2 â measures of abundance. 3 â abundance ... Recruit at 2 to 3 distinct adult ages/sizes (1SW, 2SW, 3SW) ..... Greene, C. H., and Pershing, A. J. 2007. Climate ...
Overview: status of Atlantic salmon (Salmo salar) in the North Atlantic and trends in marine mortality Gérald Chaput Fisheries and Oceans Canada Chair ICES Working Group on North Atlantic Salmon
Gérald Chaput, biologiste Fisheries and Oceans Canada / Pêches et Océans Canada Moncton
Overview: status of Atlantic salmon (Salmo salar) in the North Atlantic and trends in marine mortality Content of the presentation 1 – the fish itself (refresher) 2 – measures of abundance 3 – abundance and dynamics at the stock complex level 4 – evidence of factors that affect salmon abundance are acting 5 – cautions about stock complex assessments 6 – conclusions
Family Salmonidae Salmo salar Linneaus • Broadly distributed in North Atlantic, in over 2000 rivers
http://www.asf.ca/about_salmon.php
• Obligate freshwater spawner, with anadromous option • Iteroparous (repeat) spawner although repeat spawners are less common in the southern portion of the range
Family Salmonidae Salmo salar Linneaus • Short-lived species, age at first spawning as young as two years, and oldest salmon generally less than ten years old, oldest animals in the northern areas • Fast growth at sea compared to most marine fish, including Pacific salmon Atlantic salmon
Sockeye salmon
Chinook salmon
Smolts
10 – 20 cm (1-6 yrs)
6 – 13 cm (1-2 yrs)
6 – 13 cm (0 – 1 yr)
One year at sea
45 – 65 cm
35 – 40 cm
30 – 45 cm
45 – 60 cm
2 years at sea
60 – 90 cm
45 – 55 cm
50 – 65 cm
65 – 90 cm
3 years at sea
80 – 100 cm
50 – 60 cm
65 – 80 cm
85 – 120 cm
80 – 95 cm
100 -150 cm
4 years at sea
Bluefin tuna
• Recruit at 2 to 3 distinct adult ages/sizes (1SW, 2SW, 3SW)
Family Salmonidae Salmo salar Linneaus Stock-specific characteristics include: • sea age at maturity (grilse stocks; multi-sea-winter stocks), sex bias in age-at-maturity, fecundity increases with body size 1.0
1SW
MSW
Average stock characteristics by sea age maturity group and country in northeast Atlantic
Proportion female
0.8
0.6
0.4
0.2
0.0 0
2000
4000
6000 8000 10000 12000 14000 16000 Eggs per female
Family Salmonidae Salmo salar Linneaus • Few (2000 to 12000) and large eggs (5 – 7 mm diameter) per female, deposited in redds (protected) • Very good juvenile survival in freshwater (upwards of 3% egg to smolt survival) • Generally high natural mortality (M) at sea • for many marine fish (assumed) 16% to 30% per year • for Atlantic salmon, as high as 95% per year
Indicators of abundance • Short term view of salmon abundance (pristine state) • Reliable catches which can be an index of abundance go back to 1960, further back for some jurisidictions, • reliability of catch data is questionable prior to 1960 • Peak catch of < 12 000 mt (< 4 million fish) around 1970s 14000 North Atlantic
Landings (t metric)
12000 10000
NEAC Canada (NAC) Greenland and Faroes
8000 6000 4000 2000 0 1900
1920
1940
1960
1980
2000
• Catch ≠ abundance due to incompleteness, changes in management, variable exploitation rates, ...
Estimates of absolute abundance and trends River
River
Coast
Ocean
time (years)
Ms1 Eggs
Mriv
Smolts
Ms2 PFA
Returns
Pre-Fishery Abundance
Mad
Spawners
Catch
Mixed Stock Catch
Coastal waters Inriver Greenland: North America, Northeast Atlantic Faroes: Northeast Atlantic Newfoundland/Labrador: North America
by river, by region, by stock complex by sea age group (1SW, MSW), by smolt cohort (1970 to 2009)
Greenland fishery Nfld&Lab
Faroes fishery
North America (NAC)
Southern NEAC
Northern NEAC
USA
Iceland (south/west region)
Iceland (north/east region)
Scotia-Fundy
France
Sweden
Gulf
Ireland
Norway
Quebec
UK (N. Ireland)
Finland
Newfoundland
UK (England & Wales)
Russia
Labrador
UK (Scotland)
By stock complex
Lagged Eggs = Σregion Σage Σeggsy-(sm.age+2) Productivity
Prop. Mat.
