Сomparison of feeding ecology of chum salmon in the western part of Bering Sea and adjacent waters of Pacific Ocean

E.DulepovaLaboratory of Applied Biocenology,

TINRO -center

• To analyze annual and regional dynamics in feeding of different size groups of the fish.

Our objective wereOur objective were::

• To estimate the role of different plankton groups, particularly, gelatinous plankton in chum feeding over years.

• To estimate the place and role of chum in the trophic structure within ecosystem of the Bering Sea and adjacent waters

Structure of data

Suryes Seasons Years Regions

Bering Sea

Pacific waters of Kamchatka

Okhotsk Sea

Pacific waters ofKuril Islands

1986- 2002Summer-fall

Methods• Criterion Kolmogorov-Smirnov

(comparison of shares)• Cluster analysis

15

Differences in feeding of chum

smaller and larger than 40 sm

>40

<40

Undigested part

medusaectenophores

nekton

copepods

Feeding spectra of large chum salmon in the Bering Sea

1993, 1995

1992, 2002

ctenophores

medusae

nekton

Undigested part

Prey spectrum for chum salmon (> 40 sm)

130.00 140.00 150.00 160.00 170.00 180.00 190.00 200.00

40.00

50.00

60.00

nekton

ctenophores

130.00 140.00 150.00 160.00 170.00 180.00 190.00 200.00

40.00

50.00

60.00

nekton

Prey spectrum for chum salmon (< 40 sm)1995

Chum prey upon animals that belong to different trophic levels

• Euphausiids, copepods, tunicates - non-predatory zooplankton (II trophic level)

•Chaetognats –predatory zooplankton (III trophic level)

Amphipods-predatory zooplankton (III trophic level)

Pteropods -predatory and non-predatory zooplankton ( II, III trophic levels)Coelenterates, Ctenophores - predatory zooplankton (III trophic level)Pisces, squids - (IV trophic level

0

100

200

300

400

500

600

700

800

900

1000кал/г

A.digitale

N.crista

tus

Th. rasch

ii

P. pacifica

P.libellu

la

C.limacin

a

9

9,5

10

10,5

11

11,5

12

12,5

%

A.digitale N.cristatus Th. raschii P. Pacifica P.libellula

Gross caloric density (cal/g wet weight) for salmon prey organism

and

the estimated proportion of prey that is indigestible for salmon (Davis et al., 1998)

A. digitale

A. digitale

The dynamics of gelatinous plankton abundance in stomach contents of large

chum

0

10

20

30

40

50

1986 1987 1990 1992 1993 1995 2000 2002

CtenophoresMedusae

% 1987

1995

Chum salmon belonging to the different trophic levels in the Bering Sea

< 40 sm

15%

43%

42%III trophic level

IV trophic level

V trophic level

30%

45%

25%> 40 sm

Thank you.

Спасибо.