Ontogenetic Vertical Migration and Life cycle of Neocalanus Plumchrus (Crustacea: Copepoda) in the Oyashio Region, with Notes on Regional Variations in Body Sizes

The ontogenetic vertical migration and life cycle of Neocalanusplumchrus were investigated by anal-yzing monthly populationstructure at Site H in the Oyashio region from September 1996through October 1997. Additional sampling was also done at severalstations covering the entire subarctic Pacific, Okhotsk Seaand Japan Sea as a basis for regional comparison of life cyclesand body sizes. At Site H, N. plumchrus spawned October to Aprilbelow 250 m depth. Young copepodite stages (C1–C5) occurredduring June late in the phytoplankton bloom. The C5 migratedto the deeper layers in July–August where they moltedto adults. Development time of C5 to C6 was highly variable.The ontogenetic vertical migration of N. plumchrus ranged fromthe surface to 1000–2000 m depth, and the life cycle wasannual. Temporal data on population structure and vertical distributionsuggestedthe annual life cycle was generally synchronized throughoutthe subarctic Pacific and its marginal seas. Geographical comparisonof C5 prosome length indicated the occurrence of significantlylarge specimens in the Oyashio region and Okhotsk Sea but smallspecimens in the Japan Sea. Possible causes for regional variabilityin body sizes are discussed.     

Geographical shift of zooplankton communities and decadal dynamics of the Kuroshio–Oyashio currents in the western North Pacific

We investigated temporal and spatial variations in the zooplankton community structure in the Oyashio and Transition region of the subarctic western North Pacific from 1960 to 1999 using principal component analysis (PCA) and zooplankton samples from the historical Odate Collection. In particular, we examined the influence of Kuroshio and Oyashio decadal dynamics on geographical variations in the zooplankton community. The first principal component (PC1) closely represented the interannual variation in cold-water, large copepod species, while the second PC (PC2) represented the variation in warm-water, small copepod species. Using Rodionov's regime-shift method, we detected a significant increase in the PC score after 1976 and 1981 for PC1 and PC2, respectively. After the shift years, (1) warm-water species increased in the Transition zone, (2) the distribution center of the cold-water species shifted southward, and (3) copepod abundance and species diversity increased in the Transition zone as a result of (1) and (2). The timing of these shifts in the zooplankton community roughly coincided with the North Pacific climatic regime shift in 1976/1977. From the mid-1970s to the early 1980s, the southern boundary of the Oyashio shifted southward and increased geostrophic transport was observed in the Kuroshio, indicating spin up of the Kuroshio–Oyashio system. Change in atmospheric circulation during the 1976/1977 regime shift is thought to have caused the spin up of these currents, which subsequently affected the regional zooplankton community through advective processes.     

Specific features of distribution and ecology of sawback poacher Sarritor frenatus (Agonidae) in Pacific Waters of the Northern Kuril Islands and Southeast Kamchatka

According to materials of 1992–2002, data on the occurrence, spatial-bathymetric distribution, and size-weight composition of sawback poacher Sarritor frenatus and species accompanying it in catches in Pacific waters of the northern Kuril Islands and southeastern Kamchatka are provided. This comparatively numerous and relatively small representative of the family Agonidae (maximum length 31 cm, body weight 103 g) in the period of studies was found uniformly at depths of 78-790 m at near-bottom temperature of ?1.2 to ?4.2°C. In spring, summer, and winter months, maximum catches (over 500–1000 ind./h of trawling) were recorded in the southernmost and northernmost sites of the study area in a bathymetric range of 101–500 m; increased concentrations of this poacher were recorded also on the beam of the Fourth Kuril Strait near the southeastern extremity of Paramushir Island only in the autumn period. The ratio between the depth of catch and the sizes of sawback poacher is analyzed, and the data on the composition of its food in waters of the northern Kuril Islands is given. It is shown that the occurrence and amount of catches of this poacher in Pacific waters of the northern Kuril Islands and southeastern Kamchatka are subjected to some interannual, seasonal, and diurnal dynamics.     