PFA
PFAm
at Jan. 1 of first sea winter
PFAnm M
Catch 1SWm
Catch 1SWnm
Returns 1SW Catch MSW Spawners 1SW Returns MSW Eggs 1SW
things we estimate things we assume things things things we of we calculate interest know bywe models knowbut can never measure
Spawners MSW Eggs MSW
time (years)
1SW or small MSW or large
1.5
PFA (at Jan. 1 of first sea winter) Northern NEAC: • approx. 1.2 million (avg. 2005-2009) • small salmon: 49% decline • large salmon: 54% decline
1.0
0.5
N-NEAC Number of fish (millions)
0.0 1970
1975
1980
1985
1990
1995
2000
2005
2010
4.0
3.0
Southern NEAC: • approx. 1.5 million (avg. 2005-2009) • small salmon: 66% decline • large salmon: 81% decline
2.0
1.0
S-NEAC 0.0 1970
1975
1980
1985
1990
1995
2000
2005
2010
1.5
North America • approx. 0.9 million (avg. 2005-2009) • small salmon: 40% decline • large salmon: 88% decline
1.0
0.5
NAC 0.0 1970
1975
1980
1985
1990
1995
2000
2005
2010
Separating freshwater effects from marine survival effects River
River
Coast
Ocean
time (years)
Ms1 Eggs
Mriv
Ms2 PFA
Smolts
Returns
Pre-Fishery Abundance
Mixed Stock Catch 2.0
N-NEAC
+28 %
Spawners
Catch
Increased estimated lagged eggs for N-NEAC but a decline of 43% in PFA
0.0 6.0
Decrease of 33% for lagged eggs but decline of 66% in PFA
4.0 2.0
-33 %
S-NEAC
0.0 2.0
Increased lagged eggs for NAC but decline of 61% in PFA
1.0
010
000
995
990
985
980
005
+10 %
NAC
0.0 975
Lagged eggs (X 109)
1.0
Mad
Separating freshwater effects from marine survival effects River
River
Coast
Ocean
time (years)
Ms1 Eggs
Mriv
Ms2 PFA
Smolts
Mad Returns
Pre-Fishery Abundance
Mixed Stock Catch 20
Spawners
Catch
Return rate of Imsa (Norway) smolts declined 68% from 1982 to 2007
10
Return rate (%)
N-NEAC
0 1970
1975
1980
1985
1990
1995
2000
2005
2010
20
Return rate of Corrib (Ireland) smolts declined 61% from 1981 to 2003
10
S-NEAC
0 1970 6
1975
1980
1985
1990
1995
2000
2005
2010
Declines in return rates of 81% for wild smolts (Quebec) and 88% for hatchery smolts (Saint John), for the time series
4 2
NAC
0 1970
1975
1980
1985
1990
1995
2000
2005
2010
• Estimated declines in PFA are in opposing sign to the trends in spawning escapements but consistent with increased marine mortality • Based on the assumptions for the PFA reconstruction (M is constant in the second year at sea), declines in PFA are attributed to decreased productivity between the spawning stage and the PFA stage (freshwater and first year-at-sea effects)
River
River
Coast
Ocean
time (years)
Ms1 Eggs
Mriv
Smolts
Ms2 PFA
Returns
Pre-Fishery Abundance
Productivity = PFA / Eggs
Mad
Mixed Stock Catch
Spawners
Catch
Trends in productivity 2.0
N-NEAC
1.5
0.5 0.0 2.0
S-NEAC 1.5 1.0
Southern-NEAC: • max. of 1.2 fish per 1000 eggs • fell abruptly in 1990 • remained low since at 0.5
0.5 0.0 2.0
Productivity highest for NAC • max. of 1.7 fish per 1000 eggs • declined continually since 1989 to lowest value of 0.45 in 2001
NAC
1.5 1.0 0.5
2010
2005
2000
1995
1990
1985
1980
0.0
1975
Productivity (number of fish per 1000 eggs)
1.0
Northern-NEAC: • shorter time series, begins 1991 • max. productivity of 1.2 fish per 1000 eggs • declined beginning in 2004 • reached lowest level in 2007 at 0.5
Trends in productivity 2.0
N-NEAC
1.5
0.5 0.0 2.0
S-NEAC 1.5 1.0 0.5 0.0 2.0
NAC
1.5 1.0 0.5
2010
2005
2000
1995
1990
1985
1980
0.0
1975
Productivity (number of fish per 1000 eggs)
1.0
Rapid decline in Southern-NEAC and rapid and sustained declined in NAC began in 1989 to 1990 PFA years • the two stock complexes that migrate to Greenland for their second year at sea Similar decline may have occurred in Northern-NEAC • recent decline beginning in 2004 not observed in S-NEAC and NAC
Indicators of ecosystem changes in the North Atlantic 2.0
N-NEAC
North Sea copepod and decapod larvae.
