Distribution patterns of larval myctophid fish assemblages in the subtropical–tropical waters of the western North Pacific

We examined larval myctophid fish assemblages and their distribution patterns, based on discrete depth sampling. Samples were collected at 19 stations along a transect that crossed the subtropical–tropical waters of the western North Pacific. In total, we collected 27 189 larvae of 40 myctophid species or types, belonging to 15 genera. Three assemblages were recognized, based on their species composition: Kuroshio Axis (KuA), Kuroshio Countercurrent (KCC), and Subtropical Countercurrent–North Equatorial Current (SCC–NEC) assemblages. The distributions of these assemblages were well defined by the positions of the KuA and the Subtropical Convergence. Each species had a specific distribution depth, and none showed diel vertical migration. Larvae of the subfamily Lampanyctinae were distributed in shallower waters (0–50 m) than larvae of the subfamily Myctophinae (50–150 m). Larvae of the same species were distributed at lower depths in the SCC–NEC area than in the KCC area. This corresponded to the abundance of chlorophyll a, which would reflect abundance of prey organisms such as copepod nauplii and copepodites.     

Larval fish assemblages and water mass structure off the oligotrophic south-western Australian coast

Larval fish assemblages were sampled using replicated oblique bongo net tows along a five‐station transect extending from inshore (18 m depth) to offshore waters (1000 m depth) off temperate south‐western Australia. A total of 148 taxa from 93 teleost families were identified. Larvae of Gobiidae and Blenniidae were abundant inshore, while larvae of pelagic and reef‐dwelling families, such as Clupeidae, Engraulidae, Carangidae and Labridae were common in continental shelf waters. Larvae of oceanic families, particularly Myctophidae, Phosichthyidae and Gonostomatidae, dominated offshore assemblages. Multivariate statistical analyses revealed larval fish assemblages to have a strong temporal and spatial structure. Assemblages were distinct among seasons, and among inshore, continental shelf and offshore sampling stations. Inshore larval fish assemblages were the most seasonal, in terms of species composition and abundance, with offshore assemblages the least seasonal. However, larval fish assemblages were most closely correlated to water mass, with species distributions reflecting both cross‐shelf and along‐shore oceanographic processes and events. Similarity profile (SIMPROF) analysis suggested the presence of twelve distinct larval fish assemblages, largely delineated by water depth and season. The strength and position of the warm, southward flowing Leeuwin Current, and of the cool, seasonal, northward flowing Capes Current, were shown to drive much of the variability in the marine environment, and thus larval fish assemblages.     

Mesopelagic fish larval assemblages during El Niño‐southern oscillation (1997–2001) in the southern part of the California Current

Mesopelagic species are the principal constituents of larval fish assemblages inhabiting the southerly California Current region. Seasonal larval abundance is influenced by circulation of the California Current and subtropical Countercurrent, including regional changes of the physical, chemical, and biological characteristics during the El Niño‐Southern Oscillation. This study examines the mesopelagic fish larvae distribution and abundance patterns between seasons and years, with the aim of describing the mesopelagic larval assemblages during dynamic environmental changes induced by El Niño (1997–1998) and the rapid transition to La Niña (1998–2000) along the west coast of the Baja California Peninsula (25–31°N). Despite large oceanographic variability, larval assemblages varied principally on a seasonal basis, related to reproductive periods and the north–south gradient influenced by the seasonal pattern of the California Current. An increased diversity, number of species, and abundance of tropical species was noticeable during the northward expansion of warm‐water taxa during El Niño, principally in the northern areas (Ensenada and Punta Baja). After El Niño, population adjustments and rapid recovery occurred during La Niña conditions, which reflected seasonal differences in the mesopelagic community structure that are closely related to the seasonal pattern of oceanic currents.     

Late winter larval mesopelagic fish assemblage in the Kuroshio waters of the western North Pacific

The larval mesopelagic fish assemblage and its distribution patterns were investigated in the Kuroshio region off southern Japan in late winter. A total of 8690 fish larvae was collected, 85.8% of which were mesopelagic fish larvae. Mesopelagic fish larvae were significantly more abundant in the area east of the Kuroshio axis than west of the Kuroshio axis (660.6 versus 194.5 ind 10 m^?2). Sigmops gracile, Bathylagus ochotensis, Notoscopelus japonicus, Diaphus slender type and Myctophum asperum were the five most abundant larvae and accounted for 16.9, 16.4, 15.2, 13.9 and 9.3% of the total catch in numbers, respectively. We conclude that these larvae were transported by the Kuroshio Current to the more productive transition waters, where they spend their juvenile stage from spring to early summer. The possibility of expatriation and southward long‐distance spawning migrations of N. japonicus and B. ochotensis are discussed, based on the geographic distribution patterns of their larvae, juveniles and adults.     

