ISSN 1063-0740, Russian Journal of Marine Biology, 2008, Vol. 34, No. 7, pp. 452–460. © Pleiades Publishing, Ltd., 2008.

Feeding Interactions and Diet of Carnivorous Fishes in the Shelikhov Bay of the Sea of Okhotsk V. V. Napazakov Pacific Research Fisheries Center (TINRO-Center), Vladivostok, 690950 Russia e-mail: [email protected] Accepted June 21, 2007

Abstract—The food spectra, trophic statuses, and feeding interrelations of three most abundant benthic carnivorous fish species inhabiting the Shelikhov Bay—the Pacific cod Gadus macrocephalus, the great sculpin Myoxocephalus polyacanthocephalus, and the Okhotsk sculpin M. ochotensis—are considered based on materials collected during the complex survey of the RV Professor Kaganovsky of the TINRO-Center, in September 2004. It was found that these species were facultative predators with wide food spectra. The significance of prey objects in the diet of the Okhotsk sculpin was as follows: crustaceans, fish, and mollusks. Great sculpin and Pacific cod preyed mostly on fish, then on crustaceans, and mollusks. Pacific cod ate equal proportions of fish and decapods. All the species had age-related variability of diet. The potential competition of great sculpin and Okhotsk sculpin for food was mitigated by the difference in the depths of their ranges, as well as by morphological (body size) and behavioral peculiarities in the areas where their habitats overlapped, and in microecosystems. The most probable competition was among Pacific cod 30–60 cm long and Okhotsk sculpin 20–50 cm in length, as well as among cod and great sculpins of all sizes. DOI: 10.1134/S1063074008070031

INTRODUCTION The foraging of Pacific cod and great sculpin in Far Eastern seas is well studied. But their feeding interactions and the role they play in the trophic structure of benthic fish assemblages are less known [4, 6, 7, 8]. No trophological investigations of predatory benthic fish were conducted earlier in the Shelikhov Bay. The feeding patterns of the Okhotsk sculpin have not been studied until now, and the available information on its biology is rather scarce [1, 9, 10, 12]. The aim of this work is to give a qualitative and quantitative analysis of the prey composition of predatory fish in the Shelikhov Bay, carry out comparative analysis of their food spectra, and define their trophic status and study interspecific feeding interactions. MATERIAL AND METHODS Materials on the feeding patterns of the Pacific cod Gadus macrocephalus, the great sculpin Myoxocephalus polyacanthocephalus and the Okhotsk sculpin M. ochotensis collected during the complex expedition of the RV Professor Kaganovsky in the Shelikhov Bay (Fig. 1) in September 2004 served as the basis for this work. Bottom trawl catches were carried out using a DT 27.1 trawl with a horizontal spread of 16 m and the vertical spread of 6 m. The average trawling rate was 2.7 knots. The depths of samplings at the trawling stations varied from 41 m to 195 m. Daily food intake was

calculated according to N.S. Novikova’s method [5] modified by us [11]. The body length of fish was measured from the tip of the snout to the end of the middle caudal fin rays (FL). Altogether, the 310 stomachs of 136 Pacific cod, 112 great sculpins and 62 Okhotsk sculpins were examined. RESULTS AND DISCUSSION The total biomass of most spread benthic carnivorous fish species in the Shelikhov Bay, including the Pacific cod, great sculpin and Okhotsk sculpin is equal to nearly half the overall biomass of the local benthic fish assemblage (without the walleye pollock Theragra chalcogramma, which is caught with a bottom trawl). The share of Pacific cod amounts to 24.5%, great sculpin—15.5% and Okhotsk sculpin—3.4% of the benthic fish assemblage biomass (according to the data obtained during the expedition). Moreover, the plain sculpin M. jaok and the shaggy sea raven Hemitripterus villosus also occurred in the catches, however their biomass was not so significant in the bay. These species are also referred to benthic predators [6]. The basic food of the Pacific cod, great sculpin and Okhotsk sculpin was represented by the species from three taxonomic groups in the Shelikhov Bay: (1) decapods—the sculptured shrimp Sclerocrangon boreas, the snow crab Chionoecetes opilio, the graceful decorator crab Oregonia gracilis, the spider crab Hyas coarctatus alutaceus and the blue king crab Paralithodes

