ISSN 0032-9452, Journal of Ichthyology, 2008, Vol. 48, No. 8, pp. 644–647. © Pleiades Publishing, Ltd., 2008. Original Russian Text © V.V. Napazakov, 2008, published in Voprosy Ikhtiologii, 2008, Vol. 48, No. 5, pp. 675–678.

Feeding of Okhotsk Sculpin Myoxocephalus Ochotensis (Cottidae) in the Gulf of Shelikhov V. V. Napazakov Pacific Fisheries Research Center—TINRO-Tsentr, per. Shevchenko 4, Vladivostok, 690960 Russia e-mail: [email protected] Received July 26, 2007

Abstract—Feeding of the Okhotsk sculpin Myoxocephalus ochotensis, an endemic of the northern part of the Sea of Okhotsk, is studied on the materials of two bottom trawl surveys in 2004–2005 in the Gulf of Shelikhov. The quantitative and qualitative characteristics of its food spectrum depending on the linear sizes are given. It is revealed that its food spectrum includes the crustaceans, mollusks, fishes, and polychaeta. In the composition of crustaceans being a basic food group, the gammarids and small species of shrimps are replaced by crabs and large shrimps as the fishes grow. It is found that the individuals of the Okhotsk sculpin with a length from 15 to 20 cm have a mixed type of feeding, and the fishes larger than 20 cm are predators to a greater extent. DOI: 10.1134/S0032945208080109

It is known that the Okhotsk sculpin Myoxocephalus ochotensis is an endemic of the northern part of the Sea of Okhotsk. The feeding of this species is not studied, and the information on its biology is minimum. It occurs in the Taui Bay and Gulf of Shelikhov where it is a member of littoral ichthyocene (Borets, 2000; Sheiko and Fedorov, 2000, Fedorov et al., 2003). The present study sought to establish a tropic status of the Okhotsk sculpin and also to give the first infor-

mation on the food spectrum and its changes depending on the fish length. MATERIAL AND METHODS The material on the feeding of the Okhotsk sculpin is collected in two complex expeditions onboard R/V Professor Kaganovskii in the Gulf of Shelikhov in September 2004 and July 2005 (figure). The bottom

N

Gulf of Shelikhov 61° 100

59° 200

2004 2005 Isobaths 100 and 200 m Kamchatka Peninsula

57° 155°

157°

159°

Places of sampling in September 2004 and July 2005.

644

161°

E

FEEDING OF OKHOTSK SCULPIN MYOXOCEPHALUS OCHOTENSIS

trawling is performed by the trawl DT 27.1, the horizontal and vertical openings of which were, respectively, 16 and 6 m. Speed of trawling averaged 2.7 knots. Depth range at the trawl stations where the Okhotsk sculpin occurred in the catches changed within the limits from 35 to 136 m. In all, the contents of 105 stomachs of the Okhotsk sculpin were processed by the quantitative-weighting method (Metodicheskoe posobie…, 1974; Rukovodstvo…, 1986). When examining food components, the author was guided by the scale of degree of food digestion worked out by Chuchukalo and Napazakov (1999). The fish length was measured from the apex of snout to the end of middle rays of the caudal fin (AC). RESULTS AND DISCUSSION By the published data, the depth of dwelling of the Okhotsk sculpin does not exceed 20–40 m (Borets, 2000; Sheiko and Fedotov, 2000; Fedorov et al., 2003). By our data the depth range of dwelling of this species is significantly broader, and, quite probably, it is greater than 136 m, i.e., maximum depth at which this species was caught by bottom trawl. The information on maximum length of 19.8 cm is given only by Borets (2000). By our data the length of the Okhotsk sculpin in the catches of bottom trawls varied from 16.1 to 48 cm, and weight was in the range from 50 to 1169 g. The contents of 62 stomachs of the Okhotsk sculpin were examined in September 2004. The smallest specimen of the number of caught ones, with length of 16.1 cm, ate fish Lycodes sp (table). The basic food of the sculpins with size from 20 to 30 cm were decapods including the angle-tailed shrimp Pandalus goniurus (28%) and Okhotsk shrimps Argis ochotensis (9.9%) and hermit crabs Paguridae (12.5%), as well as Tanner crab Chionoecetes opilio (17.9%). The portion of fishes in food of the size group in question was not higher than 20% of the weight of stomach content, and Eumesogram Eumesogrammus preciesus mainly occurred (12.9%). The bivalve mollusks (Yoldia amigdalea, 4.3%) and small gastropods (1.7%) occupied third place by importance. The Okhotsk sculpins with length from 30 to 40 cm fed mainly on decapods (87.1%) and consumed mollusks significantly less (12.9%). The northern bear-cub shrimp Sclerocrangon boreas (17.8%) and Greenland shrimp Lebbeus groenlandicus (7.1%) were leaders among the shrimps, and the spider crab Hyas coarctatus alutaceus (37.3%) and kelp crab Oregonia gracilis (13.3%) were leading among the crabs. The kelp crab (46.8%), northern bear-cub shrimp (16.7%), octopus Octopus sp. (16,7%), and two species of fish, i.e., Liparis sp. (13%) and banded gunnel Pholis fasciata (3.7%), were found in the food of the largest examined sculpins with a length greater than 40 cm. The maximum number of empty stomachs (33.3%) was noted in the individual with length from 30 to 40 cm. JOURNAL OF ICHTHYOLOGY

