# Presentation: 663178

## Georges Bank Yellowtail Flounder

- Base
- Similar to TRAC 2007 Major Change results
- Change_catch
- Increase_M
- Increase_q
- Purpose: test models under conditions known to produce retrospective patterns in VPA

## GB yt basic setup

- Years 1973-2006 (34 years)
- Ages 1-15, 6+
- Lengths 1-70 cm
- 2 market categories
- 2 surveys (CVs 50%, 40%)
- CV on landings 1%
- Growth stdevs 4.0 initial, 1.5 projection
- Von B params 50, 0.33, -0.75
- 50% Mature ~30 cm
- Selectivity flat-topped, 50% selected 29 cm
- M = 0.2
- F high all years (0.6-1.9)

## GB yt test cases

- Change_catch
- L-W equation in samples reduced approx in half for 1995-2006
- causes missing catch in recent years
- Increase_M
- M increased from 0.2 to 0.5 1995-2006 all ages
- Increase_q
- All indices q tripled 1995-2006

## Georges Bank Yellowtail Flounder

|  | BASE | Change
Catch | Increase M | Increase q |
| --- | --- | --- | --- | --- |
| AIM | SSB: unbiased
F: slightly + |  |  |  |
| ASPIC |  |  |  |  |
| SCALE | SSB: unbiased
F: unbiased |  |  |  |
| VPA | SSB: 5-40% +
F: slightly - |  |  |  |
| ASAP | SSB: 2-20%
F: slightly - |  |  |  |

## ASPIC

- No contrast between catch and CPUE  (inability to estimate SPmax)
- One way trip (inability to estimate depletion in first year)
- True for all simulated data sets, no acceptable results

## Georges Bank Yellowtail Flounder

|  | BASE | Change
Catch | Increase M | Increase q |
| --- | --- | --- | --- | --- |
| AIM | SSB: unbiased
F: slightly + | SSB: unbiased
F: 50% - | SSB: unbiased
F: 10-20% + | SSB: bias window
F: 50% - |
| ASPIC | One way trip problem |  |  |  |
| SCALE | SSB: unbiased
F: unbiased |  |  |  |
| VPA | SSB: 5-40% +
F: slightly - |  |  |  |
| ASAP | SSB: 2-20%
F: slightly - |  |  |  |

## AIM

## Georges Bank Yellowtail Flounder

|  | BASE | Change
Catch | Increase M | Increase q |
| --- | --- | --- | --- | --- |
| AIM | SSB: unbiased
F: slightly + | SSB: unbiased
F: 50% - | SSB: unbiased
F: 10-20% + | SSB: bias window
F: 50% - |
| ASPIC | One way trip problem |  |  |  |
| SCALE | SSB: slightly -
F: slightly + | SSB: 10-30% -
F: +/- 30% | SSB: +/- 10%
F: +/- 25% | SSB: >50% +
F: >50% - |
| VPA | SSB: 5-40% +
F: slightly - |  |  |  |
| ASAP | SSB: 2-20%
F: slightly - |  |  |  |

## SCALE

## Georges Bank Yellowtail Flounder

|  | BASE | Change
Catch | Increase M | Increase q |
| --- | --- | --- | --- | --- |
| AIM | SSB: unbiased
F: slightly + | SSB: unbiased
F: 50% - | SSB: unbiased
F: 10-20% + | SSB: bias window
F: 50% - |
| ASPIC | One way trip problem |  |  |  |
| SCALE | SSB: slightly -
F: slightly + | SSB: 10-30% -
F: +/- 30% | SSB: +/- 10%
F: +/- 25% | SSB: >50% +
F: >50% - |
| VPA | SSB: 5-40% +
F: slightly - | SSB: >50% -
F: > 50% +/- | SSB: 50% -
F: 40% + | SSB: >50% +
F: >50% - |
| ASAP | SSB: 2-20%
F: slightly - |  |  |  |

## VPA

## Georges Bank Yellowtail Flounder

|  | BASE | Change
Catch | Increase M | Increase q |
| --- | --- | --- | --- | --- |
| AIM | SSB: unbiased
F: slightly + | SSB: unbiased
F: 50% - | SSB: unbiased
F: 10-20% + | SSB: bias window
F: 50% - |
| ASPIC | One way trip problem |  |  |  |
| SCALE | SSB: slightly -
F: slightly + | SSB: 10-30% -
F: +/- 30% | SSB: +/- 10%
F: +/- 25% | SSB: >50% +
F: >50% - |
| VPA | SSB: 5-40% +
F: slightly - | SSB: >50% -
F: > 50% +/- | SSB: 50% -
F: 40% + | SSB: >50% +
F: >50% - |
| ASAP | SSB: 2-20%
F: slightly - | SSB: >40% -
F: > 40% +/- | SSB: 10-30% +/-
F: 10-30% +/- | SSB: >50% +
F: >50% - |

## ASAP

## VPA vs SCALE vs ASAP (NAA)

## Precision (SSB and F)

- AIM: ~ 0.2-0.3, did not vary by case
- SCALE: 0.1-0.4 (increased with retros)
- VPA*: <0.05 (incr. in final year), did not vary
- ASAP: <0.05 (incr. in final year), did not vary
- *VPA CVs are for age-specific SSB, F

## GBYT Conclusions

- Small amount of bias in base case (only 100 simulated data sets?)
- All models failed on retro cases, but AIM matched ‘replacement yield’ beyond 1st window in retro years
- Increasing M and incr. q both had opposing effects on SSB and F (but acted in diff. direction)
- Chg. Catch created “spike” in F just prior to reduced catch
**General pattern**

## ASAP

**VPA**

## PopSim GBYT Final Realization

- Ran VPA and ASAP retrospective analyses for GBYT Inc_M, Inc_q, and Change_catch final realizations
- Same data given to each model
- PopSim results show both are biased
- Do both show a retro? Yes

## VPA     Increase_M   ASAP

- rho=-0.29

- rho=0.46

- rho=-0.22

- rho=0.27

## VPA     Increase_q   ASAP

- rho=-0.70

- rho=2.38

- rho=-0.72

- rho=2.13

## VPA     Change_catch   ASAP

- rho=1.33

- rho=-0.56

- rho=-0.55

- rho=1.02