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The a4a InitiativeWhat if stock assessment is as simple

as a linear model ?

Ernesto Jardim*Colin Millar

Iago MosqueiraChato Osio

Finlay Scott

JRCUnit of Maritime Affairs

Fishreg* ernesto.jardim@jrc.ec.europa.eu

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What if ...

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We could assess allstocks in a sea basin !?

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Think about stockassessment as the

starting point !

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Ok, but

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How do we do it ?

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A bit of reality

Europe spends 50-70 million euros

per year collecting data for stockassessment.

In Europe 300+ stocks are sampledfor biological information.

ICES and GFCM assess ~ 100

stocks.

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a4a initiative

(a) develop an assessment method

targeting stocks that have a reduced knowledgebase on biology and moderate time series onexploitation and abundance;

(b) trigger the discussion about the problemof massive stock assessment.

(c) capacity building

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a4a stock assessmentframework

A SCA model implemented inR/FLR(*)/ADMB that can be applied

rapidly to a wide range of situationswith low parametrizationrequirements.

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(*) http://flr-project.org

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a4a stock assessment framework

[C]

[I]

[S/R]

f model

q model

r model

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Use R's capabilities to set modelsbased on equations.

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a4a(fmodel= ~ year,qmodel= list( ~ age),

srmodel = ~ factor(year),

stock, indices)

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Log f ~ factor(age) + factor(year)

Log f ~ s(age, k=4) + s(year, k=10)

Log q ~ s(age, k=4) + year

Log f ~ te(age, year, k=c(4, 10))

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Examples

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But we want more

We want to make it

intuitive !!!

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Methods should be implemented in away that it doesn't require a highly

specialized statistician to use them.

Parametrization must have abiological meaning (when possible).

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~ factor(age) + factor(year)

~ separable()

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~ s(age, k=4) + year

~ trawl(catchability=linear)

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Testing, 1,2

WKLIFE stocks

Fishbase stocks(*)

(*) https://fishreg.jrc.ec.europa.eu/web/a4a/simulation-testing

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Testing, 1,2 ...

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Wrapping up

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The framework is opensource andfree to promote transparency,transferability.

It uses R to take advantage of R's

capabilities.It uses ADMB to take advantage ofthe statistical sophistication of AD.

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Wrapping up

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The a4a stock assessment model

provides a flexible framework forstock assessment that can be appliedrapidly to a large number (all ?)

stocks in a sea basin.

(*) web