Vertical Profiles of Bacteria in the Tropical and Subarctic Oceans Revealed by Pyrosequencing

Community composition of Bacteria in the surface and deep water layers were examined at three oceanic sites in the Pacific Ocean separated by great distance, i.e., the South China Sea (SCS) in the western tropical Pacific, the Costa Rica Dome (CRD) in the eastern tropical Pacific and the western subarctic North Pacific (SNP), using high throughput DNA pyrosequencing of the 16S rRNA gene. Bioinformatic analysis rendered a total of 143600 high quality sequences with an average 11967 sequences per sample and mean read length of 449 bp. Phylogenetic analysis showed that Proteobacteria dominated in all shallow and deep waters, with Alphaproteobacteria and Gammaproteobacteria the two most abundant components, and SAR11 the most abundant group at family level in all regions. Cyanobacteria occurred mainly in the surface euphotic layer, and the majority of them in the tropical waters belonged to the GpIIa family including Prochlorococcus and Synechococcus, whilst those associated with Cryptophytes and diatoms were common in the subarctic waters. In general, species richness (Chao1) and diversity (Shannon index H′) were higher for the bacterial communities in the intermediate water layers than for those in surface and deep waters. Both NMDS plot and UPGMA clustering demonstrated that bacterial community composition in the deep waters (500 m ∼2000 m) of the three oceanic regions shared a high similarity and were distinct from those in the upper waters (5 m ∼100 m). Our study indicates that bacterial community composition in the DOC-poor deep water in both tropical and subarctic regions were rather stable, contrasting to those in the surface water layers, which could be strongly affected by the fluctuations of environmental factors.     

Long‐term abundance trends of the northern form of the short‐finned pilot whale (Globicephala macrorhynchus) along the Pacific coast of Japan

The abundance of the northern form of the short‐finned pilot whale, Globicephala macrorhynchus, in the Pacific waters of northern Japan was estimated from a line transect survey conducted in 2006 and data from seven previous surveys collected between 1985 and 1997. To overcome the difficulty of small sample size and inconsistency in survey design, we used an adjustment method using multiple covariates and sensitivity analysis by considering several scenarios. Abundance estimates showed similar long‐term trends among scenarios. The northern form of G. macrorhynchus was more abundant in 1985 than in 1991–2006. The annual catch of the northern form of G. macrorhynchus exceeded the potential biological removal (PBR), especially in the 1980s. Thus, the commercial take in the early 1980s was suspected as a partial cause of a serious abundance decrease. These results provide valuable information for interpreting the impacts of coastal whaling, and to develop future management plans.     

Shifts in the composition and distribution of Pacific Arctic larval fish assemblages in response to rapid ecosystem change

The Pacific Arctic marine ecosystem has undergone rapid changes in recent years due to ocean warming, sea ice loss, and increased northward transport of Pacific-origin waters into the Arctic. These climate-mediated changes have been linked to range shifts of juvenile and adult subarctic (boreal) and Arctic fish populations, though it is unclear whether distributional changes are also occurring during the early life stages. We analyzed larval fish abundance and distribution data sampled in late summer from 2010 to 2019 in two interconnected Pacific Arctic ecosystems: the northern Bering Sea and Chukchi Sea, to determine whether recent warming and loss of sea ice has restricted habitat for Arctic species and altered larval fish assemblage composition from Arctic- to boreal-associated taxa. Multivariate analyses revealed the presence of three distinct multi-species assemblages across all years: (1) a boreal assemblage dominated by yellowfin sole (Limanda aspera), capelin (Mallotus catervarius), and walleye pollock (Gadus chalcogrammus); (2) an Arctic assemblage composed of Arctic cod (Boreogadus saida) and other common Arctic species; and (3) a mixed assemblage composed of the dominant species from the other two assemblages. We found that the wind- and current-driven northward advection of warmer, subarctic waters and the unprecedented low-ice conditions observed in the northern Bering and Chukchi seas beginning in 2017 and persisting into 2018 and 2019 have precipitated community-wide shifts, with the boreal larval fish assemblage expanding northward and offshore and the Arctic assemblage retreating poleward. We conclude that Arctic warming is most significantly driving changes in abundance at the leading and trailing edges of the Chukchi Sea larval fish community as boreal species increase in abundance and Arctic species decline. Our analyses document how quickly larval fish assemblages respond to environmental change and reveal that the impacts of Arctic borealization on fish community composition spans multiple life stages over large spatial scales.     

