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This is the latest DFO Chinook Returns Backgrounder. Bad news.
MEMORANDUM NOTE DE SERVICE
To
À
Jeff Grout
Salmon Co-ordinator
Fisheries and Aquaculture Management
Pacific Region, DFO
From
De
Brian Riddell
Division Manager, Salmon and Freshwater
Ecosystems, Science Branch
Pacific Region, DFO
Security Classification - Classification de sécurité
UNCLASSIFIED
Our file - Notre référence
8350-C2
Your File - Votre référence
Date
November 19, 2007
Subject
Object BACKGROUNDER: RETURN OF CHINOOK SALMON IN SOUTHERN BC IN 2007 AND
EXPECTATIONS FOR 2008
A) 2007 Chinook Spawning Observations
Chinook salmon returns were generally less than expected in 2007.
Ocean-type Chinook: Ocean-type Chinook enter the sea in the spring or summer of their first year, and
return to spawn between ages 2 to 5. Important indicator stocks with this life cycle include Robertson Creek
(hatchery, indicator for WCVI), Harrison River (wild, Fraser Late stock), Cowichan River (hatchery and
wild, Lower St. of Georgia), Lower Shuswap River (hatchery and wild, mid-Fraser summer Chinooks) and
other hatcheries in the Strait of Georgia (Puntledge summers and Quinsam fall Chinook). Additional
information will be available in early 2008 about the age structure of the 2007 returns for these stocks.
1. Roberston Creek and WCVI, fall Chinook: In 2006, age-2 jack returns (BY 2004) were
extremely low at Robertson (3rd lowest among 21 years), indicating poor survival for this brood
(projected survival rate only 0.12%). While this survival rate only applies to one brood year, the
total escapement observed in 2007 was below expectations. Age structure in the escapement is
unknown as age sampling results are not yet available. Returns to many of the wild WCVI
Chinook populations were very poor.
2. For Harrison River fall Chinook, age-2 jack returns in 2006 were the lowest among the last 11
years, indicating poor returns from the 2004 brood year. At the Chilliwack River, there was no
indication of poor survival for the 2004 brood year. Return data for 2007 are not yet available,
but early indications in the Harrison River are that it will likely meet the lower bound of the
escapement goal range.
3. For Cowichan River fall Chinook, returns in 2007 appear to continue the decreasing trend in this
stock. While high water breached the counting fence in October 2007, the returns to that point
suggest a 2007 return of only 2/3 of 2006. Low returns were anticipated in part due to the loss of
the hatchery production from BY 2004 (power failure at hatchery). Total return (naturally
spawning and hatchery brood stock) in 2007 is expected to be less than 1,000 Chinook. Returns
2
in 2007 to the Nanaimo River were similar to 2006 and exceeded the estimated return to the
Cowichan River.
4. For the Fraser Summer Run Age 0.3 stock group, 2007 spawning escapements are much lower
than expected at the Lower and Middle Shuswap Rivers, but they are consistent with or above
expectations at Adams, Little, South Thompson, and Lower Thompson Rivers. The
mechanism(s) contributing to the divergence in production patterns between the systems is
unclear currently, but freshwater production may have been low for Middle and Lower Shuswap.
Exceptionally warm water in the late summer of 2003 may have impacted egg viability in these
systems.
5. Other Strait of Georgia hatchery Chinook: returns are incomplete at this time … but
observations to-date for 2007 are similar to 2006.
Stream-type Chinook: Stream-type Chinook spend at least one year in freshwater before migrating to the sea
and return to spawn between ages 3 and 6. In southern BC, these Chinook mostly reside in the interior Fraser
River and large mainland glacial rivers in the Strait of Georgia (although data on the latter stocks are very
limited). In the Fraser River, detailed age-structure data are collected at the Nicola River (hatchery and wild)
and Nechako River, and spawning returns are monitored for three groups (Spring-Run Age 1.2, Spring-Run
Age 1.3 and Summer Run Age 1.3 stocks) described by season of up-stream migration and typical ages at
maturity. The groups differ in maturation schedules, with about 90% of the Spring, Age 1.2 group spawning
at age-4, and about 70-80% being age-5 for the Spring and Summer, Age 1.3 groups.
Spawning escapements observed in 2007 were poor for each of these groups, returning only 11%, 25%, and
29% respectively of their parental brood year levels. Age structure information sampled from the 2007
returns will not be available until early 2008.
B) Salmon Entering the Sea in 2005
Many Pacific salmon stocks in southern B.C. experienced extremely poor production for brood years
entering the ocean in 2005. Production levels have been poor and such a widespread pattern amongst Pacific
salmon species and stocks is rare and perhaps unprecedented among DFO observations.
• Pink salmon entering the sea in 2005 would have returned to spawn in 2006. The observed returns in
2006 were far below expectations and the pattern of poor returns extended from southern BC through
Southeast Alaska.
