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STOP MOTION DYNAMICS: INFERRING REEF FISH FUNCTIONAL ROLES ACROSS ECOSYSTEM STATES

AARON MACNEILNICK GRAHAM ALISTAIR CHEAL TIM MCCLANAHAN

2

(a) Observed(b) Unobserved

(a)

(b)

MARINE ECOLOGY

3

(1) Posit ive outlook

4

(11) Negative outlook

5

(111) Stable outlook

6

(1v) Actual data

(Random colleague)

(PhD project)

2003 2007

7

(v) Real ity (Nol l ie Inward Heelfl ip)

8

(v1) Something close

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OBSERVATION-BASED INFERENCE

‘A well -conducted observational study can provide a good basis for drawing causal inferences, provided that…’

Gelman et al. 2004

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OBSERVATION-BASED INFERENCE

(1) Reasonable overlap

Yes No/maybe

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OBSERVATION-BASED INFERENCE

(11) Have ‘a lot’ of data

Yes No

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OBSERVATION-BASED INFERENCE

(111) Data col lected ignorantly

Yes NoTreatment Control Treatment Control

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OBSERVATION-BASED INFERENCE

(1v) Tame missing data

Yes NoTreatment Control Treatment Control

sample from posterior

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OBSERVATION-BASED INFERENCE

(v) Acknowledge data col lection

Yes No

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MULTISPECIES REEF FISHERIES

Compiled >300 surveys of shallow coral reefs from nine countries across the Indian Ocean.

Evenly distributed among unregulated, restricted and no-take marine protected areas

Used a suite of Bayesian switchpoint models to test for trend and variance thresholds

SURVEYS AND ANALYSES

Measurable indicator

& tangible for management

Various indicators

Driver

Sta

te V

aria

ble

CAN THRESHOLDS BE IDENTIFIED

Fishable Biomass (kg/ha)

Intimately linked to fishing and overfishing known to have serious repercussions for the ecosystem

Importantly, it is tangible & influenced by managers and resource users

ECOSYSTEM DRIVER

Used ecosystem metrics that represent key ecological states and processes thought to influence ecological shifts

McClanahan et al. 2011 PNAS

ECOSYSTEM STATE INDICATORS

MPA

Gear rest.

Open

Macroalgae

Macroalg / coral

McC

lan

ah

an

et

al.

2011

PN

AS

MPA

Gear rest.

Open

Predation index

McC

lan

ah

an

et

al.

2011

PN

AS

MPA

Gear rest.

Open

Fish richness

% herbivores

Urchin biomass

McC

lan

ah

an

et

al.

2011

PN

AS

MPA

Gear rest.

Open

% calcifying

% hard coral

McC

lan

ah

an

et

al.

2011

PN

AS

McClanahan et al. 2011 PNAS

REGIONAL PERFORMANCE

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CONCLUSIONS

This talk presented concepts of how to infer patterns on reefs whilst acknowledging and trying to sensibly model the imperfect data we have available

In such a way, large data sets may be utilized to tackle complex patterns in ecology

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STOP MOTION DYNAMICS: INFERRING REEF FISH FUNCTIONAL ROLES ACROSS ECOSYSTEM STATES

AARON MACNEILNICK GRAHAM ALISTAIR CHEAL TIM MCCLANAHAN