Albacore (Thunnus alalunga) fishing ground in relation to oceanographic conditions in the western North Pacific Ocean using remotely sensed satellite data

Satellite‐based oceanographic data of sea surface temperature (SST), sea surface chlorophyll‐a concentration (SSC), and sea surface height anomaly (SSHA) together with catch data were used to investigate the relationship between albacore fishing ground and oceanographic conditions and also to predict potential habitats for albacore in the western North Pacific Ocean. Empirical cumulative distribution function and high catch data analyses were used to calculate preferred ranges of the three oceanographic conditions. Results indicate that highest catch per unit efforts (CPUEs) corresponded with areas of SST 18.5–21.5°C, SSC 0.2–0.4 mg m^?3, and SSHA ?5.0 to 32.2 cm during the winter in the period 1998–2000. We used these ranges to generate a simple prediction map for detecting potential fishing grounds. Statistically, to predict spatial patterns of potential albacore habitats, we applied a combined generalized additive model (GAM) / generalized linear model (GLM). To build our model, we first constructed a GAM as an exploratory tool to identify the functional relationships between the environmental variables and CPUE; we then made parameters out of these relationships using the GLM to generate a robust prediction tool. The areas of highest CPUEs predicted by the models were consistent with the potential habitats on the simple prediction map and observation data, suggesting that the dynamics of ocean eddies (November 1998 and 2000) and fronts (November 1999) may account for the spatial patterns of highest albacore catch rates predicted in the study area. The results also suggest that multispectrum satellite data can provide useful information to characterize and predict potential tuna habitats.     

西北太平洋公海秋刀鱼渔场浮游动物数量分布的初步研究

根据2005年7—10月在北太平洋E 150°~158°56′、N 42°34′~46°25′进行秋刀鱼资源探捕所获得的15个站点浮游动物样本资料,测得甲壳纲的桡足类、端足类、糠虾类、磷虾类,毛颚类、腔肠动物以及被囊动物等的代表种。其中桡足类占绝对优势,隶属于1目4科5属8种。浮游动物生物量4~699 mg/m3,均值168.6 mg/m3。根据浮游动物的种类、分布状况及优势种类的强弱,判断和分析黑潮暖流的强弱趋势,对确定秋刀鱼渔场的南北位置具有重要参考价值。     

北太平洋小型中上层鱼类资源对气候–海洋变化的响应研究进展

小型中上层鱼类是北太平洋海域重要的渔业资源,具有生命周期短、生长速度快、高集群性等特点,其资源年间波动显著,且受气候-海洋变化的影响。本文围绕秋刀鱼（Coloabis saira）、鲣（Katsuwonus pelamis）、鲐（Scomber japonicus）、鳀（Engraulis japonious）、竹䇲鱼（Trachurus japonicus）、沙丁鱼（Sardinops sagax）6种主要的小型中上层鱼类,回顾了厄尔尼诺-南方涛动（El Niño/La Niña-southern oscillation,ENSO）、太平洋年代际振荡（the Pacific decadal oscillation,PDO）、黑潮-亲潮（Kuroshio-Oyashio,KR-OY）等关键气候-海洋指数的特点及对鱼类栖息地环境和资源变动的影响。概括了气候-海洋变化对小型中上层鱼类的洄游分布和资源丰度的直接影响过程,以及对亲体繁殖产卵、仔稚体成活率和资源量波动间接的滞后影响过程。建议：（1）在多种气候-海洋指数基础上添加种群动态过程、捕捞方式系数、自然死亡率等参数构建生物量动态模型,揭示气候-海洋变化对渔业资源量的影响过程;（2）结合北太平洋涛动（North Pacific oscillation,NPO）、北极涛动（Arctic oscillation,AO）、北太平洋环流振荡（North Pacific gyre oscillation,NPGO）等其他北太平洋主要气候,基于物理海洋模型及空间耦合水动力学模型研究大尺度海流、中尺度涡旋对小型中上层鱼类影响。     

