Migration and behavior of juvenile North Pacific albacore (Thunnus alalunga)

Archival tags were used to study the seasonal movements, migration patterns and vertical distribution of juvenile North Pacific albacore (Thunnus alalunga). Between 2001 and 2006, archival tags were deployed in North Pacific albacore in two regions of the Northeast Pacific: (i) off Northern Baja California, Mexico and Southern California, and (ii) off Washington and Oregon. Twenty archival tagged fish were recovered with times at liberty ranging from 63 to 697 days. Tagged albacore exhibited five distinct, seasonal migratory patterns. Depth and temperature data also showed a broad range of vertical behaviors. In certain regions such as off Baja California, Mexico, juvenile albacore make frequent dives to depths exceeding 200 m during the day and remain in the surface mixed layer at night, whereas off Oregon and Washington they remain near the surface both day and night. Water temperatures encountered ranged from 3.3 to 22.7°C. Peritoneal temperatures were significantly higher by an average of approximately 4°C, as expected in these warm‐bodied fish. This study provides a comprehensive examination of horizontal and vertical movements of juvenile albacore in the Northeast Pacific. The results reveal diverse behavior that varies regionally and seasonally as albacore move among different habitats throughout the entire North Pacific.     

南太平洋长鳍金枪鱼垂直活动水层空间分析

为了解南太平洋长鳍金枪鱼(Thunnus alalunga)的垂直活动水层分布特征及其适宜的垂直活动水层深度,采用Argo 数据重构了研究海域次表层20 ℃和25 ℃等温线深度场, 并结合2010年～2012年中水集团南太平洋长鳍金枪鱼延绳钓渔船实际生产统计数据, 绘制了20 ℃和25 ℃等温线深度与长鳍金枪鱼单位捕捞努力量渔获量(CPUE) 叠加图, 分析南太平洋长鳍金枪鱼的垂直活动水层分布特征。结果表明, 研究海域20 ℃和25 ℃等温线深度存在明显的季节性变化, 且长鳍金枪鱼渔场时空分布随着20℃等温线深度的220 m等深线和25℃等温线深度的140 m等深线时空变动而季节性南北移动。长鳍金枪鱼中心渔场主要分布于10S 以南、160E～175E之间, 中心渔场所处海域, 其20 ℃等温线深度多在220 m以深, 超过250 m的海域CPUE 均偏低; 25 ℃等温线深度多在140 m以浅, 浅于80 m的海域则难以形成中心渔场。采用频次分析与经验累积分布函数( ECDF) 相结合的方法, 计算出南太平洋长鳍金枪鱼适宜的垂直活动水层深度为88～238 m。文章初步得出了南太平洋长鳍金枪鱼的垂直分布特征及其适宜的垂直活动水层深度, 可用于指导延绳钓投钩深度, 为中国南太平洋长鳍金枪鱼延绳钓生产作业提供理论参考。     

Seasonal potential fishing ground prediction of neon flying squid (Ommastrephes bartramii) in the western and central North Pacific

We explored the seasonal potential fishing grounds of neon flying squid (Ommastrephes bartramii) in the western and central North Pacific using maximum entropy (MaxEnt) models fitted with squid fishery data as response and environmental factors from remotely sensed [sea surface temperature (SST), sea surface height (SSH), eddy kinetic energy (EKE), wind stress curl (WSC) and numerical model‐derived sea surface salinity (SSS)] covariates. The potential squid fishing grounds from January–February (winter) and June–July (summer) 2001–2004 were simulated separately and covered the near‐coast (winter) and offshore (summer) forage areas off the Kuroshio–Oyashio transition and subarctic frontal zones. The oceanographic conditions differed between regions and were regulated by the inherent seasonal variability and prevailing basin dynamics. The seasonal and spatial extents of potential squid fishing grounds were largely explained by SST (7–17°C in the winter and 11–18°C in the summer) and SSS (33.8–34.8 in the winter and 33.7–34.3 in the summer). These ocean properties are water mass tracers and define the boundaries of the North Pacific hydrographic provinces. Mesoscale variability in the upper ocean inferred from SSH and EKE were also influential to squid potential fishing grounds and are presumably linked to the augmented primary productivity from nutrient enhancement and entrainment of passive plankton. WSC, however, has the least model contribution to squid potential fishing habitat relative to the other environmental factors examined. Findings of this work underpin the importance of SST and SSS as robust predictors of the seasonal squid potential fishing grounds in the western and central North Pacific and highlight MaxEnt's potential for operational fishery application.     