452

FEEDING INTERACTIONS AND DIET OF CARNIVOROUS FISHES 62°

62°

Great sculpin

Okhotsk sculpin

Shelikhov Bay 2 3

60°

4

3

2

6

58°

3 7

43

5 9

7

individuals per catch 1–4 4–10 10–20 20–50

44

56° 154° 156° 62° Pacific cod

1

3

2

158°

160°

00 200 1 10

162° 154°

156°

3

158°

6

26

4

60°

16

individuals per catch 58° 1–4 4–10 10–20 20–50 56° 160° 162°

Shelikhov Bay 16

60°

3

1

1 1

100 200

58°

56°

Shelikhov Bay

1

100 200

453

154°

22

21 21

156°

10 3

3 20

individuals per catch 1–4 4–10 10–20 20–50

4 39

158°

160°

162°

Fig. 1. Distribution of catches of Okhotsk sculpin, great sculpin and Pacific cod in the Shelikhov Bay, August–September 2004.

platypus; (2) mollusks—octopi Octopus sp.; and (3) other fish species (Tables 1–3). Pacific Cod Altogether, 136 stomachs of Pacific cod with body lengths of 20 to 84 cm from 35 catches were examined (Table 1). The highly diverse food spectrum of cod was formed basically by representatives of two taxonomic groups—decapods and fish. The humpy shrimp Pandalus goniurus (2.2–53.1%), the sculptured shrimp S. boreas (to 9%) and the spiny lebbeid Lebbeus groenlandicus (to 8.4%) prevailed among other shrimp species in the diet of 70 cm long cod. The share of hermit crabs reached 7.8% in the food of fish from the size group 30–40 cm. Fish prey of cod 20–30 cm in length included mostly the Pacific capelin Mallotus villosus (84.4%); individuals over 40 cm consumed herring Clupea pallasii (up to 43.7%), walleye pollock (5.7–34.7%), and cottids (to 8.2%). The rare quillfish Ptilichthys goodei species was found in the stomachs of individuals from the size group 50–60 cm caught at the depth of 98 m. Octopi Octopus sp. had a rather substantial significance (8.7–26.4%) in the diet of cod with body sizes of 40–70 cm. RUSSIAN JOURNAL OF MARINE BIOLOGY

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Pacific cod foraged actively. The average stomach fullness index (SFI) varied from 80 to 675‰. The size group 50–60 cm featured the greatest proportion of empty stomachs (27.5%). The daily food ration (DFR) values for cod with a body length of 30 to 60 cm were 1.6–3.9%. Okhotsk Sculpin Myoxocephalus ochotensis In all, 62 stomachs of fish 16.1–48.0 cm in length from 12 sample catches were processed. The smallest Okhotsk sculpin specimen (16.1 cm) preyed on Lycodes sp. Individuals of the size group 20–30 cm foraged diversely. In their food spectrum, decapods were widely represented by the humpy shrimp P. goniurus (28%), the kuro shrimp Argis ochotensis (9.9%), hermit crabs Paguridae gen. spp. (12.5%) and snow crab (17.9%) (Table 2). Other fish species had lower importance for the diet of this size group (up to 20% by weight). The fourline snakeblenny Eumesogrammus praecisus (12.9%) occurred most frequently in stomachs. Gastropods (4.3%) and bivalves Yoldia amigdalea (1.7%) proved to be far less significant. Feeding of the size group 30–40 cm differed from the group described above. First, the sculptured shrimp No. 7

