Indian Journal of Marine Sciences Vol. 32(2), June 2003, pp. 95-113

Impact of eddies on spatial distributions of groundfishes along waters off the northern Kuril Islands, and southeastern Kamchatka (north Pacific Ocean)

A. M. Orlov Russian Federal Research Institute of Fisheries & Oceanography (VNIRO), 17, V. Krasnosel’skaya, Moscow, 107140, Russia [ E-mail: [email protected] ] Received 11 March 2002, revised 3 March 2003

Distributional peculiarities of groundfishes, inhabiting the Pacific waters off the northern Kuril Islands and southeastern Kamchatka, where three quasi-stationary eddies occur, are considered in this paper. The possible influence of eddies on occurrence of groundfishes are discussed. Existing eddies off underwater plateau and small banks in the southern part of the study area provides specific environment (bottom relief, temperature, and currents) for inhabitation essentially differed from that of adjacent waters. Composition of ichthyofauna, off plateau area, is very specific. There are several widely distributed in the North Pacific that were caught only within plateau area. Some species widely distributed within the Pacific waters off the Kuril Island and eastern Kamchatka are abundant only in the area off plateau and banks. Feeding aggregations of plankton-feeders Atka mackerel and Pacific Ocean perch (these species are targets of specialized fishery) occur here throughout the year, probably related to fine foraging conditions in the enlarged plankton biomass in the area. Pelagic larvae and juveniles of some , permanently dwelling the area, probably grow there until settlement. The study area serves as nursery ground for some fishes, which spawn outside the area. Currents transport pelagic larvae and juveniles of these species from main spawning grounds (eastern Kamchatka and Paramushir Island coasts) to the south. The larvae fall into eddies, inhabit these waters until settlement, feed on plateau slopes and later with increase in size start reverse migrations. Thus, eddies affect occurrence and distributional patterns of various groundfish species, having different types of life cycle.

[ Key words : Distribution, eddy, groundfishes, underwater plateau, northern Kuril Islands, occurrence, southeastern Kamchatka ] The Pacific waters off the northern Kuril Islands are Ichthyofauna of the Pacific waters off the northern one of the most productive areas of the Russian Far Kuril Islands is poorly studied. Only recently, the East EEZ1. However, the relative importance of fishes completed lists of fishes, inhabiting the area from this area in the total Russian Far East catch considered, were published3,4. Until recently studies remained insignificant until now. In the 1980s, only on distributional patterns and life histories of 3 2.6-3.9 % (99 to 273.4 × 10 tons) of the total annual groundfishes, inhabiting the Pacific waters off the fish harvest from the Russian Far East seas came from northern Kurils, were scanty5-7. this area2. Low catch was associated with rocky Oceanographic conditions of the Pacific waters off bottom that restricted bottom trawling in most of the the northern Kuril Islands and southeastern Kamchatka area. Fishing in the area under consideration was are very dynamic due to interaction of East Kamchatka conducted on grounds located mainly within the 12-mile current with Strait’s currents and bottom relief. As a coastal zone and in areas with a well-developed result, two quasi-stationary anticyclonic eddies exist continental shelf. Commercially important fishes off the southeastern Kamchatka and Paramushir included walleye Theragra chalcogramma, Island coasts8. Another eddy occurs in the area off the Gadus macrocephalus, northern rock underwater plateau and several small banks that are Lepidopsetta polyxystra, and Atka mackerel located in the southern part of the northern Kuril Pleurogrammus monopterygius. Continental slope Islands area (47°45′-48°55′ N), southeast of Onekotan fishes (Greenland Reinhardtius hippoglossoides, Island9. Relations between distributional features of Kamchatka evermanni, Pacific key fish species from this area and some halibut Hippoglossus stenolepis, grenadiers oceanographic characters (water structure and Macrouridae, and rockfishes Scorpaenidae) did not temperature, currents) were considered only by 2 10 exceed 2 % of the total catch . Kantakov . There are no publications dealing with 96 Indian J. Mar. Sci., Vol. 32, No. 2, June 2003

effect of eddies on spatial distributions of the clock at depths 76-833 m using a 5-7 m groundfishes off the Kuril Islands. (vertically) by 25-30 m (horizontally) bottom trawl The main objective of this study is to characterize net constructed from 100-120 mm (stretched mesh) spatial distribution of some groundfishes in the polyethylene net. The net was outfitted with steel and Pacific waters off the northern Kuril Islands and rubber ball roller gear in the forward wings. Only southeastern Kamchatka, to assess possible relations successful trawl samples (horizontal and vertical net between character of their spatial distribution and the openings remained within normal range, the roller eddy existing over the underwater plateau in the gear maintained consistent contact with the bottom, southern part of investigated area, and to understand the net suffered no or little damage during the tow, how these eddies affect spatial distributions and some there were no conflicts with derelict fishing gear) biological features of several groundfish species. were used for analysis in the present study. Most hauls were made along isobaths. Hauls with highly Materials and Methods variable depths between the start and end of towing This paper is based on catch data obtained from 21 were excluded from the analysis. bottom trawl surveys (total over 1,500 bottom trawl On bottom trawl surveys the whole catch was stations made during 1992-2000) and numerous analyzed. On the operations a bottom trawl hauls conducted during commercial representative sample was obtained from each trawl operations from southeastern Kamchatka and northern catch. These samples were taken for analysis from Kuril Islands area (Fig. 1). The investigated area is different parts of the catch (no less than 10 % of total within 47 °30′ N to 52° N, 154°20′ E to 158°50′ E catch), sorted by species, and individuals counted and (25,012 km2). Samples were collected from three weighed. The rest of the catch was examined on the chartered commercial Japanese trawlers (Tomi-Maru conveyer to note species not found in casual samples. 53, Tomi-Maru 82, and Tora-Maru 58). Bottom trawl Results were extrapolated to the total catch. surveys were conducted during the daytime, The frequency of occurrence for each species commercial fishing operations were conducted round (FO, %) was calculated as a percentage of trawls in

Fig. 1 — Maps showed locations of bottom trawl surveys (A) and commercial bottom trawl operations (B) conducted in the Pacific waters off the northern Kuril Islands and southeastern Kamchatka aboard Japanese trawlers during 1992-2000 (broken lines are isobaths, I – Forth Kuril Strait, II – underwater plateau).

