Like coho salmon
although a recent entrant (1974) into large-scale and chinook salmon, steelhead coho salmon and
sockeye production, has grown rapidly and produced chinook salmon, steelhead coho salmon and chinook
Fig. 3 Hatchery production of (A) sockeye salmon and (B) steelhead salmon juveniles from Pacific Northwest, British
Columbia, and Alaska hatcheries and spawning channels, 1900·1992.
400
300
A SOCKEYE SALMON
[] PACIFIC NORTHWEST
200 fIl BRITISH COLUMBIA
• ALASKA
100
O+---~-'~~-=F=~~~~--~
40~----------------------------------------~
V')
C B STEElHEAD TROUT
o 30
[J PACIFIC NORTHWEST
20 1m BRITISH COLUMBIA
• ALASKA
10
O~~~~~~~~~~~~~~~~~~~~
o o
8
~ ~
ll')
~
Release Year
44Fig. 4 Production of masu salmon juveniles from Japanese hatcheries, 1960-1992.
20
"'0 MASU SALMONFig.5 Total hatchery production of coho, steelhead, masu, sockeye, chinook, pink, and chum salmon juveniles from the
Pacific Northwest, British Columbia, Alaska, and Japan, 1950-1992.
5000.-------------------------------------~
ALL SPECIES
"'0Fig. 6 Mean survival (coded-wire tags) of coho salmon released from Pacific coast hatcheries 1970-1990. (A) Georgia
Strait estuary, coastal regions of north British Columbia/outer Vancouver IslandlWashington, and coastal regions
of Oregon/California. (B) Puget Sound and the Columbia River. Error bars are 1 standard error. Asterisks denote
differences (P
.-
>
~
~
(/')
-+- 0
C 15
(l)
--0-
__......_- PUGET SOUND
U
~
(l)
.
COLUMBIA RIVER
B
0-
10
Year
stock survivals fluctuate widely and exhibit a severe Strait of Georgia, Puget Sound, and southeast Alaska.
decline in the 1980s, they remained more than twice These areas are known to be excellent areas for
as productive (approximately 5 %) as the coastal stocks juvenile rearing and for survival of sahnonids (Healey,
(approximately 2%) until 1987. After 1987, all stocks 1980; Simenstead et aI., 1982), with relatively high
declined to survivals around 2 %. survivals of 5.5-7.5% during this period.
A comparison of bi-decadal mean survival by
region revealed another interesting feature of hatchery Fall chinook salmon
coho sahnon releases from 1970-90 (Fig. When
arranged in order of declining Fan chinook sahnon exhibit different
latItudinal clines appeared among the coastal stocks, survival characteristics from coho sahnon. Because of
both north and south from the center of the geographic smaller size at release, surVIval of hatchery fall
distributIon of the species, at about the latitude of chinook sahnon is less than that of coho sahnon.
Vancouver Island. This region had the highest Furthermore, survivals and trends in survival are
survival (4%), with coastal California and coastal distinctly different between fall chinook sahnon
Alaska (at either end of the geographic having ._...._.J stocks north of Sound and those to the
the lowest survivals, at 1-1. 5 %. Latitudinal anomolies south 8). SurVIvals in Puger Sound,
were observed in large coastal estuaries such as the Strait of Georgia and outer Vancouver Island ill the
47NPAFC Bulletin No.1 Mahnken et al. (1998)
Fig. 7 Mean survival of hatchery coho salmon by region, 1970-1990.
9,--------------,-------------------------,
8- ....
7-
...• T
0 •
.L T
.>
2:
6-
• •1T
.L
Coastal
:::> 5-
T
en
C
4- •
.L
0 3-
0
« J: I-
CI::
0
!!:
-'
tti t;; iii V)
« « -'
«
(5
V)
« uZ V)
«
....
