Multispecies Virtual Population Analysis

Summary of Model, Applications, and Advances

Lance Garrison, Jim Ianelli, Megan Tyrrell, Jason Link

NEMoW Workshop28-31 August 2007

Structure of MSVPA Model

Other Food

Consumption = Predator BM * %DR

Pprey = (Suitable Biomass)prey / Total Suitable Biomass

Cprey = Consumption * Pprey

M2prey = Cprey / BMprey

M2age

Single Species VPA

BMage BMage BMage BMage BMage

Diet Data

SuitabilityParams.

Other Predators

Applications of MSVPA

North Sea – ICES Working GroupCod, Haddock, Whiting, Pout, Saithe, Herring, Sprat, Mackerel,Plaice, Sand lance

Northeast US – Tsou & CollieCod, Haddock, Dogfish, Hakes, Herring, Mackerel,Sand Lance, Skates, Flounder

Eastern Berring Sea – Livingston & Juardo-MolinaWalleye Pollock, Pacific Cod, Turbot, Yellowfin Sole, Arrowtooth Flounder, Fur Seal, Rock Sole, Pacific Herring

Implementation in the “4M” Package from ICES

A slice of the food web

Model Inputs and Data Requirements

Age-structured catch and biological information for all predator and prey species and associatedtuning indices for VPAs

Diet data including prey size/age information

Consumption parameters: daily rations or temperature dependent evacuation rates

Other food biomasses (and/or other predators)

Known Weaknesses in MSVPA

Overparameterized - not a statistical modelthat fits data and provides uncertainty

4M formulation results in a Type II feeding responsewhich leads to depensatory dynamics at low pop. Sizes

Assumes constant suitability parameters and requiresa comprehensive, large scale diet data set

Data intensive – but then so are all Ecosystem Models

Expanded MSVPA (MSVPA-X)Developed for ASMFC to address interactionsbetween Atlantic Menhaden and its major predators

Explicitly incorporates tuned VPAs in the formof extended survivors analysis

Implements a “weak” Type III feeding response

Decomposes “suitability” into preference, spatialoverlap, and size preference

- increases the ability to assimilate data- results in dynamic suitabilities

Implements a predator growth model

NEUS Application of MSVPA-X

Megan Tyrrell, Jason Link

Five most important predatorsSpiny Dogfish, Winter Skate, White Hake, Northern Goosefish,Georges Bank and South Cod

Porportional Consumption by Top 5 Predators on Major Prey Types

0%10%20%30%40%50%60%70%80%90%

100%

Prey Type

Po

rpo

rtio

nal

co

nsu

mp

tio

n GB&S Cod

Northern Goosefish

White Hake

Winter Skate

Spiny Dogfish

NEUS Application of MSVPA-X

Megan Tyrrell, Jason Link

Total Mortality of Mackerel

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

Year

Mo

rtal

ity

Average F ages 0-7

Average M2 ages 0-7

Total Mortality of Herring

0

0.2

0.4

0.6

0.8

1

1.2

Year

Mo

rtalit

y

Average F ages 0-10

Average M2 ages 0-10

NEUS Application of MSVPA-X

Megan Tyrrell, Jason Link

Multispecies statistical model

Data

Prior

information

Population Dynamics

O bjective function

Predation equations

Posterior D is tribution

Likelihood

Profile

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

Data

Jim Ianelli

MSM Implementation: Eastern Bering Sea

• Species:

– Pollock, Pacific cod and arrowtooth flounder

• Coded in C++ (ADMB)

• Tuned to:

– Fishery catch

– Survey indices

– Age (pollock) and length (arrowtooth flounder, Pacific cod) compositions

Jim Ianelli

MSM system for the Bering Sea

Walleye pollock

Pacific codFishery

Arrowtooth flounder

Pollock abundance (age 3+)

0

5000000

10000000

15000000

20000000

25000000

30000000

35000000

40000000

1975 1980 1985 1990 1995 2000 2005 2010

Year

N3+

(10

00's

)

Pollock recruitment

0.0E+00

2.0E+07

4.0E+07

6.0E+07

8.0E+07

1.0E+08

1.2E+08

1975 1980 1985 1990 1995 2000 2005 2010

MSVPA MSM SSP

Year

Rec

rutm

ent

(100

0's)

Why Use MSVPA or MSM Approaches ?

These are MRM models, so suited for specific questionsor trophic interactions

Data rich situations with age-structured catch and biological data for a few species

Both data and outputs are directly related to SSassessment models. As such, easy to compare to dataand a common “language” for managers

Poised for “tactical” advice