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.     

A study on the variability of albacore (Thunnus alalunga) longline catch rates in the southwest Pacific Ocean

Relationships between albacore tuna (Thunnus alalunga) longline catch per unit effort (CPUE) and environmental variables from model outputs in New Caledonia’s Exclusive Economic Zone (EEZ) were examined through generalized linear models at a 1° spatial resolution and 10‐day temporal resolution. At a regional (EEZ) scale, the study demonstrated that a large part of albacore CPUE variability can be explained by seasonal, interannual and spatial variation of the habitat. Results of the generalized linear models indicated that catch rates are higher than average in the northwestern part of the EEZ at the beginning of the year (January) and during the second half of the year (July–December). In the northwestern region of the EEZ, high CPUEs are associated with waters <20.5° in the intermediate layer and with moderate values of primary production. Longline CPUE also appeared to be dependent on prey densities, as predicted from a micronekton model. Albacore CPUE was highest at moderate densities of prey in the epipelagic layer during the night and for relatively low prey densities in the mesopelagic layer during the day. We also demonstrated that the highest CPUEs were recorded from 1986 to 1998, which corresponds to a period with frequent El Niño events.     

Distribution of albacore (Thunnus alalunga) in the Indian Ocean and its relation to environmental factors

The distribution pattern of albacore, Thunnus alalunga, in the Indian Ocean was analyzed based on catch data from the Taiwanese tuna longline fishery during the period 1979–85. The Taiwanese tuna fishery began operating in the Indian Ocean in 1967. We used a geographic information system to compile a fishery and environmental database and statistically explored the catch per unit effort (CPUE) distribution of albacore. Our results indicated that immature albacore were mainly distributed in areas south of 30°S although some displayed a north–south seasonal migration. Mature albacore, which were mainly concentrated between 10°S and 25°S, also showed a north–south migration. Within 10°S and 30°S, the separation of mature, spawning, and immature albacore life history stages roughly coincided with the boundaries of the three oceanic current systems in the Indian Ocean. The optimal environmental variables for CPUE prediction by stepwise discriminant analysis differed among life history stages. For immature albacore, the sea surface variables sea surface temperature (SST), chlorophyll concentration and surface salinity were significant. For mature albacore, SST was significant, while for spawning albacore, the sub‐surface variables temperature at 100 m and oxygen at 200 m were significant. Spawning albacore evidently prefer deep oceanographic conditions. Our results on the oceanographic conditions preferred by different developmental stages of albacore in the Indian Ocean were compatible with previous studies found in the Pacific Ocean.     

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.     

Habitat characteristics of skipjack tuna (Katsuwonus pelamis) in the western North Pacific: a remote sensing perspective

Skipjack tuna habitat in the western North Pacific was studied from satellite remotely sensed environment and catch data, using generalized additive models and geographic information systems. Weekly resolved remotely sensed sea surface temperature, surface chlorophyll, sea surface height anomalies and eddy kinetic energy data were used for the year 2004. Fifteen generalized additive models were constructed with skipjack catch per unit effort as a response variable, and sea surface temperature, sea surface height anomalies and eddy kinetic energy as model covariates to assess the effect of environment on catch per unit effort (skipjack tuna abundance). Model selection was based on significance of model terms, reduction in Akaike’s Information Criterion, and increase in cumulative deviance explained. The model selected was used to predict skipjack tuna catch per unit effort using monthly resolved environmental data for assessing model performance and to visualize the basin scale distribution of skipjack tuna habitat. Predicted values were validated using a linear model. Based on the four‐parameter model, skipjack tuna habitat selection was significantly (P < 0.01) influenced by sea surface temperatures ranging from 20.5 to 26°C, relatively oligotrophic waters (surface chlorophyll 0.08–0.18, 0.22–0.27 and 0.3–0.37 mg m^?3), zero to positive anomalies (surface height anomalies 0–50 cm), and low to moderate eddy kinetic energy (0–200 and 700–2500 cm² s^–2). Predicted catch per unit effort showed a trend consistent with the north–south migration of skipjack tuna. Validation of predicted catch per unit effort with that observed, pooled monthly, was significant (P < 0.01, r² = 0.64). Sea surface temperature explained the highest deviance in generalized additive models and was therefore considered the best habitat predictor.     