Grazing rates and behaviors of Neocalanus plumchrus: implications for phytoplankton control in the subarctic Pacific

Grazing rates and behaviors of the copepod Neocalanus plumchrus were investigated in shipboard experiments during the first SUPER Program cruise (May, 1984). N. plumchrus can exploit cells in the 2 to 30 m size range with equal clearance efficiency but displays considerable flexibility in responding to changes in concentration and size composition. Its functional response helps to stabilize phytoplankton at low densities. In 60-liter microcosms, a density of one copepod liter^–1 was sufficient to maintain the ambient abundance and structure of the phytoplankton community for a week. In the absence of the copepod, phytoplankton bloomed to unnaturally high levels, and the community composition was dramatically altered. Despite its grazing potential, N. plumchrus was not present in sufficient density to control phytoplankton blooms in the subarctic Pacific. However, the copepod may have an important role in regulating the abundance of smaller grazers and the size structure of the phytoplankton community.Contribution No. 2002 from Hawaii Institute of Geophysics, University of Hawaii, Honolulu, HI 96822     

Spatial distribution and features of biology of Pacific sleeper shark Somniosus pacificus in the North Pacific

The results of the investigations of spatial and vertical distribution of Pacific sleeper shark Somniosus pacificus in the North Pacific Ocean conducted for many years are presented. In addition, the size distribution and features of biology of the species are studied. The largest abundance of the species is registered in the Bering Sea, western Gulf of Alaska, eastern Aleutian Islands, and Pacific waters of northern Kuril Islands and southeastern Kamchatka. The species is the most abundant near the bottom at the depth from 200 to 700 m and in the pelagic waters at a depth of 100–200 m. The average depths of the catches of Pacific sleeper shark substantially change over the year reaching minimum values in June and maximum values in December. Vertical daily migrations (to the water column at night and to the bottom during the day) are registered. The catches are represented by fish 26–352 cm in length, and sharks 100–200 cm in length prevail. The males are noticeably smaller than the females. In general, condition of the fishes decreases and feeding intensity increases with growth. Food composition substantially changes with the increase of body length: consumption of squids decreases and consumption of crustaceans, fishes, and fishery wastes increases. The food composition is slightly different in the females and males.     

Apex marine predator declines ninety percent in association with changing oceanic climate

Three time series of pelagic bird abundance collected in disparate portions of the California Current reveal a 90% decline in Sooty Shearwater (Puffinus griseus) abundance between 1987 and 1994. This decline is negatively correlated with a concurrent rise in sea-surface temperatures; Sooty Shearwaters have declined while sea temperatures have risen. There is a nine-month lag in the response by shearwaters to changing temperatures. The geographical scale of our study demonstrates that the decline of Sooty Shearwaters is not a localized phenomenon, nor can it be ascribed to a short-term distributional shift. The Sooty Shearwater is the numerically dominant species of the California Current System (CCS) in summer (austral winter), with an estimated population in the late 1970s of 5 million individuals. If the observed warming of the waters of the California Current System is an irreversible manifestation of a changing global climate, then the impact upon Sooty Shearwater populations seems likely to be profound.     