Biogeography of pelagic food webs in the North Pacific

The tufted puffin (Fratercula cirrhata) is a generalist seabird that breeds throughout the North Pacific and eats more than 75 different prey species. Using puffins as samplers, we characterized the geographic variability in pelagic food webs across the subarctic North Pacific from the composition of ~10,000 tufted puffin meals (~56,000 prey items) collected at 35 colonies in the Gulf of Alaska (GoA) and Aleutian Archipelago. Cluster analysis of diet species composition suggested three distinct forage fish communities: (i) in the northern GoA, multiple age‐classes of coastal and shelf residents such as capelin, sand lance and herring dominated the food web, (ii) in the western GoA to eastern Aleutians, the shelf community was dominated by transient age‐0 walleye pollock, and (iii) in the western Aleutians, shelf‐edge and mesopelagic forage species such as squid, lanternfish, and Atka mackerel were prevalent. Geographic patterns of abundance of capelin and sand lance in tufted puffin diets were corroborated by independent research fisheries and diets of piscivorous fish, indicating that puffin diets reflect the local abundance of forage species, not just selection of favored species. Generalized additive models showed that habitat characteristics predict, in a non‐linear fashion, forage species distribution and abundance across two large marine ecosystems. We conclude that major biogeographic patterns in forage fish distribution follow gradients in key habitat features, and puffin diets reflect those patterns.     

北太平洋公海秋刀鱼生物学特性初步研究

根据2004年7～11月西北太平洋秋刀鱼探捕调查的生物学数据,通过统计回归方法分析了秋刀鱼的性腺成熟度,摄食等级,性比,叉长分布,叉长和体重、净重关系。结果为:性成熟度为Ⅱ期的占52．96％;摄食等级主要为2级和3级,占72．91％;性比接近1:1;体长范围为186～340mm,优势体长组为220～280mm;雌性的叉长略大于雄性;群体可能属于2个不同群体,生长参数大于3。     

Ecological effects of regime shifts in the Bering Sea and eastern North Pacific Ocean

Large‐scale shifts occurred in climatic and oceanic conditions in 1925, 1947, 1977, 1989 and possibly 1998. These shifts affected the mix and abundance of suites of coexisting species during each period of relative environmental stability—from primary producers to apex predators. However, the 1989 regime shift was not a simple reversal of the 1977 shift. The regime shifts occurred abruptly and were neither random variations nor simple reversals to the previous conditions. Timing of these anomalous environmental events in the North Pacific Ocean appears to be linked to physical and biological responses in other oceanic regions of the world. Changes in the atmospheric pressure can alter wind patterns that affect oceanic circulation and physical properties such as salinity and depth of the thermocline. This, in turn, affects primary and secondary production. Data from the North Pacific indicate that regime shifts can have opposite effects on species living in different domains, or can affect similar species living within a single domain in opposite ways. Climatic forcing appears to indirectly affect fish and marine mammal populations through changes in the distribution and abundance of their predators and prey. Effects of regime shifts on marine ecosystems are also manifested faster at lower trophic levels. Natural variability in the productivity of fish stocks in association with regime shifts indicates that new approaches to managing fisheries should incorporate climatic as well as fisheries effects.     

北太平洋公海秋刀鱼渔场初步分析

根据2004年7~11月“中远渔1号”调查船北太平洋公海秋刀鱼渔场探捕调查的生产情况,对秋刀鱼渔场进行分析。结果发现:①秋刀鱼渔场可根据渔场位置分为北部渔场和南部渔场,北部渔场范围为44°~45°N、156°~158°E,南部渔场范围为41°~42°N、150°~151°E,南部渔场的分布范围小于北部渔场。②秋刀鱼的生产以11月份生产最好,平均日产量达22.7t,其中最高日产量为60.42t;8月份的秋刀鱼生产最差,平均日产量为2.95t,与2003年的12.05t反差较大,主要是由于受到渔场环境因子变化的影响,鱼发位置偏至俄罗斯专属经济区内的缘故。③秋刀鱼舷提网作业平均日放网次数达7.6次,最高1天放网次数达到16次,而最高网次产量为11.05t。④秋刀鱼渔获组成以中小型鱼为主,占80%以上,除7月份渔获中特大型秋刀鱼占有较大比例外,其余月份很少有特大级秋刀鱼。⑤在相近的渔场位置,秋刀鱼个体随着生产月份的推迟,鱼体呈变小的趋势。     

