Analyses of egg size,otolith shape,and growth revealed two components of small yellow croaker in Haizhou Bay spawning stock

The geographical variations in life history characteristics of small yellow croaker Larimichthys polyactis, caused by experienced different environmental conditions, have been observed in China seas. Previous studies based on spatial distribution, migration route, and body morphometrics suggested a complex stock structure. In this study, to clarify the source of a spawning stock, we investigated the reproduction strategy and inter-structure of the Haizhou Bay (HZB) spawning stock in the middle Yellow Sea from both egg survey and adult otolith increment analysis. Egg and adult samples were collected from three surveys during spawning season in 2013. Distinct spatial and temporal variations were detected in egg distribution and size, and otolith shape analysis of adult fishes revealed two morphotypes with different increment growth using random forest cluster. The results indicate the existence of two components within the same spawning stock in HZB from different wintering grounds, and accordingly special protection should be required for this stock given the significance to maintain connectivity between adjacent subpopulations.     

黄海小黄鱼生物学特征对多重压力的响应

Temporal changes in biological characteristics of small yellow croaker Larimichthys polyactis in the Yellow Sea were examined for the period of 1960–2008. The body size and age of small yellow croaker decreased substantially, in particular, average length of fish in 2008 was reduced by ~85% than those occurring in 1985, and at that time ~93% of the total catch was dominated by one-year-old individuals. Correspondingly, growth parameters also varied significantly over the years, i.e., k(growth coefficient) and t_0(zero-length age) gradually increased from 0.26 and –0.58 year in 1960 to 0.56 and –0.25 year in 2008, respectively. Although, L∞(body length)sharply decreased from 34.21 cm in 1960 to 24.06 cm in 2008, and t_r(inflexion age) decreased from 3.78 year in1960 to 1.61 year in 2008. There was a great increase both in natural mortality coefficient and fishing mortality coefficient. However, according to the gray correlation analysis, changes in the biological characteristics of small yellow croaker were induced by different stressors ranked as: fishing vessel powerfeeding gradesea surface temperature. This study suggests that the active fishery management measures for biological characters of fish populations should be considered.     

应用一种基于产量数据评估方法对东海三个重要渔业的资源评估

Most fisheries in China do not have maximum sustainable yield(MSY) estimates due to limited and poor data.Therefore, finding a common method to estimate MSY or total allowable catch(TAC) for fishery management is necessary. MSYs of three important fisheries in the East China Sea were evaluated through a catch-based model.Estimates for intrinsic rate of increase(r) and five levels of process error were considered. Results showed hairtail Trichiurus japonicas(Temminck and Schlegel) and small yellow croaker Larimichthys polyactis(Bleeker) fisheries experienced overfishing from the mid-1990 s to the early 2000 s, and the suggested TACs were 55.8×10~4 t and9.06×10~4 t, respectively. Decades of overfishing in wintering and spawning grounds of large yellow croaker Larimichthys crocea(Richardson) caused the fishery's collapse in the 1980 s, and it has not recovered until today.The Catch–MSY model generated similar estimated MSYs with other methods and may be a useful choice for the assessment of regional stocks in China.     

鱼耳石碳氧同位素在黄、渤海小黄鱼种群识别中的应用

Oxygen and carbon isotope ratios(δ~(18)O and δ~(13)C) in otoliths were used to identify the stock structure of small yellow croaker,Larimichthys polyactis.Otoliths were collected from fish at five locations across the Yellow Sea and the Bohai Sea representing most of their distributional range and fisheries areas.The significant differences in the isotopic signatures showed that the five locations could be chemically distinguished and clearly separated,indicating stock subdivision.Correlation of δ~(18)O and δ~(13)C values suggested that population of L.polyactis could be divided into the Bohai Sea group,the southern Yellow Sea group and the central Yellow Sea group.Discriminant analysis of δ~(18)O and δ~(13)C values demonstrated a high significant difference with 85.7% classification accuracy.The spatial separation of L.polyactis indicated a complex stock structure across the Yellow Sea and the Bohai Sea.These results indicate that optimal fisheries management may require a comprehensive consideration on the current spatial arrangements.This study has provided further evidence that measurement of the stable isotopes ratios in otolith can be a valuable tool in the delineation of fishery management units.     