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Table 1. Food composition of Pacific cod in the Shelikhov Bay, % of total weight Prey items Polychaeta fam. gen. sp. Mollusca Octopus sp. Nuculana pernula Amphipoda Arctolembos arcticus Decapoda Pandalus goniurus Pandalus hypsinotus Pandalopsis lamelligera Sclerocrangon boreas Argis ochotensis Neocrangon communis Eualus fabricii Eualus townsendi Spirontocaris spinus Spirontocaris sp. Lebbeus groenlandicus Lebbeus speciosus Paguridae gen. sp. Paralithodes platypus Chionoecetes opilio Hyas coarctatus alutaceus Decapoda Varia Pisces Pisces gen. sp. Mallotus villosus Theragra chalcogramma Clupea pallasii Cottidae gen. sp. Liparis sp. Icelus spiniger Ptilichthys goodei Chirolophis snyderi Pholis fasciata Lumpenidae sp. Stichaeus sp. Artediellus sp. Aves fam. gen. sp. Average fullness index, ‰ Number of stomachs/samples Share of empty stomachs, % Average length (FL), cm Average weight (total), g Daily food ration, % of body weight

Size group, cm 20–30

30–40

40–50

50–60

60–70

70–80

80–90

– – – – – – 15.6 15.6 – – – – – – – – – – – – – – – – 84.4 – 84.4 – – – – – – – – – – – – 675 3/1 0 24.0 158 –

1.6 – – – – – 86.0 53.1 – – 9.0 – 3.6 – – 0.8 – 5.2 – 7.8 – 1.5 – 5.0 12.4 2.0 9.2 – – – – – – – – – – 1.2 – 349 23/5 8.7 37.2 601 3.9

0.6 8.70 8.60 0.05 – – 55.10 38.30 – – 0.20 – 0.40 – 0.20 0.04 – 8.40 – 0.80 – – – 6.80 35.60 2.40 13.40 – 11.40 8.20 – – – 0.20 – – – – – 193 51/8 9.8 44.5 1063 2.5

– 26.40 26.40 – – – 41.00 13.80 – 2.80 6.20 0.10 – 2.00 0.02 0.02 1.30 7.70 – – – 1.50 5.00 0.70 32.60 17.40 – 5.70 – 6.60 0.04 1.80 0.20 – 0.80 0.04 – – – 122 40/9 27.5 53.8 1860 1.6

– 9.98 9.98 – – – 16.30 2.20 1.50 1.50 1.90 – – – – 0.50 0.10 5.00 0.10 – – – – 3.50 73.80 – – 13.80 43.70 – – 9.20 – – – – 7.00 – – 262 9/6 11.1 66.1 3543 –

– 2.80 2.80 – 0.10 0.10 37.30 4.20 – – 3.10 – – – – – – – – – 30.00 – – – 48.80 0.70 – 34.70 12.40 – – – – – 1.00 – – – 11.05 326 9/5 0 73.2 5103 –

– 0.4 0.4 – – – 99.6 – – – – – – – – – – – – – 99.6 – – – – – – – – – – – – – – – – – – 80 1/1 0 83.5 6900 –

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Total 0.30 9.30 9.30 0.01 0.03 0.03 43.80 17.90 0.20 0.80 3.40 0.01 0.50 0.40 0.05 0.20 0.30 4.60 0.02 1.00 10.50 0.40 0.90 2.60 43.10 4.20 4.30 14.20 13.60 3.00 0.01 1.90 0.04 0.05 0.50 0.01 1.20 0.10 3.43

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Table 2. Food composition of Okhotsk sculpin in the Shelikhov Bay, % of total weight Prey items Polychaeta fam. gen. sp. Mollusca Octopus sp. Gastropoda gen. sp. Yoldia amigdalea Criptonatica (egg laying) Gammaridea Arctolembos arcticus Decapoda Decapoda gen. sp. Decapoda (shrimps) Pandalus goniurus Sclerocrangon boreas Argis ochotensis Eualus fabricii Eualus townsendi Spirontocaris spinus Lebbeus groenlandicus Paguridae gen. sp. Paralithodes platypus Chionoecetes opilio Oregonia gracilis Hyas coarctatus alutaceus Pisces Pisces gen. sp. Lycodes sp. Liparis sp. Pholis fasciata Eumesogrammus praecisus Average fullness index, ‰ Number of stomachs/samples Share of empty stomachs, % Average length (FL), cm Average weight (total), g Daily food ration, % of body weigh

