【作者】 卞晓东；

【导师】 张秀梅；

【作者基本信息】 中国海洋大学 ， 增殖养殖工程， 2010， 博士

【摘要】 本文主要从探索鱼卵种类鉴别方法,鱼类早期发育生物学特征及其环境影响因子,鱼卵、仔稚鱼海域生态调查三方面,开展了鱼卵、仔稚鱼生物生态学研究。论文绪论部分综述了鱼卵种类鉴别方法、鱼类早期发育特征及其环境影响因子、鱼卵、仔稚鱼生态调查等诸方面研究进展。论文第一部分：鱼卵种类鉴别方法探索研究。主要研究了四种鲆鲽类鱼卵受精前后形态特征变化,并归纳了可用于鱼卵种类鉴别和系统发生研究的主要形态特征；同时以自然海区采集的沙氏下鱵鱼Hyporhamphus sajori卵为研究对象,探索了运用光学显微镜、扫描电镜和遗传学手段来准确鉴别鱼卵种类的方法。论文第二部分：鱼类早期发育生物学和实验生态学研究。主要研究了北太平洋亚寒带海域关键种大头鳕Jadus macrocephalus胚胎和卵黄囊仔鱼发育的生物学特征和主要环境因子对其发育的影响；在此基础上初步探讨了造成大头鳕胚胎死亡原因,以及胚胎发育过程中鱼卵密度及其粘性的动态变化、鱼卵异率孵化的生态学意义；同时,探讨了大头鳕胚胎及卵黄囊仔鱼发育生物学特性及其在鳕属鱼类系统发生研究中的应用。论文第三部分：鱼卵、仔稚鱼生态调查研究。采用鱼卵、仔稚鱼生态调查方法,调查了2007年春、夏季黄河口海区鱼类浮游生物的种类组成和数量分布,并初步分析了环境因子对其种类组成及数量分布的影响。主要研究结果如下：一、鱼卵种类鉴别方法研究1、四种鲆鲽类未受精卵与受精卵的形态学比较研究借助光学显微镜和扫描电镜观察方法,观察并测量了四种具有较高经济价值分批产卵型鲆鲽鱼类,星突江鲽Platichthys stellatus、圆斑星鲽Verasper variegates、大菱鲆Scophthalmus maximus及褐牙鲆Paralichthys olivaceus未受精与受精卵的形状及卵膜结构。首先,比较了同种受精前后处在不同发育期鱼卵的形态特征,以期揭示受精前后鱼卵卵膜及受精孔区变化；其次用方差分析(ANOVA)及欧氏聚类(Hierarchical cluster)方法分析了四种鲆鲽类未受精成熟卵卵膜及受精孔区的结构,以期为四种鲆鲽类鱼卵的形态分类及系统发生研究积累基础资料。研究结果显示：同种鱼卵在受精前后卵膜及受精孔区分别呈现不同形态特征。4种鱼卵受精后卵膜变得平整,且为防止多精授精,均具有受精后受精孔阻塞现象。星突江鲽、褐牙鲆、大菱鲆鱼卵均具无凹陷长孔道Ⅲ型受精孔,而与星突江鲽属于同一亚科的圆斑星鲽鱼卵具有浅凹陷长孔道的Ⅱ型受精孔。鱼卵卵膜的亚显微结构如壁孔大小及密度,卵径大小等特征均能为鱼卵分类鉴定和系统发生研究提供有用的数据资料,但受精孔区的结构是最主要的形态分类特征。2、沙氏下鱵鱼卵的形态学及遗传学鉴别研究利用光学显微镜、扫描电镜和遗传学方法开展了采自南黄海海区(33°49’N,122°10’E)附着在海藻上的鱼卵种类的综合鉴别研究。在光学显微镜下：卵呈微扁圆形,卵径1.95-2.38mm粘着沉性；卵黄间隙较窄,卵黄囊呈乳白色,无龟裂；卵膜平滑,在其表面有5-7根细长角质管状卵膜丝；多油球数不定(4-145),油球径0.05-0.50mm球在卵黄囊中的位置随不同的发育时期而不断发生变化；胚体处在不同的发育阶段,其特征符合颌针鱼目鱼卵的特征。在扫描电镜(SEM)下观察：鱼卵受精孔明显,位于动物极的卵膜丝之间,外缘孔径12.3μm卵膜壁孔不明显,在卵膜表面有大量颗粒状突起,密度约为50个/100μm2。遗传学分析结果显示：鱼卵与沙氏下鱵鱼mtDNA Cyt b基因片段序列之间无差异,遗传距离为0,而与其它颌针鱼目鱼类序列间差异达18.72-21.3%,遗传距离在21.9-26.4%之间。NJ分子系统树的聚类结果也显示鱼卵与沙氏下鱵鱼序列聚为一支,他们共享一个单倍型,而与其它颌针鱼目鱼类序列分为两大支,其亲缘关系较远。进化速率较快的控制区片段序列的分析结果也显示鱼卵与沙氏下鱵鱼片段序列间遗传距离仅为0-0.7%,两者差异应为种内水平的遗传分化。以上分析结果表明该鱼卵为沙氏下鱵鱼卵。二、鱼类早期发育生物学和实验生态学研究1、大头鳕胚胎发育的生物学研究实验室内利用显微镜和显微数码摄像系统,通过电脑活体观察测量拍摄大头鳕受精卵胚胎发育和初孵仔鱼的形态特征,详细描述记录其发育过程和时间,并利用斯托科斯定律(Stokes’law)对大头鳕卵子以发育天数为单位进行活体密度测定。此外,利用扫描电镜观察了大头鳕7个胚胎发育期受精孔及卵膜的形态结构。大头鳕产沉性带微弱粘性卵子,无油球,未受精卵径0.95-1.08mm,密度为1.0422±0.001 g/cm3,卵膜表面具有弱的网状纹理。水温6.30±1.24℃、盐度34 psu受精后约2 hpf (hours post fertilization)胚盘形成,23 hpf进入囊胚期,38 hpf后进入胞胚期且卵子间粘性消失,52 hpf后进入原肠胚,196 hpf左右进入胚体器官分化期,228 hpf左右尾部游离,252 hpf后心跳开始,胚体搐动,296 hpf开始孵化,330.56 hpf时50%孵化。受精后大头鳕卵子的卵径与密度处于动态变化之中,卵径随胚胎发育呈逐渐上升趋势,密度则呈逐渐降低趋势；50%孵化时卵径为1.09±0.02mm度变为1.0395±0.001 g/cm3。孵化后20d,仔鱼卵黄吸收完毕。亚显微观察显示,大头鳕具有深凹陷,短孔道的Ⅰ型受精孔；未受精时精孔管开放,精孔管径3.28±0.55μm,受精孔前庭外缘径18.13±2.03μm、内缘径10.22±3.07μm,卵膜具有六角形网纹且褶皱明显,卵膜壁孔间距为1.95±0.29 gm。受精后,卵子精孔管被卵周液分泌物阻塞,卵膜褶皱逐渐消失但整个卵膜逐渐变得粗糙；在胚胎发育过程中,受精孔的大小、形状及卵膜壁孔间距也处于动态变化之中；2细胞期受精孔前庭径和卵膜壁孔间距最大,杆状细菌在原口关闭期及胚体包卵5/8期布满受精孔前庭及卵膜,胚体包卵5/8期时整个受精孔已经完全塌陷。大头鳕卵子粘性、卵径和密度的动态变化也与整个胚胎发育过程相关联,该特性对提高卵子受精率及卵子在海底正常发育及散布具有重要生态学意义；此外,在整个胚胎发育过程中卵子受精孔与卵膜结构也处于动态变化之中,这对防止大头鳕胚胎在较长发育期内免遭其他微生物及病菌侵袭具有重要的生物生态学意义。2、温度对大头鳕早期发育影响的研究实验室内研究了不同温度对日本陆奥湾海域大头鳕受精卵发育速率、日死亡率、孵化率及初孵仔鱼形态特征的影响。人工受精方法获取受精卵,在水温0℃、1℃、2℃、4℃、6℃、8℃、10℃、12℃,正常海水盐度34 psu,光周期11L：13D的条件下进行孵化。据不同孵化温度下受精卵各发育期的中点时间,利用最小2乘法非线性多项式回归拟合曲线,研究孵化温度对胚胎发育速率和各发育阶段持续时间的影响。在各检测温度中,除0℃无受精卵孵化外,其余各温度下受精卵均能正常发育至孵化,且温度4-8℃时正常发育至孵化的比率最高。大头鳕受精卵死亡率最高的关键期从原肠初期一直持续到原孔关闭期。受精卵发育速率与孵化温度呈正相关,其达到特定发育阶段所需时间与温度呈负相关。受精卵孵化期、50%孵化时间和孵化终点时间与孵化温度呈指数函数关系。1℃水温条件下,50%孵化所需时间为817.87h,12℃仅需217.9 h。