Interannual distribution of Pacific hake Merluccius productus larvae in the southern part of the California Current

The interannual distribution of early life stages of Pacific hake Merluccius productus , within the southern part of the California Current (32–23° N) from 1951 to 2001, was examined to describe the relationship between spawning habitat and environmental conditions. Mean annual abundance was affected by different factors along the west coast of the Baja California Peninsula. In the northern areas (Ensenada and Punta Baja), reduced abundance of larvae coincided with the El Niño and a North Pacific Ocean climatic regime shift, but in the southern areas (San Ignacio to Bahía Magdalena), the drastic reductions suggested a fishery effect for large adults of the coastal migratory population, starting in 1966. Two spawning stocks, coastal and dwarf, were evident in comparisons of latitudinal differences in occurrence of early stages and differences in temperature preferences that seemed to break at Punta Eugenia.     

Erythropsidinium (Gymnodiniales, Dinophyceae) in the Pacific Ocean, a unique dinoflagellate with an ocelloid and a piston

The distribution and morphology of the dinoflagellate Erythropsidinium (=Erythropsis) was studied in the vicinity of the Kuroshio and Oyashio Currents, the Philippine, Celebes, Sulu and South China Seas, western and central equatorial and southeast Pacific Ocean. Ninety-four specimens were observed, most of them collected from depths of less than 90m. The highest abundance (15cellsL(-1)) was recorded in the north Philippine Sea in May (32 degrees N, 138 degrees E, 30-m depth). Twenty-four specimens were found in a station in the offshore Perú-Chile Current (31 degrees 52'S, 91 degrees 24'W). The transition regions between open warm waters and productive currents or upwellings seem to favour the abundance of Erythropsidinium. Specimens with duplicate pistons, with two protuberant ocelloids, and specimens with a piston that attains up to 20 times the body length are illustrated for the first time. All the specimens have been ascribed to the type species, Erythropsidinium agile, until stable taxonomical criteria are established for the species diagnosis. Despite the complexity of its organelles, the ocelloid and piston, the competitiveness of Erythropsidinium in the pelagic ecosystem seems to be low.     

On the Persistence of Stereotypes Concerning the Marine Ecology of Pacific Salmon (<Emphasis Type="Italic">Oncorhynchus</Emphasis> spp.)

Some of the views on the marine ecology of Pacific salmon (Oncorhynchus spp.) that were popular in the second half of the 20th century are discussed critically: the absolutization of the influence of sea surface temperature on distribution of salmon and strength of their year classes, as well as the conclusions on the shortage of food (particularly in winter) and the fierce competition for food, the “suppression” of other salmon species and own adjacent broodline by pink salmon, the limited carrying capacity of the pelagic zone of subarctic ocean waters for salmon, the distortion of the structure of epipelagic communities in ecosystems of the North Pacific due to the large-scale stock enhancement of chum salmon, etc. Most of these ideas have not been confirmed by the data of long-term monitoring conducted in the form of complex marine expeditions by the Pacific Research Fisheries Center (TINRO Center) in the Far-Eastern Seas and adjacent North Pacific waters since the 1980s. The data show that Pacific salmon are ecologically very flexible species with a wider temperature range of habitat than was previously believed. Salmon are able to make considerable vertical migrations, easily crossing zones of sharp temperature gradient and different water masses. Having the wide feeding spectra and being dispersed (as non-schooling fish) when feeding in the sea and ocean, they successfully satisfy their dietary needs in vast areas even with relatively low concentrations of prey organisms (macroplankton and small nekton). The total biomass of all the Pacific salmon species in the North Pacific is not greater than 4–5 million t (including 1.5–2.0 million t in Russian waters), whereas the biomass of other common species of nekton is a few hundreds of millions of tons. Salmon account for 1.0–5.0% of the total amount of food consumed by nekton in the epipelagic layer of the western Bering Sea, 0.5–1.0% in the Sea of Okhotsk, less than 1% in the ocean waters off the Kuril Islands, and 5.0–15.0% in the ocean waters off East Kamchatka. Thus, the role of Pacific salmon in the trophic webs of subarctic waters is rather moderate. Therefore, neither pink nor chum salmon can be considered as the species responsible for the large reorganization in ecosystems and the population fluctuations in other common nekton species.     

