Climate variability and its effects on major fisheries in Korea

Understanding in climate effects on marine ecosystem is essential to utilize, predict, and conserve marine living resources in the 21s t century. In this review paper, we summariz ed t h e past history and current status of Korean fisheries as well as the changes in climate and oceanographic phenomena since the 1960s. Ocean ecosystems in Korean waters can be divided into three, based on the marine commercial fish catches; the demersal ecosystem in the Yellow Sea and the East China Sea, the pelagic ecosystem in the Tsushima Warm Current from the East China Sea to the East/Japan Sea, and the demersal ecosystem in the northern part of the East/Japan Sea. Through the interdisciplinary retrospective analysis using available fisheries, oceanographic, and meteorological information in three important fish communities, the trend patterns in major commercial catches and the relationship between climate/ environmental variability and responses of fish populations were identified. Much evidence revealed that marine ecosystems, including the fish community in Korean waters, has been seriously affected by oceanographic changes, and each species has responded differently. In general, species diversity is lessening, and mean trophic level of each ecosystem has decreased during the last 3~4 decades. Future changes in fisheries due to global warming are also considered for major fisheries and aquaculture in Korean waters.     

New estimates of Southern Ocean biological production rates from O2/Ar ratios and the triple isotope composition of O2

We report O₂/Ar ratios (a constraint on net community production) and the triple isotopic composition of dissolved O₂ (a constraint on gross primary production) in samples collected from the surface mixed layer on 23 Southern Ocean transits. Samples were collected at 1–2° meridional resolution during the austral summer. Methodological limitations notwithstanding, the results constrain the net/gross production ratio, net O₂ production, and gross O₂ production at unprecedented resolution throughout the Southern Ocean mixed layer. Gross O₂ production rates inferred from the oxygen triple isotopes are greater than production rates calculated from a model based on remotely sensed chlorophyll. This result agrees with previous ¹⁸O and ¹⁴C incubations along 170°W. O₂/Ar ratios exceeding saturation are consistently observed within the Subantarctic and Polar Frontal Zones south of New Zealand and Australia, showing that a net autotrophic community predominates during austral summer. Lower O₂/Ar values are observed within the Drake Passage and Antarctic Zone, suggesting unresolved influences of low net community production, net heterotrophy, and upwelling of O₂-undersaturated waters. In autotrophic waters of the austral summer mixed layer, ratios of net community production/gross O₂ production scatter about 0.13, corresponding to f ratios of ∼0.25. Net community/gross O₂ production ratios show no meridional gradient across the Antarctic Circumpolar Current, suggesting that an approximately constant fraction of gross primary productivity is regenerated or exported. Our calculated net O₂ production rates are in satisfactory agreement with comparable published estimates. Net and gross O₂ production rates are highest in the Subantarctic and decline to the south, paralleling the well-known trend of chlorophyll a concentrations. In an analysis of variance of net O₂ production and gross O₂ production with other environmental variables, the strongest correlations are between net O₂ production and sea surface temperature (SST) (direct correlation), climatological [NO₃⁻] (inverse correlation), and estimates of primary productivity derived from a remote sensing (direct correlation). These trends are as expected if aerosol iron input is the most important influence on production. They are unexpected if upwelling-derived SiO₂ and iron are the leading influence or if lower SSTs promote greater export in this region.     

Enhanced biological activity by an anticyclonic warm eddy during early spring in the East Sea (Japan Sea) detected by the geostationary ocean color satellite

The high primary production enhanced by anticyclonic eddies and hourly variation pattern in the productivity during the spring season in the East Sea were first investigated using the first Korean Geostationary Ocean Color Imager (GOCI). Even though the stratification for a seasonal spring bloom is not well developed in the water column in early April in the East Sea, a physical upward water flux movement at the periphery of the anticyclonic eddies could remain the phytoplankton in euphotic zone to sustain high chlorophyll-a concentration conditions in the Ulleung Basin. At this time, nutrients were no major controlling factor for phytoplankton growth since concentrations of major nutrients (nitrate, silicate, and phosphate) were relatively high in the observed eddy sites based on the observation data from the Korean Oceanographic Data Center (KODC). The estimated mixed layer depth (MLD) significantly shallower at the periphery supports for this mechanism. The hourly primary productivity estimation based on a Carbon-based Productivity Model (CbPM) provides a bimodal pattern along the time especially in L1 with an approximately one order magnitude difference between the lowest and highest values of productivities on 5 April, 2011. Potential possibilities for this large discrepancy in the hourly productivity and some thoughts on a short time in situ incubation method were discussed.     

