Megafaunal Composition of Cold-Water Corals and Other Deep-Sea Benthos in the Southern Emperor Seamounts Area, North Pacific Ocean

Galaxea, Journal of Coral Reef Studies 19: 19-30（2017）

Original paper

Megafaunal composition of cold-water corals and other deep-sea benthos in the southern Emperor Seamounts area, North Pacific Ocean

Mai MIYAMOTO1*, Masashi KIYOTA1, Takeshi HAYASHIBARA2, Masanori NONAKA3, Yukimitsu IMAHARA4, and Hiroyuki TACHIKAWA5

1 Oceanic Ecosystem Group, National Research Institute of Far Seas Fisheries, Japan Fisheries Research and Education Agency, 2-12-4 Fukuura, Kanazawa, Yokohama, Kanagawa, 236-8648 Japan 2 Coastal Resource and Ecosystem Group, Seikai National Fisheries Research Institute, Japan Fisheries Research and Education Agency, 148 Fukaiota, Ishigaki, Okinawa, 907-0451 Japan 3 Okinawa Churaumi Aquarium, Okinawa Churashima Foundation, 424 Ishikawa Motobu-Cho, Okinawa 905-0206, Japan 4 Wakayama Laboratory, Biological Institute on Kuroshio, 300-11 Kire, Wakayama 640-0351 Japan 5 Coastal Branch of Natural History Museum and Institute, Chiba, 123 Yoshio, Katsuura, Chiba 299-5242, Japan

* Corresponding author: Mai Miyamoto E-mail: [email protected]

Communicated by Michio Hidaka (Biology Editor)

Abstract Recent developments in deep-sea surveys have The results demonstrates that the regional characteristics revealed the widespread distribution of cold-water corals of deep-sea benthic megafauna in the southern Emperor over the deep-sea floor of the world ocean. There are no Seamounts area is more similar to that near the Hawaiian reports, however, concerning the taxonomic composition Islands than those reported from Aleutian, other Alaskan, of cold-water corals and other benthic megafauna in the Californian and Japanese waters. southern Emperor Seamounts area of the North Pacific Ocean. We analyzed benthic samples collected from a Keywords benthic megafauna, cold-water corals, Emperor research vessel during scientific surveys and by scientific Seamounts, habitat-forming species, vulnerable marine observers onboard commercial fishing vessels to examine ecosystems the faunal composition of cold-water corals and other megabenthos in the southern Emperor Seamounts area. Seventy-eight genera of cold-water corals were identified. Introduction Gorgonians (Alcyonacea with solid axis) occurred at high frequencies with wide vertical distribution ranges, and Recent developments in deep-sea surveys that use appeared to be the major components of habitat-forming acoustic and submersible devices have revealed the cold-water corals in the area. Scleractinia occurred at widespread distribution of cold-water corals on the deep- frequencies similar to those of gorgonians, but over lim­ sea floor throughout the world ocean (Heifetz et al. 2005; ited depth ranges. Among other benthic megafauna, Crus­ Lundsten et al. 2009; McClain et al. 2010; Mol et al. 2002; tacea and Echinodermata occurred at high frequencies. Reed et al. 2006; Roberts et al. 2006). Reports from 20 Miyamoto et al.: Cold-water coral fauna in the Emperor Seamounts