Specific features of distribution and ecology of two species of sea poachers of genus Podothecus (Agonidae) in pacific waters off the northern Kuril Islands and southeastern Kamchatka

According to materials of studies in 1992–2002, data on occurrence, spatial-bathymetric distribution, and size-weight composition of two species of sea poachers of the genus Podothecus (P. accipenserinus and P. sturioides) and species accompanying them in catches in Pacific waters off the northern Kuril Islands and southeastern Kamchatka are provided. The distribution of these relatively large representatives of the family Agonidae (maximum length of the first species is 38 and that of the second species is 33 cm, body weight of both 200 g) noticeably differ. In the period of observations, P. accipenserinus was found in catches only to the north of the Fourth Kuril Strait at depths of 80–570 m at near-bottom temperature of ?0.70 to +4.25°C, while P. sturioides was found over the entire studied area in a wider bathymetric range (85–786 m) exclusively at positive values of near-bottom water temperature (0.10–3.55°C). However, more frequently and in greater amounts, both species of sea poachers were recorded in catches off the southeastern extremity of Kamchatka and from the oceanic side of the Shumshu and Paramushir islands. The relationship between the depth of catch and sizes of P. accipenserinus and P. sturioides was analyzed. It is shown that their occurrence and the magnitude of catches in Pacific waters off the northern Kuril Islands and southeastern Kamchatka are subjected to some interannual, seasonal, and diurnal dynamics.     

Effects of decadal climate change on zooplankton over the last 50 years in the western subarctic North Pacific

Decadal‐ to multi‐decadal variations have been reported in many regional ecosystems in the North Pacific, resulting in an increasing demand to elucidate the link between long‐term climatic forcing and marine ecosystems. We detected phenological and quantitative changes in the copepod community in response to the decadal climatic variation in the western subarctic North Pacific by analyzing the extensive zooplankton collection taken since the 1950s, the Odate Collection. Copepod species were classified into five seasonal groups depending on the timing of the annual peak in abundance. The abundance of the spring community gradually increased for the period 1960–2002. The spring–summer community also showed an increasing trend in May, but a decadal oscillation pattern of quasi‐30‐year cycles in July. Phenological changes coincided with the climate regime shift in the mid‐1970s, indicated by the Pacific decadal oscillation index (PDO). After the regime shift, the timing of the peak abundance was delayed one month, from March–April to April–May, in the spring community, whereas it peaked earlier, from June–July to May–June, in the spring–summer community, resulting in an overlap of the high productivity period for the two communities in May. Wintertime cooling, followed by rapid summertime warming, was considered to be responsible for delayed initiation and early termination of the productive season after the mid‐1970s. Another phenological shift, quite different from the previous decade, was observed in the mid‐1990s, when warm winters followed by cool summers lengthened the productive season. The results suggest that climatic forcing with different decadal cycles may operate independently during winter–spring and spring–summer to create seasonal and interannual variations in hydrographic conditions; thus, combinations of these seasonal processes may determine the annual biological productivity.     

Population structure of three species of Anisakis nematodes recovered from Pacific sardines (Sardinops sagax) distributed throughout the California Current system