初孵仔鱼平均体长和卵黄贮存量与孵化温度呈二次曲线相关。即使在相同孵化条件下,大头鳕受精卵异率孵化现象明显,各孵化温度下早期孵化仔鱼体长较短但残留卵黄囊较多,而后期孵化仔鱼体长较长但残存卵黄囊较少。综上,在自然水域中大头鳕受精卵发育对温度较敏感；适温范围内受精卵发育速率、存活率、孵化率及初孵仔鱼形态特征受温度变化影响显著。由此,海水温度的时空异质性明显影响自然水域大头鳕沉性卵的发育及其仔鱼散布的潜能,受精卵的异率孵化被认为是其应对这种风险的一种进化策略。3、温、盐度对大头鳕胚胎和卵黄囊仔鱼发育影响的研究实验室内研究了不同温、盐度对大头鳕受精卵及卵黄囊仔鱼发育的影响。1)受精卵发育期。人工采集实验室内暂养成鱼精卵并授精获取受精卵。受精卵分别置于9个温度梯度、5个盐度梯度组合的135(9×5×3)个有机塑料培养皿中进行孵化。孵化光照条件为11L：13D。分别检测大头鳕受精卵的孵化时间,孵化率及初孵仔鱼形态特征。2)初孵仔鱼培育实验。为研究大头鳕受精卵孵化后初孵仔鱼由海底相对稳定环境上浮至环境温度多变的表层或散布至不同水团后的存活状态,在一个9×5×3温盐度全因子实验中(温盐度同受精卵孵化实验)分别研究了孵化水温6℃、盐度34 psu条件下初孵仔鱼自孵化后在饥饿状态中持续至死亡的时间变化。研究结果显示,大头鳕受精卵在温度4℃和6℃下,各盐度的孵化率均较高(53.67-73.66%)；温度14℃已经超出了大头鳕受精卵的耐温极限；在接近大头鳕受精卵耐温极限时,各温度的孵化率受盐度影响显著。尽管0℃时在盐度30和34psu下没有受精卵正常孵化,但较低盐度的15-25 psu处理组仍有受精卵正常孵化；较高孵化水温下低盐处理组受精卵孵化率显著降低。上述现象体现了低温低盐对受精卵孵化率的增效作用,同时也体现了高温低盐的限制性作用。温度对大头鳕受精卵发育速率影响较显著,但不同水温条件下盐度对受精卵发育时间影响不显著。在各孵化盐度下各温度处理组大头鳕初孵仔鱼的标准体长与孵化水温成凸型二次曲线相关；但在各监测温度条件下不同盐度对初孵仔鱼形态特征影响不显著。同时发现,初孵仔鱼耐温、盐范围远超过受精卵,多数初孵仔鱼在各监测的温、盐度范围内都能存活直至卵黄耗尽因饥饿而死亡。各盐度下饥条件下饥饿未投喂仔鱼50%存活时间随着温度的升高显著降低,其相关性可用有效指数函数公式来描述。陆奥湾大头鳕卵子与仔鱼多分布在水温4℃和6℃的自然水域,室内试验证实,该水温范围内受精卵孵化率最高、耐盐范围最广,初孵仔鱼的标准体长最大,且饥饿仔鱼50%的存活时间适中,适合大头鳕卵子孵化和仔鱼发育。三、鱼卵、仔稚鱼生态调查研究1、2007年春、夏季黄河口海域鱼卵、仔稚鱼种类组成与数量分布2007年春季和夏季,利用浅水Ⅰ型浮游生物水平和垂直拖网对黄河口海域鱼卵、仔稚鱼种类组成与数量分布进行了调查。春季和夏季分别设置19个(6个断面)相同的调查站位。每站表层水平拖网10 min,拖网速度为2.0 n mile/h;垂直拖网由底到表,拖网速度约0.5 m/s。调查结果表明：春季和夏季共采集鱼卵7661粒、仔稚鱼70尾,共18种,能鉴定到种的有17种,隶属于5目12科16属,其中1种虾虎鱼类的稚鱼仅能鉴别到科的水平。优势种为斑鰶(Konosirus punctatus)、油魣(Sphyraena pinguis)、短吻红舌鳎(Cynoglossus joyneri)。春季的水平和垂直拖网分别采集6932粒鱼卵、6尾仔稚鱼和11粒鱼卵、0尾仔稚鱼。鱼卵、仔稚鱼的出现频率分别为84.21%、10.53%和26.32%、0%,平均密度分别为364.84粒/网、0.32尾/网和0.59粒/m3、0尾/m3；夏季的水平和垂直拖网分别采集658粒鱼卵、57尾仔稚鱼和60粒鱼卵、7尾仔稚鱼,鱼卵、仔稚鱼的出现频率分别为84.21%、63.16%和31.58%、15.79%,平均密度分别为34.63粒/网、3尾/网和1.85粒/m3、0.22尾/m3。分析结果表明：黄河口海域鱼卵、仔稚鱼种类季节更替明显分成春夏季—夏季两种生态类型,种类更替率高达83.33％；河口南部海域鱼卵和仔稚鱼的群落结构相对较稳定,优势种突出,优势度较大,物种多样性水平与种间分布均匀度高于北部海域。上述规律符合该海域的水文地理学特性和硬骨鱼类的繁殖生物学规律。此外本研究分别对春季和夏季鱼卵、仔稚鱼的数量分布以及斑鰶、油魣、短吻红舌鳎等优势种类鱼卵的数量分布绘制了密度等值分布图。与1982-1983、1984-1985、1992-1993年同期调查结果比较发现,2007年春季和夏季黄河口海域鱼卵、仔稚鱼的种类组成与数量分布发生了显著变化,分析认为,在渔业捕捞压力和环境条件变化的双重扰动下,黄河口生态系统中鱼类资源的种群交替和群落结构发生了很大变化,从而导致资源补充群体也随之改变。更多还原

【Abstract】 Fish eggs and larvae contain much important information of fish life history and fish ecology. So they play an important role in environmental impact assessment, fishery stock analysis, fish propagation, seeding release, and fish farming. The objectives of this study were to establish a standard procedure for identifying fish eggs, understand the biological characteristics of early development of fishes and the factors that affect its development, carry out ecological investigation of ichthyoplankton. First, this paper reviews the research advances at home and abroad on the identification methods of fish eggs, the main developmental events occurred at each stage of early development, factors that have been proposed to alter early development, and the ecological investigation on fish eggs and larvae. Section A, identification methods of fish eggs. The shape and surface structures of unfertilized mature and fertilized developing pelagic eggs of four flounders were studied, characters differences observed that