Alaska and Florida in the USA, the northern Atlantic the target species and the area of operations (Grigg 1993). Ocean, and many other areas have shown that some Since 1969, the southern Emperor Seamounts south of species of cold-water corals build complex structures and 45°N have been used as fishing grounds of commercial produce unique demersal communities in the same way as fisheries targeting bottom fish such as North Pacific do shallow-water coral reefs (Heifetz 2002; Heifetz et al. armorhead (Pentaceros wheeleri) and splendid alfonsino 2005; Lundsten et al. 2009; McClain et al. 2010; Mol et (Beryx splendens; Kiyota et al. 2016). To fulfill the global al. 2002; Morris et al. 2013; Reed et al. 2006; Roberts et requirement for ecosystem-based fishery management, it al. 2006; Stone et al. 2015). Such frameworks of cold- is urgent that relevant management bodies assess and water corals provide habitats or spawning and nursery manage bottom fisheries impacts on VMEs considering grounds for fish and many other animals and thereby the regional characteristics of benthic fauna and the support diverse ecosystems (Baillon et al. 2012; Roberts history of the fisheries (FAO 2009). For the southern et al. 2006). Because of their slow growth, long lifespans, Emperor Seamounts area, however, there is no basic in­ and slow recovery from physical damage, cold-water formation on benthic fauna, such as the taxonomic compo­ corals attract attention as important components of vul­ sition of cold-water corals and other benthos. nerable marine ecosystems (VMEs) in the context of In this study, we analyzed samples of megabenthos marine biodiversity conservation and management collected during scientific surveys and as part of asci­ (Roberts et al. 2009). entific observer program for commercial fisheries to ex­ The Emperor Seamount chain is located from 30°N to amine the composition of cold-water corals and other 55°N and from 168°E to 178°E, extending from the benthic megafauna in the southern Emperor Seamounts Northwestern Hawaiian Islands to the Aleutian Trench in area. We identified cold-water corals to the lowest taxon the western North Pacific Ocean (Fig. 1). In 1965, precious possible and analyzed their bathymetric distribution. This corals were discovered in this area. At the peak in 1981, study provides the first description of the faunal compo­ ­ more than 100 coral fishing boats from Taiwan and Japan sition of cold-water corals and other megabenthos in the are believed to have harvested approximately 300 metric southern Emperor Seamounts area for which there has tons of precious corals from this area; however, many been little information. things about this coral fishery remain unclear, including

Materials and Methods

Study area and benthic sampling We analyzed samples of megabenthos that were col­ lected from a research vessel during scientific surveys, and by participants in the scientific observer program covering the commercial bottom fisheries in the southern Emperor Seamounts area. Scientific observers have been onboard all Japanese commercial bottom trawl and gillnet fishing vessels (at most six bottom trawlers and one bottom gillnet vessel) operating in the area since June 2009. The fishing operations were conducted mainly on flat tops by trawlers and at upper slopes by the gillnet vessel. The scientific observer samples analyzed in this Fig. 1 Map of the Emperor Seamount chain. Benthos study were collected from the fishing operations at the samples were collected from the south bank of Suiko, Yomei, Nintoku, Northern Koko, Koko, Kinmei, Yuryaku, following seamounts during the fishing season (January to Kammu, Colahan and C-H seamounts. October), 2009-2014: south bank of Suiko (44.5-45°N, Miyamoto et al.: Cold-water coral fauna in the Emperor Seamounts 21

Table 1 Number of sampling hauls by each gear type and number of taxa collected per seamount.