1.5
0.5 0.0 2.0
S-NEAC
1.5 1.0 Beaugrand, G. 2009. Decadal changes in climate and ecosystems in the North Atlantic Ocean and adjacent seas. Deep Sea Research II, 56: 656–673.
0.5
Northwest Atlantic (Gulf of Maine, Georges Bank) copepod
0.0 2.0
NAC
1.5 1.0 0.5
2010
2005
2000
1995
1990
1985
1980
0.0
1975
Productivity (number of fish per 1000 eggs)
1.0
Greene, C. H., and Pershing, A. J. 2007. Climate drives sea change. Science, 315: 1084–1085.
Cautions regarding stock complex assessments Change in spawners (1971 – 2010) -100%
0%
100%
200%
300%
400%
1SW
MSW N-NEAC 1SW
MSW S-NEAC 1SW
MSW
NAC
complex
region
In Southern-NEAC and NAC • spawner abundance in some regions has declined by more than 80%, and spawning escapements are substantially below the region specific conservation requirements Large numbers of assessed rivers are not meeting their spawning requirements % of rivers above CL (2009, 2010) UK(England&Wales): 59% (of 64) Ireland: 43% (of 141) France: 12% (of 17) Canada: 41% (of 76) USA: 0% (of 6)
Conclusions What constitutes a “healthy” population? • interpretation based on the abundance of salmon over the past half century at best • in some portions of its range, Atlantic salmon was extirpated as early as the late 1800s (MacCrimmon and Gots, 1979) • in the past four decades, adult-sized anadromous Atlantic salmon totaled less than 10 million animals annually, minor component, by number and biomass, of the pelagic ecosystem in the North Atlantic Changes in the marine ecosystem of the North Atlantic have been noted • there appears to be a North Atlantic wide factor(s) that is constraining productivity at sea at the stock complex level in both the northwest and northeast Atlantic areas • reduced productivity is expressed in terms of increased mortality
Conclusions Stock complex assessments that provide catch advice for mixed stock fisheries mask the regional and river-specific situations of Atlantic salmon populations • this poses particular threats to stocks that are at low abundance and subject to other threats unrelated to fishing, such as freshwater habitat degradation • still a number of mixed stock fisheries on salmon in the North Atlantic Ideally, stock assessments would be conducted for every stock and fisheries would be prosecuted on stocks that are meeting their conservation requirements. • reality is that annual river specific stock assessments are only available on about 25% of the 2000 river populations
Conclusions Abundant river-specific scale assessments are crucial to improving our knowledge of Atlantic salmon population abundance and regulation as they provide the foundation upon which to test hypotheses of factors that define salmon survival both in freshwater and in the ocean. Must maintain and expand diverse river-specific monitoring and assessment programs • monitoring programs are not scientifically glamorous • require long term engagement and investment of resources
Acknowledgements • Members of the ICES Working Group on North Atlantic Salmon from more than 13 countries over the past three decades • Countless individuals involved in the monitoring of stocks, compilation of catch data and biological characteristics from national governments, NGOs and aboriginal communities