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.     

Habitat differentiation between sei (Balaenoptera borealis) and Bryde's whales (B. brydei) in the western North Pacific

Two closely related baleen whale species, sei and Bryde's whales, in the western North Pacific were studied to identify differences in habitat use. Data were obtained from May to August 2004 and 2005. This study examined the relationship between oceanographic features derived from satellite data and the distribution of sei and Bryde's whales using basic statistics. We investigated oceanographic features including sea surface temperature (SST), sea surface chlorophyll a (Chl‐a), sea surface height anomalies (SSHAs), and depth of the habitat. These two whale species used habitats with different SST, Chl‐a, and SSHA ranges. The 0.25 mg m^?3 Chl‐a contour (similar to the definition of the Transition Zone Chlorophyll Front) was a good indicator that separated the habitats of sei and Bryde's whales. Then generalized linear models were used to model the probabilities that the whale species would be present in a habitat and to estimate their habitat distribution throughout the study area as a function of environmental variables. The potential habitats of the two species were clearly divided, and the boundary moved north with seasonal progression. The habitat partitioning results indicated that SST contributed to the patterns of habitat‐use and might reflect differences in prey species between the two whales. This study showed that the habitats of the sei and Bryde's whales were clearly divided and their potential habitat‐use changed seasonally.     

热带中西太平洋海域黄鳍金枪鱼的摄食生物学特性

利用延绳钓作业方式,于2018年5月—2019年2月对热带中西太平洋海域(163°14'E—173°35'E,2°03'S—11°17'S)的黄鳍金枪鱼(Thunnus albacares)进行了取样.对取样的919尾黄鳍金枪鱼叉长进行了组成和性比分析,对其中的551尾进行了摄食生物学研究,并使用方差分析(ANOVA)...     

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。     

Solar and lunar influences on the spawning activity of Pacific bluefin tuna (Thunnus orientalis) in the south‐western North Pacific spawning ground

Pacific bluefin tuna (Thunnus orientalis) migrate to the south‐western North Pacific spawning grounds (area off Taiwan and the Ryukyu Islands) from mid‐April to early July. Reproductive traits of the species in this area have been studied for some time; however, temporal changes in spawning activity during this season are not well understood. In this study, the spawning fraction (proportion of females with post‐ovulatory follicles to total mature females) in relation to solar calendar date and lunar day was investigated using a generalized linear model. Sampling was conducted almost every day throughout the fishing season at Ishigaki Fishing Port (24°21′N, 124°09′E), southern Japan between 2012 and 2014, and a total of 212 ovaries were histologically observed. Spawning fraction continued to increase from the beginning to the end of the season. This indicates that the peak season of occurrence in the area and the peak of spawning activity did not co‐occur. Spawning fraction also changed with the lunar day and significantly increased around the new moon. Eggs and early larvae hatched around the new moon may have reduced the predation risk during night‐time. These findings improve the current knowledge of reproductive biology and resource evaluation of Pacific bluefin tuna and indicate that spawning activity is not constant, and has two or three peaks in each season.     

西北太平洋秋刀鱼CPUE标准化研究

秋刀鱼(Cololabis saira)是西北太平洋海域重要的渔业种类之一,其资源评估工作已成为热点问题,单位捕捞努力量渔获量(CPUE)标准化可以为开展有效的资源评估研究提供科学依据。为此,本研究利用2003~2017年中国大陆西北太平洋秋刀鱼渔业生产统计资料,结合卫星遥感获得的海洋环境数据,如海表面温度、海表温度梯度、海表面高度等,基于广义线性模型(General linear model, GLM)和广义可加模型(Generalized additive model, GAM)对中国大陆西北太平洋秋刀鱼渔业进行CPUE标准化。结果显示,根据BIC准则,在GLM模型结果中,年份、月份、经度、纬度、海表面温度、海表面高度、海表温度梯度及年份与月份对CPUE具有显著影响,并组成了GLM模型的最佳模型,对CPUE偏差的解释率为52.47%;在GAM模型结果中,除上述8个影响变量外,交互项月份与经度和月份与纬度也对CPUE影响较大,GAM的最佳模型对CPUE偏差的解释率为61.9%。通过5-fold交叉验证分析发现,GAM模型标准化结果较优于GLM模型,更适合于西北太平洋秋刀鱼渔业CPUE标准化。     

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.     