Orlov : Impact of eddies on spatial distributions of groundfishes 97

which this species was recorded. Catch per hour was from the plateau more frequently than outside. calculated as average values of catches for each Opposite, outside plateau area, codfishes, Gadidae species standardized to a trawl duration of one hour, (cumulative FO 123.5 % vs. 41.7 %, respectively), and expressed in numbers of fishes (ind.) per hour or , , Hemitripteridae, and weight (kg) per hour. Average catch per unit effort Psychrolutidae (291.0 % vs. 236.8 %), poachers, (CPUE) expressed in number or weight of individuals Agonidae (96.8 % vs. 75.9 %), eelpouts, Zoarcidae per unit of fishing effort was used to describe the (126.5 % vs. 75.7 %), and righteye , relative abundance of a fish species. (306.4 % vs. 141.7 %) were caught Along the Pacific waters off the northern Kuril frequently in comparison with plateau area. Islands and southeastern Kamchatka several eddies The possible reasons of above differences in exist, which occurred to depths of 100-200 m. Some occurrence of fishes off and outside plateau areas are of them have stationary character in inter-annual and due to distinctions in life history patterns of species seasonal aspects. Data on localities of eddies and its considered. Most of fishes abundant off plateau prefer spatial seasonal and inter-annual variations were to inhabit areas with complex relief. They have taken from published sources8,10-12 and unpublished pelagic eggs, larvae and juveniles that are feeding on materials13. Consideration of oceanographic plateau slopes. Sculpins inhabiting plateau area are characters of eddies is not the objective of present represented by small-sized species of genera study, but deals only with distributional patterns of Thyriscus, Rastrinus, Icelus, Archaulus, which inhabit groundfishes in relation to possible impact of eddies. the areas with numerous sponges (Poryfera). It can be presumed that pelagic larvae and juveniles develop in Results and Discussion eddy waters around underwater plateau until settlement. Eddy probably does not allow them to Differences of species composition between areas off disperse outside this area, and as a result, distribution and outside plateau of these species are limited, as a rule, by surrounding Ichthyofauna of the underwater plateau area that underwater plateau waters. Moreover, sponges also located in the southern part of study area is very have pelagic larvae14, whose development until specific. Its species composition considerably differ settlement probably occurred in eddy waters. from that of other part of area investigated (Table 1). Most of fishes abundant outside plateau also have The study revealed that the number of groundfish pelagic eggs, larvae and juveniles. However, juveniles species found in the plateau area is considerably and adults of these species spawn, feed, and have lesser than those found outside plateau area (106 vs. maximum abundance in the areas with rather well 139). There are several species, widely distributed in developed shelf and smooth continental slope that are the North Pacific Ocean, which were captured only placed from the Fourth Kuril Strait to southeastern off the plateau area and not from outside. These Kamchatka. Sculpins were represented by medium- species are proboscis snailfish, scaled , sized and large-sized species from genera Gymnocanthus, nutcracker prickleback, tough eelpout, fourhorn , Melletes, Myoxocephalus, Hemitripterus, , slime flounder. Most of spiny eel and and Ulca, which spawn and feed within the shelf waters skilfish specimens were caught within the plateau area (similar to many other species from this group) and, and their capture outside plateau were incidental. On migrate from lower shelf to upper continental slope the other hand, there are about 40 groundfish species areas, only during cold period. (mostly from families Cottidae, Agonidae, and Pleuronectidae), which were caught only from outside Plankton-feeding species plateau area and not from within the plateau. Eddy waters due to its rich zooplanktonic However, the most significant distinctions between biomass15 serve as feeding grounds for some ichthyofaunas off and outside plateau areas were plankton-feeding species such as Atka mackerel, found in occurrence and relative abundance of Pacific Ocean perch, and prowfish. species, belonging to the same families. Thus, Atka mackerel Pleurogrammus monopterygius grenadiers, Macrouridae (cumulative FO 83.8 % vs. inhabits mostly Pacific waters from the central Kuril 55.8 %, respectively), rockfishes, Scorpaenidae (218.4 % Islands (Friza Strait) to the Gulf of Alaska including vs. 147.5 %), snailfishes, Liparidae (328.8 % vs. 275.9 %), the . Its pelagic juveniles are feeding partly 16 and prowfishes, Zaproridae (12.1 % vs. 3.3 %) occurred in the Sea of Okhotsk . Dense concentrations of this

98 Indian J. Mar. Sci., Vol. 32, No. 2, June 2003

Table 1 — Frequency of occurrence (FO, %) of most abundant groundfishes in bottom trawl catches within (1) and outside (2) underwater plateau area

