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George Bank Cod. Base Similar to GARM2005 assessment Fleet_dome Survey_dome Survey_and_Fleet_dome Purpose: test models ability to estimate correctly when doming occurs. GB cod basic setup. Years 1978-2005 (27 years) Ages 1-25, 10+ Lengths 1-170 cm 3 market categories

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george bank cod
George Bank Cod
  • Base
    • Similar to GARM2005 assessment
  • Fleet_dome
  • Survey_dome
  • Survey_and_Fleet_dome
  • Purpose: test models ability to estimate correctly when doming occurs
gb cod basic setup
GB cod basic setup
  • Years 1978-2005 (27 years)
  • Ages 1-25, 10+
  • Lengths 1-170 cm
  • 3 market categories
  • 3 surveys (CVs 20%, 30%, 25%)
  • CV on landings 5%
  • Growth stdevs 5.0 initial, 2.0 projection
  • Von B params 148.2, 0.1198, -0.6173
  • 50% Mature ~42 cm
  • Selectivity flat-topped, 50% selected 64 cm
  • M = 0.2
  • F high (0.5-2.4) then reduced in final years (0.48, 0.35)
gb cod test cases
GB cod test cases
  • Fleet_dome
    • Moved ascending limb of selectivity curve left to allow for nearly full selectivity at peak of dome
gb cod test cases4
GB cod test cases
  • Survey_dome
    • Each survey mirrored for descending limb of selectivity curve at age 7
slide6
AIM

Issues with low (or no) sampling in some years

scale
SCALE

Issues with very low sampling in some years

vpa ssb
VPA (SSB)

Poor performance for ages>6

vpa faa
VPA (FAA)

Poor performance for ages>6

precision ssb and f
Precision (SSB and F)
  • AIM: ~ 0.1, did not vary by case
  • SCALE: 0.2-0.5 (increased with retros)
  • VPA*: 0.05-0.4 (poor ages>6), did not vary
  • ASAP: <0.05, did not vary

*VPA CVs are for age-specific SSB, F

gb cod conclusions
GB Cod Conclusions
  • Simulation set-up precluded model comparisons for AIM, ASPIC, and SCALE
  • Between VPA and ASAP, bias was similar, but VPA estimates at age degraded faster than ASAP; ASAP more precise
  • Dome not an issue for survey because of age-specific indices (rather than age comp. for total N index)
  • Dome effect in fleet probably minimized because of large simulated F (fewer older fish, so misspecifying those selectivities added little bias)
vpa pr

Base

Fleet Dome

VPA PR

2002

2003

2004

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