MANAGEMENT RESPONSES TO REGIME SHIFTS IN MARINE ECOSYSTEMS

Brad deYoung

Memorial UniversityCanada

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DEFINITION OF THE REGIME SHIFT

Working definition : a regime shift is a relatively abrupt change between contrasting persistent states in an ecosystem

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Erosion of resilience

Environmental driver

Env

ironm

enta

l sta

te

Erosion of resilience

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Explore characteristics with a few examples

• Coral reef systems – driven by human action by ‘tipped’ by natural driver

• North Pacific – complex natural state change(s)• North Sea – combined drivers: natural=biogeographic shift

and human=fishing

Explore characteristics of the drivers and response of differing examples – time and space scales, trophic structure, predictability

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Coral reef systems –Jamaican example

An example of the abruptness of a change and the extension of the changes

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Bottom trawl surveys, Pavlov Bay, AK(from Alverson 1992)(from Anderson and

Piatt, 1999)

Climate shifts perturb fisheries and have socio-economic impacts

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Loss of resilience

Overfishing Nutrient loading

Parasite infection

Sea urchin collapse

Rock

Stressed state

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Scotian Shelf – Frank et al. 2005

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Colour display of 60+ indices

for Eastern Scotian Shelf

Red –below average

Green –above average

Grey seals, pelagic fish abundance, invertebrate landings, fish species richness, phytoplankton

Bottom temp., exploitation, groundfish biomass & landings, growth-CHP, avg. fish weight, copepods

Top Predators

(Piscivores)

Forage (fish+inverts)(Plankti-,Detriti-vores)

Zooplankton

(Herbivores)

Phytoplankton

(Nutrivores)

+

-

+

-

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North Sea regime shift – a mixture of biogeography, environmental change and fishing

Mean number of calanoidspecies per CPR sample

58 62 66 70 74 78 82 86 90 94 98123456789

101112

11.522.533.544.55

Years

MONTHS

Warm

Temperate

-10 -5 0 5 10

50

55

60

North Sea

France

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0%

20%

40%

60%

80%

100%

C. finmarchicus

C. helgolandicus

1962

1964

1966

1968

1970

1972

1974

1976

1978

1980

1982

1984

1986

1988

1990

1992

1994

1996

1998

2000

Long

-term

chan

ges i

n the

abun

danc

e of

two k

ey sp

ecies

in th

e Nor

th Se

a

Perc

enta

ge o

f C

. hel

gola

ndic

us

Reid et al. (2003)

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Mismatch between the timing of calanus prey and larval codAbundance of C. finmarchicus

60 65 70 75 80 85 90 95123456789101112

0.20.40.60.81.01.21.41.6 Abundance (in log(x+1))

10

Gadoid Outburst

Abundance of C. helgolandicus

123456789101112

60 65 70 75 80 85 90 95

0.10.20.30.40.50.60.70.80.91.0 Abundance (in log(x+1))

10

Gadoid Outburst

Beaugrand, et al. (2003) Nature. Vol. 426. 661-664.

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Meteorological/oceanographicforcing

Ocean circulation

Biogeographic shift

Ocean conditions

Ecosystem status and function

Fishing

North Sea - dynamics

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Bringing together different aspects of the management problems

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Summary introductory points Regime shifts have been detected in all parts of the world’s oceans

Regime shifts can encompass all aspects of the ocean ecosystem, fromnutrients to plankton to fish

The detection of regime shifts requires good data and careful analyses as thereis the potential for false identification

Resilience is an important aspect of ecosystem function that strongly influences the likelihood of the occurrence of a regime shift.

Human activities in the ocean are generally disruptive, leading to a decline in resilience and thus an increase in the potential for regime shifts.

The prediction of a regime shift is possible in particular circumstances although always likely to be uncertain

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One fundamental challenge in fisheries management

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Regime shifts and fisheries management

Fishing can cause the decline in ecosystem resilience that enhances the potential for the development of a regime shift

After a regime shift, the marine ecosystem may not return to its original state and even if it does the process can take a long time, decades or longer

The Ecosystems Approach to Fisheries (EAF) is a necessary improvementrequired for fisheries management

The definition and measurement of resilience will be necessary to ensure effective management.

Regime shifts could lead to the large-scale redistribution of marine species and this potential should be considered in fisheries management and international planning

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Key recommendations

A genuine ecosystems approach to fisheries should be implemented

Resilience must be included in any ecosystems management strategy

There should be greater international coordination of the study of regime shifts and the development of monitoring strategies to identify regime shifts

Fisheries management should include consideration of regime shifts and their potential to disrupt ecosystem structures, patterns and distributions as presently observed