Scientific name* Common name* Area 1 2

Total number of species 106 139 Total number of hauls 1038 1257 Rajidae Skates Bathyraja aleutica (Gilbert, 1896) 50.2 45.5 B. maculata Ishiyama et Ishihara, 1977 Whiteblotched skate 61.4 34.1 B. matsubarai (Ishiyama, 1952) Matsubara skate 50.0 28.6 B. violacea (Suvorov, 1935) Okhotsk skate 30.5 60.4 Macrouridae Grenadiers Albatrossia pectoralis (Gilbert, 1892) Giant grenadier 46.7 29.4 Coryphaenoides cinereus (Gilbert, 1896) Popeye grenadier 37.1 25.1 Moridae Morid cods Antimora microlepis Bean, 1890 Pacific flatnose 18.5 21.4 Gadidae Codfishes Gadus macrocephalus Tilesius, 1810 Pacific cod 11.9 53.7 Theragra chalcogramma (Pallas, [1814]) Walleye pollock 29.8 67.0 Sebastidae Rockfishes Sebastes aleutianus (Jordan et Evermann, 1898) Rougheye rockfish 18.6 13.2 S. alutus (Gilbert, 1890) Pacific ocean perch 40.4 26.2 S. borealis Barsukov, 1970 Shortracker rockfish 65.0 33.2 Sebastolobus alascanus Bean, 1890 Shortspine thornyhead 18.7 26.1 S. macrochir (Günther, 1877) Broadbanded thornyhead 71.0 44.0 Hexagrammidae Greenlings Pleurogrammus monopterygius (Pallas, 1810) Atka mackerel 33.9 41.6 Cottidae Sculpins Gymnacanthus detrisus Gilbert et Burke, 1912 Purplegray scupin 4.0 26.6 Hemilepidotus jordani Bean, 1881 Yellow Irish lord 0.9 23.0 H. zapus Gilbert et Burke, 1912 Longfin Irish lord 30.2 1.7 Icelus canaliculatus Gilbert, 1896 Blacknose sculpin 36.9 12.0 I. perminovi Taranetz, 1936 Scaly-belly sculpin 24.0 2.2 Myoxocephalus polyacanthocephalus (Pallas, [1814]) Great sculpin - 27.4 Triglops scepticus Gilbert, 1896 Spectacled sculpin 28.0 37.1 Psychrolutidae Soft sculpins Malacocottus zonurus Bean, 1890 Darkfin sculpin 88.5 57.3 Agonidae Poachers Bathyagonus nigripinnis Gilbert, 1890 Blackfin starsnout 27.5 24.3 frenatus (Gilbert, 1896) 38.3 37.5 Liparidae Snailfishes Careproctus cypselurus (Jordan et Gilbert, 1898) Falcate snailfish 19.8 11.9 C. furcellus Gilbert et Burke, 1912 Forktail snailfish 57.4 58.5 C. rastrinus Gilbert et Burke, 1912 Salmon snailfish 13.8 35.2 C. roseofuscus Gilbert et Burke, 1912 Round snailfish 24.7 23.9 Careproctus sp. nov. 56.6 6.5 Elassodiscus obscurus Pitruk et Fedorov, 1993 32.0 22.6 E. tremebundus Gilbert et Burke, 1912 Dimdisc snailfish 64.8 43.4 Liparis ochotensis Schmidt, 1904 Okhotsk snailfish 2.5 20.2 Polypera simushirae (Gilbert et Burke, 1912) 23.1 0.9

* - Scientific and common names are given according to Sheiko & Fedorov4 Contd…….

Orlov : Impact of eddies on spatial distributions of groundfishes 99

Table 1 — Continued……… Scientific name* Common name* Area 1 2 Zoarcidae Eelpouts Bothrocara brunneum (Bean, 1890) Twoline eelpout 25.8 19.9 Lycodes albolineatus Andriashev, 1955 Whitebar eelpout 14.6 49.6 L. brunneofasciatus Suvorov, 1935 Tawnystripe eelpout 12.6 36.0 Pleuronectidae Righteye flounders Athereshtes evermanni Jordan et Starks, 1904 67.8 67.5 Hippoglossoides elassodon Jordan et Gilbert, 1880 Flathead sole 0.4 40.8 Hippoglossus stenolepis Schmidt, 1904 10.6 44.8 Lepidopsetta polyxystra Orr et Matarese, 2000 Northern rock sole 0.8 53.8 Reinhardtius hippoglossoides matsuurae Jordan et Snyder, 1901 Pacific black halibut 41.8 53.9 * - Scientific and common names are given according to Sheiko & Fedorov4

species with catches up to 10,000 no/h were registered occurred from central Paramushir Isl., where its off the southeastern Kamchatka (area of the catches did not exceed several specimens per hour, to “northern” eddy) but largest catches exceeding 48° N with maximum relative abundance, reaching 100,000 no/h occurred at the northwestern slope of 100-300 no/h, at the western slope of underwater underwater plateau between 48°15′ N and 48°35′ N plateau (Fig. 3A). This species often occurred in (Fig. 2A). Atka mackerel was found there often in catches that contained sponges. Prowfish feed on bottom trawl hauls with large amount of sponges. It jellyfish-like invertebrates such as Hydrozoa, 21 should be noted that western slope of underwater Ctenophora, Salpa, Appendicularia . The high plateau serves as feeding grounds for Atka mackerel, abundance of prowfish within the plateau area is where commercial schooling exist in plateau area all probably related to enlarged biomass of above jellyfish- the year around17. like organisms representing the basis of its diet. Pacific Ocean perch Sebastes alutus is only single planktophage fish species permanently dwelling in Species, whose whole life cycle occur within plateau continental slope waters of the North Pacific18. It is waters As generally known, snailfishes and broadbanded distributed from the northern Honshu (Myagi 22 Prefecture) along the Kuril and Aleutian Islands to the thornyhead have pelagic larvae and juveniles . southern California including the Bering Sea19. In the Pelagic life stages of these species, inhabiting Pacific waters off the northern Kuril Islands and underwater plateau area until settlement, probably southeastern Kamchatka, this species occurred within occur within the eddy waters that do not allow them the whole area but it is most abundant in the southern to leave underwater plateau area. part of area considered southerly the Fourth Kuril Proboscis snailfish Careproctus simus is distri-