Climate-change driven range shifts of anchovy biomass projected by bio-physical coupling individual based model in the marginal seas of East Asia

Recent studies in the western North Pacific reported a declining standing stock biomass of anchovy (Engraulis japonicus) in the Yellow Sea and a climate-driven southward shift of anchovy catch in Korean waters. We investigated the effects of a warming ocean on the latitudinal shift of anchovy catch by developing and applying individual-based models (IBMs) based on a regional ocean circulation model and an IPCC climate change scenario. Despite the greater uncertainty, our two IBMs projected that, by the 2030s, the strengthened Tsushima warm current in the Korea Strait and the East Sea, driven by global warming, and the subsequent confinement of the relatively cold water masses within the Yellow Sea will decrease larval anchovy biomass in the Yellow Sea, but will increase it in the Korea Strait and the East Sea. The decreasing trend of anchovy biomass in the Yellow Sea was reproduced by our models, but further validation and enhancement of the models is required together with extended ichthyoplankton surveys to understand and reliably project range shifts of anchovy and the impacts such range shifts will have on the marine ecosystems and fisheries in the region.     

Improved Chlorophyll-a Algorithm for the Satellite Ocean Color Data in the Northern Bering Sea and Southern Chukchi Sea

The Bering and Chukchi seas are an important conduit to the Arctic Ocean and are reported to be one of the most productive regions in the world’s oceans in terms of high primary productivity that sustains large numbers of fishes, marine mammals, and sea birds as well as benthic animals. Climate-induced changes in primary production and production at higher trophic levels also have been observed in the northern Bering and Chukchi seas. Satellite ocean color observations could enable the monitoring of relatively long term patterns in chlorophyll-a (Chl-a) concentrations that would serve as an indicator of phytoplankton biomass. The performance of existing global and regional Chl-a algorithms for satellite ocean color data was investigated in the northeastern Bering Sea and southern Chukchi Sea using in situ optical measurements from the Healy 2007 cruise. The model-derived Chl-a data using the previous Chl-a algorithms present striking uncertainties regarding Chl-a concentrations – for example, overestimation in lower Chl-a concentrations or systematic overestimation in the northeastern Bering Sea and southern Chukchi Sea. Accordingly, a simple two band ratio (R_rs(443)/R_rs(555)) algorithm of Chl-a for the satellite ocean color data was devised for the northeastern Bering Sea and southern Chukchi Sea. The MODIS-derived Chl-a data from July 2002 to December 2014 were produced using the new Chl-a algorithm to investigate the seasonal and interannual variations of Chl-a in the northern Bering Sea and the southern Chukchi Sea. The seasonal distribution of Chl-a shows that the highest (spring bloom) Chl-a concentrations are in May and the lowest are in July in the overall area. Chl-a concentrations relatively decreased in June, particularly in the open ocean waters of the Bering Sea. The Chl-a concentrations start to increase again in August and become quite high in September. In October, Chl-a concentrations decreased in the western area of the Study area and the Alaskan coastal waters. Strong interannual variations are shown in Chl-a concentrations in all areas. There is a slightly increasing trend in Chl-a concentrations in the northern Bering Strait (SECS). This increasing trend may be related to recent increases in the extent and duration of open waters due to the early break up of sea ice and the late formation of sea ice in the Chukchi Sea.     