北太平洋公海日本鲭资源分布及其渔场环境特征

根据2014~2015年两年收集的北太平洋公海围拖网作业的日本鲭(Scomber japonicas,又称鲐鱼)生产月度数据,结合同期卫星遥感反演技术获取的海表温度(SST)、海水叶绿素a(Chl-a)浓度、海流等环境数据,运用渔获量重心法,地统计插值等方法,分析了北太平洋公海鲐鱼的资源分布情况与渔获量重心的时空变化及其与主要环境因子之间的关系。研究表明,鲐鱼渔场季节性差异明显,渔场重心集中分布在39°N~43°N、147°E~154°E范围内。两年渔场重心均呈现先向东北方向移动,自9月开始再向西南方向移动的趋势。GAM模型显示,北太平洋鲐鱼渔场的最适海表温度范围是16~18℃,最适叶绿素a浓度范围是0.3~0.8 mg·m~(-3),空间上集中分布在40°N~41°N、148°E~151°E,海流对鲐鱼渔场形成尤为重要。     

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。     

Vertical behavior of bigeye tuna (Thunnus obesus) in the northwestern Pacific Ocean based on archival tag data

The behavior of bigeye tuna (Thunnus obesus) in the northwestern Pacific Ocean was investigated using archival tag data for 28 fish [49–72 cm fork length (FL) at release, 3–503 days] released in Japanese waters around the Nansei Islands (24–29°N, 122–132°E) and east of central Honshu (Offshore central Honshu, 32–36°N, 142–148°E). Vertical behavior was classified into three types based on past studies: ‘characteristic’ (non‐associative), ‘associative’ (associated with floating objects) and ‘other’ (behavior not fitting into these two categories). The proportion of fish showing associative behavior decreased and that of characteristic behavior increased as fish grew, and this shift was pronounced at 60–70 cm FL. The fish usually stayed above the 20°C isotherm during the daytime and nighttime when showing associative behavior and below the 20°C isotherm during daytime for characteristic behavior. A higher proportion of characteristic behavior was seen between December and April around the Nansei Islands, and between September and December for offshore central Honshu. Seasonal changes in vertical position were also observed in conjunction with changes in water temperature. In this study, ‘other’ behavior was further classified into five types, of which ‘afternoon dive’ behavior, characterized by deep dives between around noon and evening, was the most frequent. The present study indicated that in the northwestern Pacific Ocean, the vertical behavior of bigeye tuna changes with size, as well as between seasons and regions.     

太平洋大眼金枪鱼延绳钓渔获分布及渔场环境浅析

本文主要根据收集到的渔获量数据、海水表层温度数据和有关文献资料 ,应用GIS技术对太平洋大眼金枪鱼延绳钓渔业进行了定量或定性分析。结果表明 :太平洋大眼金枪鱼延绳钓渔场主要分布在 2 0°N～2 0°S之间的热带海域 ,具纬向分布特征。对渔获产量同海表温度的分月统计显示 :太平洋大眼金枪鱼渔场最适月平均表层水温约 2 8～ 2 9℃ ,渔场出现频次为偏态分布型。最后 ,结合有关文献综合讨论分析了海表温度、溶解氧含量、海流等环境因子与金枪鱼渔场分布和形成机制的关系     

东南太平洋智利竹筴鱼中心渔场的月间变动研究

根据2003年～2011年中国东南太平洋智利竹筴鱼（Trachurus murphyi）大型拖网渔捞数据和海表温度（SST）数据,利用ArcGIS 10.0绘制渔场产量重心时空分布图,用最短距离法对中心渔场进行聚类,对智利竹筴鱼渔场月间重心变动规律及其与SST之间的关系进行分析。结果表明,随着月份的变化,中心渔场从3月开始由南逐渐向西北方向移动,到10月之后逐渐向东南方向移动。3月～6月渔场主要分布在80°W～90°W、40°S～45°S,最适宜SST为12～14℃;7月～8月渔场主要分布在80°W～90°W、35°S～40°S,SST为13～14℃;9月～10月渔场分布为85°W～95°W、30°S～35°S,SST这15～16℃;11月～12月渔场分布在90°W～95°W、30°S～40°S,SST为16～17℃;而1月～2月渔场分布在85°W～95°W、35°S～45°S,最适宜SST为16～17℃。