Early life migration and population discrimination of the small yellow croaker Larimichthys polyactis from the Yellow Sea:inferences from otolith Sr/Ca ratios

The small yellow croaker Larimichthys polyactis is a benthic marine fish species of high ecological and commercial importance and is widely distributed in the northwestern Pacific Ocean, especially in the Chinese coastal waters of the Bohai, Yellow, and East China Seas. As a highly migratory species, the whole life migration of L. polyactis has been intensively studied. However, knowledge about its early life migration is scarce, and population divisions are inconsistent, limiting the ability of...     

Spatial-temporal dynamics of bacterioplankton communities in the breeding area of large yellow croaker Larimichthys crocea in Sansha Bay,China

As an important spawning ground for large yellow croaker Larimichthys crocea, Sansha Bay,South China Sea has been a research hotspot. However, studies on the influence of the bacterioplankton community and assessments of its seasonal succession of bacterioplankton in different sea areas in Sansha Bay are still limited. To address the issue, we use 16S rRNA gene amplicon sequencing and functional prediction to investigate the spatial-temporal dynamics of the bacterioplankton community in three di...     

A New model to forecast fishing ground of Scomber japonicus in the Yellow Sea and East China Sea

The pelagic species is closely related to the marine environmental factors, and establishment of forecasting model of fishing ground with high accuracy is an important content for pelagic fishery. The chub mackerel(Scomber japonicus) in the Yellow Sea and East China Sea is an important fishing target for Chinese lighting purse seine fishery. Based on the fishery data from China's mainland large-type lighting purse seine fishery for chub mackerel during the period of 2003 to 2010 and the environmental data including sea surface temperature(SST), gradient of the sea surface temperature(GSST), sea surface height(SSH) and geostrophic velocity(GV), we attempt to establish one new forecasting model of fishing ground based on boosted regression trees. In this study, the fishing areas with fishing effort is considered as one fishing ground, and the areas with no fishing ground are randomly selected from a background field, in which the fishing areas have no records in the logbooks. The performance of the forecasting model of fishing ground is evaluated with the testing data from the actual fishing data in 2011. The results show that the forecasting model of fishing ground has a high prediction performance, and the area under receiver operating curve(AUC) attains 0.897. The predicted fishing grounds are coincided with the actual fishing locations in 2011, and the movement route is also the same as the shift of fishing vessels, which indicates that this forecasting model based on the boosted regression trees can be used to effectively forecast the fishing ground of chub mackerel in the Yellow Sea and East China Sea.     

西北太平洋环境变化对柔鱼冬春生群体资源丰度的影响

During 1995–2011, annual production of winter-spring cohort of Ommastrephes bartramii for Chinese squidjigging fishery has greatly fluctuated, which is closely related to the environmental conditions on the spawning and fishing grounds. To better understand how squid recruitment and abundance were influenced by ocean environmental conditions, biological and physical environmental variables including sea surface temperature(SST), SST anomaly(SSTA), chlorophyll a(Chl a) concentration and the Kuroshio Current were examined during years with the highest(1999), intermediate(2005), and lowest(2009) catches. Catch per unit effort(CPUE) of the squid-jigging vessels was used as an indicator of squid abundance. The results indicated that high SST and Chl a concentration on the spawning ground in 1999 resulted in favorable incubation and feeding conditions for squid recruitment. Whereas the suitable spawning zone(SSZ) in 2009 shifted southward and coincided with low SST and Chl a concentration, resulting in a reduction in the squid recruitment. The small difference of SSZ area in the three years suggested the SSZ provided limited influences on the variability in squid recruitment. Furthermore,high squid abundance in 1999 and 2005 was associated with warm SSTA on the fishing ground. While the cool SSTA on the fishing ground in 2009 contributed to adverse habitat for the squid, leading to extremely low abundance. It was inferred that strengthened intensity of the Kuroshio force generally yielded favorable environmental conditions for O. bartramii. Future research are suggested to focus on the fundamental research on the early life stage of O. bartramii and mechanism of how the ocean-climate variability affects the squid abundance and spatial distribution by coupling physical model with squid biological process to explore transport path and abundance distribution.     