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The average values of the indices of fullness of stomachs of ‰. the feeding fishes were relatively high, i.e., up to 288‰ The contents of 43 stomachs of the Okhotsk sculpin with length from 15 to 40 cm were examined in July 2005. The individuals with length up to 20 cm fed mainly on the small species of shrimps such as the Townsend’s eualus Eualus townsendi, spiny spirontocaris Spirontocaris brevidigitata, big-headed spirontocaris Spirontocaric prionota, and small kelp crabs. In total, the portion of decapods made up 69.5%, and the rest of the food consisted of polychaeta (table). The food spectrum of sculpins of the next size group of 20– 30 cm significantly changed. So, the portion of small species of shrimps reduced more than twice and, on the contrary, that of kelp crab increased. Total mass of isospine crab Lithodes aequipinus and Grebnitski’s sculpin Hapalogaster grebnizkii made up 62.3%. The hermit crabs were noted in the food. The portion of Alaska pollock Theragra chalcogramma was insignificant, i.e., 3.9%. Total portion of decapods in the food spectrum of the largest examined sculpins (30–40 cm) made up 94.6% with the predominance of the Grebnitskii’s sculpin, kelp crab, and hermit crabs and complete absence of small species of shrimps. The interannual differences in food spectrum consisting mainly in the fact that the “decapod” food predominantly consisted of the kelp crab, northern bearcub shrimp, and spider crab in 2004 and of the Tanner crab, kelp crab, and Townsend eualus in 2005 are probably explained by the fact that the samples were taken from different depths and in a different calendar time. From the other representatives of the genus Myoxocephalus, the plain sculpin M. jaok and great sculpin M. polyacanthocephalus also dwell in the Gulf of Shelikhov. Like in the Okhotsk sculpin, their basic food consists of the decapods and, to a less extent, of fishes. The different species of decapods become basic preys for each species. Thus, it was noted that the great sculpin mainly ate blue crab Paralithodes platypus (8.6%), spider crab (6.4%), and northern bear-cub shrimps (6%), and the plain sculpin fed on the northern bear-cub shrimp (25.2%), hermit crab Pagurus spp. (11.%), and comb shrimp Pandalus hypsinotus (10.5%). There are studies confirming likeness of food spectra between the sculpins from the different regions. Thus, for example, the snow sculpin M. brandtii close by linear sizes to the Okhotsk sculpin and belonging to the sublittoral ichthyocene, in the coastal waters of the Amur Bay, with a length less than 15 cm, predominantly feeds on the large-footed palaemon Palaemon macrodactylus (50–60%), snapping shrimp Alpheus japonicus, and mud shrimp Upogebia major. With the growth it goes over to feeding on the coastal crabs of the genus Hemigrapsus and fish (Panchenko and Pushchina, 2004). The fishes (the young eelpouts, poachers, and shrimps, Pandalus borealis, Crangon dalli, and Sclerocrangon derjugini, were predominant in the diet of the Steller’s sculpin as long as 10–20 cm caught in the area

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NAPAZAKOV

Food composition of the Okhotsk sculpin Myoxocephalus ochotensis in the Gulf of Shelikhov in September 2004 and July 2005 (% of weight) Size group, mm Food composition

September 2004

July 2005

15–20

20–30

30–40

>40

total

15–20

20–30

30–40

total

Polychaeta Mollusca Octopus sp. Gastropoda gen. sp. Yoldia amigdalea Criptonatica (egg clutch) Gammaridea Arctolembos arcticus Decapoda Decapoda gen. sp. Decapoda (shrimps) Pandalus goniurus Sclerocrangon boreas Argis ochotensis Eualus fabricii Eualus townsendi Spirontocaris spinus Lebbeus groenlandicus Spirontocaris brevidigitata Spirontocaris prionota Spirontocaris sp. Paguridae gen. spp. Paralithodes platypus Lithodes aequispinus Hapalogaster grebnitzkii Chionoecetes opilio Oregonia gracilis Hyas coarctatus alutaceus Pisces Theragra chalcogramma Enophrys diceraus Pholis fasciata Eumesogrammus preciesus Lycodes sp. Liparis sp. Pisces gen. sp. Average index of fullness ‰ of stomach, ‰