Groundfish species diversity and assemblage structure in Icelandic waters during recent years of warming

Elevated ocean temperatures have been predicted to lead to a poleward shift in the latitudinal distribution ranges of fish species. Different responses of fish species to increased temperatures might lead to changes in assemblage structure and local species richness. In this study, the assemblage structure and diversity of groundfish in Icelandic waters were examined using data from a standardized groundfish survey conducted annually in 1996–2007. We used hierarchical cluster analysis to define assemblages in two time periods and canonical correspondence analysis to explore the relationships between the assemblages and temperature, depth, latitude, longitude and year. We further used two estimates of diversity, species richness and the Shannon index. Four major species assemblages were identified. Assemblages in the hydrographically stable deep waters north of the country were consistent during the study, while assemblage structure in the more variable shallow waters underwent some changes. For this period of generally increasing sea temperature, the canonical correspondence analysis also revealed a shift towards species representative of warmer temperatures. Diversity was shown to be highly variable both temporally and spatially, and also to vary with depth and temperature. Species richness increased with temperature and time southwest of the country, but decreased northeast of the country. The different trends detected between the northern and southern areas illustrate the importance of performing analyses at the most appropriate scale.     

Distribution patterns of leptocephali in the Kuroshio–Oyashio transitional region of the western North Pacific

Leptocephalus assemblages and distribution patterns were studied in the Kuroshio–Oyashio transitional region of the western North Pacific. A total of 479 leptocephali, representing at least 21 species (types) including eight undescribed types, were collected during a cruise of the T/V Hokuho Maru from 8 to 30 May 2002. The most abundant leptocephali were the congrids Gnathophis nystromi nystromi and Gnathophis nystromi ginanago. The assemblages at each station were clustered into four groups (one group in the Kuroshio region and three in the transition zone) using the ordination and the fuzzy c‐means method based on species composition similarities between stations. Each leptocephalus species was also clustered by the same method into one of three groups. The first group had the greatest numbers of species and mainly occurred at the station group in the Kuroshio region, sharing a similar distribution to G. n. nystromi. The second group had the greatest abundance, especially in the transition zone, but contained only one species, G. n. ginanago, which also occurred at all stations. Moreover discrimination of station groups in the transition zone corresponded well with the assemblage pattern of this species group. The last species group comprised rare and low abundance species. Most leptocephali in the study area were reported from the Kuroshio upstream region, so the discrimination of leptocephali assemblages in the study area may reflect their different ecology. Furthermore, the analytical methods used in this study yielded more meaningful and clearer groups than the other usual methods, validating application of this analysis to complex areas such as the transition zone.     

Entrainment of larval fish assemblages from the inner shelf into the East Australian Current and into the western Tasman Front

Entrainment and transport of larval fish assemblages by the East Australian Current (EAC) were examined from the coastal waters of northern New South Wales (NSW) to the western Tasman Front, via the separation of the EAC from the coast, during the austral spring of 2004. Shore‐normal transects from the coast to the EAC off northern NSW revealed an inner shelf assemblage of near‐shore families (Clupeidae, Engraulidae, Platycephalidae and Triglidae), an EAC assemblage dominated by Myctophidae and Gonostomatidae, and a broadly distributed assemblage over the continental shelf dominated by Scombridae and Carangidae. Further south and after the EAC had separated from the coast, we observed a western Tasman Front assemblage of inner shelf and shelf families (Clupeidae, Engraulidae, Serranidae, Scombridae, Carangidae, Bothidae and Macroramphosidae). The abundance of these families declined with distance from the coast. Surprisingly, there was no distinctive or abundant larval fish assemblage in the chlorophyll‐ and zooplankton‐enriched waters of the Tasman Sea. Water type properties (temperature‐salinity, T‐S), the larval fish assemblages and family‐specific T‐S signatures revealed the western Tasman Front to be an entrained mix of EAC and coastal water types. We found an abundance of commercially important species including larval sardine (Sardinops sagax, Clupeidae), blue mackerel (Scomber australasicus, Scombridae) and anchovy (Engraulis australis, Engraulidae). The entrainment and transport of larval fish from the northern inner shelf to the western Tasman Front by the EAC reflects similar processes with the Gulf Stream Front and the Kuroshio Extension.     