would be useful for species identification and phylogenetic inference were summarized; and Japanese halfbeak Hyporhamphus sajori eggs, which collected in field, were used to establish a standard procedure for identifying fish eggs by using the light microscope, scanning electronic microscopy, and genetic analysis simultaneously. Section B, biological and experimental ecology studies of early development of fish. The embryo and yolk sac larvae of Pacific cod Gadus macrocephalus, one of the key species in the subarctic Pacific, were studied. We focused on the main developmental events occurred at each stage and the effects of temperature or temperature and salinity combinations on early stage of Pacific cod. Based on these studies, we aim at exploring the possibility causes of mortality; the using of developmental characters and their implication in phylogenic determination of the Gudas species; bio-ecological implications of the dynamic process of the adhesive characteristics, the diameters and mass density; also the ecological implications of hatching asynchronously were determined. Section C, ichthyoplankton surveys. The categories composition and distributional patterns of ichthyoplankton surveys were carried out in waters over the Yellow River estuary during spring and summer 2007, the preliminary analysis of environmental factors on category composition and distribution patterns of ichthyoplankton were discussed.Section A, identification methods of fish eggs1. Morphology of the unfertilized mature and fertilized developing marine pelagic eggs in four multiple spawning floundersStarry flounder Platichthys stellatus, spotted halibut Verasper variegates, turbot Scophthalmus maximus, and Japanese flounder Paralichthys olivaceus are four commercially cultivated multiple spawning flounders that spawn pelagic eggs. Through appropriate light and scanning electron microscope processing, the shape and surface structures (such as micropyle, pores, pore density, and paten) of unfertilized mature and fertilized developing eggs of the four species were observed and measured. First, individual or intraspecific comparisons in the surface structures of eggs at different developmental stages were made. Second, interspecific differences in the four species at the same developmental stage of unfertilized mature eggs were statistically computed and analyzed through one-way analysis of variance and hierarchical cluster. Eggs of the same species collected at different stages of development tend to be different in morphology. Smoothing of the convoluted egg envelope surface and closure of the micropyle to serve as a final step of the polyspermy-preventing reaction are common after fertilization. Based on detailed morphology of micropyle of just-mature fertilizable eggs, turbot, starry flounder, and Japanese flounder each has a micropyle with a long canal but no distinct micropylar vestibule, type III of Riehl and Gotting (1974). In contrast, spotted halibut owns a micropyle with a distinct flat micropylar vestibule and a long canal, type II. Ultrastructure