Size group, cm 10–20

20–30

30–40

40–50

– – – – – – – – – – – – – – – – – – – – – – – 100 – 100 – – – 200 1/1 0 17 50 –

0.4 6.0 – 1.7 4.3 – 1.5 1.5 72.2 – 1.3 28.0 – 9.9 0.5 0.9 1.3 – 12.5 – 17.9 – – 19.8 6.0 0.9 – – 12.9 98 44/6 29.5 25.4 245 2.6

– 12.9 6.2 – – 6.7 – – 87.1 11.6 – – 17.8 – – – – 7.1 – – – 13.3 37.3 – – – – – – 252 9/4 33.3 34.4 478 –

– 16.7 16.7 – – – – – 66.6 – – – 16.7 – – – – – – 3.0 – 46.8 – 16.7 – – 13.0 3.7 – 288 8/1 0 43.1 1169 –

(17.8%) and spiny lebbeid (7.1%) prevailed among shrimp species, and, second, spider crab (37.3%) and graceful decorator crab (13.3%) replaced the snow crab in the diet. The food spectrum of the largest Okhotsk sculpin specimens became narrower and consisted of the graceful decorator crab (46.8%), sculptured shrimp (16.7%), octopus (16.7%), as well as the Liparis sp. (13%) and Pholis fasciata (3.7%) fish species. The proportion of empty stomachs in the size group 30–40 cm reached 33.3% of all those examined. Nevertheless average SFI values were relatively high—up to 288‰. The DFR of Okhotsk sculpins from the size group 20–30 cm was 2.6%. RUSSIAN JOURNAL OF MARINE BIOLOGY

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Total 0.1 13.3 10.4 0.4 1.0 1.5 0.3 0.3 72.4 2.6 0.3 6.5 13.0 2.3 0.1 0.2 0.3 1.6 2.9 1.6 4.2 28.3 8.4 13.8 1.4 0.4 7.0 2.0 3.0

Great Sculpin In all, 112 stomachs of individuals 15–80 cm in length from 24 sample catches were analyzed. One great sculpin less than 20 cm in length preyed on Stichaeus sp. (100%) (Table 3). Individuals of the size group 20–30 cm consumed decapods and fish. The former were represented mainly by the graceful decorator crab (55.2%). Sculpins 30– 40 cm in length actively fed on O. gracilis (47%) and sculptured shrimp (28.2%). Individuals over 40 cm took enough large prey—snow crabs (up to 52.3%), octopi Octopus sp. (15.1–24.5%) and large fish such as salmon Oncorhynchus sp. The SFIs of Okhotsk sculpins averaged from 117 to 1240‰ and increased No. 7

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Table 3. Food composition of great sculpin in the Shelikhov Bay, % of total weight Size group, cm Prey items Mollusca Octopus sp. Echinoidea Strongilocentrotus sp. Cirripedia Amphipoda Arctolembos arcticus Decapoda Pandalus goniurus P. hypsinotus Sclerocrangon boreas Argis ochotensis Spirontocaris spinus Lebbeus groenlandicus Paguridae gen. sp. Paralithodes camtschaticus P. platypus Chionoecetes opilio Oregonia gracilis Hyas coarctatus alutaceus Pisces Pisces gen. sp. Theragra chalcogramma Cottidae gen. sp. Liparis sp. Pholis fasciata Stichaeus sp. Oncorhynchus sp. Eumicrotremus soldatovi Liparis latifrons Average fullness index, ‰ Number of stomachs/samples Share of empty stomachs, % Average length (FL), cm Average weight (total), g Daily food ration, % of body weight

Total 20–30

30–40

40–50

50–60

60–70

70–80

80–90

– – – – – – – – – – – – – – – – – – – – 100 – – – – – 100 – – – 247 2/1 50.0 20.0 85 –

– – – – – – – 60.7 2.6 – – – 1.0 – – 2.0 – – 55.2 – 39.3 35.5 – – – 3.8 – – – – 117 16/2 43.8 25.9 222 –

– – – – – – – 98.0 – 4.3 28.2 4.3 – 5.4 3.7 – 0.3 – 47.0 4.9 2.0 0.3 1.6 – – – – – – – 142 23/3 13.0 33.8 498 2.6

