Biological response to climate in marine ecosystems: what are sardine and hake telling us? Vera N....
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Transcript of Biological response to climate in marine ecosystems: what are sardine and hake telling us? Vera N....
Biological response to climate in marine
ecosystems: what are sardine and hake telling
us?
Vera N. AgostiniAdvisor: Robert C. Francis
School of Aquatic an Fisheries Sciences
Outline
• Why sardine and hake?• Habitats in the CCS• Hypotheses formulated• Life history comparison• Conceptual model• Ongoing research directions
Merluccius productus: Pacific hake
Sardinops sagax: Pacific sardine
•Life span: <8yrs (13-25)•Adult length: 15-22 cm
•Life span: 12 (25) •Adult length: 34-40cm
Cape blanco
Pt. Conception
Fewer stormsWeaker windsWeak upwellingNegligible freshwater input
Damped seasonality in primary productivity
Winds mostly upwelling favorable
Strongest coastal upwellingPrim. prod. strongly
seasonal
Winter storms frequentand strongSignificant freshwater input
Prim. prod. strongly seasonal
Cape Mendocino
Pt. Eugenia
Redrawn from GLOBEC-EBC working group report, 1995
PICES symposium on transitional areas in the North Pacific:“..to examine recent advances in understanding the dynamics of marine ecosystems..” in transitional areas
Main overall conclusions of PICES symposium:
•Incredible diversity of areas •Variability in time and space unique to each area•Relationship amongst areas needs further attention
Hake and Sardine as a link between these areas
Cape Blanco
Cape Mendocino
Pt. Conception
Pt. Eugenia
Transition: “a passing from one condition, form, stage, activity place to another” (Webster’s dictionary)
Lynn and Sympson, 1982
Pacific Sardine
0
5000
10000
15000
20000
1970 1975 1980 1985 1990 1995 2000 2005
Re
cru
its
0
400
800
1200
Bio
ma
ss
Recruits (millions) Biomass (1000 mt)
Pacific Hake
0
4
8
12
1970 1975 1980 1985 1990 1995 2000 2005
Re
cru
its
0
2
4
6
Bio
ma
ss
Recruits (billions) Biomass (million mt)
Recr. lag 1 AC-0.21
Recr. lag 1 AC
0.65
QUESTION: Why are population dynamics so different?
HYPOTHESIS:Response of each species to climate is different
Response to climate
Life history strategies
Characteristics Habitats Forcing
Climate
Life history strategies
Why are their pop.dyn. so different?
Why do they do wellwhen all else is doing poorly (i.e. El Nino)?
How do they successfully coexist?
How can we explain link between climate and
population variability of sardine and hake?
Number of hypotheses that have been formulated to address the potential link between each of these species and climate
SARDINE HAKE
Eddies, jets and meanders X X
Coastal upwelling X XAlongshore advection X XFrontal zones X XZooplankton distribution andabundance
X X
Vertical mixing X X
EARLY LIFE HISTORY
ADULT
Habitat quality
Environ. disturbance
Predation
SARDINE HAKEBasin hypothesis XEffect of Nino North on southern extent of sp. and northern extent of migration
X X
Effects of temperature on growth and stage duration X X
Loophole hypothesis XSharp transition in climate(Nino North)
Scramble competition leading to dominance
School-mixed feedback XDifferences in duration at lengths vulnerable to predation
X
Outline
• Why sardine and hake?Why sardine and hake?• Habitats in the CCSHabitats in the CCS• Hypotheses formulatedHypotheses formulated• Life history comparison• Conceptual model• Ongoing research directions
Climate variability
Ocean habitat
Fish population
1. What habitats or features of habitat are important?
2. How does each habitat vary with climate?
Linking climate and fish populations
1-6 months(January-June)
Adult (15-22cm) Adult (34-40cm)
Larvae (3.5mm)
1-3 months (January-March)
2-4 days 4-5 days
3 months
3-4 months
Larvae (2.4 mm)
Juveniles (35 mm)
Juveniles(34 mm)
Eggs (1.6mm)
Eggs (1.2mm)
LIFE HISTORIES
Pacific Sardine Pacific Hake
Shelf & shelf breakShelf
‘core’ & slope‘core’ & shelf
Dec.