山东北部沿海幼鱼种类组成特征的研究

2008年5月—2009年9月通过双船拖网采样,对山东北部沿海28个站位进行了调查,分析研究了该海域的幼鱼种类组成及优势种。调查结果表明,该海域共出现幼鱼75种,属14目41科65属,以底层鱼类为主要组成,占总种类数的78.67%;优势种有鳀鱼、方氏云鳚、玉筋鱼、黄鲫、蓝点马鲛、小黄鱼、矛尾刺鱼叚虎鱼等;幼鱼种类组成具有显著的季节变化,但年间变化较小。     

Larval fish distribution and retention in the Canary Current system during the weak upwelling season

The spatial distribution of fish larvae was studied in the Canaries‐African Coastal Transition Zone, outside the strong upwelling season. An onshore–offshore transition in the larval fish community structure was observed, from a coastal assemblage dominated by small pelagics (sardine, anchovy, mackerel), bounded by the upwelling front, to an offshore assemblage dominated by mesopelagic species (mainly Myctophidae, Phosichthydae, Gonostomatidae). Distribution of the neritic larvae was deeply influenced by the intense mesoscale activity found in the area, both horizontally (larvae were advected offshore but were always retained within the upwelling area) and vertically (larvae were deepened in the vicinity of two anticyclonic eddies). A combined effect of the upwelling front and a cyclonic–anticyclonic eddy dipole is likely the successful retention mechanism for these larvae. These results support the current belief that retention may be higher than previously thought in upwelling areas. Oceanic larvae were also collected in higher abundances near the front and an anticyclonic eddy. Neritic and oceanic larvae frequently showed a differentiated position in the water column, although they sometimes coexisted. Finally, larval connectivity between Islands within the Canary archipelago is suggested. The present study thus contributes to the understanding of the complex dispersal and retention processes in the Canaries‐African Coastal Transition Zone. However, results also highlight the poor knowledge of this region compared with the other three main Eastern Boundary Upwelling Systems in terms of ichthyoplankton dynamics. The importance of routine monitoring programs of commercial and non‐commercial species in the area is emphasized.     

Migration of kawakawa Euthynnus affinis in the waters near Taiwan

ABSTRACT:   Kawakawa Euthynnus affinis is the most abundant species among the small tuna in the coastal waters of Taiwan. The migration pattern of kawakawa to Taiwan was determined in the present study based on the species' feeding habits and reproductive biology and on temporal variation of catch for kawakawa and its prey fishes. Schools of this species successively migrate to Taiwan from September to May, and then move away in June. They travel to the waters off Taiwan with the warm Kuroshio current, migrate toward coastal waters for feeding and move away for spawning. It is suggested in the present study that the kawakawa spawning ground is in the waters of the northern Philippines. The migration of kawakawa exhibits size-segregating behavior. Schools of immature young fish first arrive in the coastal waters around Taiwan, followed by the adults.     

Biogeography of small odontocetes in relation to wide‐scale oceanographic structure in the North Pacific Ocean

Information regarding the distributional patterns of top predators is undoubtedly important for the monitoring and management of marine ecosystems. Nevertheless, previous knowledge on the distributional patterns of cetacean species in relation to physical oceanography is usually limited to a small fraction of each species' range because of their vast distribution and infrequency of encountering many species. We carried out comprehensive analyzes on the distributions of small odontocetes covering almost the entire North Pacific Ocean. Using data from over 300 000 nautical miles (≈ 555 600 km) of dedicated sighting surveys and 7000 school sightings of 14 small odontocete species, which have accumulated for approximately a quarter of a century, we describe interspecific habitat differences in small odontocetes with respect to physical oceanography. Multivariate analyzes were used to discriminate the 14 species into four ecological groups: (i) Subtropical Domain species; (ii) Subarctic Boundary species; (iii) Transitional Domain species; and (iv) Subarctic Domain species. By comparing environmental variables in their habitats with variables indicative of water mass and frontal structures, the four species groups were further divided into several subgroups. Groups at higher latitudes comprised fewer species than those at lower latitudes, while species diversity was maximal at lower and intermediate latitudes. Our findings indicate that large‐scale oceanographic structures are important determinants for the present patterns in biogeography and species diversity of small odontocetes.     