24.50 24.50 1.70 1.70 0.70 0.05 0.05 44.10 – – 0.10 – 0.05 1.30 – 4.10 4.80 3.80 29.70 0.20 29.00 0.90 10.20 16.30 0.03 1.50 – – – – 161 54/9 35.2 45.5 1733 2.4

16.4 16.4 – – – – – 63.8 – – 0.7 – – – – – – 52.3 – 10.8 19.8 15.6 – – 4.3 – – – – – 260 11/6 27.3 55.1 2904 −

15.1 15.1 – – – – – 16.6 – – – – – – – – – 2.2 – 14.4 68.2 – – – – – – 68.2 – – 483 5/2 0 64.3 4384 −

– – – – – – – 7.1 – – – – – – – – – 7.1 – – 92.9 9.0 – – – – – – 33.5 50.4 1240 1/1 0 72.0 8300 −

with body size. The DFR values of fish 30–50 cm in length were 2.6–2.4% of body weight. After analyzing the food spectra of Pacific cod, great sculpin and Okhotsk sculpin we came to the conclusion that they are based on such objects as shrimp, crabs, fish and octopi, and have a strong similarity (Fig. 2).

13.50 13.50 0.50 0.50 0.20 0.01 0.01 33.90 0.02 0.20 1.40 0.20 0.02 0.60 0.20 1.10 1.30 12.40 10.60 5.90 51.90 5.40 2.80 4.40 0.70 0.40 0.10 18.00 8.00 12.00

All the studied predators featured age-related variability of food composition, as is shown in Fig. 2. Okhotsk sculpin individuals under 30 cm in length preyed mainly on small size species of shrimp and fish, as well as bivalves and gastropods, and larger ones— over 30 cm—consumed large shrimp, for instance

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457

100 72.4

60

20

9.3 Mollusca 0.03 Amphipoda 0.3 Polychaeta sp.

0.3 0.1

0.01 0.7

16–20 20–30 30–40 40–50 50–60 60–70 70–80

Decapoda Pisces

.8 13.3

13.5

Others

20–30 30–40 40–50 50–60 60–70 70–80 80–90

40

0

.8 43.1

51.9.9

10–20 20–30 30–40 40–50

Share, %

80

Myoxocephalus Myoxocephalus Gadus macrocephlus polyacanthocephalus ochotensis Size of fish, cm Fig. 2. Food composition for various size groups of carnivorous fishes in the Shelikhov Bay, % of total weight.

sculptured shrimp, spider crabs, graceful decorator crab, and octopi (Fig. 2). The great sculpin diet had a decreasing share of crustaceans and an increasing share fish with increasing age. In the decapod part of their diet, the share of large snow crabs grew, and the share of shrimp and small species of crabs, such as the graceful decorator crab, dropped proportionally with age. The share of crustaceans in the diet of larger Pacific cod decreased in favor of fish. Before characterizing the feeding interactions among both sculpin species and Pacific cod, we should provide some figures concerning the overlap of their habitats. According to B.A. Sheiko and V.V. Fyodorov [12], Okhotsk sculpin live at depths 0–40 m, and the great sculpin lives within the 0–775 m range. Our data show that the biomass of Okhotsk sculpin in the water layer 100–200 m is nearly 20 times smaller than in the 41–100 m layer, and the biomass of the great sculpin is only 2.2 times less. That means that the main aggregations of these two species are disconnected, despite the fact that they belong to one elittoral fish assemblage. Pacific cod is known to be an interzonal species [2], consequently it shares common feeding areas with both sculpins. It should be noted that the studied species of sculpins can scarcely be distinguished visually—they are morphologically similar, which can result from the similarity of both their food spectra and dietary habits [14]. The difference in the sets of decapod species in their diets means that the sculpins act in different microecosystems, which may be conditioned by the intricate relief structure of the bottom. On the other hand, the fact that the habitats of the great sculpin, Okhotsk sculpin and Pacific cod overlap spatially is confirmed by the presence of all three species in the same catches. Since the degree of diet similarity depends on the accuracy of determination of food composition, we calRUSSIAN JOURNAL OF MARINE BIOLOGY

