# Presentation: 218836

## Gulf of Maine codSCAA/ASPM vs ADAPT-VPADoug Butterworth and Rebecca Rademeyer

- __________________________________________________________________
- Marine Resource Assessment and Management Group, University of Cape Town

## METHODS

**ADAPT-VPA**- Backward calculation- Oldest-age *F*  assumption- Catches-at-age exact

**SCAA/ASPM**- Based on separability:  *F**y,a* = *S**a**F**y*- Forward estimation, typically likelihood based- Errors in proportions-at-age

**SCAA****	**- Statistical treatment of age data errors	   May include S/R relationship**ASPM **- Age-structured dynamics	   Must include S/R relationship	   Age data not necessary

## ASPM methodology updates

* **M* fixed (0.2) (not estimated)

-  MSY calculated internally

- - All *S**a*’s estimated (no functional form imposed)

- - Model to 11+, though fit to 7+ data

- - Fully Bayesian PI computations

## VPA methodology

* ***RC-VPA**: as Mayo and Col (2006) – asymp. flat selectivity

- Fit either to ages 1-6 or 1-7+MSY calculated externally

- - **Alt-VPA (**********=1)**: removes inconsistency in plus-group eqns

## Data used

- Mayo and Col (2006)

## 2003 ResultsGulf of Maine cod

## ResultsRC-ASPM (M=0.2, Ricker)

- Shading shows 95% PIs

## Abundance index fitsRC-ASPM (M=0.2, Ricker)

## Average age-proportion fitsRC-ASPM (M=0.2, Ricker)

## Selectivity estimatesRC-ASPM (M=0.2, Ricker)

**Commercial, pre-1992**
**Commercial, post-1991**

## Selectivity estimatesRC-ASPM (M=0.2, Ricker)

**Commercial, pre-1992**
**Commercial, post-1991**
**NEFSC-Spring**
**NEFSC-Autumn**

## ASPMStock-recruit relationships

**ASPM****Stock-recruit relationships**

**-****l****nL = -46.3**

**Ricker**

## ASPMStock-recruit relationships

**-****l****nL = -46.3**

**Ricker**

**Beverton-Holt**

**-****l****nL = -39.9**

**If estimate ********** parameter (********** =1 for Ricker): 1.05 [0.54; 1.15]**

## ASPMSelectivity dome

**-****l****nL = -46.3**

***S*****7****/*****S*****6**** =0.52 [0.41; 0.64]**

## ASPMPast catch selectivity

**1992-2004: Estimated**
**1981-1991: Estimated**
**Pre-1982: Set equal to 1982-1991**

**Second order effect**

**(Important assumption is unchanging survey selectivity)**

## ASPM Results

## ASPM Results

## ASPM Results

## ADAPT-VPA comparisons

**VPA as Mayo and Col (2006)**

## ADAPT-VPA comparisons

**VPA as Mayo and Col (2006)**
**RC-VPA**

## ADAPT-VPA comparisons

**VPA as Mayo and Col (2006)**
**RC-VPA**
**Alt-VPA, **********=1**

## ADAPT-VPA comparisons

**VPA as Mayo and Col (2006)**
**RC-VPA**
**Alt-VPA, **********=1**
**Alt-VPA, **********=est**

## ADAPT-VPA comparisons

**VPA as Mayo and Col (2006)**
**RC-VPA**
**Alt-VPA, **********=1**
**Alt-VPA, **********=est**
**ASPM – Data from 1982**

## ADAPT-VPA comparisons

**VPA as Mayo and Col (2006)**
**RC-VPA**
**Alt-VPA, **********=1**
**Alt-VPA, **********=est**
**ASPM – Data from 1982**
**RC – ASPM**

## ADAPT-VPA comparisons

**VPA as Mayo and Col (2006)**
**RC-VPA**
**Alt-VPA, **********=1**
**Alt-VPA, **********=est**
**ASPM – Data from 1982**
**RC – ASPM**

## ADAPT-VPASelectivities

**RC-VPA**

## ADAPT-VPASelectivities

**RC-VPA**
**Alt-VPA, **********=1**

## ADAPT-VPASelectivities

**RC-VPA**
**Alt-VPA, **********=1**
**Alt-VPA, **********=est**

## ADAPT-VPASelectivities

**RC-VPA**
**Alt-VPA, **********=1**
**Alt-VPA, **********=est**
**ASPM – Data from 1982**

## ADAPT-VPASelectivities

**RC-VPA**
**Alt-VPA, **********=1**
**Alt-VPA, **********=est**
**ASPM – Data from 1982**
**RC – ASPM**

## ADAPT-VPA Results

## ADAPT-VPA Results

## ADAPT-VPA Results

## ConclusionsGeneral

*** ***Careful treatment of plus-group

*** ***Fully flexible *S**a* parametrization

*** ***Take care with use of Beverton-Holt S/R relationship

## ConclusionsGulf of Maine cod

*** ***2003 difference as ADAPT-VPA imposed asymp. flat selectivity

*** ***Asymp. flat selectivity statistically inconsistent with data

- Independent evidence of mechanisms to give dome shape ?

- Robust to sensitivities

*** ***SCAA to be preferred

- Enables use of pre-1982 data

- Greater range of *B**sp*

- Better precision of estimates

- M-S Act focus on MSY

## Thank you for your attention