170°E, 969-1190 m deep); Yomei (42-42.5°N, 170.5°E, times mainly on the bedrock or sandy flat tops of sea­ 1038-1220 m deep), Nintoku (41°N, 170.5°E, 979-1050 mounts, and large and small dredges were deployed 54 m deep); Northern Koko (36.5-37°N, 171.5°E, 840-1250 times as supplements on sloped and rough bottomed areas m deep); Koko (34.5-35°N, 171-172°E, 275-1070 m deep); (Table 1). The seamounts surveyed were Northern Koko Kinmei (33.5-34°N, 171-172°E, 575-1340 m deep), (550-1115 m), Koko (229-1299 m), Yuryaku (460-882 Yuryaku (32.5°N, 172°E, 391-1225 m deep), Kammu m), Kammu (283-1317 m), Colahan (256-981 m) and (32°N, 172-173°E, 349-1300 m deep); and Colahan (31°N, C-H (30.5°N, 177.5-178°E, 336-1121 m). The sampling 175-176°E, 8221365 m deep). Megabenthos samples­ were depths were determined by a depth-temperature sensor collected from 116 trawl hauls (275-651 m deep) and 111 (COMPACT-TD for deep-sea, JFE Advantech Co, Ltd, gillnet sets (378-1365 m deep; Table 1). The sam­pling Hyogo, Japan) attached to the beam trawl or by the sea depths were determined by depth at the end of trawl hauls floor depths at the end of dredge tows observed bythe recorded by the net monitoring system (SCANMAR, ship-mounted precision depth recorder (Deep-sea preci­ Simrad Co. Ltd., Vancouver, Canada) or by the seafloor sion depth recorder, NEC Corporation, Tokyo, Japan). depths at the beginning of gillnet retrievals measured by The benthos samples were examined preliminary onboard the echo sounder (JFW-820, Japan Radio Co. Ltd., Tokyo, and preserved in 70% ethanol for more detailed later Japan). The sampled benthos specimens were cryo-pre­ examination on shore. served onboard and were brought back to the laboratory for later examination. Sample analysis The scientific surveys were conducted from 2009 to Cold-water coral specimens were identified to the 2014 by using R/V Kaiyo-maru (93 m, 2942 GT) of the lowest possible taxon such as species or genus based on Fisheries Agency of Japan. During these scientific sur­ external morphology and by microscopic observation of veys, megabenthos were sampled from 170 hauls using a sclerites for Alcyonacea. As surveys of deep-sea animals sea-urchin beam trawl (mouth widgh 1.5 m wide, inner such as cold-water corals are time-consuming and expen­ net mesh size 5×5 mm) and a large (mouth width 1.0 m, sive and there are not many experts in classification of mesh 5×5 mm) or a small (mouth width 0.5 m, mesh 5 cold-water corals, information for some taxa is limited. In ×5 mm) dredge. During sampling, vessel speed was set at the North Pacific, information is relatively abundant for approximately 1 knot (max 1.5 knots); the towing duration the Alcyonacea (especially the Scleraxonia, Holaxonia was set at 5-10 min for the sea-urchin beam trawl or and Calcaxonia) and the Scleractinia; in contrast, infor­ 2-10 min for the dredges after first contact of the sampling mation is very limited for the Antipatharia. Because this gear with the sea floor. The beam trawl was deployed 116 study aimed to clarify the regional characteristics of the 22 Miyamoto et al.: Cold-water coral fauna in the Emperor Seamounts benthic megafauna in the southern Emperor Seamounts area, cold-water corals were identified to the genus level Results for most samples, and detailed taxonomic examination such as more complicated microscopic observations of Composition of cold-water corals alcyonacean sclerites was deferred as a future task. How­ We examined 213 cold-water coral specimens from the ever, specimens of the Coralliidae were subject to detailed commercial trawl, 211 from the commercial gillnet, and taxonomic examination because of their importance in the 1174 from the scientific surveys. The specimens included past targeted fishery (Grigg 1993). The Scleraxonia, 34 Stylasterina, 2 Pennatulacea, 69 Alcyonacea (excluding Holaxonia and Calcaxonia, which constituted the order gorgonians), 998 gorgonians, 125 Antipatharia and 370 Gorgonacea in the previous classification system, were Scleractinia. In total 29 families and 78 distinct genera of treated separately from the rest of Alcyonacea and grouped coral were identified. Many genera were considered to as “gorgonians” in this study, because gorgonians (Al­ include multiple species as indicated by “spp.” in Table 2. cyonacea with solid axis) and other Alcyonacea (soft One family (Stylasteridae) and two genera were identified corals) have different growth-forms and are treated as in the Stylasterina (hydrocorals), Hydrozoa (Table 2). The separate VME indicator taxa by many fishery management identified taxa in the Octocorallia included one genus in bodies. Hereafter, we designate Scleraxonia, Holaxonia the family Pennatulidae (sea pens) and one unknown and Calcaxonia as “gorgonians” and Alcyonacea exclud­ genus of the order Pennatulacea, three genera and one ing these three suborders as “Alcyonacea (excluding gor­ unknown genus in the family Clavulariidae of the suborder gonians)”. Stolonifera, and two genera in the family Alcyoniidae The bathymetric range and occurrence frequency of and, one genus in each of the families Nephtheidae, gorgonians, Antipatharia and Scleractinia, which were Nidaliidae and Paralcyoniidae of the Alcyoniina, Al­ found in relatively large numbers in the samples, were cyonacea (excluding gorgonians). The specimens iden­ analyzed in 50 m depth intervals. In the bathymetric range tified as scleraxonian gorgonians included six taxa in analysis, colonial and habitat-forming Scleractinia were three families (Anthothelidae, Paragorgiidae, and Coral­ analyzed by species, but other cold-water corals were liidae), 14 genera in four families of the Holaxonia, and aggregated at the family level. 15 genera in three families of the Calcaxonia (Table 2). To determine the benthic composition and the per­ Among the gorgonians sampled, more genera were in the centage of cold-water corals in the total benthos biomass, Plexauridae (11) of the Holaxonia and the Primnoidae we analyzed the entire catch collected by scientific (12) of the Calcaxonia than in other families. The genus surveys. The megabenthos samples other than cold-water Acanthogorgia was the most abundant of the gorgonians, corals were classified to the family or higher taxonomic accounting for 119 of the 998 (11.9%) gorgonian speci­ levels, such as order or phylum. Cold-water corals were mens. Several gorgonian specimens belonged to the aggregated to the order or suborder levels. The occurrence family Coralliidae, known as precious corals, including and total wet-weight of these taxa in the catch was Hemicorallium abyssale (Bayer 1956) and Hemicorallium measured, and the occurrence frequency was calculated as laauense (Bayer 1956). In the Antipatharia (black corals), the number of hauls in which the focal taxa appeared Hexo­corallia, nine genera in four families were identified. divided by the total number of hauls. The genus Antipathes was the most abundant of the Anti­ Most of the specimens examined in this study are stored patharia (25 out of 86 specimens). The Scleractinia (stony in the National Research Institute of Far Seas Fisheries, corals) comprised 22 genera in 7 families, of which 17 Yokohama, Japan. Some cold-water coral specimens are were identified to species. Most of the scleractinian speci­ temporarily retained for further taxonomic examination at mens were of small, unattached solitary species (e.g., the Natural History Museum and Institute, Chiba and the Letepsammia formosissima (Moseley 1876), Flabellum Okinawa Churaumi Aquarium. sp.), however, some colonial framework-building species such as Solenosmilia variabilis Duncan 1873, Desmo­ Miyamoto et al.: Cold-water coral fauna in the Emperor Seamounts 23