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culated the similarity degrees, both at the species level and at the level of taxonomic groups using the method of A.A. Shorygin [13] (Tables 4 and 5). Calculations at the species level definitely showed lower similarity [3], they can be interpreted as actual similarity, and those at a higher taxonomic level as probable similarity. Thus, the similarity degree for predatory fishes in the Shelikhov Bay was mostly low (Table 4): however, it could potentially change to a middle or high one (Table 5). The resemblance of the food spectra of the great sculpin and Okhotsk sculpin and the partial overlap of their habitats testify that these two species can be potential competitors. We can even hypothesize that some competition among sculpins under 50 cm in length exists. The length of the Okhotsk sculpin does not exceed 48 cm, while the great sculpin is larger and large individuals prey mostly on fish. A potential competition is probable among Pacific cod 30–60 cm and Okhotsk sculpin 20–50 cm in length, as well as among Pacific cod and great sculpin of all size groups. CONCLUSION Such fish species in the Shelikov Bay as the Pacific cod, Okhotsk sculpin, and great sculpin are the main facultative predators and have broad food spectra. The significance of prey objects in the diet of the Okhotsk sculpin was as follows: crustaceans, fish, and mollusks. Great sculpin and Pacific cod preyed mostly on fish, crustaceans, and mollusks. All the species had agerelated variability in their diets. The potential competition of the great sculpin and Okhotsk sculpin for food was mitigated by the difference in depths of their ranges, as well as by their morphological (body size) and behavioral features in the areas where their habitats overlapped and in microecosystems. The most probable competition was among Pacific cod 30–60 cm in length No. 7

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l

40–50

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No. 7

l

l

l

l

l

40–50

50–60

60–70

70–80

80–90

l

70–80

l

l

60–70

30–40

l

50–60

l

l

40–50

20–30

l

30–40

l

l

l

l

l

m

l

l

l

l

l

l

l

l

l

l

l

l

l

l

l

l

l

l

l

l

m

l

l

m



0

0

l

l

l

l

l

l

l

l

l

l

m

m

m

l



36.2

0

0

l

l

l

l

l

l

l

l

l

l

l

l

l



0

0

0

0

l

l

l

l

l

l

l

l

l

l

m

m



0

46.8

13.3

9.6

0

l

l

l

l

l

l

l

l

l

l

m



47.3

0

64.0

41.4

8.3

0

l

l

l

m

l

l

l

l

l

l



33.5

34.2

0

51.0

21.1

4.8

0

Note: Degree of diet similarity: l is low (< 33%); m is middle (34–66%); h is high (> 67%).

Pacific cod

l

20–30

l

l

30–40

15–20



l l

0.9



Great sculpin

Size groups, cm

Great sculpin

Pacific cod

l

l

l

m

l

l

l

l

l



21.4

5.9

0

0

21.4

17.7

23.9

0

l

l

l

l

l

l

l

l



2.8

17.5

4.9

0

0

15.1

20.6

2.2

0

l

l

l

l

l

l

l



2.2

16.1

4.7

0.3

9.0

0

0

0

13.1

0

l

l

l

l

l

l



0

0

0

0

18.2

2.6

0

0

0

15.6

0

l

l

l

l

m



24.8

3.5

1.5

4.2

2.9

6.7

5.4

0

9.0

14.2

40.5

0

l

l

l

m



61.7

29.0

2.4

8.6

11.2

11.9

13.1

5.0

0

8.8

14.8

31.6

0

l

l

l



40.0

29.4

13.8

10.5

21.6

39.2

41.7

10.0

20.8

0

23.7

24.5

21.9

0

l

l



28.9

30.9

13.1

2.2

0

10.0

10.7

21.6

5.3

2.7

7.0

11.9

13.1

2.7

0

l



31.1

17.3

19.3

8.0

4.2

0.7

2.8

4.2

19.7

0.3

4.3

0

8.9

5.9

5.0

0



30.4

0.4

0.4

0.4

0

0

0

0.4

0.4

5.2

3.7

0

0

3.4

0.4

0

0

15–20 20–30 30–40 40–50 15–20 20–30 30–40 40–50 50–60 60–70 70–80 20–30 30–40 40–50 50–60 60–70 70–80 80–90