Strait, where its catches exceed 1 000 no/h (Fig. 2B). buted in the North Pacific Ocean from 45° to 60° N However, the most dense schoolings Pacific Ocean from Pacific waters off Japan along Kuril Islands to perch formed at the western slope of underwater the Aleutian Islands including the Sea of Okhotsk and 23,24 plateau and off small banks near the northern edge of Bering Sea . However, the data on its distribution plateau with catches, reaching 10,000 no/h and more. are limited. In the Pacific waters off the northern Similar to Atka mackerel, Pacific Ocean perch feed Kuril Islands several specimens of proboscis snailfish mainly on copepods and euphausiids20. Dense were caught at the eastern slope of underwater plateau concentrations of the species occurred in the above (47о50′-48о40′ N) in the southern part of study area area all the year around17. (Fig. 4). Prowfish Zaprora silenus is rather common species Stout snailfish Allocareproctus pycnosoma is of the North Pacific Ocean that is widely distributed distributed in the Pacific waters off Japan, Kuril from northern Japan (Hokkaido) along the Kuril and Islands and eastern Kamchatka25. In the study area Aleutian Islands and eastern Kamchatka to the North this species occurred from 47°50′ N to 51° N America including the Sea of Okhotsk, Bering Sea (Fig. 5A) but its maximum catches, reaching 10 no/h, and Gulf of Alaska21. In the study area prowfish were noted off the Forth Kuril Strait and at the

100 Indian J. Mar. Sci., Vol. 32, No. 2, June 2003

Fig. 2 — Spatial distribution and relative abundance categorized by CPUE (no/h trawling) of Atka mackerel Pleurogrammus monoptery- gius (A) and Pacific Ocean perch Sebastes alutus (B).

Fig. 3 — Spatial distribution and relative abundance categorized by CPUE (no/h trawling) of prowfish Zaprora silenus (A) and Fedorov’s eelpout Lycenchelys fedorovi (B).

Orlov : Impact of eddies on spatial distributions of groundfishes 101

Fig. 4 — Capture localities of some rare fish species off the underwater plateau: 1 – proboscis snailfish Careproctus simus, 2 – scaled sculpin Archaulus biseriatus, 3 – nutcracker prickleback Bryozoichthys lysimus, 4 -tough eelpout Puzanovia rubra, 5 - fourhorn poacher quadricornis, 6 – slime flounder achne.

Fig. 5 — Spatial distribution and relative abundance categorized by CPUE (no/h trawling) of stout snailfish Allocareproctus pycnosoma (A) and gloved snailfish Palmoliparis beckeri (B).

102 Indian J. Mar. Sci., Vol. 32, No. 2, June 2003

Fig. 6 — Spatial distribution and relative abundance categorized by CPUE (no/h trawling) of blacktip snailfish Careproctus zachirus (A) and unidentified snailfish Careproctus cf. cyclocephalus (B). southern slope of underwater plateau. In the latter area Northern boundary of its distribution is limited by the stout snailfish was especially abundant. Fourth Kuril Strait (Fig. 6B). The maximum Gloved snailfish Palmoloparis beckeri was abundance of this species occurred at the eastern originally described from the Pacific waters off the slope of underwater plateau, where its catches reached northern Kuril Islands only recently26 and is endemic 300-600 no/h. Size of snailfish decreased with to the study area. All presently known captures of this increase in depth, i.e. its adults inhabit shallower species were obtained exclusively within the Pacific water as compared to juveniles. waters off the northern Kuril Islands southward the Big-disc snailfish Squaloliparis dentatus was 27,28 Fourth Kuril Strait . In the study area, distribution originally described from the Sea of Okhotsk off of gloved snailfish is limited by the Fourth Kuril Hokkaido, relatively recently29. This species is rather Strait in the north and southern edge of underwater common and widely distributed in the bathyal realm plateau in the south (47°50′ N). The maximum of the Sea of Okhotsk, and also in the Pacific waters catches of this species (over 2 no/h trawling) were off the northern Kuril Islands28,30. In the area under noted only at the southern slope of underwater plateau consideration, this species occurred in its southern (Fig. 5B). part from 47°50′ N to the Fourth Kuril Strait Blacktip snailfish Careproctus zachirus was (Fig. 7A). The largest catches of big-disc snailfish (up originally described from the Bering Sea off the to 200 no/h trawling) were registered at the northern Aleutian Islands23. This species is distributed in the and southern slopes of underwater plateau. Pacific waters off the northern Kuril Islands and Simushir snailfish Polypera simushirae was eastern Kamchatka and also in the western Bering Sea originally described from the littoral of Simushir 28 off the Aleutian Islands . In the study area, blacktip Island (central Kurils)31 and very recently was snailfish occurred from 47°50′ N to 51°30′ N reported only from above area32. Reporting33 of this (Fig. 6A) but its largest catches, reaching 20 no/h species from northern Hokkaido is probably trawling were registered at the southeastern slope of erroneous because later Simushir snailfish were not underwater plateau. included in the list of species inhabiting Japanese Snailfish Careproctus cf. cyclocephalus is one of waters29,34,35. In the Pacific waters off the northern most abundant liparid species of the study area28. Kuril Islands, Simushir snailfish is distributed from

Orlov : Impact of eddies on spatial distributions of groundfishes 103

Fig. 7 — Spatial distribution and relative abundance categorized by CPUE (no/h trawling) of big-disc snailfish Squaloliparis dentatus (A) and Simushir snailfish Polypera simushirae (B). 48° N to the central Fourth Kuril Strait (Fig. 7B). The degree of heterogeneity. The largest fish occurred in main areas of its inhabitation are slopes of underwater three areas: the underwater plateau in the south part of plateau. The maximum abundance of Simushir region, a localized section southeast of Onekotan snailfish was registered at the western slope, where its Island, and the southeastern Kamchatka coast near catches reached 50-100 no/h trawling. Depths of 52° N (Fig. 8C). In each of these areas, mean body 166-833 m limit vertical distribution of this species in length increased from deeper to shallower waters. As the study area but more than 50 % of its relative it is generally known, thornyheads are egg-layers with abundance is distributed at depth < 200 m. internal fertilization37 with the eggs being released Broadbanded thornyhead Sebastolobus macrochir within gelatinous balloons into the water column. The is an endemic species of the northwestern Pacific balloons have positive buoyancy and float to surface Ocean being distributed from the Pacific coast of where the larvae hatch and further development Japan (Sagami Bay) to the central Bering Sea and occurs38. Capture sites of benthic juveniles and the Aleutian Islands including continental slope areas of locations of larger catches of post spawners nearly the Sea of Okhotsk36. The maps of mean multi-annual coincide with localized eddies occurring near the distribution of broadbanded thornyhead shows that southeastern Kamachatka and Paramushir coasts and catches over 50 kg/h (Fig. 8A) were observed along within the underwater plateau and adjacent banks much of the slope with the largest catches (over southeast of Onekotan Island. The co-occurrence of 500 kg/h trawling) occurring off the underwater these two groups indicates that early development of plateau area indicating that spawning may occur the larvae and pelagic juveniles of broadbanded continuously within the entire investigated area, but thornyhead might have occurred within the southern more strongly in the southern part. This feature is eddy until settlement. The locations and depths of confirmed by the pattern of distribution of capture of predominantly small-sized benthic broadbanded thornyhead benthic juveniles (Fig. 8B), juveniles may indicate that settlement of broadbanded which are also caught more frequently in the above thornyhead occur within the deeper depths (400-650 m) area. Size composition of broadbanded thornyheads in with larger fish migrating into shallower waters the Kuril-Kamchatka region is characterized by a high (150 m and deeper).