Table 2 Cold-water coral taxa collected in the southern Emperor Seamounts area. 24 Miyamoto et al.: Cold-water coral fauna in the Emperor Seamounts

Table 2 Continued.

phyllum pertusum (Linnaeus 1758), Enallopsammia ros­ 14 stylasterinan, pennatulacean, alcyonacean, gorgonian, trata (Pourtalès 1867) and Madrepora oculata Linnaeus antipatharian and scleractinian genera, respectively; Table 1758 were also collected at Northern Koko, Koko, 1). Yuryaku, Kammu, Colahan and C-H seamounts. The largest number of cold-water corals taxa were Bathymetric distribution of cold-water corals collected from Koko seamount (2 stylasterinan genera, 2 Gorgonians were distributed over the widest depth pennatulacean genera, 9 alcyonacean genera, 38 gorgonian range, from 275 to 1353 m (Fig. 2). Most of the Acantho­ ­ genera, 6 antipatharian genera and 21 scleractinian gorgiidae, Plexauridae and Primnoidae occurred at rela­ genera); Koko is the largest seamount in the Emperor tively shallower depth ranges, down to 500-600 m. In seamount chain and the sampling there was the most contrast to other gorgonian families, Chrysogorgiidae oc­ intensive (Table 1). Also rich in cold-water coral taxa curred over a relatively wider range, between 250 and were Colahan (2, 9, 22, 4, and 12 stylasterinan, alcyo­ over 1300 m. Antipatharia also were found over wide nacean, gorgonian, antipatharian and scleractinian genera, depth ranges but mainly in zones shallower than 500 m. respectively) and Kammu seamounts (2, 1, 3, 20, 3, and The family Schizopathidae showed the widest vertical Miyamoto et al.: Cold-water coral fauna in the Emperor Seamounts 25 distribution among the Antipatharia, reaching depths of species, from 306 to 1245 m. Desmophyllum pertusum 1299 m. Among Scleractinia, Solenosmilia variabilis, was distributed shallower than 700 m; this species is Enal­lopsammia rostrata and Madrepora oculata, were known as a framework-builder in many other regions, but principally distributed deeper than 550 m. E. rostrata was only fragments have been collected from the southern confirmed over the widest depth range among the three Emperor Seamounts. Most of the other solitary and small

