# Presentation: 016075

## Spatial distribution and ontogenetic movement of walleye pollock in the eastern Bering Sea

**Spatial distribution and ontogenetic movement of walleye pollock in the eastern Bering Sea**

- _Presenters:_
- Troy Buckley, Angie Greig,
- James Ianelli, Patricia Livingston,
- and Gary Walters

## Bottom trawl survey area

## Considerations:

**- These are bottom trawl data for a semi-pelagic species.**
- - Walleye pollock becomes increasingly demersal with age,
-   so older fish are sampled better by the bottom trawl.
- - But length to age conversion is better for younger walleye
-   pollock (there is less overlap of length ranges).
- - Border effects may influence apparent patterns if large
-    numbers of fish move into, or out of, the survey area.
- - Twenty consecutive years of standardized data!

## Considerations:

- - These are bottom trawl data for a semi-pelagic species.
**- Walleye pollock becomes increasingly demersal with age,**
**  ****so older fish are sampled better by the bottom trawl.**
- - But length to age conversion is better for younger walleye
-   pollock (there is less overlap of length ranges).
- - Border effects may influence apparent patterns if large
-    numbers of fish move into, or out of, the survey area.
- - Twenty consecutive years of standardized data!

## Considerations:

- - These are bottom trawl data for a semi-pelagic species.
- - Walleye pollock becomes increasingly demersal with age,
-   so older fish are sampled better by the bottom trawl.
**- But length to age conversion is better for younger walleye **
**  ****pollock (there is less overlap of length ranges).**
- - Border effects may influence apparent patterns if large
-    numbers of fish move into, or out of, the survey area.
- - Twenty consecutive years of standardized data!

## Considerations:

- - These are bottom trawl data for a semi-pelagic species.
- - Walleye pollock becomes increasingly demersal with age,
-   so older fish are sampled better by the bottom trawl.
- - But length to age conversion is better for younger walleye
-   pollock (there is less overlap of length ranges).
**- Border effects may influence apparent patterns if large**
**   ****numbers of fish move into, or out of, the survey area.**
- - Twenty consecutive years of standardized data!

## Considerations:

- - These are bottom trawl data for a semi-pelagic species.
- - Walleye pollock becomes increasingly demersal with age,
-   so older fish are sampled better by the bottom trawl.
- - But length to age conversion is better for younger walleye
-   pollock (there is less overlap of length ranges).
- - Border effects may influence apparent patterns if large
-    numbers of fish move into, or out of, the survey area.
**- Twenty consecutive years of standardized data!**

## 1990 age-6

## Slide 9

## 1.  Will the centroids reflect previously described spatial

**     ****patterns relative to:**
**   ****- Temperature?**
**   ****- Ontogeny?**
- 2.  What other spatial patterns are apparent?
-    - Northwest vs. Southeast Yearclasses
-    - What might cause these patterns?
-    - What are some implications of this result?

## Slide 11

## Slide 12

## Slide 13

## 1.  Will the centroids reflect previously described spatial

-      patterns relative to:
-    - Temperature?         **Yes**
-    - Ontogeny?           **Yes**
**2.  What other spatial patterns are apparent?**
**   ****- Northwest vs. Southeast Yearclasses**
-    - What might cause these patterns?
-    - What are some implications of this result?

## Slide 15

## 1982 yc

- 1989 yc

- 1992 yc

## Year-Class Estimates

## Yearclass

## 1.  Will the centroids reflect previously described spatial

-      patterns relative to:
-    - Temperature?
-    - Ontogeny?
- 2.  What other spatial patterns are apparent?
**   **- Northwest vs. Southeast Yearclasses
-    **- What might cause these patterns?**
-    - What are some implications of this result?

## 1982 yc

- 1989 yc

- 1992 yc

##    - What might cause these patterns?

**     ****A) Successful reproduction only in the SE with eggs**
**        ****and larvae being transported to the NW or the SE **
**        ****areas where the majority remain.**
**                                              ****OR**
**     ****B) Successful reproduction in the SE and NW areas**
**        ****with the majority of juveniles returning to their**
**        ****area of origin.  **

## Slide 22

## Slide 23

## “Strong year classes in 1972 and 1973 appear to have supported

- “Strong year classes in 1972 and 1973 appear to have supported
- the fishery in the northwest in the early and mid 1970’s...
- whereas a strong 1978 year class appears to be supporting the
- recent fishery in the southeast...”
- Francis, R.C. and K.M. Bailey.  1983.  Factors Affecting
-      Recruitment of Selected Gadoids in the Northeast Pacific
-      and East Bering Sea.  Pages 35-60 *in* W. Wooster. (ed.)
-      From Year to Year.  Washington Sea Grant, University
-      of Washington, Seattle.

## 1.  Will the centroids reflect previously described spatial

-      patterns relative to:
-    - Temperature?
-    - Ontogeny?
- 2.  What other spatial patterns are apparent?
**   **- Northwest vs. Southeast Yearclasses
-    - What might cause these patterns?
-    **- What are some implications of this result?**

## Slide 26

## Conclusions:

**Conclusions:**

**The age-specific spatial distribution of walleye pollock in the**
**eastern Bering Sea is highly variable.**
**Warm years allow walleye pollock to move further on-shelf**
**during the summer.**
**The spatial distribution of a yearclass appears to persist for**
**many years.  Few yearclasses appear to contribute many **
**walleye pollock to the southeast area.**
**Patterns in surface current simulations appear to correlate**
**with the recruitment success of large yearclasses and with **
**the geographic area of the recruitment.**

## Slide 28

## Spatial distribution and ontogenetic movement of walleye pollock in the eastern Bering Sea

_**Presenters:**_
**Troy Buckley, Angie Greig, **
**James Ianelli, Patricia Livingston, **
**and Gary Walters**