CI::
«
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~
:::>
-'
0
U
3:
-'
«
0
U a«
-' U
-'
«
t;;
t;;
«
0
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V)
l- V)
U
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u
0 0
u
mid-1970s at between 3-4%, then declined sharply to satiation of predators at higher levels of juvenile
less than 2 % in the 1980s following the EI Nifio of production. However, Kaeriyama (1996) presented
1977 (Fig. 8A). A further decline to about 0.5% evidence that other life history characteristics of
survival followed the 1983 EI Nifio and survival has enhanced chum salmon, namely decreased body size
continued downward since. Stocks south of Puget and an increase of age-at-maturity may indicate the
Sound showed the opposite trend, with survival rates beginning of a density-dependant effect of continued
of less than 1 % through 1982 rising to around 2% large-scale releases from Japanese hatcheries.
following the 1983 El Nifio (Fig. 8B). It appears that
the 1983 El Nifio acted to enhance survival of DISCUSSION
southern fall chinook salmon in the mid-1980s rather
than to decrease survival. However, mean survival of Researchers from North America and Japan have
fall chinook salmon, aggregated by region, failed to noted the dramatic decline in salmon stock abundance
show the same geographic cline as that of coho and body size in the southern portion of the species
salmon. range in North America. These declines have been
especially apparent over the past two decades (NeWsen
Chum salmon et al. 1991; Bigler et al. 1996; Ricker 1981).
However, while the abundance of stocks in the Pacific
Survival of chum salmon released from Hokkaido Northwest has declined, the abundance of populations
hatcheries has followed a trend that appears to be less to the north, both in Asia and North America, remain
influenced by ocean conditions and more by healthy and some have reached historical highs (Heard
improvements in hatchery technology (Figure 9). 1995; Kaeriyama and Urawa 1992; Burger and
Survival of Hokkaido chum salmon has risen Wertheimer 1995; Zorpette 1995). Attempts have
uniformly from 2.5 to 4% from 1965-1988, a period been made to assess the cause of these declines based
in which production increased from 550 to 970 million on changes in freshwater conditions, fishing, or on
fry released. The number of juveniles released and variations in the marine environment (Beamish and
their survival both increased with time. This apparent Bouillon 1993; Cooper and Johnson 1992; Johnson
inverse density-dependant survival has been noted by 1984; Lawson 1993; Lichatowich 1993; Nickelson
McNeil (1991) who suggests that the relationship may 1986; Northcote and Atagi 1994; Pearcy 1992;
be an artifact of improved hatchery technology, or Richards and Olsen 1993; Olsen and Richards 1994;
48Fig.8 Mean survival (coded-wire tags) of fall chinook salmon released from Pacific coast hatcheries 1970-1990. (A) Puget
Sound, Strait of Georgia, and outer Vancouver Island regions. (B) upper and lower Columbia River, and Washington
and Oregon coastal regions. Error bars are omitted for simplicity. Asterisks denote differences (P
.-
>
I.-
::)
V) 0
-+- 3
C
Q)
U 2.5
I.-
B
Q) ----.--- UPPER COLUMBIA RIVER
CL 2
--0-- OREGON COASTAL
-a- WASHINGTON COASTAL
1.5 --+--- LOWER COLUMBIA R.
0.5
o l.{') o
CO CO 0-..
0-.. 0-.. 0-..
Year
Fig.9 Mean survival of chum salmon released from Japanese hatcheries in Hokkaido, 1963-1988.
5
HOKKAIDO CHUM SALMON
0 4
.2:
2:
::J 3
-
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49NPAFe Bulletin No.1 Mahnken et al. (1998)
Francis and Sibley 1991; Kaeriyama 1996). Most Nino events is most evident in regions where survival
researchers have concluded that, whatever the major has been historically high (southeast Alaska and
factor(s) affecting survival of Pacific salmonids, they Georgia Strait following the 1982-83 EI Nino, Puget
are most likely to occur in the ocean environment. Sound following the 1976-77 EI Nino). In the past 40
Cooper and Johnson (1992), compared trends in years, nine EI Ninos have affected the coastal regions
abundance of Washington, Oregon, and British of the eastern Pacific. In the 1970s and 1980s, the
Columbia steelhead and concluded that there were coastal regions of the Pacific Northwest and Canada
similarities in trends over the entire geographic range have been beset by a series of four moderate-to-strong
that indicated common factors were responsible for the El Nino events, most notably the 1982-83 EI Nino,
observed changes in survival. Because freshwater, which by many measures was the strongest this
estuarine, and nearshore conditions differ considerably century. Since 1970, El Ninos have occurred in 1972-
from year to year within this region, they concluded 73, 1976-77, 1982-83, and 1987-88.
