# Presentation: 142686

## Multispecies Virtual Population Analysis

**Summary of Model, Applications, and Advances**
**Lance Garrison, Jim Ianelli, Megan Tyrrell, **
**Jason Link**
**NEMoW Workshop**
**28-31 August 2007**

## Structure of MSVPA Model

**Other Food**

**Consumption = Predator BM * %DR**

**P****prey**** = (Suitable Biomass)****prey**** / Total Suitable Biomass **

**C****prey**** = Consumption * P****prey**

**M2****prey**** = C****prey ****/ BM****prey**

**M2****age**

**Single Species VPA**

**BM****age**

**BM****age**

**BM****age**

**BM****age**

**BM****age**

**Diet Data**

**Suitability**
**Params.**

**Other **
**Predators**

## Applications of MSVPA

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

- Northeast US – Tsou & Collie
- Cod, Haddock, Dogfish, Hakes, Herring, Mackerel,
- Sand Lance, Skates, Flounder

- Eastern Berring Sea –
-   Livingston & Juardo-Molina
- Walleye 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

**A slice of the food web**

## Model Inputs and Data Requirements

- Age-structured catch and biological information
- for all predator and prey species and associated
- tuning 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 model
- that fits data and provides uncertainty
- 4M formulation results in a Type II feeding response
- which leads to depensatory dynamics at low pop. Sizes
- Assumes constant suitability parameters and requires
- a comprehensive, large scale diet data set
- Data intensive – but then so are all Ecosystem Models

## Expanded MSVPA (MSVPA-X)

- Developed for ASMFC to address interactions
- between Atlantic Menhaden and its major predators

- Explicitly incorporates tuned VPAs in the form
- of extended survivors analysis

- Implements a “weak” Type III feeding response

- Decomposes “suitability” into preference, spatial
- overlap, 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*

## NEUS Application of MSVPA-X

- Spiny Dogfish, Winter Skate, White Hake, Northern Goosefish,
- Georges Bank and South Cod

**NEUS Application of MSVPA-X**

*Megan Tyrrell, Jason Link*

## NEUS Application of MSVPA-X

**NEUS Application of MSVPA-X**

*Megan Tyrrell, Jason Link*

## Multispecies statistical model

*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

** ****MSM system for the Bering Sea**

- Walleye pollock

- Pacific cod

**Fishery**

- Arrowtooth flounder

## Pollock abundance (age 3+)

## Pollock recruitment

## Why Use MSVPA or MSM Approaches ?

- These are MRM models, so suited for specific questions
- or trophic interactions
- Data rich situations with age-structured catch and
- biological data for a few species
- Both data and outputs are directly related to SS
- assessment models.  As such, easy to compare to data
- and a common “language” for managers
- Poised for “tactical” advice