Members of the Anisakidae are known to infect over 200 pelagic fish species and have been frequently used as biological tags to identify fish populations. Despite information on the global distribution of Anisakis species, there is little information on the genetic diversity and population structure of this genus, which could be useful in assessing the stock structure of their fish hosts. From 2005 through 2008, 148 larval anisakids were recovered from Pacific sardine (Sardinops sagax) in the California Current upwelling zone and were genetically sequenced. Sardines were captured off Vancouver Island, British Columbia in the north to San Diego, California in the south. Three species, Anisakis pegreffii, Anisakis simplex 'C', and Anisakis simplex s.s., were identified with the use of sequences from the internal transcribed spacers (ITS1 and ITS2) and the 5.8s subunit of the nuclear ribosomal DNA. The degree of nematode population structure was assessed with the use of the cytochrome c oxidase 2 (cox2) mitochondrial DNA gene. All 3 Anisakis species were distributed throughout the study region from 32°N to 50°N latitude. There was no association between sardine length and either nematode infection intensity or Anisakis species recovered. Larval Anisakis species and mitochondrial haplotype distributions from both parsimony networks and analyses of molecular variance revealed a panmictic distribution of these parasites, which infect sardines throughout the California Current ecosystem. Panmictic distribution of the larval Anisakis spp. populations may be a result of the presumed migratory pathways of the intermediate host (the Pacific sardine), moving into the northern portion of the California Current in summer and returning to the southern portion to overwinter and spawn in spring. However, the wider geographic range of paratenic (large piscine predators), and final hosts (cetaceans) can also explain the observed distribution pattern. As a result, the recovery of 3 Anisakis species and a panmictic distribution of their haplotypes could not be used to confirm or deny the presence of population subdivision of Pacific sardines in the California Current system.     

Vertical distribution and seasonal numerical abundance of the Calanidae in oceanic waters to the south-west of the British Isles

The vertical distribution and seasonal abundance of the copepodite and adult stages of Calanus finmarchicus, C. helgolandicus, C. tenuicornis, Neocalanus gracilis, Nannocalanus minor and Calanoides carinatus from a series of Longhurst Hardy Plankton Recorder hauls taken in the oceanic waters, off the continental shelf, to the south-west of the British Isles are described. The sampling area was selected because the geographical distributions of the major Calanidae copepods of the north-east Atlantic Ocean are shown to overlap in this region. It marks the southern boundary of the distribution of C. finmarchicus, the central area of C. helgolandicus and the approximate northern limit of distribution of C. tenuicornis, N. gracilis, N. minor and C. carinatus. These four southern species occasionally penetrate further north (60° N) in the open ocean but do not breed at these northern latitudes. In autumn and winter, when C. finmarchicus and C. helgolandicus were overwintering below 400 m primarily as Stage V copepodites, N. gracilis occurred in the upper 200 m of the water column in a breeding condition; all copepodite stages were present. This copepod reproduced throughout the year in this regions while C. tenuicornis was observed to breed primarily in spring and summer. The geographical and vertical distributions of the Calanidae are related to the observed seasonal temperatures of the North Atlantic and the breeding strategies of species are compared.     

Summer feeding habits of the Pacific pomfret Brama japonica in the transitional and subarctic waters of the central North Pacific

Feeding habits of the Pacific pomfret Brama japonica , ranging from 30 to 40 cm in standard length, were quantitatively evaluated using the index of relative importance and were compared between the transitional domain and subarctic region in the central North Pacific. In the transitional domain (between the subarctic boundary and the subarctic front), this species fed mainly on subarctic and transitional‐water gonatid squids such as Berryteuthis anonychus , Gonatus middendorffi and Gonatopsis borealis , the transitional‐water squid Onychoteuthis borealijaponica , and a subtropical and transitional‐water amphipod, Phronima sedentaria . These prey items accounted for 52·8% by wet mass of total stomach contents. In the subarctic region (north of the subarctic front), Pacific pomfrets preyed primarily on subarctic and transitional‐water squids, such as B. anonychus and G. middendorffi , and secondarily on subarctic amphipods such as Hyperia medusarum and Hyperia glaba . These four prey items comprised 71·6% by mass of total stomach contents. Major transitional domain prey items, such as G. borealis, O. borealijaponica and P. sedentaria , were almost non‐existent in stomachs of fish from the subarctic region. The mean wet stomach content mass expressed as a percentage of body mass was significantly higher in the subarctic region (2·35%) than in the transitional domain (0·75%), suggesting that, for this fish, prey items are more readily available in the subarctic region during summer and their northward migration is a feeding migration. Feeding strategy of the Pacific pomfret was discussed in relation to their seasonal south‐north migration.     