Geographic variability in taxonomic composition,standing stock,and productivity of the mesozooplankton community around the Kuroshio Current in the East China Sea

Despite the low productivity that has been thought to characterize plankton communities in the western boundary current of the North Pacific Subtropical Gyre, many migratory fishes risk encountering low food availability during crucial life history stages by reproducing and recruiting in the Kuroshio region (i.e., the Kuroshio Paradox). Here, we report on geographic variability in taxonomic composition, biomass, and productivity of the mesozooplankton community in the Kuroshio Current and neighboring waters in the East China Sea. Calanoid copepods were the most abundant mesozooplankton taxon throughout our sampling stations. Small copepods, which include nauplii and poecilostomatoids, and gelatinous metazoans were the next most abundant. Seasonal variability in mesozooplankton standing stock (i.e., abundance and biomass) and productivity (i.e., production rate and protein synthetase activity) exceeded spatial variability across the stations and regions. The mesozooplankton community was characterized by high biomass and production rates in the summer, as well as high abundance and protein synthetase activity in the fall. No significant differences were found for mesozooplankton standing stock and productivity in the Kuroshio Path relative to those on the continental shelf or on the outside of the Kuroshio Path. Our results indicate that the standing stock and productivity of the mesozooplankton community in the Kuroshio Path are equivalent to those on the continental shelf, and that these communities are supported by small copepods and gelatinous zooplankton. We suggest that the mesozooplankton standing stocks and productivity provide adequate food availability for migratory fishes in the Kuroshio and neighboring waters in the East China Sea.     

High abundance of larval rockfish over Cobb Seamount, an isolated seamount in the Northeast Pacific

The larval fish community in the region of Cobb Seamount (500 km west of Oregon) is dominated by myctophid species commonly encountered in the subarctic North Pacific. However, during a survey in June 1992, the ichthyoplankton community within 30 km of the seamount summit was almost completely dominated by larvae of various rockfish ( Sebastes ) species. Given their very small size (and hence very young age) and the fact that they occurred only rarely in samples collected > 30 km from the seamount summit, we conclude that these Sebastes larvae were produced locally over Cobb Seamount. Previous studies have shown that the Cobb fish fauna is dominated by various Sebastes spp. and that, unlike other fish present on the seamount, the rockfish populations may be self-recruiting. We suggest that a persistent clockwise (i.e. downwelling) eddy, consistent with a stratified Taylor cone, plays a critical role in retaining larval rockfish over Cobb Seamount and may contribute to the process of self-recruitment. The key to the success of rockfish on Cobb and other shallow Northeast Pacific seamounts seems to be linked to their viviparous life history.     

海州湾及邻近海域春夏季典型断面鱼类浮游生物群落的结构特征

根据2015年5―7月在海州湾及邻近海域存在空间异质性的南北两个典型断面进行的鱼卵、仔稚鱼水平拖网调查数据,采用多元统计分析等方法研究了该海域春、夏季鱼类浮游生物群落的空间变化。结果表明,本次调查共获得鱼卵33587粒,仔稚鱼713尾。出现鱼卵25种(未定种1种),隶属于14科25属,仔稚鱼13种(未定种1种),隶属于13科13属。鱼卵优势种主要是鳀(Engraulis japonicus)、多鳞鱚(Sillago sihama)、(魚銜)属(Callionymus spp.)、皮氏叫姑鱼(Johnius belengerii)、江口小公鱼(Stolephorus commersonni)和短吻红舌鳎(Cynoglossus joyneri);仔稚鱼优势种主要是(魚銜)属和斑鰶(Konosirus punctatus)。鱼类浮游生物种类组成年代际变化明显,目前以生命周期短、个体小、资源更新节律快的小型鱼种为主;研究表明,鱼类浮游生物的优势种在不同月份和断面之间存在一定变化,5、6月南北两断面优势种组成不同,7月开始出现共同优势种。从鱼类浮游生物的空间分布来看,近岸海域的丰度较高,5、6月鱼类浮游生物的平均丰度均为北面断面1高于南面断面2,7月反之。鱼类浮游生物群落在两个典型断面随月份呈现出不同特征,水深、温度和盐等海洋环境因子综合影响着春、夏季海州湾及邻近海域鱼类浮游生物群落结构。     