• Coho salmon had very low returns compared to expectations in 2006. They have a predominantly 3-
year life cycle, and smolts that went to ocean in 2005 (brood year 2003) returned in 2006. The 2006
spawning escapement to the Interior Fraser was the lowest recorded since 1975. The pattern of
extremely low marine survival and spawning escapements extended to other southern B.C. stocks,
and the Strait of Georgia hatchery and wild stocks experienced record low marine survival (since
1985).
• Sockeye salmon in southern BC had very low returns in 2007 compared to expectations. Sockeye
salmon return mainly at ages 3-5 in southern BC with most at age-4, and smolts from brood year
2003 entered the ocean in 2005. In Barkley Sound, age-3 jack returns in 2006 were 10% of the long
term average, indicating poor marine survival. In-season run size estimates were two-thirds of
expectations and the 2007 spawning escapement was the lowest among all years since 1992. The total
3
return of Fraser sockeye in 2007 was estimated at slightly less than 25% of the pre-season forecast of
6,247,000 fish (50% probability level) due to the extremely low return of age-4 sockeye. The
estimated survival rate for Chilko Lake sockeye smolts was the lowest on record (~1.2%). Reports of
Lake Washington and Baker Lake sockeye (in the United States) also indicated weakness in the
return of age-4 sockeye.
• Chum salmon are currently returning and data are insufficient to make strong statements about return
patterns however returns to the WCVI are lower than expected and unlikely to achieve their
escapement targets.
C) Comments on 2008 Chinook expectations
The poorer than expected returns of Chinook salmon in southern BC can not be adequately explained by
poor survival of smolts entering the sea in 2005. While this could be a contributing factor to the returns of
WCVI Chinook (Age-3 returns in 2007), the multiple age structure of Chinook salmon requires an
explanation to account for declines across all age classes (although the exact age classes in the 2007 returns
remain to be verified). However, even if we can not adequately explain the decline in 2007, the signal from
other species concerning the survival of smolts entering the sea in 2005 must be considered for Chinook
returns expected in 2008 and 2009. Age4 and age-5 returns from the 2004 brood year will account for most
of the females spawners in southern BC Chinook stocks during 2008 and 2009. The poor returns in 2007
and the over-whelming evidence of a 2005 at-sea impact suggests returns in 2008 will continue to be poor,
particularly for WCVI natural Chinook, Cowichan River, and interior Fraser River Spring and Summer
stream-type Chinook.
Prepared by Stock Assessment programs (Fraser River, South Coast, and Regional Core assessment)
(original signed by Brian Riddell)
MEMORANDUM NOTE DE SERVICE
To
À
Jeff Grout
Salmon Co-ordinator
Fisheries and Aquaculture Management
Pacific Region, DFO
From
De
Brian Riddell
Division Manager, Salmon and Freshwater
Ecosystems, Science Branch
Pacific Region, DFO
Security Classification - Classification de sécurité
UNCLASSIFIED
Our file - Notre référence
8350-C2
Your File - Votre référence
Date
November 19, 2007
Subject
Object BACKGROUNDER: RETURN OF CHINOOK SALMON IN SOUTHERN BC IN 2007 AND
EXPECTATIONS FOR 2008
A) 2007 Chinook Spawning Observations
Chinook salmon returns were generally less than expected in 2007.
Ocean-type Chinook: Ocean-type Chinook enter the sea in the spring or summer of their first year, and
return to spawn between ages 2 to 5. Important indicator stocks with this life cycle include Robertson Creek
(hatchery, indicator for WCVI), Harrison River (wild, Fraser Late stock), Cowichan River (hatchery and
wild, Lower St. of Georgia), Lower Shuswap River (hatchery and wild, mid-Fraser summer Chinooks) and
other hatcheries in the Strait of Georgia (Puntledge summers and Quinsam fall Chinook). Additional
information will be available in early 2008 about the age structure of the 2007 returns for these stocks.
1. Roberston Creek and WCVI, fall Chinook: In 2006, age-2 jack returns (BY 2004) were
extremely low at Robertson (3rd lowest among 21 years), indicating poor survival for this brood
(projected survival rate only 0.12%). While this survival rate only applies to one brood year, the
total escapement observed in 2007 was below expectations. Age structure in the escapement is
unknown as age sampling results are not yet available. Returns to many of the wild WCVI
Chinook populations were very poor.
2. For Harrison River fall Chinook, age-2 jack returns in 2006 were the lowest among the last 11
years, indicating poor returns from the 2004 brood year. At the Chilliwack River, there was no
indication of poor survival for the 2004 brood year. Return data for 2007 are not yet available,
but early indications in the Harrison River are that it will likely meet the lower bound of the
escapement goal range.