Fig. 2 Bathymetric distribution (50 m bins) of cold-water corals in the southern Emperor Seamounts area. Shading in the cells indicates the frequency of occurrence of the taxa in the samples. Arrows indicate the total depth range of occurrence. 26 Miyamoto et al.: Cold-water coral fauna in the Emperor Seamounts species of the Scleractinia were found at relatively shal­ hauls). The wet-weight of Echinoidea was highest (63.6 lower depths. Among the solitary Scleractinia, the family kg in total) with Ophiuroidea second (41.7 kg). Porifera Caryophylliidae showed the widest vertical distribution had a high wet-weight (40.6 kg), comparable to Ophiu­ (250-1149 m). roidea, although its frequency of occurrence was relatively low (33.7%). Gorgonians and Scleractinia followed these Composition of benthic megafauna taxa and had the highest and second highest wet-weights In total, 21 classes of 10 phyla of benthic megafauna among the cold-water corals (29.7 and 23.1 kg, respec­ were collected during the scientific surveys and classified tively). The frequencies of occurrence and total wet- into 35 taxonomic groups for which frequencies of occur­ weights of Alcyonacea (excluding gorgonians), Sty­ rence and wet-weights were calculated (Fig. 3). Among lasterina and Antipatharia were relatively low. The fre­ all of the benthic taxa identified, Ophiuroidea, Anomura, quency of occurrence and total wet-weight of Pennatulacea other Decapoda and Echinoidea occurred at the highest were the lowest of all identified cold-water corals. frequencies (i.e. in more than 70% of all hauls). Gorgo­ Several specimens of Zoantharia, Anomura and Ophiu­ nians, Scleractinia, Asteroidea and Prosobranchia also roidea were confirmed to live on the colonies of gorgonians occurred at high frequencies (in more than 60% of all such as Primnoidae. Other sessile megafauna such as