Springtime ichthyoplankton of the slope region off the north-eastern United States of America: larval assemblages, relation to hydrography and implications for larval transport

Larval transport in the slope region off north‐eastern North America influences recruitment to juvenile habitats for a variety of fishes that inhabit the continental shelf. In this study, collections of larval fishes were made during springtime over the continental slope to provide insights into larval distributions and transport. Ichthyoplankton composition and distribution mirrored the physical complexity of the region. Three larval fish assemblages were defined, each with different water mass distributions. A Gulf Stream assemblage was found predominantly in the Gulf Stream and associated with filaments of discharged Gulf Stream water in the Slope Sea. Larvae of this assemblage originated from oceanic and shelf regions south of Cape Hatteras. Several members of this assemblage utilize habitats in the Middle Atlantic Bight (MAB) as juveniles (Pomatomus saltatrix, Peprilus triacanthus) and other members of the assemblage may share this life cycle (Mugil curema, Sphyraena borealis, Urophycis regia). A Slope Sea assemblage was found in all water masses, and was composed of epi‐ and mesopelagic fish larvae, as well as larvae of benthic shelf/slope residents. Larvae of one member of this assemblage (U. tenuis) are spawned in the Slope Sea but cross the shelf‐slope front and use nearshore habitats for juvenile nurseries. A MAB shelf assemblage was found in MAB shelf water and was composed of larvae that were spawned on the shelf. Some of these species may cross into the Slope Sea before returning to MAB shelf habitats (e.g. Enchelyopus cimbrius, Glyptocephalus cynoglossus). Previous studies have examined the effect of warm‐core rings on larval distributions, but this study identifies the importance of smaller‐scale features of the MAB shelf/slope front and of filaments associated with Gulf Stream meanders. In combination with these advective processes, the dynamic nature of larval distributions in the Slope Sea appears to be influenced, to varying degrees, by both vertical and horizontal behaviour of larvae and pelagic juveniles themselves.     

Diet of the mesopelagic fish Notoscopelus japonicus (Family: Myctophidae) associated with the continental slope off the Pacific coast of Honshu, Japan

The diet of Notoscopelus japonicus , one of the dominant mesopelagic fishes in the transitional waters of the western North Pacific, was examined in 106 specimens collected over the continental slope off the Pacific coast of northern Japan during April and October 1996. The prey comprised mainly crustaceans, such as copepods, ostracods, euphausiids and amphipods. Euphausia pacifica was the dominant prey, representing 83.1% by number and 72.4% by wet weight of the total diet. Between April and October, there was no shift in prey species consumed, but prey size decreased significantly and prey number per fish stomach increased in October. These results indicate that, in October, N. japonicus consumed larger numbers of smaller E. pacifica , rather than shifting to other prey taxa. The pronounced importance of E. pacifica in the diet was ascribed to its co-occurrence with N. japonicus at night in the surface layer and during the daytime in the near-bottom layer.     

Influence of mesoscale eddies on ichthyoplankton assemblages in the Gulf of Alaska

Mesoscale eddies (100–200 km in diameter) propagating along the shelf‐break in the Gulf of Alaska are ubiquitous and have been shown to influence the ecosystem, but their influence on ichthyoplankton species composition and diversity has not been described. Evidence for larval fish entrainment in these eddies was examined using data from a cruise in 2005 that sampled three eastern Gulf of Alaska mesoscale eddies, and sampling that compared shelf to slope ichthyoplankton assemblages in the northern Gulf of Alaska (2002–2004). Hierarchical cluster analysis of oceanographic data showed that stations grouped according to location within an eddy. Species hierarchical cluster analysis revealed a latitudinal turnover in species composition, and an abundant species group. Species richness was correlated with distance from eddy center (P = 0.00025), and assemblages within eddies were significantly different (P < 0.05) from those in surrounding basin and shelf waters. These results suggest that mesoscale eddies propagating along the continental shelf‐break influence larval fish assemblages over the shelf and slope, which has implications for the timing and extent of larval fish distribution in the Gulf of Alaska.     