TAGGING EXPERIMENTS OF THE PENAEID SHRIMP IN THE BOHAI SEA AND HUANGHAI SEA IN AUTUMN SEASON

There exists obvious difference in recapture rate of tagged shrimp in various sea areas and years in autumn season, but the majority of them (98%) are recaptured in the releasing year. Although the main portion of each shrimp group in the Bohai Sea has separate distribution area, they intermingle in autumn season to search for food, thus forming a principal fishing ground located in the central Bohai Sea.Those shrimps wintering in south-central portion of the Huanghai Sea are generally divided into two populations. One is called the Korean population, inhabiting along the western coast of Koera, which is less in abundance and smaller in shrimp size; and the other is called the Chinese population, inhibiting along the Bohai Sea coast and the Huanghai Sea coast of China, which is richer in abundance and larger in shrimp size. The spawning grounds of the latter extend throughout the Bohai Sea and off the Huanghai Sea coast of China, from the Yalujiang Estuary area in the north to the coastal waters of Haiz     

ESTIMATION OF FISHING MORTALITY AND ABUNDANCE OF PACIFIC HERRING IN THE HUANGHAI SEA BY COHORT ANALYSIS (VPA)

In this paper Cohort Analysis (VPA) with the data on catch in number by age and year is used to estimate independently fishing mortality, abundance and actual number of spawning stock of the Pacific herring in the Huanghai Sea. The results show that catch rate of the fishery is very high, and that the fishing mortality of the dominant age group aged 2-4 was 0.87-2.97 during the years 1971-1984. The size of year class has been decreased since 1982 although the variability for this species in the Huanghai Sea is frequent. This results in reducing the recruitment of the fishery, the abundance and the actual number of spawning stock. Therefore, an urgent management measure should be considered.The magnitude of several sources of errors in Cohort Analysis (VPA) are examined, and the precision of the estimates is mainly dependent on an accurate natural mortality.     

Factors Affecting the Wintering Habitat of Major Fishery Resources in Southwestern Korean Waters

We investigated the temperature and salinity effects on the major fish species in the wintering grounds based on trawl surveys and oceanographic observations in the southwestern waters of Korea during March-early April in 2002-2003. The influence area of warm Kuroshio water was limited to the southwestern area of Korea in 2003 with a range of 7.7-16.3°C, 32.54-34.70 of salinity, wider than that of 2002. The number of fish species and density of major fish species in 2003 were higher than in 2002. Geographical estimation showed high proportions of species number and catches in the areas around Jeju Islands, southwestern waters and the southeastern coast of Korea. Five species; silver pomfret (Pampus echinogaster), hairtail (Trichiurus lepturus), anchovy (Engraulis japonicus), small yellow croaker (Larimichthys polyactis) and yellow goosefish (Lophius litulon) were most abundant, composing above 60% of the total catch in 2002 and 2003. More than 50% of catch in the major fish species were mostly distributed in the range of 9.5-11.0°C of temperature and 33.1-33.9 of salinity. Non-parametric estimation for the major species showed the 1st mode around 10°C and the 2nd mode at 8-9°C in 2002 and 11-14°C in 2003. A m o n g major fish species, hairtail was principally composed of juveniles, and larger individuals were caught in southeastern waters. These results are considered to be helpful for the areabased fishery management strategy for the wintering grounds of the Yellow Sea and coastal waters of Korea.     

渤海小黄鱼生殖力及其变化

根据2004年5月在渤海进行的拖网调查资料,分析了小黄鱼(Pseudosciaenapolyatics)在经过近半世纪的捕捞后的生殖群体生殖力及其与体长、纯体质量的关系,并对小黄鱼生殖力的变化作了比较。结果表明,小黄鱼的个体绝对生殖力为14729粒±1360粒;个体绝对生殖力与叉长、纯体质量的关系变化较大;与1964年历史资料相比,相同体长组小黄鱼的个体绝对生殖力F和相对生殖力FL都显著增大(P<0.01)。小黄鱼的生殖力增加可能是小黄鱼在长期捕捞等外部环境影响下的遗传进化以及对其生存环境的适应性响应。     