Fig. 3 Frequency of occurrence (A) and total wet-weights (B) of benthic megafauna collected by scientific surveys in the southern Emperor Seamounts area. Only top 25 groups are shown in this figure. Other groups (e.g. Pennatulacea, Sipuncla or Pycnogoida) were uncommon and are excluded. The Actiniaria, Polychaeta and Crustacea are epibenthos. Black bars indicate cold-water coral taxa. * Alcyonacea (excluding gorgonians) Miyamoto et al.: Cold-water coral fauna in the Emperor Seamounts 27 gorgonians and Stylasterina attached to the dead skeletons Pacific Oceans (Cairns 1995). TheS. variabilis specimens of living colonial Scleractinia. Similarly, epibenthos such collected from Koko, Kammu and Colahan seamounts in as commensal Polychaeta and Crustacea also inhabited this study provide the first record of this species in the colonial Scleractinia. North Pacific Ocean. The result of a visual seafloor surveys using a remotely operated vehicle (ROV) and drop camera suggested that there might be small reefs of Discussion S.variabilis, E rostrate and M. oculata on Colahan sea­ mount (Hayashibara and Nishida 2017). But framework- Our results demonstrate that gorgonians and Scleractinia building capacity of D. pertusum has not been confirmed contribute substantially to the species richness and abun­ by the seafloor observation in the southern Emperor Sea­ dance of benthic megafauna in the southern Emperor mounts area. Seamounts area. Both coral groups had high frequency of Guinotte et al. (2006) noticed a striking relationship occurrence and wet-weights compared to other cold-water between the vertical distribution of cold-water Scleractinia corals and most other benthic taxa. Among corals, the and the depth of the aragonite saturation horizon (ASH). number of gorgonian taxa was highest, with 38 genera in They indicated that the ASH in the North Pacific (50- 10 families confirmed. Two species of the family Coral­ 600 m) is substantially shallower than that in the North liidae (Hemicorallium abyssale and H. laauense) were Atlantic and other oceans. The bathymetric distribution of iden­tified, and several additional species, including new framework-building Scleractinia in the southern Emperor spe­cies were suspected. Most of the specimens of these Seamounts may be partially affected by the shallow depth additional species were identified tentatively as Pleuro­ ­ of the ASH (approximately 400-800 m deep at present corallium cf. pusillum (Kishinouye 1904), because of the day; Guinotte et al. 2006). For example, in this study, inadequate taxonomic description and the absence of type colonial framework-building scleractinian species were specimens for P. pusillum. These results indicate that distributed at 300-1250 m but in other regions, Sclerac­ several species of the Coralliidae inhabit the southern tinia are known to occur and construct large reefs even in Emperor Seamounts area and might have been harvested zones deeper than 2000 m (Guinotte et al. 2006; Roberts by the past coral fishing (Grigg 1993). et al. 2006). The depth of the ASH is likely to be the factor Many of the gorgonians collected were in the family limiting the calcification capacity of Scleractinia in the Primnoidae, a group known to provide important habitat southern Emperor Seamounts area. In this area, gorgonians structure for commercially important fish and other occurred over the widest depth range and at the highest animals (Krieger and Wing 2002; Buhl-Mortensen and frequencies compared to other cold-water corals. The Mortensen 2004, 2005; Stone 2006; Stone et al. 2015). axes of gorgonian corals are composed of protein, calcite The Scleractinia comprised large number of taxa (22 and aragonite (Fabricius and Alderslade 2001). Thus, the genera in 7 families) but their bathymetric range was calcification capacity of gorgonians are thought to be less slightly narrower than that of the gorgonians. Most of the dependent on ASH than are those of Scleractinia but more scleractinians sampled were solitary and small species. dependent on the calcite saturation horizon that is typically Scleractinia are known to form large reef structures in the deeper than the ASH (Guinotte et al. 2006). Antipatharia North Atlantic Ocean and other regions (Mol et al. 2002; generally occurred at low frequency, but some families Morris et al. 2013; Reed et al. 2006). In this study, some were distributed down to the depths comparable to gor­ framework-building species of the Scleractinia were gonians. Growth rates of Antipatharia are not dependent identified, such asSolenosmilia variabilis, Desmophyllum on the ASH because their axes are composed of protein pertusum, Enallopsammia rostrata and Madrepora (Goldberg et al. 1994). oculata. S. variabilis is generally known to have a cosmo­ Cold-water corals provide habitats for other animals politan distribution, but it had not previously been re­ (Roberts et al. 2006). Various invertebrates such as corded