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

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

Bottom trawl survey area

Considerations:Considerations:

- These are bottom trawl data for a semi-pelagic species.- 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:Considerations:

- These are bottom trawl data for a semi-pelagic species.

- Walleye pollock becomes increasingly demersal with age,- Walleye pollock becomes increasingly demersal with age, so older fish are sampled better by the bottom trawl.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: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 - But length to age conversion is better for younger walleye pollock (there is less overlap of length ranges).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: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- Border effects may influence apparent patterns if large numbers of fish move into, or out of, the survey area.numbers of fish move into, or out of, the survey area.

- Twenty consecutive years of standardized data!

Considerations: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!- Twenty consecutive years of standardized data!

1990 age-6

1. Will the centroids reflect previously described spatial1. Will the centroids reflect previously described spatial patterns relative to:patterns relative to: - Temperature?- Temperature? - Ontogeny?- Ontogeny?

2. What other spatial patterns are apparent? - Northwest vs. Southeast Yearclasses - What might cause these patterns? - What are some implications of this result?

0

1

2

3

4

Year

Mea

n B

ott

om

Tem

p. (

C)

1. Will the centroids reflect previously described spatial patterns relative to: - Temperature? YesYes - Ontogeny? YesYes

2. What other spatial patterns are apparent?2. What other spatial patterns are apparent? - Northwest vs. Southeast Yearclasses- Northwest vs. Southeast Yearclasses - What might cause these patterns? - What are some implications of this result?

1982 yc 1989 yc 1992 yc

0

25,000

50,000

75,000

1963 1966 1969 1972 1975 1978 1981 1984 1987 1990 1993 1996 1999

Year Class

Nu

mb

ers

at a

ge

1

Year-Class EstimatesYear-Class Estimates

0

20

40

60

80

100

3 4 5 6 7 8 9 10

Age

% N

o. b

y ye

arcl

ass

in S

E

1978

1982

1984

1989

1992

1996

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 might cause these patterns? - What are some implications of this result?

1982 yc 1989 yc 1992 yc

- What might cause these patterns?- What might cause these patterns?

A) Successful reproduction only in the SE with eggsA) Successful reproduction only in the SE with eggs and larvae being transported to the NW or the SE and larvae being transported to the NW or the SE areas where the majority remain.areas where the majority remain.

OROR

B) Successful reproduction in the SE and NW areasB) Successful reproduction in the SE and NW areas with the majority of juveniles returning to theirwith the majority of juveniles returning to their area of origin. area of origin.

““Strong year classes in 1972 and 1973 appear to have supportedStrong year classes in 1972 and 1973 appear to have supportedthe fishery in the northwest in the early and mid 1970’s…the fishery in the northwest in the early and mid 1970’s…

whereas a strong 1978 year class appears to be supporting thewhereas a strong 1978 year class appears to be supporting therecent fishery in the southeast…”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?- What are some implications of this result?

1996

19921984

1982

0.0E+00

2.0E+09

4.0E+09

6.0E+09

8.0E+09

1.0E+10

Survey year

No

. b

y y

earc

lass (

NW

)

19891978

0.0E+00

2.0E+09

4.0E+09

6.0E+09

8.0E+09

1.0E+10

Survey year

No

. b

y y

earc

lass (

SE

)

Conclusions:Conclusions:The age-specific spatial distribution of walleye pollock in theThe age-specific spatial distribution of walleye pollock in theeastern Bering Sea is highly variable.eastern Bering Sea is highly variable.

Warm years allow walleye pollock to move further on-shelfWarm years allow walleye pollock to move further on-shelfduring the summer.during the summer.

The spatial distribution of a yearclass appears to persist forThe spatial distribution of a yearclass appears to persist formany years. Few yearclasses appear to contribute many many years. Few yearclasses appear to contribute many walleye pollock to the southeast area.walleye pollock to the southeast area.

Patterns in surface current simulations appear to correlatePatterns in surface current simulations appear to correlatewith the recruitment success of large yearclasses and with with the recruitment success of large yearclasses and with the geographic area of the recruitment.the geographic area of the recruitment.

Spatial distribution and ontogenetic Spatial distribution and ontogenetic movement of walleye pollock in the movement of walleye pollock in the

eastern Bering Seaeastern Bering Sea

Presenters:Presenters:Troy Buckley, Angie Greig, Troy Buckley, Angie Greig, James Ianelli, Patricia Livingston, James Ianelli, Patricia Livingston,

and Gary Waltersand Gary Walters