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Fig. 8 — Spatial distribution and relative abundance categorized by CPUE (kg/h trawling) (A), capture localities of benthic juveniles < 12 cm (B), and distribution of mean body length (cm) (C) of broadbanded thornyhead Sebastolobus macrochir. Species inhabiting among sponges Sponge sculpin Thyriscus anoplus is distributed in Some species such as nutcracker pricleback, the Bering Sea off Aleutian Islands, off the fourhorn poacher, slime flounder, small sculpins, Commander Islands, in the Pacific waters off the Atka mackerel, etc. inhabit areas that are covered by northern Kuril Islands and eastern Kamchatka41. This dense sponges. Eddy waters probably limit species is small mesobenthic sculpin that inhabit distribution of sponges outside underwater plateau mainly lower shelf and upper continental slope within and create favourable environmental conditions for the depth range 104-800 m. In the study area, sponge inhabitation of above species only in this area. sculpin is rather common but not abundant representative of ichthyofauna that inhabits areas with Nutcracker prickleback Bryozoichthys lysimus complex bottom relief and rocky grounds42. Sponge being widely distributed in Asian waters occurred from northern Hokkaido along the Kuril Islands and sculpin occurred there from 47°50´ N to the Fourth eastern Kamchatka to the Bering Sea including the Kuril Strait (only single specimen was caught off the northern Sea of Japan and Sea of Okhotsk34. In the southern tip of ). However, the Pacific waters off the northern Kuril Islands, this main area of its inhabitation is placed at slopes species was caught only within the underwater plateau (especially western) of underwater plateau (47°50′- area (Fig. 4). Most of individuals were found in the 48°40′ N), where catches of sponge sculpin sometimes reaches over 100 no/h trawling (Fig. 9A). catches from the plateau top at depths < 200 m in association with sponges. Roughskin sculpin Rastrinus scutiger is distributed in the Bering Sea, off the Commander and Kuril Scaled sculpin Archaulus biseriatus was originally Islands43. In the area under consideration, this species described from Petrel Bank, in the southern Bering occurred only south 50° N (Fig. 9B). Roughskin Sea off Semisopochnoi Island of the Aleutian sculpin catches varied 1-25 no/h trawling. The 39 Archipelago . Since the original description, only a maximum catch values were registered in both single additional specimen has been recently collected northern and southern parts of area. However, from the central Kuril Archipelago off Simushir maximum number of captures of species was noted in 40 Island . During present study, two specimens of the area of underwater plateau. In the Pacific waters scaled sculpin were collected on the top of underwater off the northern Kuril Islands, roughskin sculpin plateau (Fig. 4) at 48°14.2′ N 154°35.1′ E (138-140 m inhabits depth range of 170-480 m but most of its depth) and 48°16.5′ N 154°32.0′ E (100-117 m individuals (over 81 %) were captured within depth depth). Specimens have been caught on hard bottom 200 to 300 m. in association with sponges, barnacles, brittle stars, Spatulate sculpin Icelus spatula is rather common sea urchins, sea cucumbers, bryozoans, ascidians, and species in the Sea of Okhotsk, Bering Sea, arctic basin primnoid corals. and the Pacific waters off Kuril Islands and

Orlov : Impact of eddies on spatial distributions of groundfishes 105

Fig. 9 — Spatial distribution and relative abundance categorized by CPUE (no/h trawling) of sponge sculpin Thyriscus anoplus (A) and roughskin sculpin Rastrinus scutiger (B).

Kamchatka43,44. In the study area, spatulate sculpin longfin Irish lord until settlement occurred within the was caught only between 47°50′ N and 50°20′ N eddy over underwater plateau. After transition from (Fig. 10A). Its maximum abundance (100-150 no/h pelagic to benthic stage, juveniles start migrating trawling) was registered at the top of underwater gradually from upper slope areas to shallower waters. plateau at depth < 200 m (73 % of relative abundance) Scaly-belly sculpin Icelus perminovi is distributed among numerous sponges. Outside plateau area, from the Pacific coast of Hokkaido to the northern captures of spatulate sculpin were incidental. Sea of Okhotsk including waters along Kuril Islands 48,49 According to the last revision of sculpins, and Kamchatka . In the Pacific waters off the belonging to Hemilepidotus45, all the vouchered northern Kuril Islands and southeastern Kamchatka, records of adults and benthic juveniles of longfin Irish this species occurred within the entire study area at lord H. zapus were recently known only from coastal depths 200 to 840 m. Scaly-belly sculpin was found waters off the Aleutian Islands, although pelagic mostly in the catches conducted over continental larvae of this species were found in the eastern Bering slope areas with complex relief and rocky grounds Sea46. Present study showed that longfin Irish lord is covered by numerous sponges. Its maximum catches one of most abundant sculpins in the Pacific waters (over 300-400 no/h trawling) were obtained at the off the northern Kuril Islands. In this area, the species eastern slope of underwater plateau (Fig. 11A). considered occurred only between 47°50′ N and Blacknose sculpin Icelus canaliculatus is 50°10′ N (Fig. 10B) but its maximum catches (5-10 distributed from Hokkaido coast of the Sea of thousands no/h) are registered at the western slope of Okhotsk to the Bering Sea including the Pacific underwater plateau (48°10′ N 48°30′ N). Hemilepidotus waters off the northern Kuril Islands and eastern zapus inhabit mainly shelf and continental slope areas Kamchatka49. Its distributional features in the study with complex relief and rocky grounds that are area are very similar to that of scaly-belly sculpin. covered by numerous sponges. Juveniles of this Blacknose sculpin is occurred there from the southern species dwell shallower waters in comparison with edge of underwater plateau in the south to 52°N in the adults. Irish lords have pelagic larvae and juveniles47, north (Fig 11B) but its maximum abundance is noted which were captured in offshore waters7. This allows at the eastern slope of plateau, where catches of to assume that development of pelagic young of species considered constituted 100 to 150 no/h.