中国海域潮汐非调和常数的计算与分析

联合利用中国沿岸长期验潮站实测资料和全球海潮模型NAO.99b在中国海域的结果,进行潮汐非调和常数的计算.分别对渤海、黄海、东海和南海进行分析,结果表明,中国海域潮汐类型复杂,渤海、黄海、东海以半日潮性质为主,南海以日潮性质为主;渤海、南海平均大潮差多分布在0.42～2.09 m,平均小潮差分布在0.27～1.33 m,东海、黄海平均大潮差多分布在1.12～4.44 m,平均小潮差多分布在0.41～2.41 m;渤海、黄海平均大潮高潮位分布在0.48～1.77 m,东海在0.42～2.41 m,南海在0.21～1.35 m;渤海、东海以及南海北部浅海海域潮高日不等现象显著.     

东海对马暖流水来源的数值模拟

本文通过二维数值模拟对1986年6月～1988年12月东海对马暖流水的来源问题进行了初步探讨,结果得出东海对马暖流水的来源基本上分为三种类型:(1)东海对马暖流水主要为东海黑潮水继续北上部分构成;(2)东海对马暖流水由东海黑潮水、东海陆架水以及东海北部黄海大陆沿岸水几部分混合而成;(3)东海对马暖流水几乎全部由东海北部的黄海大陆沿岸水构成。模拟与实测结果基本一致.     

东黄海星康吉鳗渔业生物学特性研究

Whitespotted conger Conger myriaster is a commercially important species in the seas around China, Korea and Japan. The coastal waters of China serve as an important feeding ground for congers, but the spatio-temporal variations in the fishery and biological characteristics of the population have been rarely evaluated and less well understood in this area. We studied the growth, spawning and feeding characteristics of C. myriaster on the basis of samples collected from October 2016 to April 2017 in the Yellow Sea and East China Sea. A total of 529 specimens were collected, with ages ranging from 1 to 6 years and total length ranging from 132 mm to 834 mm.The parameters of von Bertalanffy growth equation L_∞ and k were 1 026 mm and 0.226 a~(–1), respectively; the sex ratio was 88:0(female: male) in the East China Sea and 2.67:1 in the South Yellow Sea; the development stage of ovary ranged from peri-nucleolus stage to secondary yolk globule stage, and the testis of two males was at midmeiotic stage; Crustacean was the major prey for conger of small length, and food source shift to fish with somatic growth. The results showed substantial differences from previous studies in Japan and Korean waters, as well as from China seas in the 1980 s, suggesting potential spatiotemporal changes in the biological characteristics of C.myriaster. This study may improve current understanding of the fishery biology of C. myriaster in the Yellow Sea and East China Sea.     

Population structure of the Korean gizzard shad, <Emphasis Type="Italic">Konosirus punctatus</Emphasis> (Clupeiformes,Clupeidae) using multivariate morphometric analysis

The gizzard shad, Konosirus punctatus, is one of the most important fish species in Korea, China, Japan and Taiwan, and therefore the implementation of an appropriate population structure analysis is both necessary and fitting. In order to clarify the current distribution range for the two lineages of the Korean gizzard shad (Myoung and Kim 2014), we conducted a multivariate morphometric analysis by locality and lineage. We analyzed 17 morphometric and 5 meristic characters of 173 individuals, which were sampled from eight localities in the East Sea, the Yellow Sea and the Korean Strait. Unlike population genetics studies, the canonical discriminant analysis (CDA) results showed that the two morphotypes were clearly segregated by the center value “0” of CAN1, of which morphotype A occurred from the Yellow Sea to the western Korean Strait with negative values, and morphotype B occurred from the East Sea to the eastern Korean Strait with positive values even though there exists an admixture zone in the eastern Korean Strait. Further studies using more sensitive markers such as microsatellite DNA are required in order to define the true relationship between the two lineages.     

黄东海浮游生物群落呼吸率对碳平衡的重要性

黄东海接受长江冲淡水和黑潮带来的大量营养盐和有机物质,其碳循环对陆架海碳源汇格局至关重要.浮游生物群落呼吸是影响碳循环的重要过程.为揭示黄东海浮游生物群落呼吸率(PCR)对碳平衡的贡献,于2011年四季使用黑白瓶培养法测定黄海南部及东海北部浮游群落呼吸率和初级生产力,并同步测定温度、盐度、营养盐、叶绿素和细菌丰度等环境...     