from the Antarctic, North Pacific and Eastern Porifera, Crustacea and Ophiuroidea are known to be 28 Miyamoto et al.: Cold-water coral fauna in the Emperor Seamounts associated with cold-water corals in the North Pacific and Stone and Shotwell (2007) reported that Crustacea, Ocean (Parrish and Baco 2007; Stone and Shotwell 2007, Ophiuroidea, Polychaeta and many species of Porifera are Miyamoto and Kiyota 2017). We confirmed that many associated with cold-water corals in the Aleutian archi­ specimens of Zoantharia, Anomura and Ophiuroidea in pelago. In the Bering Sea, cold-water corals are patchily our samples were attached to colonies of gorgonians such distributed on the broad continental shelf and along the as Primnoidae. Similarly, colonial Scleractinia were at­ shallow continental slopes, but the coral fauna in this tached or inhabited by other benthic animals in the region appear to be less diverse. There are no records of southern Emperor Seamounts area. colonial or habitat-forming Scleractinia from the Aleutian Many environmental factors and biological processes and Alaskan regions (Heifetz 2002; Stone and Shotwell affect the regional species composition and diversity of 2007). the benthic fauna of the deep-sea floor and seamounts Lundsten et al. (2009) reported from ROV video (Levin et al. 2001; Samadi et al. 2007). For example, in observation that Cnidaria, Porifera and Echinodermata the North Atlantic Ocean, regionally distinctive habitats were the dominant megabenthic taxa on three seamounts such as scleractinian reefs and large patches of the Pen­ off California. Among Cnidaria, gorgonians were the natulacea and Porifera have been documented and iden­ most frequently observed cold-water corals, and Anti­ tified as VMEs (Henry and Roberts 2007; Kenchington et patharia increased in deeper zones. However, the Cali­ al. 2014). The benthic megafauna of the southern Emperor fornian seamounts differed from the southern Emperor Seamounts area is characterized by the dominance of Seamounts in higher occurrences of the Alcyonacea gorgonians and Scleractinia and lower occurrence fre­ (excluding gorgonians) and scarcity of the Scleractinia. quencies of Pennatulacea, Stylasterina, and Porifera. In Limited information is available for the composition of this study, Echinodermata, Crustacea and Prosobranchia benthic megafauna in northwestern Pacific Ocean around were most prevalent, while Echinodermata and Porifera Japan. Tow camera and submersible surveys from Hok­ contributed most to the wet weight. Porifera wet weights kaido through Ryukyu Island revealed the differences in were relatively large due to their high water contents. the dominant taxa by location. Brachiopoda was dominant Prosobranchia was not reported as a main component of on Shiribeshi Seamount off the west coast of Hokkaido the deep-sea communities in Hawaiian and Alaskan (observed at 115-620 m deep; Fujikura et al. 1991), while waters (Parrish and Baco 2007; Stone and Shotwell 2007). Ophiuroidea was dominant in the western Tsugaru Strait Even within the North Pacific Ocean, deep-sea faunas (569-580 m deep; Wakutsubo and Koganezaki 1987). On are known to vary regionally. In Alaskan waters, Al­ the Ogasawara Ridge (210-400 m) and Kerama Bank cyonacea (excluding gorgonians), gorgonians, Pennatu­ (185-310 m), several cold-water corals were confirmed lacea and Stylasteridea are main components of habitat- by sea-floor observation surveys from ROVs and sub­ forming species (Heifetz 2002; Heifetz et al. 2005; Stone mersibles. However, major components of cold-water and Shotwell 2007). Stone and Shotwell (2007) compared corals in these areas, Stylaster sp. as Stylasterina, Plu­ the deep-sea coral ecosystems within the Alaskan region: mulariidae as gorgonian and Parantipathes sp. as Anti­ In the Gulf of Alaska, extensive Pennatulacea groves in patharia (Fujioka 1995; Okamura 1989), differed from the western Gulf of Alaska around the Kodiak Islands are those in the southern Emperor Seamounts area. In Sagami known as important coral features in the region. Gulf of Bay, 260 species of octocorals were recorded, including Alaska seamounts share the major taxonomic components 144 gorgonians, 80 Alcyonacea and 36 Pennatulacea of of the continental shelf but are characterized by the which Alcyonacea and Pennatulacea occurred most absence of Stylasterina and a paucity of Pennatulacea. frequently (Matsumoto et al. 2007). More than 300 islands comprise the Aleutian archipelago, The composition of the deep-sea benthic megafauna in form the boundary between the deep North Pacific Ocean the southern Emperor Seamounts area appears to be most and shallower Bering Sea, and support the most abundant similar to that of the Hawaiian Islands. In the Hawaiian and diverse cold-water coral fauna in Alaska. Stone (2006) Islands, gorgonians, Antipatharia, zoantharina gold corals Miyamoto et al.: Cold-water coral fauna in the Emperor Seamounts 29