106 Indian J. Mar. Sci., Vol. 32, No. 2, June 2003

Fig. 10 — Spatial distribution and relative abundance categorized by CPUE (no/h trawling) of spatulate sculpin Icelus spatula (A) and longfin Irish lord Hemilepidotus zapus (B).

Fig. 11 — Spatial distribution and relative abundance categorized by CPUE (no/h trawling) of scaly-belly sculpin Icelus preminovi (A) and blacknose sculpin Icelus canaliculatus (B).

Orlov : Impact of eddies on spatial distributions of groundfishes 107

Fig. 12 — Capture localities of spiny eel Notacanthus chemnitzi (A) and skilfish Erilepis zonifer (B).

Fourhorn poacher Hypsagonus quadricornis is a larvae of corals in underwater plateau slopes. As a rare fish species widely distributed in the North result, eel-like fish species occurred predominantly Pacific Ocean from the Japan Sea coast (Niigata off underwater plateau area. Prefecture) to the northern part of the sea and from Tough eelpout Puzanovia rubra is rather common the Pacific coast of Honshu (Iwate Prefecture) along fish species that is widely distributed in the north- the Kuril and Aleutian Islands and eastern Kamchatka western Pacific Ocean from Hokkaido (Cape Erimo) to Puget Sound including the Sea of Okhotsk, Bering along the Kuril Islands and eastern Kamchatka to the Sea (Gulf of Anadyr in the north and Bristol Bay in Bering Sea including the Sea of Okhotsk52. In the the east) and Gulf of Alaska50. This species in the study area, only two specimens were caught at the study area occurred only within the southern part, southern slope of underwater plateau and at the small mostly at the western section of underwater plateau bank located to the north of this plateau (Fig. 4) (Fig. 4) at depths < 200 m at which numerous sponges According to Fedorov53 this species lives among also occurred. corals and feed on soft coral tissues. The life cycles of Slime flounder Microstomus achne is a rare eelpouts are poorly understood and there is no data on species that inhabit the East China and Yellow Seas, early life stages of this species. Gulf of Po-Hai, Sea of Japan, Suruga Bay (central Spiny eel Notacanthus chemnitzi is cosmopolitan Honshu), waters off Sakhalin and Kuril Islands51. In rare species that is distributed worldwide in deep the study area, only three specimens of slime flounder waters34. Single specimens represented captures of were caught at the western slope of underwater spiny eel in the study area usually but most of them plateau (Fig. 4) at depths 116 to 450 m. Some (95 %) were obtained from its southern part (Fig. 12A). individuals were found in the catches that contained However, spiny eel was caught frequently at the large amount of sponges. eastern plateau slope, and occurred in association with primnoid corals. Species inhabiting corals Fedorov’s eelpout Lycenchelys fedorovi was Several species such as spiny eel, tough eelpout, originally described from the Pacific waters off the and Fedorov’s eelpout dwell among primnoid corals. northern Kuril Islands only recently54 and at present is Eddy waters may also limit distribution of pelagic considered as endemic species of this area. In the

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Fig. 13 — Spatial distribution and relative abundance categorized by CPUE (no / h trawling) (A), and distribution of mean body weight (kg) (B) of darkfin sculpin Malacocottus zonurus. Pacific waters off the northern Kuril Islands gradual reverse migrations to spawning grounds. Fedorov’s eelpout occurred only southerly Fourth Darkfin sculpin Malacocottus zonurus is Kuril Strait (Fig. 3B). However, this species has the distributed in the North Pacific from the northern maximum abundance in the northern and southern Japan to the Gulf of Alaska55. In the study area, it parts of the eastern plateau slope, where its catch occurred from the southern tip of underwater plateau sometimes reaches 10 no/h trawling. This species in the south to 52° N in the north (Fig. 13A) within inhabits relatively deep waters (300 to 650 m), but the depth range 100-824 m. Catches of species most of the fishes (70.1 % of relative abundance) were considered varied from several specimens to 1,000- distributed within the depth range 450-600 m, the 3,000 no/h trawling. In the northern part of areas being inhabited by primnoid corals. The life investigated area, its abundance was low, catches cycle of Fedorov’s eelpout is probably associated with increased south of the Fourth Kuril Strait, and the these corals because some invertebrates, dwelling on maximum abundance was noted at slopes of coral branches, were found in its stomach54. underwater plateau. Some young bathyal species occupy deeper waters while adults dwell shallower Species, for which plateau waters serves as areas56. Vertical distributions of different size groups nursery area of darkfin sculpin exhibit the same pattern. In the Eddy waters also serve as nursery grounds for southern part of study area darkfin sculpin was some species such as shortraker rockfish and darkfin considerably smaller than in the northern areas. Thus, sculpin. They spawn off Paramushir Island and on the shelf and continental slope off Shumshu and southeastern Kamchatka coast. Only juveniles of Paramushir Islands and southeastern Kamchatka these species are caught off underwater plateau area. mostly adults with length of 20-35 cm were caught It is possible that the East Kamchatka current while within underwater plateau area, juveniles with transports their pelagic larvae and juveniles to the length of 6-20 cm constituted the base of catches. south, and then they fall into eddy waters, inhabit this There are several areas, where largest specimens of area until settlement and with increase in size start darkfin sculpin occurred: from the Lopatka Cape