– – – – – – – – – – – – – – – – – – – – – – – – – – – – 100 – – – – 100 – – 200

0.4 6.0 – 1.7 4.3 – 1.5 1.5 72.3 – 1.3 28.0 – 9.9 0.5 0.9 1.3 – – – – 12.5 – – – 17.9 – – 19.8 – – – 12.9 0.9 – 6.0 98

– 12.9 6.2 – – 6.7 – – 87.1 11.6 – – 17.8 – – – – 7.1 – – – – – – – – 13.3 37.3 – – – – – – – – 252

– 16.7 16.7 – – – – – 66.6 – – – 16.7 – – – – – – – – – 3.0 – – – 46.9 – 16.7 – – 3.7 – – 13.0 – 288

0.1 13.4 10.5 0.4 1.0 1.5 0.3 0.3 72.3 2.6 0.2 6.1 13.1 2.3 0.1 0.2 0.3 1.6 – – – 2.9 1.6 – – 4.2 28.6 8.5 13.9 – – 2.0 3.0 0.4 7.1 1.4 –

30.5 – – – – – – – 69.5 8.0 – – – – – 36.7 – 5.3 9.3 4.9 – – – – – – 5.3 – – – – – – – – – 262

– – – – – – – – 96.1 – – – – – – 18.1 – – 0.8 1.9 – 1.6 – 14.5 47.9 – 11.3 – 3.9 3.9 – – – – – – 207

– – – – – – – – 94.6 8.1 – – – – – – – – – – 2.2 8.0 – – 42.7 – 33.6 – 5.4 – 5.4 – – – – – 168

3.5 – – – – – – – 92.3 4.5 – – – – – 12.2 – 0.6 1.4 1.4 1.0 4.2 – 6.5 40.1 – 20.4 – 4.2 1.8 2.4 – – – – – –

Number of stomachs/samples Portion of empty stomachs, % Average length (AC), cm Average weight (total), g Depth, m

1/1 0 17 50

44/6 29.5 25.4 245

9/4 33.3 34.4 478 41–124

8/1 0 43.1 1169

62/12 – – –

12/1 25 16.5 72

21/2 10/2 23.8 20 26.5 35 235 492 41–43

43/5 – – –

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of the northern Okhotsk shelf (Chuchukalo et al., 1999). By the data of Panchenko and Pushchina (2004) in the Amur Bay, the Steller’s sculpin fingerlings with size up to 5 cm consume the amphipods, isopods, and polychaeta. In the food of the fishes with length from 5 to 10 cm, the sand shrimps Crangon septempspinosa begin to occur with the indicated components. The basic diet of the fishes with length from 5 to 10 cm is formed by the common shore crab Hemigrapsus penicillatus, their own juvenile, and juvenile of greenlings. The tubercled sculpin M. tuberculatus, also being endemic to the northern part of the Sea of Okhotsk and belonging to the lithosublittoral ichthyocene with length from 31 to 36 cm, predominantly ate the northern shrimp and juvenile of queen crabs in the central part of the western Kamchatka shelf. The fish part of the diet included the young leptocline Leptoclinus maculates diaphanocarus and gobies of genus Gymnacanthus. The individuals with length from 50 to 60 cm predominantly ate the young queen crabs and, to a lesser degree, fishes such as sandfish Trichodon trichodon, capeline Mallotus villosus catervarius, and flounders (Chuchukalo et al., 1999). The European sculpin M. scorpius in the southwestern part of the Baltic Sea mainly feeds on the isopod Mesidotea entomon, mysid Mysis mixta, and herring Clupea harengus. The sculpins of all size groups feed on isopod while predominantly small sculpins eat mysids, and only individuals longer than 21 cm feed on the herring (Cardinale, 2000). Thus, the Okhotsk sculpin dwelling in the northern part of the Sea of Okhotsk and belonging to the sublitholittoral ichthyocene is benthoichthyophage with the broad food spectrum changing with growth and including the preys of four systematic groups: crustaceans, mollusks, fishes, and polychaeta. The crustaceans, whose species composition changes from the gammarides and small shrimps to the crabs and prawns when the predator length increases, are the most important in the feeding of all of the examined size groups. The changeover from benthic feeding to predation occurs in the fishes with length from 10 to 20 cm. The sculpins longer than 20 cm are mainly predators. To judge both from our data and materials of the other trophological investigations (Tokranov, 1983, 1986a, 1986b, 1992; Borets, 1997; Mito et al., 1999; Cardinale, 2000; Napazakov and Chuchukalo, 2003; Napazakov, 2004; Chuchukalo, 2006; et al.), the food spectra of the Okhotsk sculpin and other species of sculpins, including the Far Eastern sculpins, are similar between themselves. REFERENCES 1. L. A. Borets, Bottom Ichthyocenoses of the Russian Shelf of Far Eastern Seas: Composition, Structure, Elements of Functioning, and Commercial Importance (TINROTsentr, Vladivostok, 1997) [in Russian]. 2. L. A. Borets, Annotated List of Fish of Far Eastern Seas (TINRO-Tsentr, Vladivostok, 2000) [in Russian]. JOURNAL OF ICHTHYOLOGY