of the envelope surface, size and distribution density of pores, and size of eggs are also useful characters for distinguishing and phylogenetic analysis among the four species. However, ultrastructural features of the micropyle are the most important envelope surface characters for egg identification.2. Morphological and genetic identification of Japanese halfbeak Hyporhamphus sajori eggsA larger number of fertilized eggs with attaching filaments attached to some seaweeds were collected in the southern Yellow Sea (33°49’N,122°10’E).Inorder to make an accurate identification of the fish eggs, light microscope, scanning electronic microscopy (SEM), and genetic analysis were used. Under light microscope, the egg is an oblated and agglutinated demersal with a narrow perivitelline space; eggs ranged in diameter from 1.95 to 2.38 mm with a mean of 2.18±0.03 mm; their membrane are smooth and they have 5 to 7 cannular keratose egg-filaments; the oil globules are multiple, ranged in diameter from 0.05 to 0.50 mm and in number from 7 to 145 with a mean of 28±2, the position of them migrate during embryonic development; the yolks are ivory-white with no segments, ranged in diameter from 1.00 to 2.30 mm with a mean of 1.90±0.03 mm; the development phases of the embryo are variable. So they were identified as the eggs of one Beloniformes. Under SEM:the egg’s micropyle is apparent, it lines in the middle of the attaching filaments and the outer diameter of it is about 12.3μm; the pores on the envelope are unapparent, but there are many grain substances on it, with the density was about 50 pieces/100μm2. The result of genetic analysis conveyed that in partial sequences of mtDNA Cyt b gene there were no variable sites between the eggs and Japanese halfbeak, and the genetic distance between them was 0, however, many variable sites between the eggs and the other fishes of Beloniformes were exised, the variable rate was 18.72-21.3%, and the genetic distance between them were 21.9-26.4%. The result of Neighbor-joining (NJ) molecular phylogenetic tree also indicated that the eggs and the Japanese halfbeak were assembled at the same embranchment, they shared one haplotype, but the eggs were assembled at different embranchments with the other species of Beloniformes so the fish eggs were alienated from them. The validity of test results by using mtDNA Cyt b gene has been examined with a 443 bp segment of mtDNA control region, the result conveyed that only 0-0.7% in the genetic distance between the fish eggs and Japanese halfbeak. It is also the diversity within specie. Based on the results above, it is suggested that the fish eggs to be Japanese halfbeak.Section B, biological and experimental ecology studies of early development of fish1. The biological study on the embryonic development of Pacific cod Gadus macrocephalusIn order to know the embryonic development pattern of Pacific cod Gadus macrocephalus, the morphological characteristics of fertilized eggs and larvae were observed and recorded by Nikon SMZ1500 photomicroscope equipped