南海中南部中层鱼资源声学积分值及时空分布初探

本研究利用Simrad EK60科学探鱼仪(38 k Hz)于2013年春季和2014年春季采集的南沙和中沙、西沙海域渔业声学数据,结合中层拖网取样,采用回声积分法研究了南海中南部中层鱼的资源量及其时空分布特征。结果显示,2014年春季中、西沙海域9次中层拖网作业共捕获和鉴定鱼类和头足类79种,隶属于3纲16目37科60属,其中硬骨鱼纲的种类最多(65种),鞘亚纲次之(13种),软骨鱼纲1种,硬骨鱼纲中巨口鱼科、灯笼鱼科和钻光鱼科的种类最多,分别有20种、13种和6种;南沙海域中层鱼声学积分值(nautical area scattering coefficient,m~2/nmi~2)显著低于中沙、西沙及邻近海域,前者夜间向上迁移的强度高于后者;2013年春季南沙海域夜间10~200 m和白天200~1000 m声学积分值构成没有显著差异(P0.05),而2014年春季中沙、西沙海域夜间10~200 m和白天200~1000 m声学积分值构成有极显著差异(P0.01);南沙海域白天200~1000 m不同纬度组间中层鱼声学积分值构成有极显著差异(P0.01),中沙、西沙海域声学积分值构成亦有极显著差异(P0.01);南海中南部中层鱼声学积分值是(2387±601)m~2/nmi~2,基于现存公开发表的中层鱼的声学目标强度数据并取其均值,推算南海中南部中层鱼资源量是(8200±2100)万t。研究表明,南海中南部中层鱼声学积分值比全球平均值高约29.2%,可能是我国未来具有开发价值的大宗生物资源。     

Differing body size between the autumn and the winter–spring cohorts of neon flying squid (Ommastrephes bartramii) related to the oceanographic regime in the North Pacific: a hypothesis

The neon flying squid (Ommastrephes bartramii), which is the target of an important North Pacific fishery, is comprised of an autumn and winter–spring cohort. During summer, there is a clear separation of mantle length (ML) between the autumn (ML range: 38–46 cm) and the winter–spring cohorts (ML range: 16–28 cm) despite their apparently contiguous hatching periods. We examined oceanic conditions associated with spawning/nursery and northward migration habitats of the two different‐sized cohorts. The seasonal meridional movement of the sea surface temperature (SST) range at which spawning is thought to occur (21–25°C) indicates that the spawning ground occurs farther north during autumn (28–34°N) than winter–spring (20–28°N). The autumn spawning ground coincides with the Subtropical Frontal Zone (STFZ), characterized by enhanced productivity in winter because of its close proximity to the Transition Zone Chlorophyll Front (TZCF), which move south to the STFZ from the Subarctic Boundary. Hence this area is thought to become a food‐rich nursery ground in winter. The winter–spring spawning ground, on the other hand, coincides with the Subtropical Domain, which is less productive throughout the year. Furthermore, as the TZCF and SST front migrate northward in spring and summer, the autumn cohort has the advantage of being in the SST front and productive area north of the chlorophyll front, whereas the winter–spring cohort remains to the south in a less productive area. Thus, the autumn cohort can utilize a food‐rich habitat from winter through summer, which, we hypothesize, causes its members to grow larger than those in the winter–spring cohort in summer.     

Species associations of epipelagic nekton of the North Pacific Ocean, 1978–1993

Strong latitudinal gradients in species composition were revealed by two-way indicator species analysis (TWINSPAN) and detrended correspondence analysis (DCA) of 41 species of epipelagic fishes and squids in 513 gillnet collections by research vessels of Hokkaido University over a huge area of the northern North Pacific during the summers of 1978–1993. Salmonids inhabited northern subarctic water and skipjack tuna (Euthynnus pelamis) and flying squid (Ommastrephes bartrami) inhabited the region of the Subarctic Boundary, but distinct boundaries between species groups and sample groups were lacking, largely because abundant species, such as Pacific saury (Cololabis saira) and Pacific pomfret (Brama japonica), migrated across most of this region during the summer. Longitudinal differences were not pronounced, but some species, including Japanese sardine (Sardinops melanostictus) and Japanese anchovy (Engraulis japonicus), were only found in the western Pacific. Pacific saury was more common in the western Pacific, whereas sockeye salmon (Oncorhynchus nerka) was concentrated in the eastern Pacific. Interannual fluctuations in the latitude of species groups were most closely correlated with changes in sea surface temperatures. In the western Pacific, 1982, 1983, 1985, 1987-88, and 1992-93 were cool years when subarctic and transitional assemblages were found farther to the south than other years. Temperature and salinity at various depths were highly correlated with each other and with first-axis DCA ordinations scores. Long-term trends in community structure were not apparent during the 1.6 decades.