Copepod communities related to water masses in the southwest East China Sea

The East China Sea is characterized by a complex hydrographic regime and high biological productivity and diversity. This environmental setting in particular challenged a case study on the use of mesozooplankton community parameters as indicators of water masses. In order to reveal spatial patterns of zooplankton communities during summer, a large scale oceanic transect study was conducted. Two transects were taken in the southwest East China Sea region, covering for the first time the China shelf, slope, and the estuaries of the Yangtze river and of the Minjiang river, the northern Taiwan Strait, and the Kuroshio Current region. A total of 77 copepod species were quantified. Copepod abundance was significantly higher in the estuary of the Yangtze River runoff mixture waters and lowest at the Kuroshio Current Region. The calanoid Parvocalanus crassirostris was the most frequently occurring and abundant species retrieved from 27 samples of a total of 39 samples. The use of multivariate cluster analysis separated the Mainland China Shelf from the northern Taiwan Strait and the Kuroshio Current Region at the first hierarchical level. The use of an indicator value method (IndVal) associated with each cluster of stations revealed characteristic species assemblages. Two hierarchical levels defined 4 assemblages within geographical sectors representing copepod assemblages of the Kuroshio Current Region, of the northern Taiwan Strait and the southern China Shelf near the estuary of the Minjiang River and northern stations near the estuary of the Yangtze River. Overall, there was a strong correspondence between the distribution of certain copepod species and water masses. Differences between the Mainland China shelf, the northern Taiwan Strait and the Kuroshio Current Region were characterized by differences in species composition and abundance. Water mass boundaries in the study area were exclusively indicated by distinct differences in species composition, emphasizing a correlation between copepod communities and water masses of the southwest East China Sea in summer.     

The impact of El Niño events on the pelagic food chain in the northern California Current

The zooplankton of the northern California Current are typically characterized by an abundance of lipid‐rich copepods that support rapid growth and survival of ecologically, commercially, and recreationally valued fish, birds, and mammals. Disruption of this food chain and reduced ecosystem productivity are often associated with climatic variability such as El Niño events. We examined the variability in timing, magnitude, and duration of positive temperature anomalies and changes in copepod species composition in the northern California Current in relation to 10 tropical El Niño events. Measurable impacts on mesozooplankton of the northern California Current were observed during seven of 10 of these events. The occurrence of anomalously warm water and the response of the copepod community was rapid (lag of zero to 2 months) following the initiation of canonical Eastern Pacific (EP) events, but delayed (lag of 2–8 months) following ‘Modoki’ Central Pacific (CP) events. The variable lags in the timing of a physical and biological response led to impacts in the northern California Current peaking in winter during EP events and in the spring during CP events. The magnitude and duration of the temperature and copepod anomalies were strongly and positively related to the magnitude and duration of El Niño events, but were also sensitive to the phase of the lower frequency Pacific Decadal Oscillation. When fisheries managers and biological oceanographers are faced with the prospect of a future El Niño event, prudent management and observation will require consideration of the background oceanographic conditions, the type of event, and both the magnitude and duration of the event when assessing the potential physical and biological impacts on the northern California Current.     

The food supply of the pacific salmon of the genus Oncorhynchus in the northwestern pacific ocean. 1. The dynamics of the food spectra and feeding intensity

Based on the data of 28 surveys that were carried out by the Pacific Fisheries Research Center in the Sea of Okhotsk, Bering Sea, and Pacific waters during 2001–2010, we analyzed the interannual variability of indirect indices of the food supply of the Pacific salmon (Oncorhynchus): the daily food ration, daily consumption rate, diel feeding chronology, diet overlap, trophic niche breadth, number of prey items, and the share of minor food. The years of the most pronounced changes in the diet composition and consumption rate of Pacific salmon were revealed. The variability of different trophic characteristics as indicators of the salmon food supply is discussed. Despite a significant increase in salmon abundance in the 2000s compared to previous years, no marked changes occurred in their feeding spectra and consumption rates.