(Kulamanamana haumeaae Sinniger, Ocaña and Baco, Buhl-Mortensen L, Mortensen PB (2004) Symbiosis in deep- 2013), and Scleractinia are considered the main compo­ water corals. Symbiosis 37: 33-61 nents of the cold-water coral fauna whereas Stylaserina Buhl-Mortensen L, Mortensen PB (2005) Distribution and di­ and Pennatulacea occur low frequently (Parrish and Baco versity of species associated with deep-sea gorgonian corals off Atlantic Canada. In: Freiwald A, Roberts JM 2007). Many commensal invertebrates such as Zoantharia, (eds) Cold-water corals and ecosystems. Springer-Verlag, sea anemones, Crustacea, Polychaeta and Ophiuroidea are Heidelberg, pp 849-879 known to be associated with these cold-water corals Cairns SD (1995) The marine fauna of New Zealand: Scleractinia (Parrish and Baco 2007). (Cnidaria: Anthozoa). New Zealand Oceanographic Insti­ This study demonstrated 78 unique coral taxa at a depth tute Memoir 103: 1-210 range between 275 and 1353 m and along a broad region Fabricius K, Alderslade P (2001) Soft Corals and Sea Fans -A of the southern Emperor Seamount chain. Gorgonians Comprehensive Guide to the Tropical Shallow-Water were the most common and diverse cold-water coral taxa; Genera of the Central-West Pacific, the Indian Ocean and they provide structural habitats and attachment substrate the Red Sea. Australian Institute of Marine Science, for other benthic animals. The Scleractinia, including Townsville 272 pp framework-building species occurred at frequencies sim­ FAO (2009) International guidelines for the management of ilar to those of gorgonians, but they were only found over deep-sea fisheries in the high seas. Food and agriculture limited depth ranges. Within the North Pacific, the deep- organization of the United Nations, Rome, Italy sea benthic megafauna on the southern Emperor Sea­ Fujikura K, Hashimoto J, Tanaka T, Hotta H (1991) Biological community at Shiribeshi Seamount off the west coast of mounts is more similar to that around the Hawaiian Is­ Hokkaido. J Deep Sea Res 7: 283-291 (in Japanese) lands than in the Aleutian Islands, other Alaskan waters, Fujioka Y (1995) Cnidarian communities on the rocky bottom of the Californian seamounts and the seamounts and conti­ the Kerama Bank. J Deep Res 11: 285-304 (in Japanese) nental slopes off Japan. Continued collection and detailed Goldberg WM, Hopkins TL, Holl SM, Schaefer J, Kraber KJ, taxonomic examination of cold-water coral specimens Morgan TD, Kim K (1994) Chemical composition of the from the southern Emperor Seamounts region would sclerotized black coral skeleton (Coelenterata: Antipa­ provide for species-level comparisons of the deep-sea tharia): A comparison of two species. Comparative Bio­ coral megafauna with different regions. chemistry and Physiology 107B: 633-643 Grigg RW (1993) Precious coral fisheries of Hawaii and U. S. Pacific islands. Mar Fish Rev 55: 50-60 Acknowledgments Guinotte JM, Orr J, Cairns S, Freiwald A, Morganand L, George R (2006) Will human-induced changes in seawater chem­ This study was conducted as part of the “Project on istry alter the distribution of deep-sea scleractinian corals? - Evaluation of the Status of the Sea Floor Environment of Front Ecol Environ 4: 141 146 Hayashibara T, Nishida K (2017) Results of the bottom envi­ Fishing Grounds in the High Seas”, Fisheries Agency of ronmental survey of the Emperor Seamounts Chain trawl Japan. We are grateful to the captain, crew, and researchers fishing grounds in2016: Exploration for spatial extent of of R/V Kaiyo-maru for their cooperation in scientific known coral assemblages and distribution of bycatch surveys. We are also grateful to the two reviewers,­ Dr. corals collected by a trawl operation. NPFC-2017-SSC Robert Stone and Dr. Amy Baco-Taylor for their valuable VME02-WP4. 13pp comments and suggestions. Heifetz J (2002) Coral in Alaska: Distribution, abundance, and species associations. Hydrobiologia 471: 19-28 References Heifetz J, Wing BL, Stone RP, Malecha PW, Courtney DL (2005) Coral of the Aleutian Islands. Fish Oceanogr 14: Baillon S, Hamel J-F, Wareham VE, Mercier A (2012) Deep 131-138 cold-water corals as nurseries for fish larvae. Front Ecol Henry L A, Roberts JM (2007). Biodiversity and ecological Environ 10: 351-356 composition of macrobenthos on cold-water coral mounds 30 Miyamoto et al.: Cold-water coral fauna in the Emperor Seamounts

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