北太平洋柔鱼渔场浮游动物数量分布及与渔场的关系

根据2001年6-7月在北太平洋152°E～171°W、39°～42°N水域生态环境和资源综合调查资料,分析结果表明调查水域浮游动物总生物量均值为92.12mg·m-3(0.81～1035.68 mg·m-3),其中中部(160°～180°E、39°～42°N)及西经水域(170°～178°W、40°～41°N)为113.51mg·m-3,西部水域(152°～157°E、41°～43°N)为22.89mg·m-3;桡足类丰度居首(42.11%),其次为海樽类(30.91%);伪细真哲水蚤(Eucalanus pseudattenuatus)、太平洋哲水蚤(Calanus pacifica)和软拟海樽(Dolioletta gegenbauri)为主要优势种.甲壳类的分布与柔鱼中心渔场存在较好的对应关系,中心渔场位于浮游动物总生物量高密集区(250～500mg·m-3)和甲壳类的最高丰度区(50～100 ind·m-3)内或边缘区;头足类幼体分布于磷虾类和端足类的高丰度区(10～25ind·m-3)内或边缘水域.     

北太平洋柔鱼资源与渔场的时空分析

利用相关系数和灰色关联评价方法对1995-2001年北太平洋各海域鱿钓产量及其作业渔场进行时空分析,结果表明主要作业渔场分布在145°E～148°E、153°E～161°E海域,其产量约占各年总渔获量的70%～85%。从作业纬度来看,1999年以前主要产量集中在40°N～43°N海域,而2000和2001年则分布在39°N～41°N和43°N～45°N海域。相关系数分析表明,2000和2001年作业渔场和各海域产量比重均发生了较大的变化,特别是在160°E以西和170°E以东海域,而在1999年以前未发生较大变化。灰色关联评价表明,1998年北太平洋柔鱼资源状况为最好,而2000、2001和1996年较差,1999、1995和1997年处在中间水平。这与实际生产情况和海洋环境条件基本上是相符的。2000和2001年北太平洋资源状况下降,可能与150°E～160°E海域的柔鱼种群资源出现下降有关。     

Interannual variability in stock abundance of the neon flying squid, Ommastrephes bartramii, in the North Pacific Ocean during 1979–1998: impact of driftnet fishing and oceanographic conditions

Variability in catch-per-unit-effort (CPUE) was examined for the autumn cohort of Ommastrephes bartramii collected with research driftnets during 1979–1998 along five longitudinal transects passing through the Subarctic, Transitional and Subtropical Domains in the North Pacific. CPUE was generally low during the period of intensive commercial driftnet fishing (1980–1992) and increased following the 1992 moratorium on the use of large-scale driftnets. However, CPUE levels were low for the cohorts hatched in 1992 and 1996 (captured in subsequent years owing to a one-year life of O. bartramii ) that experienced low sea surface temperatures from hatching to recruitment. Among similar-aged squid collected from 180° and 179°30'W in June, mantle lengths were significantly greater in 1997 than during 1995–96. These findings suggest that the driftnet fishery and sea surface temperatures from hatching to recruitment strongly affected stock abundance and possibly growth.     

Mid-latitude wind stress: the energy source for climatic shifts in the North Pacific Ocean

Analyses of atmospheric observations in the North Pacific demonstrate extensive decadal-scale variations in the mid-latitude winter surface wind stress. In the decade after 1976 winter, eastward wind stress doubled over a broad area in the central North Pacific and the winter zero wind stress curl line was displaced about 6° southward. This resulted in increased southward Ekman transport, increased oceanic upwelling, and increased turbulent mixing as well as a southward expansion of the area of surface divergence. All these factors contributed to a decadal winter cold anomaly along the subtropical side of the North Pacific Current. In summer the cold anomaly extended eastward, almost reaching the coast of Oregon. The increased gradient in wind stress curl and southward displacement of the zero curl line also resulted in an increase in total North Pacific Current transport, primarily on the Equator side of this Current. Thus, surface water entering the California Current was of more subtropical origin in the post-1976 decade. Southward (upwelling favourable) wind stress and sea surface temperature (SST) in the area off San Francisco exhibit at least three different types of decadal departures from mean conditions. In association with the 1976 climatic shift, marine fishery production in the Oyashio, California and Alaska Currents altered dramatically, suggesting that these natural environmental variations significantly alter the long-term yields of major North Pacific fisheries.     