with amicrometer ocular lens at the laboratory from January to March,2008. Moreover the mass density of Pacific cod embryos at each day of development was determined by using the Stokes’law equation and the fine structures of both the micropyle and the egg envelope surface of 7 development stages were studied with scanning electron microscopy. Eggs of Pacific cod were spherical, slightly adhesive, and semidemersal with none of oil globule in diameter of 0.95-1.08mm, mass density of 1.0422±0.001g/cm3 at the time spawning, with weak striations under light micropyle. With the incubated temperature 6.30±1.24℃, salinity 34psu, the blastoderm formed at 2 hours post fertilization (hpf), blastula stage at 23hpf, blastodermal cap stage with the adhesive characteristics lost at 38hpf, early germ ring stage at 52hpf; the segmentation period began at 196hpf, the tail separated at 228hpf, heart beat and body shrink at 252hpf. Hatching occurred at 330.56hpf, after which most of the individuals remained motionless at the water’s bottom. The diameter and the mass density of the Pacific cod eggs were in dynamic process over embryonic development. The diameters of the eggs rise during the embryonic development; however, the mass density of eggs was downtrend. The larvae were incubated until full use of the yolk sac (20 days post hatching). Under SEM, the micropyles of Pacific cod eggs belong to type I with deep micropylar vestibule and short canal. In unfertilized ones, the micropylar canal is in diameter of 3.28±0.55μm, the outer diameter of the micropylar vestibule is 18.13±2.03μm and the inner one is 10.22±3.07μm; the outer envelope surface has numerous hexagonal reticulated patterns and is characterized by a crisscross pattern of depressions in distance 1.95±0.29μm between the pore canals on the envelope. After fertilization the micropylar canal was blocked by secretions of the perivitelline, the wrinkles on the outer surface of the envelope were indistinct and the whole surface becomes roughness. The shape of the micropyle and the distance between the pore canals on the envelope were in the dynamic process along with the development stage forward. The maximum diameter of the micropylar vestibule and the maximum distance between the pore canals on the envelope occurred at the 2 cell stage. Numerous bacilli deposited at the micropyle and the outer surface of envelope at the blastopore closure and embryo 5/8 around yolk stages; the micropyle was whole deformed at embryo 5/8 around yolk stage. The dynamic process of the adhesive characteristics, the diameters and mass density were associated with the development process of the embryo and it has bio-ecological significance for increasing the fertilization rate and influencing the dispersal potential of the eggs in the field. So does the dynamic process of the micropyle, the ultrastructure changes on the envelope surface and it has bio-ecological significance for protecting the Pacific cod embryo in the long incubation period from microorganism infections. 