3. For Cowichan River fall Chinook, returns in 2007 appear to continue the decreasing trend in this
stock. While high water breached the counting fence in October 2007, the returns to that point
suggest a 2007 return of only 2/3 of 2006. Low returns were anticipated in part due to the loss of
the hatchery production from BY 2004 (power failure at hatchery). Total return (naturally
spawning and hatchery brood stock) in 2007 is expected to be less than 1,000 Chinook. Returns
2
in 2007 to the Nanaimo River were similar to 2006 and exceeded the estimated return to the
Cowichan River.
4. For the Fraser Summer Run Age 0.3 stock group, 2007 spawning escapements are much lower
than expected at the Lower and Middle Shuswap Rivers, but they are consistent with or above
expectations at Adams, Little, South Thompson, and Lower Thompson Rivers. The
mechanism(s) contributing to the divergence in production patterns between the systems is
unclear currently, but freshwater production may have been low for Middle and Lower Shuswap.
Exceptionally warm water in the late summer of 2003 may have impacted egg viability in these
systems.
5. Other Strait of Georgia hatchery Chinook: returns are incomplete at this time … but
observations to-date for 2007 are similar to 2006.
Stream-type Chinook: Stream-type Chinook spend at least one year in freshwater before migrating to the sea
and return to spawn between ages 3 and 6. In southern BC, these Chinook mostly reside in the interior Fraser
River and large mainland glacial rivers in the Strait of Georgia (although data on the latter stocks are very
limited). In the Fraser River, detailed age-structure data are collected at the Nicola River (hatchery and wild)
and Nechako River, and spawning returns are monitored for three groups (Spring-Run Age 1.2, Spring-Run
Age 1.3 and Summer Run Age 1.3 stocks) described by season of up-stream migration and typical ages at
maturity. The groups differ in maturation schedules, with about 90% of the Spring, Age 1.2 group spawning
at age-4, and about 70-80% being age-5 for the Spring and Summer, Age 1.3 groups.
Spawning escapements observed in 2007 were poor for each of these groups, returning only 11%, 25%, and
29% respectively of their parental brood year levels. Age structure information sampled from the 2007
returns will not be available until early 2008.
B) Salmon Entering the Sea in 2005
Many Pacific salmon stocks in southern B.C. experienced extremely poor production for brood years
entering the ocean in 2005. Production levels have been poor and such a widespread pattern amongst Pacific
salmon species and stocks is rare and perhaps unprecedented among DFO observations.
• Pink salmon entering the sea in 2005 would have returned to spawn in 2006. The observed returns in
2006 were far below expectations and the pattern of poor returns extended from southern BC through
Southeast Alaska.
• Coho salmon had very low returns compared to expectations in 2006. They have a predominantly 3-
year life cycle, and smolts that went to ocean in 2005 (brood year 2003) returned in 2006. The 2006
spawning escapement to the Interior Fraser was the lowest recorded since 1975. The pattern of
extremely low marine survival and spawning escapements extended to other southern B.C. stocks,
and the Strait of Georgia hatchery and wild stocks experienced record low marine survival (since
1985).
• Sockeye salmon in southern BC had very low returns in 2007 compared to expectations. Sockeye
salmon return mainly at ages 3-5 in southern BC with most at age-4, and smolts from brood year
2003 entered the ocean in 2005. In Barkley Sound, age-3 jack returns in 2006 were 10% of the long
term average, indicating poor marine survival. In-season run size estimates were two-thirds of
expectations and the 2007 spawning escapement was the lowest among all years since 1992. The total
3
return of Fraser sockeye in 2007 was estimated at slightly less than 25% of the pre-season forecast of
6,247,000 fish (50% probability level) due to the extremely low return of age-4 sockeye. The
estimated survival rate for Chilko Lake sockeye smolts was the lowest on record (~1.2%). Reports of
Lake Washington and Baker Lake sockeye (in the United States) also indicated weakness in the
return of age-4 sockeye.
• Chum salmon are currently returning and data are insufficient to make strong statements about return
patterns however returns to the WCVI are lower than expected and unlikely to achieve their
escapement targets.
C) Comments on 2008 Chinook expectations
The poorer than expected returns of Chinook salmon in southern BC can not be adequately explained by
poor survival of smolts entering the sea in 2005. While this could be a contributing factor to the returns of
WCVI Chinook (Age-3 returns in 2007), the multiple age structure of Chinook salmon requires an
explanation to account for declines across all age classes (although the exact age classes in the 2007 returns
remain to be verified). However, even if we can not adequately explain the decline in 2007, the signal from
other species concerning the survival of smolts entering the sea in 2005 must be considered for Chinook
returns expected in 2008 and 2009. Age4 and age-5 returns from the 2004 brood year will account for most
of the females spawners in southern BC Chinook stocks during 2008 and 2009. The poor returns in 2007
and the over-whelming evidence of a 2005 at-sea impact suggests returns in 2008 will continue to be poor,
particularly for WCVI natural Chinook, Cowichan River, and interior Fraser River Spring and Summer
stream-type Chinook.
Prepared by Stock Assessment programs (Fraser River, South Coast, and Regional Core assessment)
(original signed by Brian Riddell)