中国沿海小黄鱼种群动力学及其空间异质性研究

小黄鱼是我国近海四种最重要的经济鱼类之一,在过去的几十年中小黄鱼种群及其两个地理亚种群经历了巨大的变化。小黄鱼的种群动力学研究,对于维持这一重要渔业的可持续管理是至关重要的。目前仅有的两个小黄鱼种群动力学模型只涵盖了较短的时间,且没有关注其空间差异。本文研究了1968年至2015年间黄渤海和东海小黄鱼的种群动力学模型,包含和不包含空间分层结构的两种贝叶斯模型被用于分析其种群动力学的大尺度空间异质性。本文分析了不同的假设,来研究小黄鱼种群动力学潜在的变化趋势。研究结果表明小黄鱼种群动力学特征具有明显的时间和空间变化。种群的增长速度从20世纪八十年代开始增加,而可捕系数从1981年到2015年增加了两倍多。与黄渤海亚种群相比,东海的小黄鱼亚种群生长速度更快,遭受的捕捞压力也更大。基于最大可持续产量MSY的参考点表明,无论是整个小黄鱼种群还是两个亚种群,近年来都有非常高的过度捕捞风险。因此我国小黄鱼的渔业管理急需更加保守的管理策略,同时考虑其地域差异。本文所用的方法可以应用于其他种类的资源评估和渔业管理,尤其是具有空间异质性和数据有限的种类。     

黄、渤海小黄鱼耳石元素指纹分析及其在种群补充群体识别中的应用

利用电感耦合等离子质谱ICP-MS元素分析方法,测定了黄、渤海125尾小黄鱼的耳石元素指纹图谱,共检测到Mg、Al、Mn、Cu、Zn、Sr、Ba、Ca等8种指纹元素。不同采样站位小黄鱼耳石元素含量均存在显著性差异,线性判别分析可以有效识别不同站位的小黄鱼群体,判别成功率为65%~96%,整体判别成功率为86%。基于耳石元素指纹图谱特征进行聚类分析,可以将黄、渤海小黄鱼早期补充群体划分为渤海种群、黄海中部种群和南黄海种群,其中黄海中部种群站位交叉明显。     

基于Tweedie-GAM模型研究海州湾小黄鱼资源丰度与栖息环境的关系

本研究根据2011年及2013—2016年春季和秋季在海州湾及其邻近海域进行的底拖网调查数据,结合同步采集的底层海水温度、底层海水盐度、水深、底质类型,以及脊腹褐虾(Crangon affinis)、细螯虾(Leptochela gracilis)、鳀(Engraulis japonicus)、赤鼻棱鳀(Thrissa kammalensis)等小黄鱼(Larimichthys polyactis)主要饵料生物的资源丰度数据,采用条件数κ和方差膨胀因子(VIF)度量多重共线性的程度,选取关键环境因子,再应用基于Tweedie分布的广义可加模型(GAM)研究不同季节和不同生长阶段的小黄鱼资源丰度与环境因子的关系。多重共线性的检验表明,所有初始变量之间没有显著的多重共线性,均可作为解释变量代入模型。结果表明:不同季节和生长阶段,影响小黄鱼资源分布的主要因子及其偏差解释率各不相同,各变量所对应的适宜范围也不同。例如:影响春季小黄鱼幼体资源分布的主要因子有底层海水温度、底层海水盐度、水深和脊腹褐虾的分布,其中偏差解释率最大的因子为水深(16.09%);而影响春季成体资源分布的因子为底层海水温度、底层海水盐度、水深及脊腹褐虾和鳀的分布,其中偏差解释率最大的因子为底层海水盐度(13.56%)。本研究表明,海州湾及其邻近海域不同季节和不同生长阶段小黄鱼的资源分布与其自身的生态习性、海洋环境以及饵料生物的分布密切相关。     

应用模糊数学方法对厦门近海大黄鱼生殖群体渔获年龄组成低龄化的分析

本文应用模糊数学方法分析了厦门海区大黄鱼生殖群体的渔获年龄组成,计算了1980—1984年厦门海区大黄鱼的低龄度。结果表明:该海区大黄鱼群体资源正处于加剧衰退阶段,必须限制大机围和流钓等在捕捞期限内的船数投入。