2. Effects of temperature on embryonic development of the Pacific cod Gadus macrocephalusLaboratory experiments were conducted to determine the effect of water temperature on development, survival and hatching of Pacific cod Gadus macrocephalus eggs from the Mutsu Bay. The eggs were reared at 0℃,1℃,2℃,4℃,6℃,8℃,10℃,12℃and under a diel light cycle (13 h light,11 h dark) at the salinity of 34psu (normal sea water). A piece-wise least squares nonlinear regression model with midpoints of each stage describes the relation between time to each stage of development and incubation temperatures. Development was normal for all temperatures except 0℃, with no eggs hatched. Eggs survived to hatching and produced viable embryos at the highest temperature range 4-8℃, reflecting this species’winter spawning season. "Critical periods" of high mortality during the egg development did occur through the gastrula stage to blastopore closure at each temperature checked. The developmental rate was sequential with and directly proportional to incubation temperature while the time spent in each developmental stage was inversely proportional to temperature. An exponential relationship between times, over which initiated hatched,50% hatched and eggs all hatched, and temperature were found. Time to 50% hatch ranged from 817.87 h at 1℃to 217.9h at 12℃. Fish larvae hatch asynchronously from egg batches despite experiencing a common environment during their development. The combined observations of recent studies suggest a dome-shaped relationship between size at hatch, yolk storage and incubation temperature. At all temperatures, early hatching larvae were smaller but had more yolk storage; late-hatching larvae were generally larger and had smaller yolk sacs than early hatched larvae. Together these data suggest that variations in water temperatures within an ecological range can markedly influence development rates, survival and hatching of the eggs also the stage at hatch larvae of Pacific cod. Hence, temporal and spatial heterogeneity in sea temperatures should be considered along with hydrodynamic conditions in estimating chances for survival and hatching of demersal Pacific cod eggs and the dispersal potential of Pacific cod larval in the field. Hatching asynchronously is considered to be an evolutionary strategy of "bet hedging" against such dynamic variation in the Pacific cod.3. Some effects of temperature and salinity on laboratory-reared eggs and yolk sac larvae of Pacific cod Gadus macrocephalusThe combined effects of temperature and salinity on eggs and yolk sac larvae of Pacific cod Gadus macrocephalus were examined under controlled laboratory conditions. Two developmental phases were investigated:1) fertilization to hatch. Artificially fertilized eggs, obtained by induced spawning of captive broodstock at 6℃and 34psu, salinity, were stocked (100 eggs/piece) into one hundred and thirty five shallow sterile plastic petri dishes at combinational of constant temperatures (0,1,2,4, 6,8,10,12,14℃) and salinities(15,20,25,30,34psu). Photoperiod was 11 h light:13 h dark. Responses of Pacific