Input values to spr models estimated from stock assessment models fixed parameters assumptions
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Input values to SPR models Estimated from Stock assessment models Fixed parameters Assumptions. Estimated in stock assessment models. Fishery selectivity curves for retained and discarded crab by sex and shell condition Trawl bycatch selectivity and F Growth transition matrix by sex

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Estimated in stock assessment models

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Input values to spr models estimated from stock assessment models fixed parameters assumptions

Input values to SPR modelsEstimated from Stock assessment modelsFixed parametersAssumptions


Estimated in stock assessment models

Estimated in stock assessment models

  • Fishery selectivity curves for retained and discarded crab by sex and shell condition

  • Trawl bycatch selectivity and F

  • Growth transition matrix by sex

  • Molting probability by size – male king crabs


Fixed and assumed parameters

Fixed and assumed parameters

  • Natural mortality – agreed upon by workgroup as 0.23 for snow and Tanner crabs and 0.18 for King crabs.

  • Maturity curves by size for males and females – estimated from survey data

  • Mean weight by size and sex – estimated from survey data


Assumed parameters

Assumed parameters

  • Mating Ratio – number of females one male will mate with

  • Mortality of discarded crab in directed pot fisheries (agreed upon as 50% for base runs)

  • Groundfish trawl discard mortality (80%).

  • Form (Beverton and Holt or Ricker) and steepness of the SR curves


Estimated in stock assessment models

  • Tanner and snow crab males and females have terminal molt at maturity.

  • Both males and females have only one year of their mature life when they should be new shell (if new shell was equivalent to shell age < 1 year)


Snow crab calculation of effective female spawning biomass

Snow CrabCalculation of effective female spawning biomass

  • Total effective sp biomass = efspbio + old shell male sp biomass


Estimation of effective male spawning biomass using mating ratio

Estimation of effective male spawning biomass using mating ratio

  • If an assumed mating ratio is used then emspbio is,

  • , if NMM0 > (NMF/MR).

  • This is applied only if there are more males than are needed to fertilize the females, that is if NMM0 > (NMF/MR). The use of the mating ratio reduces the male spawning biomass at F=0, to only the biomass that is needed to fertilize the mature females (at F=0).


Estimated in stock assessment models

Spawning biomass per recruit model results for snow crab. Mating ratio = 1.7(sex ratio at F=0). Total effective spawning biomass is female effective spawning biomass plus effective male spawning biomass (no mating ratio).


Estimated in stock assessment models

Figure 3. Mating ratio = 3.0. Primiparous and mulitparous separate. Total effective spawning biomass is female effective spawning biomass plus old shell male spawning biomass(no Mating ratio).


Estimated in stock assessment models

Red King Crab mating ratio 1:2(sex ratio at F=0), discard mortality 50%, all females together in effective spawning biomass calculation, nonmolting males


Red king crab mating ratio 1 3 50 discard mortality prim and mult together nonmolting males

Red King crab Mating ratio 1:3, 50% discard mortality,prim and mult together, nonmolting males


Estimated in stock assessment models

Red King Crab mating ratio 1:3, discard mortality 50%, MR applied separately to primiparous and multiparous in effective spawning biomass calculation, nonmolting males(each male can potentially mate with 6 females)


Estimated in stock assessment models

Red King crab Mating ratio 1:3, 50% discard mortality,prim and mult separate, all males (2005 F for red king crab = 0.31, max target F=0.76)


Red king crab mating ratio 1 3 50 discard mortality prim and mult separate nonmolting males

Red King crab Mating ratio 1:3, 50% discard mortality,prim and mult separate, nonmolting males


Total effective spawning biomass red king crab

Total effective spawning biomass, Red king crab


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