# Presentation: 245490

## Comments and developments on extended single-species and minimally realistic models

- James N. Ianelli
- Alaska Fisheries
- Science Center
- Seattle, WA

- This information is distributed solely for the purpose of predissemination peer review under applicable guidelines.  It has not been formally disseminated by NOAA Fisheries and should not be construed to represent any agency determination or policy.

**Notes:**
CPUE in the Navarin area 
September - 65 t/day  
July - 89 t/day 
August - 86 t/day 

Fish 40-45 cm predominates in catch (about 65%), 
fish 46-50 cm - about 15%.

Todd’s Russian numbers:
2002 900
2003 1,100
2004 1,000

## Age-structured models used at the AFSC

|  | Single-species | Predators as fleets | TIM (Bycatch) | MSM | MSVPA/MSFOR |
| --- | --- | --- | --- | --- | --- |
| Statistical approach |   |   |   |   |   |
| Multispecies model |   |   |   |   |   |
| Biological interactions |   |   |   |   |   |
| Technical interactions |   |   |   |   |   |

**Notes:**
Types of models used in the AFSC

## Predators as “fleets” approach...

- Hollowed, A.B., Ianelli, J.N., and Livingston, P.A. 2000. Including predation mortality in stock assessments: a case study for Gulf of Alaska walleye pollock. ICES J. Mar. Sci. 57: 279–293.

## Extended single species models

**	****Case study of Eastern Bering Sea Pollock: impact of environmental/ecosystem variability on management advice**

## Tactics from our management guidelines...

- Tactics from our management guidelines...

## Some sources of error in Fmsy 

**Selectivity**

- 	Natural mortality		Growth
- 	Stock-recruitment relationship:

## How does SRR affect EBS pollock management?

**Directly by adjusting the maximum permissible harvest level**
- TAC level would be considerably higher under the following
- Fixed selectivity
- Deterministic mean-mass-at-age
- Fixed natural mortality

## Characterizing cannibalism

**Month**

**Predator concentrations**

- 10

**	****Prey length**

**Prey sizes**

- Studies linking water column data to predator-prey overlap so far inconclusive

**Notes:**
All years, all pollock sizes, 1981-2006, fewer in month 4, most non-summer is observer data

## Regimes?

## Recruitment responses to putative regimes relatively weak for pollock

- Early period

- Recent
- history

- Mean

- 1977-2004

- 1977-1988

- 1989-2004

- 1977-1998

## Body-weight loss/gain

- Based on average for males E of 170W, 1991-2006

## Impact on management due to growth changes are important

## Adding uncertainty in future mean mass-at-age affects quota limit

- Adding future mass-at-ageuncertainty lower the TAC by >20,000 t

## Retrospective diagnostics

- Balloons proportional to uncertainty

## MSM

**Starts w/ age-structured assessment model**
**Same fisheries and survey data, some structural simplifications**
**Diet data incorporated**
**Easy evaluation of alternative predator functional responses**
**Coded in C++ (ADMB)**
- Ease of estimation and evaluating uncertainty (MCMC, non-linear mixed-effects approaches)

**Incomplete data are ok!**

**Notes:**
extends AMAK
uses diet data; allows alternative functional responses
multispecies and single-species use same fisheries and survey data

## Schematic changes

- where
- 	*k* = prey species
- 	*a* = prey age
- 	*y* = year
- 	*f* = fishery

- 	*r* = predator species
- 	*u* = predator age

*From Kinzey*

## Predator functional responses

**Type I: linear**
**Type II: asymptotic**
**Type III: S-shaped**
**Type IV: ratio interference**
**Type V: ratio pre-emption, asymptotic**
**Type VI: Hassel-Varley**
**Type VII: “Ecosim”**

- Predation mortality is allowed to vary among predator age-classes to better mimic the ration data.

*From Kinzey*

## Data vs model fit:daily ration (Types I - VII)

*From Kinzey*

## Model communication

## Pollock

## Age-1 pollock predation

**Notes:**
Predation and cannibalism increases with predator abundance

## Resource utilization

## Age-1 pollock predation

**Notes:**
Predation and cannibalism increases with predator abundance

## Conclusions

**Extended single species models**
- Implied affects on quota limits exist
- Direct affect on quota limits work
**MSM **
- Allow focus on prey sizes and tailored suitabilities
- Provides ability for statistical evaluation
- Fit to real “Data”
- Can be adapted to encompass alternative functional responses
- Are limited in scope
- Only a few elements of the ecosystem included