Orlov : Impact of eddies on spatial distributions of groundfishes 109

Fig. 14 — Spatial distribution and relative abundance categorized by CPUE (kg/h trawling) (A), capture localities of benthic juveniles < 13 cm (B), and distribution of mean body length (cm) (C) of shortraker rockfish Sebastes borealis. (southern tip of Kamchatka Peninsula) to 52° N, areas as potential spawning grounds. It is suggested central Paramushir, off the Fourth Kuril Strait, and that pelagic larvae of shortraker rockfish produced off local sections off underwater plateau and banks the southeastern Kamchatka and Paramushir Island (Fig. 13B). This species has pelagic larvae and are transported by East Kamchatka current to juveniles22 that were found over deeper depths in underwater plateau area, where they fall into the eddy offshore waters7. It is possible to assume that early waters and develop in that area until settlement. Then life stages of darkfin sculpin are associated with they feed along the plateau slopes and with increase in eddies existing in the study area. Distributional size, gradually start reverse migrations to the patterns of its different size groups indicates that spawning grounds. settlement of pelagic juveniles occur in continental slope areas, followed by gradual migration of growing Species feeding within the plateau area fish to the shelf. Feeding of skilfish, sablefish, Kamchatka flounder, Shortraker rockfish Sebastes borealis is distributed and spectacled sculpin occurs mostly within within the shelf and continental slope waters underwater plateau area. These species do not spawn continuously from the Pacific waters of Honshu here (except for spectacled sculpin). Since they (Iwate Prefecture) and southeastern Sakhalin along consume mainly benthic and benthopelagic fish and Hokkaido coast of the Sea of Okhotsk, Pacific side of large invertebrates, it is presumed that preys of above Kuril Islands, eastern Kamchatka, Aleutian Islands, species in the area considered are more abundant in Gulf of Alaska, and British Columbia to the southern comparison with waters outside underwater plateau. California at 40°46′ N including waters of the Bering Skilfish Erilepis zonifer is distributed from the Sea34. The map of the multi-annual spatial distribution Pacific coast of Japan and Monterey Bay in the south (Fig. 14A) shows that shortraker rockfish is most to the Gulf of Alaska and Aleutian Islands in the north abundant within only two areas (CPUE over 500 including waters along the Kuril Islands19. kg/h): off southeastern Kamchatka and off the Information exists on capture of this species in the underwater plateau south of Onekotan Isl. At the same North Pacific high sea57. Large mature specimens time, shortraker rockfish juveniles < 15 cm were were caught mostly on continental slope in coastal abundant (Fig. 14B) in the second of the above areas. waters by trawl and long-line gears while pelagic Smaller shortraker rockfish occurred also, only in the juveniles occurred mainly in the offshore waters of southern part of the investigated area off the the eastern North Pacific, where they are often underwater plateau (Fig. 14C). Within the same time captured during gill net fishery for salmons and 58 frame, larger specimens with a mean length > 60 cm nectonic . According to Safran & Omori , are caught off Paramushir Island and southeastern skilfish juveniles were found among drifting seaweed in offshore waters of Honshu. The captures of large Kamchatka to the north of 52 °N, suggesting these

110 Indian J. Mar. Sci., Vol. 32, No. 2, June 2003

Fig. 15 — Spatial distribution and relative abundance categorized by CPUE (no/h trawling) of Kamchatka flounder Atheresthes evermanni (A), sablefish Anoplopoma fimbria (B), and spectacled sculpin Triglops scepticus (C). mature skilfish in the Pacific waters off the northern Kuril Strait, and off underwater plateau. Maximum Kuril Islands increased in the recent years59. All the catches (over 100 no/h) were registered south of captures of skilfish in the study area (except of single Fourth Kuril Strait but largest catches, reaching record) were noted at slopes of underwater plateau 250 no/h, were obtained at slopes of underwater (Fig. 12B). Most of them occurred in the southern part plateau. of plateau. The occurrence of skilfish exclusively Sablefish Anoplopoma fimbria inhabit continental within the plateau area cannot be substantiated yet, slope waters from the Pacific coast of Hokkaido because this species does not spawn in the area (Volcanic Bay) to the southern California including considered and its pelagic juveniles inhabit areas that the Bering Sea and Sea of Okhotsk19. There are two are very distant from the northern Kuril Islands areas in the Pacific waters off the northern Kuril waters. Increasing number of recent skilfish captures Islands and southeastern Kamchatka, where sablefish in study area are probably associated with increase in has maximum abundance (Fig. 15B): the southeastern its abundance and extension of its distribution Kamchatka coast from Lopatka Cape (southern tip of eastward. It may be suggested that skilfish find most peninsula) to 51°30´ N (“northern” eddy area) and favourable conditions for feeding within plateau area, southeastern slope of underwater plateau. In the because the adults consume squids and octopi which northern area maximum sablefish catches were 50- are abundant in this area60,61. 100 no/h trawling while in the southern one respective Kamchatka flounder Atheresthes evermanni inhabit values were 100 to 150 no/h. Sablefish is most mainly Asian waters and distributed from Sendai Bay abundant off the North America coast that is (Pacific coast of Honshu) and Sea of Japan off considered as its breeding area. Some authors reported that sablefish, inhabiting Asian waters, Hokkaido in the south to southern Bering Sea in the 64 north including continental slope waters of the most migrate there from the eastern North Pacific and part of the Sea of Okhotsk18. Eastern boundary of its does not spawn in this area. Therefore it is difficult to distribution is the Gulf of Alaska62. Although once associate existence enlarged abundance of sablefish Kamchatka flounder was captured off Canadian coast within eddies waters, with its breeding patterns. Since 63 sablefish in the study area consume mostly benthic near Vancouver Island . This species in the Pacific 18 waters off the northern Kuril Islands occurred almost and bentho-pelagic invertebrates and fish , the above within the whole area except for some shelf sections distribution pattern may be related only to feeding from Paramushir coast to the southern Kamchatka tip. factor, i.e. probable enlarged biomass of its preys There are two areas with most dense schoolings of occurred in eddy areas. Kamchatka flounder that occurred throughout the year Spectacled sculpin Triglops scepticus is common (Fig. 15A): off the southeastern Kamchatka coast and rather abundant, widely distributed in the North (area of “northern” eddy), central part of the Fourth Pacific Ocean from Toyama Bay (central Honshu)