中国近海区域浮游植物生态对气候变化的响应

我国近海区域对气候变化高度敏感,浮游植物生态的变化关系到我国近海生态安全.采用重构的遥感数据等资料,分析并综述我国近海区域浮游植物叶绿素a浓度、初级生产力和浮游植物群落结构对气候变化背景下海水升温、风场等环境因子的响应.结果表明,东(南)中国海叶绿素a浓度略有上升(下降)的趋势,但浮游植物群落结构和生物量有明显的变化;其中,微微型浮游植物和甲藻占比增加,小型浮游植物物种成为海区优势种,暖水性种分布区北扩,而这与气候变化背景下海洋热动力环境的长期变化及其对营养盐供给的影响关系密切.分析还指出了气候变化对我国近海区域海洋生态影响研究迫切需要开展的若干工作.     

南黄海叶绿素a与初级生产力之间的相关分析

本文依据南黄海海域的调查资料,探讨了叶绿素ａ与初级生产力和真光层内叶绿素ａ积分值之间的相关关系。并对表层叶绿素ａ是否可以作为海洋中浮游植物蕴藏量的指标加以验证。验证的具体方法是分析表层叶绿素ａ（ＳＣ）;真光层内叶绿素ａ积分值（ＩＣ）和初级生产力（ＰＰ）三者之间的相关关系。分析表明：在叶绿素ａ含量高且变化梯度大的高生产力海域,ＳＣ、ＩＣ和ＰＰ之间存在着非常显著的相关性,ＳＣ可以作为某海域浮游植物现存量及其生产力的指标;而在叶绿素ａ和初级生产力低且分布均匀的海域,ＳＣ、ＩＣ和ＰＰ之间不相关。故指出利用ＳＣ作为某海域浮游植物蕴藏量和初级生产力指标时应慎重。     

Abundance and distribution of Nemopilema nomurai (Scyphozoa,Rhizostomeae), in Korean waters in 2005–2013

Nemopilema nomurai have appeared massively since 2003 in Korean waters, and regular offshore monitoring has been performed since 2005 in the eastern Yellow Sea (YS), northwestern East China Sea (ECS), Korean southern waters (Ksw), and western East Sea (ES). Korea Jellyfish Monitoring Network (KoJEM) was established in 2006 for coastal jellyfish monitoring. From these, sight survey monitoring data were gathered and analyzed to extract the yearly and seasonal fluctuation of N. nomurai’s abundance and distribution. The first massive annual appearance of N. nomurai occurred in the northwestern ECS, off Shanghai, China, in mid May of 2005–2008 and of 2012–2013. In other years or concurrently with the appearance in the northwestern ECS in the same year, several individuals were found in the mid-eastern YS and Ksw, and southwestern ES. The population of N. nomurai at the northwestern ECS moved to the southeastern YS and Jeju Strait in June, and from the July to August it extended its distribution all around the Korean peninsula and persisted till October. Since October, the distribution was retracted into the southern YS and Ksw, and disappeared slowly. N. nomurai’s yearly abundance varied a lot, from nearly 0 inds 10^?4m^?2 in 2010 to 62.4 inds 10^?4m^?2 in 2005. The highest abundance was recorded in 2005, followed by 2007 and 2009, and the least abundance was in 2008 and 2010–2013. The results were compared with those of the Liaoning Bay, Bohai Sea, which led to speculation about a new seeding place of N. nomurai, and mortality during the early planktonic phase of N. nomurai was proposed as the determinant of the yearly variation in abundance.     