S (Baja)
N (CAN)
JuneMarchJan.
Spawning habitat: temporal and horizontal dimensions
shelf core slope
sardinehake
(From Wilson, 2000)Hake NMFS acoustic data, summer 1998
Extent of northern migration related to:•Age•Temperature•Poleward flow•Food
Migratory behavior
Migratory behavior: transport effects
•Poleward flow, both at the surface (Davidson current) and subsurface (California Undercurrent).•Northern migration possibly aided by poleward current
Evidence:•Sex specific timing of post spawning migration (Saunders and MacFarlane, 1997)
Females move closer to shore and earlier than males.
Migratory behavior: food effects
From Fulton & Brasseur, 1985
Northern extent of migration possibly dependent on location of sub-arctic boundary
What could we learn by looking at the remarkable persistence of these
species?
• Pacific Hake and Sardine use and have evolved to cope with a constantly varying habitat
• Strategies developed to target different components of the habitats they occupy
• These strategies have allowed them to persist
Life history summary
CHARACTERISTIC PACIFIC HAKE PACIFIC SARDINE
Batch spawners Yes Yes
Number of eggs x 3x
Location of spawning SCBBelow mixed layer
SCBMixed layer
Duration of spawning Dec.-Mar. (Jan, Feb.) Jan-June (April-May)
Spawning time Not flexible Flexible
Earl
y lif
e h
isto
ryA
du
lts
Feeding Carnivorous with some piscivory at older ages
Filter feeders
Migratory behavior Timed with seasonal onset of poleward flow
Not consistent
CONCEPTUAL MODEL
•SARDINE-----’hitting it big’ strategy–Traits allowing them to do well when all else is doing poorly (“loophole hypothesis”)–Life history is plastic–Short lived
•HAKE-----’long period integration’ strategy–Traits allowing them to do well when all else is doing poorly (“loophole hypothesis”)–Life history is not very plastic–Strategies focused on overcoming constraints–Long lived
Climate variability
Ocean habitat Fish population
1. What habitats or features of habitat are important?
2. How does each habitat vary with climate?
Linking climate and fish populations
Ongoing research
–Extent of migration has indirect influence on year
class success
•Spatially explicit description of habitats and ecological interactions of key life history stages•Two hypotheses to guide further studies:
–Survival of early life history stages main driver of year class success
Trophic Level
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
phytoplankton
Infauna amphipods
epibenthic
pelagic shp
pandalid shp
benthic shp
micro-zoop
meso-zoopeuphausiids
juv fish
macrourids
benthic fishjellies
juv salmonsalmon
hakeskates
dogfish sablefish
POPcanary
widow
yellowtailother rock
thorny
flatfish
dover
largeflat
sardine
mackerel
mesopelagics
albacore/sharks
forage fish
cephalopods
shearwaters
murres
transient orcas
toothed whalespinnipeds
baleen whales
climateforcerbenthicdetritus pelagicdetritus
bottom-trawlhook-line
hake fisheryshrimp trawlsalmon fleet
?
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91
Year
Bio
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s (m
illi
on
mt)
Pelagic Predators (Hake andMackerel)Pelagic Planktivores (Sardinesand Anchovy)Flatfish and Roundfish
Rockfish
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Year
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mas
s (m
illi
on
mt)
Pelagic Planktivores(Anchovy)Flatfish and Roundfish
Rockfish
Summer (left) and Winter (right) biomass estimates of major commercial species in the NCCE
Summer Winter
?
PNW Ecosystems:Salmon
Food web
Management
Climate Ecology
Incorporation of climate information in assessments
Ecological consequence of a fishery (i.e. sardine)
Effects of fishery on resilience of populations
Take home messages
–Awareness of variability in time and space scales and relationships amongst them
–Importance of ecology (life history strategies)
Research: Understanding the response of ecosystems to climate variability
Management: Ecological consequences of a fishery (Ecosystem based management)