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3. M. Cardinale, “Ontogenetic Diet Shifts of Bull-Rout, Myoxocephalus scorpius (L.), in the South-Western Baltic Sea,” J. Appl. Ichthyol. 16 (6), 231–239 (2000). 4. V. I. Chuchukalo, Feeding and Feeding Relations of Nekton and Nektobenthos in Far Eastern Seas (TINROTsentr, Vladivostok, 2006) [in Russian]. 5. V. I. Chuchukalo and V. V. Napazakov, “On Methods of Determination of Daily Diets and the Rate of Food Digestion in Predatory and Benthos-Eating Fish,” Izv. Tikhookean. Nauchno-Issled. Inst. Rybn. Khoz. Okeanogr. 126, 160–171 (1999). 6. V. I. Chuchukalo, V. V. Lapko, Kuznetsova, et al., “Feeding of Bottom Fish at the Shelf and the Continental Slope of the Northern Part of the Sea of Okhotsk in Summer 1997,” Izv. Tikhookean. Nauchno-Issled. Inst. Rybn. Khoz. Okeanogr. 126, 24–57 (1999). 7. V. V. Fedorov, I. A. Chereshnev, M. V. Nazarkin, et al., Catalog of Marine and Freshwater Fish of the Northern Part of the Sea of Okhotsk (Dal’nauka, Vladivostok, 2003) [in Russian]. 8. Guide on Study of Fish, Compiled by V.I. Chuchukalo, A.F. Volkov (TINRO, Vladivostok, 1986), p. 32 [in Russian]. 9. Methodical Aid for Study of Feeding and Feeding Relations of Fish in Nature (Nauka, Moscow, 1974), p. 254 [in Russian]. 10. K. Mito, A. Nishimura, and T. Yanagimoto, “Ecology of Groundfishes in the Eastern Bering Sea, with Emphasis on Food Habits,” in Dynamics of the Bering Sea, Ed. by T.R. Laughlin and K. Ohtani (Alaska Sea Grant College Program, Fairbanks, 1999), pp. 537–580. 11. V. V. Napazakov, “Trophic Relations of Fish in Bottom Ichthyocenoses in the Western Part of the Bering Sea,” Izv. Tikhookean. Nauchno-Issled. Inst. Rybn. Khoz. Okeanogr. 139, 19–42 (2004). 12. V. V. Napazakov and V. I. Chuchukalo, “Diet and Trophic Status of Mass Species of Sculpins (Cottidae) in the Western Part of the Bering Sea in Autumn,” Vopr. Ikhtiol. 43 (2), 200– 208 (2003) [J. Ichthyol. 43 (3), 236–244 (2003)]. 13. V. V. Panchenko and O. I. Pushchina, “Biological Characteristic of Sculpins of the Genus Myoxocephalus (Cottidae) in Peter the Great Bay of the Sea of Japan,” Izv. Tikhookean. Nauchno-Issled. Inst. Rybn. Khoz. Okeanogr. 138, 120–153 (2004). 14. B. A. Sheiko and V. V. Fedorov, Catalog of Vertebrates of Kamchatka and Adjacent Sea Water Areas. Chapter 1. Pisciformes and Fish (Kamchat. Pechat. Dvor, Petropavlovsk-Kamchatskii, 2000), pp. 7–69 [in Russian]. 15. A. M. Tokranov, “Feeding of Sculpins off the Western Coast of Kamchatka,” in Biological Resources of the Shelf, Their Rational Use, and Protection (DVNTS Akad. Nauk SSSR, Vladivostok, 1983), pp. 74–75. 16. A. M. Tokranov, “Sculpins and Lords,” in Biological Resources of the Pacific Oean (Nauka, Moscow, 1986a), pp. 319–328. 17. A. M. Tokranov, “Feeding of Myoxocephalus polyacanthocephalus Pallas and M. jaok (Cuvier) (Cottidae) in Coastal Waters of Kamchatka,” Vopr. Ikhtiol. 26 (6), 980–989 (1986b). 18. A. M. Tokranov, “Specific Features of Feeding of Bottom Predatory Fish at the Western-Kamchatka Shelf,” Vopr. Ikhtiol. 32 (2), 119–128 (1992).

Translated by G.B. Medveshchuk