Molecular identification of anisakid nematodes third stage larvae isolated from common squid (Todarodes pacificus) in Korea

The occurrence of Genus Anisakis nematode larvae in marine fishes and cephalopods is epidemiologically important because Anisakis simplex larval stage can cause a clinical disease in humans when infected hosts are consumed raw. Common squid (Todarodes pacificus) from Korean waters were investigated for anisakid nematodes infection during 2009～2011. In total, 1,556 larvae were collected from 615 common squids and 732 of them were subsequently identified by PCR-RFLP analysis of ITS rDNA. Depending on the sampling locations, the nematode larvae from common squid showed different prevalence, intensity and species distribution. A high prevalence (P) and mean intensity (MI) of infection were observed in the Yellow Sea (n = 250, P = 86.0%, MI = 5.99 larvae/host) and the southern sea of Korea (n = 126, P = 57.1%, MI = 3.36 larvae/host). Anisakis pegreffii was dominantly found in common squid from the southern sea (127/ 140, 90.7%) and the Yellow Sea (561/565, 98.9%). In contrast, the P and MI of infection were relatively low in the East Sea (n = 239, P = 8.37%, MI = 1.25 larvae/host). A. pegreffii was not found from the East Sea and 52.0% (13/25) of the nematodes were identified as A. simplex. Most of them were found in the body cavity or digestive tract of common squid, which are rarely consumed raw by humans. Considering the differenences in anisakid nematode species distribution and their microhabitat in common squid, it remains unclear whether common squid plays an important role in the epidemiology of human anisakis infection in Korea. Further extensive identification of anisakid nematodes in common squid, with geographical and seasonal information will be necessary.     

Validation of semi-analytical inversion models for inherent optical properties from ocean color in coastal Yellow Sea and East China Sea

The performances of three semi-analytical retrieval models for water inherent optical properties were validated in the coastal Yellow Sea and East China Sea, including the Quasi-Analytical Algorithm (QAA), the Garver-Siegel-Maritorena model (GSM) and the Over Constrained Linear Matrix (LM). The model-retrieved parameters, namely absorption coefficients of phytoplankton (a _ph), colored dissolved and detrital particulate matter (a _dg), total absorption coefficients (a _t), and backscattering coefficient of particles (b _bp), were compared. The bio-optical datasets collected from a Yellow Sea and East China Sea cruise in April and September 2003 were used in the study. The QAA model performed the best in retrieval for all the coefficients, showing log-transformed root mean square errors of 0.306 for a _ph, 0.268 for a _dg, 0.144 for a _t, and 0.273 for b _bp at 443 nm. The LM model showed a slightly larger deviation than the QAA model with a similar error trend for absorption coefficients, but it returned the largest uncertainties for b _bp, with log-transformed root mean square error up to 0.646. The GSM model, however, yielded the largest and fluctuating errors along with wavelength for absorption coefficient retrievals. Substituting the fitting parameters from measured data for the empirical spectral parameters, all three models returned better results. These improvements demonstrated that semi-analytical algorithms designed for ocean water need regional modifications before applying to coastal areas. The QAA algorithm may be the most suitable model for retrieval for the Yellow Sea and East China Sea, and future model refinements should concentrate on regional modeling of inherent optical properties.     

南黄海物理-生物地球化学过程的时空异质性及内在关联和机制

研究多重物理过程控制下陆架边缘海生物地球化学过程的时空异质性及其生态响应,对于深入认识海洋生态系统具有重要的意义。基于相关历史观测资料和卫星遥感海表温度,本文综合分析了南黄海物理-生物地球化学过程的时空变化和空间异质性特征,探讨了该海域内部典型地理单元之间的内在关联和机制。结果显示,冷季沿岸流南向输送和暖季锋面上升流垂向输运的季节性交替是影响石岛外海与海州湾外侧海域生物地球化学和初级生产的重要物理过程。夏季苏北沿岸水的东北向扩展可形成浒苔离岸/跨区域输送的动力驱动。暖季水体层化显著影响着南黄海中部冷水团海域的生物地球化学过程,春至秋季冷水团海域底层水体中的营养盐逐渐累积,形成了营养盐的重要贮库;层化季节黄海冷水团边界锋区上升流系统的存在使得南黄海叶绿素a和初级生产力高值区位置同海表低温涌升流区总体相一致。冷季南黄海西部南下的冷水与中部北向入侵的暖水共同导致了“S”型锋面的形成;暖季黄海冷水团边界锋区的上升流系统是连接层化海域和近岸区的纽带,可实现对冷水团内部营养盐的提取,从而将冷水团内部和边界区的生物地球化学过程形成有机连接,并在成山角-石岛外海、海州湾外侧、苏北浅滩东部形成三个典型的物理-生物地球化学相互作用区。本研究细化和整合了南黄海区域海洋学研究,揭示了该海域物理-生物地球化学过程的空间异质性特征和不同地理单元之间的关联性及机制,获得了对南黄海水文-生物地球化学-生态过程的综合、系统认知。     