北太平洋150°～165°E海域柔鱼鱿钓渔场及其预报模型研究

根据1998-2000年8～10月在150°～165°E海域我国北太平洋鱿钓生产数据以及海况资料,分析柔鱼中心渔场与海洋环境之间的关系,建立柔鱼渔场预报模型。结果显示,黑潮势力的强弱及其分支分布与柔鱼渔场形成关系密切。8～10月柔鱼作业渔场基本上处在黑潮第2、第3暖水分支的前锋。柔鱼渔场分布与月份、20℃等温线分布的关系密切。8～10月中心渔场的预报模型为:经度方向FGLong=141.535+1.8435×T;纬度方向FGLati=-8.461+1.165×T+(Lat155+Lat160)/2。     

A study on relationships between large‐scale climate indices and estimates of North Pacific albacore tuna productivity

A logistic production model was used to examine potential relationships between three climate indices, the North Pacific Gyre Oscillation (NPGO), the Pacific Decadal Oscillation (PDO), and the Multivariate El Niño‐Southern Oscillation Index (MEI), and productivity estimates of the North Pacific albacore tuna (Thunnus alalunga) population. Catch and standardized catch‐per‐unit‐effort data from three longline fisheries (Japan, US, and Taiwan) were used in the model. The climate indices were incorporated into the model by correlating time‐varying intrinsic population growth rate (r_y) of the production model with the annual mean value for each index. The estimated probability that the NPGO is positively correlated with stock productivity, as measured by r_y, was 0.99, and the calculated probability that MEI is negatively correlated with the productivity was 0.95. The time lag for these correlations is 4 yr, which is consistent with the timing of recruitment to the Japan longline fishery. The PDO did not seem to have any detectable relationship with stock productivity. However, it remains uncertain if there is a conclusive linkage between the albacore productivity and the NPGO or the MEI index, because model fit to the data is about the same as that of a base model which does not use any climate index and assumes a time‐invariant r.     

Migration of albacore, Thunnus alalunga, in the North Pacific Ocean in relation to large oceanic phenomena

On the basis of Japanese long-line fishery data during 1970–1988, anticlockwise migration routes of albacore in the North Pacific are newly proposed. The annual migration route for mature albacore is described as a closed ellipse with a centre at 20°N and 170°E, and is wider in El Niño years than non-El Niño years associated with an appearance of a cold-water region in the central and south-western North Pacific. Immature albacore also have an anticlockwise migration route in winter which extends from 25°N to 35°N and from 130°E to 180°E, when the Kuroshio has a relatively straight path. However, the migration does not persist when the Kuroshio takes a large meander path.     

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.     

北太平洋狭鳕资源声学评估调查研究

１９９３年夏季使用“北斗”号渔业调查船对北太平洋的狭鳕进行资源声学评估和渔场环境调查，调查覆盖面积达７６万平方公里。调查结果表明：夏季白令海阿留申海盆区５０－２００ｍ为冷水团占据，水温为１．３－４．９℃。狭鳕成鱼主要分布于海盆区东南部及公海区，主要栖息在１７５－２２５ｍ层。在公海区东北部与陆架之间，首次发现大量狭鳕当生幼鱼，主要栖息在８０－１００ｍ层。成鱼和幼鱼均有明显昼夜垂直移动。海盆区狭鳕平均     

Northerly shift of warm‐water copepods in the western subarctic North Pacific: Continuous Plankton Recorder samples (2001–2013)

Spatial and temporal variation in copepod community structure, abundance, distribution and biodiversity were examined in the western subarctic North Pacific (40–53°N, 144–173°E) during 2001–2013. Continuous Plankton Recorder (CPR) observational data during the summer season (June and July) were analyzed. The latitudinal distribution of warm‐water species in June shifted northward after 2011 while no apparent latitudinal shift of cold‐water and other species was observed. Species number and the Shannon–Wiener biodiversity index (H′) in June tended to increase in the northern area after 2011. The warm‐water species abundance and center latitude of warm‐water distribution were positively correlated with sea surface temperature (SST) across sampling locations, whereas no significant correlations with SST were observed for cold‐water species or other species. Warm SSTs in June after 2011 appeared to cause the northward shift of warm‐water species distribution, which in turn contributed to the higher biodiversity in the northern area. This study demonstrated the rapid response of warm‐water species to warm SST variation, whereas cold‐water and other species did not exhibit such clear responses. These findings indicate that the response of copepods to environmental changes differs among copepod species, highlighting the importance of investigating lower trophic levels to the species level to evaluate individual species’ responses to climate change.     