cod eggs were measured in terms of incubation period, hatchability and morphological characters at stage of hatching larvae.2) hatch through yolk sac absorption. Time to 50% survival of the newly hatching unfed larvae (incubation at 6℃,34psu) were studied in a 9×5 (temperature×salinity, the same as the egg incubation experiment) array of treatments to determine how environment will influence the survival rate when they were emergence and dispersed into various water mass and the fluctuate sea surface at the time of hatching. The results indicated that temperature 14℃were beyond the tolerance limits for normal embryonic development; hatching rate was moderate to high (53.67-73.66%) at 4℃and 6℃in all salinities. Viable hatch was significantly influenced by the effect of salinity as the upper and lower thermal limits were approached. Though there was no eggs hatching at salinity of 30psu and 34 psu in 0℃, when the salinity was lower (15,20,25psu) there would still be some hatching; hatching success was moderate under temperature range 8-10℃at the high salinity but the hatching rate was markedly reduced at low salinity 15psu. This indicated that low-temperature-low-salinity synergism, as well as high-temperature-low-salinity inhibitory effects. While data on developmental rates and as influenced by temperature are presented, no significant differences in temperature influences on developmental times between the tested salinities were found. As expected, dome-shaped relationship between size of stage at hatch larvae and incubation temperature at each salinity, no such affecting existed when concerned to the affecting of salinity at each tested temperature. Larvae were more tolerant to extreme high temperatures than were newly fertilized eggs, most larval could survival when they were dispersed into various temperature and salinity combination till the yolksac is exhausted. Average time from hatching to 50% survival in unfed larvae was markedly reduced along with the increased temperature, ranged from 39 days in 0℃to 6 days in 14℃, and the influence could be described in all cases by a power function. The temperature of 4℃and 6℃, possibly associated with peak abundance of eggs and larvae in nature, is optimal for culture of Mutsu Bay embryos and yolk sac larvae. At this two temperatures, hatchability, size of stage of hatch larvae, tolerance to reduced salinities are maximized and time to 50% survival of the unfed larvae was moderate.Section C, ichthyoplankton surveys1. Category composition and distribution patterns of ichthyoplankton in the Yellow River estuary during spring and summer 2007The categories composition and distributional patterns of ichthyoplankton surveys were carried out in waters over the Yellow River estuary during spring and summer 2007. In the investigated area where were 119°05’-119°31’E,37°35’-37°57’N,19 fixed sampling stations (6 transects) were set up respectively. The distributional patterns of ichthyoplankton were investigated by horizontal tows associated with vertical tows with a zooplankton net (mouth