Orlov : Impact of eddies on spatial distributions of groundfishes 111

along Kuril and Aleutian Islands and eastern Kamchatka flounder occur within underwater plateau Kamchatka to the Gulf of Alaska including waters of area, where they do not spawn. High abundance of the Sea of Japan, Sea of Okhotsk, and Bering Sea34. these species feeding on demersal fish and large There are two areas in the Pacific waters off the invertebrates may be explained by enlarged biomass northern Kuril Islands and southeastern Kamchatka, of preys within plateau in comparison with outside where spectacled sculpin has maximum abundance waters. (Fig. 15C): the southeastern Kamchatka coast from Lopatka Cape to 51°30´ N (“northern” eddy area) and Acknowledgement top and slopes of underwater plateau, especially in its Author expresses deep gratitude to all his northern part. In the northern area maximum catches colleagues from Russian Federal Institute (VNIRO), of spectacled sculpin were 500-1,000 no/h trawling Sakhalin (SakhNIRO), and Kamchatka (KamchatNIRO) while in the underwater plateau area some catches Institutes of Fisheries & Oceanography, Institute of reached 1,000 to 3,500 no/h. This species is typically of Far East Branch of the Russian benthophagic sculpin, consuming mainly benthic Academy of Sciences (IMB FEB RAS), Zoological invertebrates65. However, sometimes off underwater Institute of the Russian Academy of Sciences (ZIN plateau mesopelagic fishes were found in its stomach. RAS), and Kamchatka Branch of Pacific Institute of Geography of the Russian Academy of Sciences Conclusion (KBPIG FEB RAS), who participated in numerous Eddies may affect spatial distribution and some life research cruises conducted aboard Japanese trawlers history patterns of various groundfish species, having within the frame of joint scientific program. Special different life cycles. Eddies may limit distribution of thanks to Dr. D. Pitruk (IMB FEB RAS), Dr. V. Polutov species with pelagic eggs, larvae, and fry (such as (KamchatNIRO), Dr. S. Leontiev (VNIRO), snailfishes, sculpins, flounders, and broadbanded Dr. I. Biryukov, and Dr. O. Nemchinov (both from thornyhead), which until settlement inhabit eddy SakhNIRO), who assisted me in this study, and to waters that do not allow them to leave underwater Dr. A. Balanov (IMB FEB RAS) and Dr. B. Sheiko plateau area. Among these fishes only broadbanded (ZIN RAS) for identification of some species. thornyhead has commercial importance. Localization of dense schools of this species within eddy waters References supports commercial fishery along underwater plateau 1 Orlov A M, Tokranov A M & Tarasyuk S N, Composition slopes throughout the year. and dynamics of the bottom fish communities on the Pacific Some species inhabit areas that are covered by upper continental slope off the northern Kuril Islands and southeast Kamchatka, Vopr. Rybolovstva, 1 (2000) 21-45 dense sponges (nutcracker pricleback, fourhorn (In Russian). poacher, slime flounder, small sculpins) or corals 2 Suponitsky V A, Fishery results of commercially important (spiny eel, eelpouts). Eddy waters may limit species in basic fishing grounds by «Dal’ryba» fishing distribution of sponges and corals outside underwater vessels, 1988-1985. Collection of fishery statistics. Pt. 2 plateau and create favourable environmental (Northern Kuril Islands statistical region), (Dal’ryba, Vladivostok, Russia) 1987, pp. 75 (In Russian). conditions for these species. Eddies are able to 3 Fedorov V V, Species composition, distribution and concentrate plankton that results in increasing of its habitation depths of the Northern Kuril Islands fish and fish- biomass. Therefore feeding of some plankton-feeders like species, in: Commercial and biological studies of fishes including commercially important Atka mackerel and in the Pacific waters of the Kuril Islands and adjacent areas Pacific Ocean perch within eddy waters at underwater of the Okhotsk and Bering Seas in 1992-1998, edited by B.N. plateau occurred throughout the year that supports Kotenev, (Izd. VNIRO, Moscow) 2000, pp. 7-41 (In Russian). commercially fishery in this area. Eddy waters serve 4 Sheiko B A & Fedorov V V, Class Cephalaspidomorphi – as nursery grounds for some species as well Lampreys. Class Chondrichthyes – Cartilaginous Fishes. (shortraker rockfish and darkfin sculpin). They spawn Class Holocephali – Chimaeras. Class – Bony off Paramushir Island and southeastern Kamchatka Fishes, in: Catalog of vertebrates of Kamchatka and adjacent coast. East Kamchatka current transports their pelagic waters, edited by R.N. Moiseev and A.M. Tokranov, larvae and juveniles to the southern eddy, where they (Kamchatskiy Pechatniy Dvor, Petropavlovsk-Kamchatsky) 2000, pp. 7-69 (In Russian). inhabit until settlement and with increasing in size 5 Kuronuma K, Fishes obtained from Paramushir Island. The perform gradual reverse migrations to spawning fishes of the northern parts of Kuril Island, Bull. grounds. Feeding of skilfish, sablefish, and Biogeograph. Soc. Jap., 13 (1943) 101-123 (In Japanese).

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