Okhotsk 15–20 sculpin 20–30

Size Species groups, cm

Okhotsk sculpin

Table 4. Diet similarity coefficients for various size groups of predatory fish in the Shelikhov Bay, calculated at the species level

458 NAPAZAKOV

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h

l

m

l

h

m

l

20–30

30–40

40–50

50–60

60–70

70–80

80–90

h

m

m

h

h

h

m

l

m

h

h

h

h

l

h

h

m

l

m

m

h

l

l

l

h

m

h

m

l

h



78.2

0

h

m

m

l

h

h

l

l

m

h

h

h

h

l



79.5

89.6

17.0

l

m

h

l

m

l

h

h

h

l

l

l

m



17.0

0

20.0

100.0

m

h

m

h

h

h

m

m

m

h

h

m



39.0

77.7

60.7

80.7

39.0

h

m

l

m

m

h

l

l

h

m

m



62.7

2.0

68.6

87.1

74.2

2.0

m

h

m

h

h

m

m

m

m

h



46.1

73.1

29.0

77.8

57.0

70.2

29.0

Note: Degree of diet similarity: l is low (<33%); m is middle (34–66%); h is high (>67%).

Pacific cod

h

l

50–60

70–80

l

40–50

h

l

30–40

60–70

m

20–30

l

40–50

h

l

30–40

15–20



l h

20.0



Great sculpin

Size groups, cm

Great sculpin

Pacific cod

m

m

m

h

h

h

m

l

m



80.5

65.8

80.7

20.0

97.2

76.7

89.9

20.0

l

l

h

m

m

l

h

h



51.7

60.7

84.4

55.6

68.0

48.7

29.5

42.6

68.0

l

m

h

m

m

l

h



75.1

27.1

36.1

9.1

46.1

93.0

24.1

7.1

27.1

93.0

l

h

h

m

m

l



91.1

83.6

35.6

44.6

17.6

54.6

84.0

32.6

15.6

35.6

84.0

h

m

l

m

h



27.6

19.1

28.6

75.8

56.1

88.0

72.7

12.0

78.6

86.0

84.6

12.0

m

h

m

h



67.7

51.6

43.1

61.3

83.8

81.8

57.1

91.1

36.0

80.8

63.8

81.5

36.0

m

h

m



82.7

53.0

48.6

40.1

64.7

77.4

94.5

43.0

80.0

33.0

74.7

53.9

67.0

33.0

l

h



59.3

61.0

28.3

89.6

81.1

94.3

46.3

55.3

18.3

55.3

74.0

43.3

26.3

42.3

74.0

m



68.1

73.1

76.1

49.3

64.6

56.1

19.4

60.1

69.2

39.3

76.3

49.0

57.1

40.1

60.2

49.0



37.7

16.7

41.4

55.5

86.0

15.6

7.1

17.0

64.2

44.5

98.0

60.7

0

67.0

87.5

72.6

0

15–20 20–30 30–40 40–50 15–20 20–30 30–40 40–50 50–60 60–70 70–80 20–30 30–40 40–50 50–60 60–70 70–80 80–90

Okhotsk 15–20 sculpin 20–30

Size Species groups, cm

Okhotsk sculpin

Table 5. Diet similarity coefficients for various size groups of predatory fish in the Shelikhov Bay, calculated at the level of higher taxonomic groups