that these factors alone could not explain the A strong negative cline in survival of coho salmon
similarities in steelhead survivals. They suggested is observed moving both north and south from the
that similarities in steelhead abundance trends in center of the species distribution in British Columbia,
widely separated geographical regions indicated that with stocks in western Alaska and California
common factors were responsible for the observed exhibiting the lowest survival. Fall chinook salmon,
declines, and that oceanic conditions were responsible. on the other hand, do not show the same strong
Olsen and Richards (1994) came to a similar latitudinal cline.
conclusion while working with aggregated coastwide Fall chinook salmon survival, although apparently
chinook salmon production data, namely that similar also affected by EI Nino events, seems directed by
chinook salmon run-size trends can be observed other external factors. Stock survival north of the
between several west coast river basins, and that the Columbia River peaked in the mid 1970s, while
data support the hypothesis that ocean conditions have survival for regions south of the river peaked in the
had a marked and uniform impact on chinook salmon mid-1980s. Furthermore, mean survival of fall
production in the Pacific Northwest. Lichatowich chinook salmon aggregated by region failed to show
(1993) has pointed out that the magnitude of oceanic the same geographic cline as coho salmon. The Strait
environmental changes and their impacts on salmon of Georgia estuary produced highest survivals, but
survival may be so large as to mask changes that Puget Sound fall chinook salmon did not produce
occur in the freshwater habitat. He cautioned that this higher survivals than Coastal Oregon, and produced
may cause managers to falsely attribute increased only slightly better survival than outer Vancouver
ocean survival to restoration effects in freshwater. Island or coastal California. This is surprising, given
Hilborn et al. (1993) further emphasizes the same the well-documented importance of estuaries for
point by stating that attempts to understand the impact growth and survival of juvenile chinook salmon
of in-river (Columbia River) actions on survival will (Healey 1991; McCabe et al. 1986). Nevertheless,
be confounded by changes in ocean conditions. there is some indication that hatchery fall chinook
Coded-wire tag data shows that for the period salmon juveniles spend less time in estuaries than wild
1970-1990, coho salmon adult survival was highest for juveniles which may reduce the benefits of such areas
stocks released into large coastal estuaries. Survival to artificially propagated fish (Levings et al. 1986). It
in these estuaries is typified by widely fluctuating may be that the overall lower survival of fall chinook
mean survivals. Conversely, survival of hatchery salmon masks regional geographic differences so
coho salmon released into coastal regions that lack evident with coho salmon.
protective coastal estuaries is typified by lower, more It is tempting to postulate a cause and effect
constant survival. However, differences in survival relationship between the occurrence of EI Nino events
between estuarine and coastal releases of fall chinook and declines in survival of hatchery fish in the eastern
salmon are not as dramatic, with regions like outer Pacific, but no convincing ecological relationship
Vancouver Island and coastal Oregon performing as exists. Climate conditions are known to have changed
well or better than Puget Sound and the Strait of recently in the Pacific Northwest. Most Pacific
Georgia. It is possible that such factors as size and salmonid stocks south of British Columbia have been
orne of entry to seawater, location and length of time affected by changes in ocean production that occurred
in estuaries prior to outmigration, and predation may during the 1970s. Pearcy (1992) and Lawson (1993)
influence differences in absolute survival and temporal attribute this decline largely to ocean factors, but do
trends between the species. not identify specific effects. However, given the
Coho salmon survivals were depressed following increased frequency of EI Nino events in the past two
the unusually strong El Nino events of the past two decades, and large-scale secular warming of the region
decades (Fig. 6) and continued to decline throughout (Freeland 1990), it is certainly plausible that there is
the 1980s. Depressed survival associated with El at least some response to EI Nino events in the form
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