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

(From Ware and McFarlane, 1989)

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

Cape Blanco

Cape Mendocino

Pt. Conception

Pt. Eugenia

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

Habitats of Sardine and Hake in the CCS

?

From Saunders and McFarlane, 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

Focus

Spawning behavior

Migratory behavior

From Saunders and MacFarlane, 1982

50m

200m

0m Mix

ed la

yer

Spawning habitat: vertical dimensions

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: age effects

From Dorn, 1995

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.

From Wilson, unpublished

Migratory behavior, cont.

Migratory behavior: food effects

From Fulton & Brasseur, 1985

Northern extent of migration possibly dependent on location of sub-arctic boundary

Sardine migration

• Not as consistent• Truncated age structure by fishery

Migratory behavior, cont.

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

PNW Ecosystems:Salmon

Food web

Climate Ecology

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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77

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91

Year

Bio

mas

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mt)

Pelagic Predators (Hake andMackerel)Pelagic Planktivores (Sardinesand Anchovy)Flatfish and Roundfish

Rockfish

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91

Year

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mas

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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)