FEEDING INTERACTIONS AND DIET OF CARNIVOROUS FISHES 459

460

NAPAZAKOV

and Okhotsk sculpins 20–50 cm in length, as well as among cod and great sculpins of all sizes. REFERENCES 1. Borets, L.A., Annotirovannyi spisok ryb dal’nevostochnykh morei (The Annotated List of Fishes of Far Eastern Seas), Vladivostok: TINRO-Tsentr, 2000. 2. Borets, L.A., Patterns of Vertical Distribution of Benthic Fishes on the Western Kamchatka Shelf for Summer Period, Vopr. Ikhtiol., 1989, vol. 29, issue 3, pp. 370– 376. 3. Metodicheskoye posobiye po izucheniyu pitaniya i pischevykh otnosheniy ryb v yestestvennykh usloviyakh (Methodical Handbook for the Study of Feeding and Food Interrelations of Fishes in a Natural Environment), Moscow: Nauka, 1974. 4. Napazakov, V.V., Trophic Interrelations of Fishes in Benthic Ichthyocenes of the Western Bering Sea, Izv. TINRO, 2004, vol. 139, pp. 19–42. 5. Novikova, N.S., On Opportunity to Calculate Daily Rations of Fishes in Natural Conditions, Vestn. MGU, 1949, no. 9, pp. 107–111. 6. Tokranov, A.M., Dietary Habits of Carnivorous Fishes on the Western Kamchatka Shelf, Vopr. Ikhtiol., 1992, vol. 32, issue 2, pp. 119–128. 7. Tokranov, A.M. and Vinnikov, A.V., Dietary Habits of the Pacific cod Gadus morhua macrocephalus and Its Place in the Trophic System of Kamchatkan Coastal Waters, Vopr. Ikhtiol., 1991, vol. 31, issue 2, pp. 253– 266. 8. Poltev, Yu.I. and Nemchinova, I.A., On Foraging of the Cod Gadus morhua macrocephalus and Its Place in the Trophic Structure of Communities in Pacific Waters of the Northern Kurile Islands and South-Eastern End of Kamchatka in the Late Fall 1994, Promyslovo-biolog-

9.

10.

11.

12.

13.

14.

icheskiye issledovaniya ryb v tikhookeanskikh vodakh Kurilskikh o-vov and pribreznykh raionakh Okhotskogo i Beringova morei v 1992–1998 gg. (The Commercial and Biological Investigations of Fish in Pacific Waters of the Kurile Islands and in Near-Shore Areas of the Sea of Okhotsk and Bering Sea in 1992–1998), Moscow: VNIRO, 2000, pp. 142–153. Fyodorov, V.V., Chereshnev, I.A., Nazarkin M.V., et al., Katalog morskikh i presnovodnykh ryb severnoi chasti Okhotskogo moria (The Catalogue of Marine and Freshwater Fishes in the Northern Sea of Okhotsk), Vladivostok: Dal’nauka, 2003. Chuchukalo, V.I., Pitaniye i pischevye otnosheniya nektona i nektobentosa v dal’nevostochnykh moryakh (Feeding and Food Interrelations of Nekton and Nektobentos in Far Eastern Seas), Vladivostok: TINROTsentr, 2006. Chuchukalo, V.I. and Napazakov, V.V., To the Method of Calculating Daily Food Ration and Digestion Rate for Predatory and Benthos-Eating Fish, Izv. TINRO, 1999, vol. 126, pp. 160–171. Sheiko, B.A., Fyodorov, V.V., Chapter 1. Fishlike Organisms and Fishes, in Katalog pozvonochnykh Kamchatki i sopredel’nykh morskikh akvatorii (The Catalog of Vertebrates of Kamchatka and Adjacent Sea Areas), Petropavlovsk-Kamchatskii: Kamchatskii Pechatnyi Dvor, 2000, pp. 7–69. Shorygin, A.A., Pitaniye i pischevye otnosheniya ryb Kaspiiskogo morya (Feeding Interrelations and Foraging of Fish in the Caspian Sea), Moscow: Pischepromizdat, 1952. Platell, M.E. and Potter, I.C., Partitioning of Food Resources Amongst 18 Abundant Benthic Carnivorous Fish Species in Marine Waters on the Lower West Coast of Australia, J. Mar. Biol. and Ecol., 2001, vol. 261, issue 1, pp. 31–54.

RUSSIAN JOURNAL OF MARINE BIOLOGY

Vol. 34

No. 7

2008

Feeding Interactions and Diet of Carnivorous Fishes in ...

39.2. 10.7. 4.2. 0.4. 60–70 l l l llllll. –. 2.2. 0. 1.5. 8.6. 21.6. 10.0. 2.8. 0.4. 70–80 l l l lllllll. –. 0. 3.5. 2.4. 10.5. 0. 0.7. 0. Pacific cod. 20–30 l l l llllllll. –. 24.8. 29.0.

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