Plankton abundance and size structure in the northern North Pacific Ocean in early summer

Phyto- and zooplankton abundance and size structure were investigated in the northern North Pacific Ocean (37.0–49.5^oN along 180^o longitude) during June of 1987. The area between 41.5^oN and 47.5^oN was expected to be abundant in phytoplankton since both water column stability and nutrient availability were favourable for phytoplankton growth. Actual phytoplankton abundance was, however, low between 41.5^oN and 45.5^oN. In particular, abundance of net phytoplankton (>10μm) was low although picophytoplankton (<2 μm) was abundant between 41.5^oN and 43.5^oN. The zooplankton community between 41.5^oN and 45.5^oN was characterized by a large amount of net zooplankton and a small amount of microzooplankton. This situation may be best explained by top-down control; that is, net zooplankton grazing suppressed net phytoplankton and microzooplankton abundance. The diminished microzooplankton promoted the increase of picophytoplankton. Because planktivorous Pacific saury were abundant between 40.0^oN and 41.0^oN, it is further speculated that the low biomass of net zooplankton south of 41.0^oN resulted from feeding by Pacific saury. The reduced grazing pressure of net zooplankton may have enhanced the growth of net phytoplankton and microzooplankton in this region.     

Horizontal and vertical movements of juvenile bluefin tuna (Thunnus orientalis) in relation to seasons and oceanographic conditions in the eastern Pacific Ocean

Electronically tagged juvenile Pacific bluefin, Thunnus orientalis, were released off Baja California in the summer of 2002. Time‐series data were analyzed for 18 fish that provided a record of 380 ± 120 days (mean ± SD) of ambient water and peritoneal cavity temperatures at 120 s intervals. Geolocations of tagged fish were estimated based on light‐based longitude and sea surface temperature‐based latitude algorithms. The horizontal and vertical movement patterns of Pacific bluefin were examined in relation to oceanographic conditions and the occurrence of feeding events inferred from thermal fluctuations in the peritoneal cavity. In summer, fish were located primarily in the Southern California Bight and over the continental shelf of Baja California, where juvenile Pacific bluefin use the top of the water column, undertaking occasional, brief forays to depths below the thermocline. In autumn, bluefin migrated north to the waters off the Central California coast when thermal fronts form as the result of weakened equatorward wind stress. An examination of ambient and peritoneal temperatures revealed that bluefin tuna fed during this period along the frontal boundaries. In mid‐winter, the bluefin returned to the Southern California Bight possibly because of strong downwelling and depletion of prey species off the Central California waters. The elevation of the mean peritoneal cavity temperature above the mean ambient water temperature increased as ambient water temperature decreased. The ability of juvenile bluefin tuna to maintain a thermal excess of 10°C occurred at ambient temperatures of 11–14°C when the fish were off the Central California coast. This suggests that the bluefin maintain peritoneal temperature by increasing heat conservation and possibly by increasing internal heat production when in cooler waters. For all of the Pacific bluefin tuna, there was a significant correlation between their mean nighttime depth and the visible disk area of the moon.     

Pacific herring, Clupea pallasi, recruitment in the Bering Sea and north-east Pacific Ocean, I: relationships among different populations

We examined recruitment and average weight-at-age time series for Pacific herring ( Clupea pallasi ) populations from the Bering Sea and north-east Pacific Ocean to determine similarities. Statistical correlation and multivariate clustering methods indicated Pacific herring populations form large-scale groups. Large year classes occur synchronously among several Pacific herring populations. Multivariate cluster analyses of recruitment and weight-at-age data indicated that Bering Sea herring populations are distinct from north-east Pacific Ocean populations. Within the NE Pacific Ocean, there appear to be three groups of herring populations: a British Columbia group, a south-east Alaska coastal group, and an outer Gulf of Alaska group. Jackknife and randomization tests indicate these groups are robust and not the result of random chance. Deviations from observed herring population groups were examined for indications of anthropogenic perturbations. The Prince William Sound herring populations did not show any strong deviations corresponding to the oil spill of 1989. There might not yet be enough data since the spill to detect changes in the recruitment or weight-at-age data since that time, particularly if oil spill effects were concentrated on the early life history stages.