2015年5月黄海及东海北部大型水母分布及生物量估算

2015年5月搭载“北斗”渔业调查船、使用渔拖网的采样方式,在整个黄海及东海北部进行系统的走航式大面调查,记录了30°N—39°N海区内的大型水母种类组成、伞径大小及生物量分布,估算和比较了大型水母与其他渔业生物的生物量。结果表明,5月整个调查区,大型水母的总生物量估算值5.9万t,绝大部分由黄海中部的多管水母和洋须水母生物量贡献所致。出现的大型水母种类伞径分布呈单峰型。不同种类的水母分布具有明显地理区域和水文偏好性。其中,洋须水母主要分布于黄海中、北部50m水深以深水域,多管水母主要分布于黄海中部50m水深以浅的西侧以及整个东海北部;沙海蜇多为幼体,分布于黄、东海交汇区31°N—33°N间;霞水母较为集中出现于31°N以南、123°N以西近海。各水母种类的高密区的底层水温按洋须水母、沙海蜇、四叶小舌水母、霞水母呈升高趋势。东海多管水母分布区的底层水温与沙海蜇相近;黄海多管水母分布区的底层水温较洋须水母略高。沙海蜇和四叶小舌水母较其他水母的适温范围宽。霞水母和洋须水母处于相对高盐区域。     

冬季东海及南海北部海域初级生产力和新生产力的初步研究

采用14C与15 N核素示踪方法,于2008年12月—2009年1月对东海和南海北部海域的初级生产力和新生产力的分布进行了研究,并对其环境制约机制进行了初步探讨。结果表明:调查海域叶绿素a质量浓度在空间分布上呈近岸高、外海低,表层高、真光层底部低的分布趋势。东海海域的积分初级生产力(IPP)和积分新生产力(INP)均低于南海北部海域,f比值为东海海域>南海北部海域,东海海域新生产力(NP)对初级生产力(PP)的贡献大于南海北部海域。浮游植物对氨盐的吸收速率(ρNH4)显著大于对硝酸盐的吸收速率(ρNO3)(P<0.05)。水柱平均新生产力与环境参数的相关性分析结果表明,营养盐是影响冬季调查海域新生产力的主要因素,温度和盐度为次要因素。     

中国沿海真鲷种群鉴别研究

对1990-1998年期间取样于中国沿海5个不同海区的真鲷(Pagrosomus major Temminck et Schlegel)样品的23项形态性状进行测量,并应用差异系数、均数差异显著性、方差分析和判别函数分析等数理统计学方法对性状特征的差异进行比较,结合产卵场、分布洄游习性以及海洋环境条件进行综合分析,存此基础上对上述海区的真鲷种群分群问题进行了探讨。结果表明．中国沿海真鲷可分为4个不同地方种群．即黄渤海地方种群、东海地方种群、闽南-南海地方种群和北部湾地方种群。文中还讨论了真鲷种质资源保护问题。     

The study of productivity in the Bohai Sea——Ⅱ. Primary productivity and estimation of potential fish catch

-On the basis of the data obtained from the surveys in the Bohai Sea during 1982-1983, this paper analysed and discussed the distribution and seasonal variation of primary productivity in the Bohai Sea, and the correlations between the primary productivity and environmental factors. The organic carbon production and prospect of fishery production in the waters of this sea are estimated. It is shown that, there exists production patential in the Bohai Sea, the primary production is 112 gC/ (m2 ?a)the production of organic carbon being 10 million ton per year, the fishery yields 1 million ton and the maximum catch of sea products 0. 5 million ton. The results of the investigation can serve as the basic data for the exploitation, utilization and management of the fishery resources in the Bohai Sea.