diameter 50 cm,140 cm in length, mesh size 0.50 mm). The horizontal tows were of 5 min duration at a speed of 2.0 nmile/h on the sea surface, while the vertical tows were from surface to near-bottom at a speed of 0.5 m/s at each sampling station. According to the investigation results,7661 eggs and 70 larvae of fishes of 18 taxa were collected during spring and summer 2007, of which,17 taxa were identified as species, belonging to 16 genera,12 families and 5 orders,1 taxa of gobiidae fishes as only family level. The preponderant species were Konosirus punctatus, Sphyraena pinguis, Cynoglossus joyneri. During late spring, a total of 6943 eggs and 6 larvae fishes were captured respectively. In the horizontal tows,6932 eggs and 6 larvae were captured, and in the vertical tows,11 eggs and 0 larvae were captured. The occurrence frequencies of eggs and larvae were 84.21% and 10.53% in the horizontal tows,26.32% and 0% in the vertical tows, respectively. The average density of eggs and larvae were 364.84 ind/net,0.32 ind/net respectively in the horizontal tows, and 0.59 ind/m3 and 0 ind/m3 respectively in the vertical tows. During summer, total of 718 eggs and 64 larvae of fishes were captured respectively. In the horizontal tows 658 eggs and 57 larvae were captured, and in the vertical tows,60 eggs and 7 larvae were captured, respectively. The occurrence frequencies of eggs and larvae were 84.21% and 63.16% respectively in the horizontal tows,31.58% and 15.79% in the vertical tows. The average density of eggs and larvae were 34.63ind/net and 3ind/net respectively in the horizontal tows,1.85 ind/m3 and 0.22 ind/m3 respectively in vertical tows. Further analyzing showed that two seasonal ecological groups could be distinguished. A pronounced seasonal succession from spring-summer group to summer group regarding the category composition of ichthyoplankton can be observed throughout the two cruises. The succession rate was about 83.33%. The distribution patterns of species were different on account of different waters environmental conditions. In waters of southern Yellow River estuary the community structure of ichthyoplankton was relatively stable, the dominant species was evident and the dominance value was high. The diversity index of species and the uniformity of interspecific distribution in waters of southern Yellow River estuary was higher than that of in waters of northern Yellow River estuary. The variability in the spatio-temporal distribution patterns of ichthyoplankton may result from the interaction of hydrological and biological factors at different scales. The equivalency density distribution of ichthyoplankton and fish eggs of preponderant species, such as Konosirus punctatus, Sphyraena pinguis, Cynoglossus joyneri were drawn. The category composition and distribution patterns of ichthyoplankton in the Yellow River estuary changed evidently from 1982 to 2007, it was in correspondence with the alternation of fishery resources strongly affected by double disturbances of overfishing and ecological environment changes.更多还原