鲐鱼幼鱼耳石日轮的初步观察与研究

对长江口海区鲐鱼幼鱼耳石标本的扫描电镜观察发现，鲐鱼耳石上存在着宽度为数微米到十几微米的细微轮纹，通过对其中３尾鲐鱼的耳石不同放大倍数图像的拍摄，再根据照片对耳石上轮纹和耳石轮纹辐射半径的测量、计数和计算，得出３尾鲐鱼耳石轮纹的平均宽度分别为９．５２、８．５２和８．５７微米，耳石轮纹辐射半径分别为１２６２．２、１１６４．８和１１８７．５微米，由此计算得出的耳石轮纹数分别为１３３、１３７和１３９轮。     

Gonadal morphogenesis and sex differentiation in cultured chub mackerel,Scomber japonicus

The timing of primordial germ‐cell (PGC) migration with regard to the gonadal anlagen, gonad formation and sex differentiation was examined histologically in the chub mackerel (Scomber japonicus) at 5–190 days post hatching (dph). At 5 dph, PGCs appeared on the peritoneal epithelium surface or in the mesentery, on the dorsal side of the abdominal cavity. By 10 dph, stromal cells around the PGCs proliferated. The gonadal primordium was formed by 15 dph. The gonadosomatic index was 0.01% at 30 dph and increased thereafter (0.32% in females and 0.04% in males at 160 dph). Ovarian differentiation occurred at 30–40 dph, indicated by ovarian cavity formation (elongation and fusion of the upper and lower ovarian edges). Meiosis was subsequently initiated. A few meiotic oocytes surrounded the cavity at 50 dph; most were in the perinucleolus stage at 60 dph and attained a diameter of 60–70 μm at 190 dph. Testicular differentiation occurred at 30 dph, indicated by the formation of the sperm duct primordium. Spermatogonia gradually proliferated, developing into spermatocytes at the chromatin–nucleolus stage (after 90 dph) and subsequently into spermatids and spermatozoa (160 dph). These data could aid the development of seeding and cell‐engineering technologies for scombrid fish.     

温台渔场日本鲭的繁殖生物学特征

利用2012年春季在温台渔场对日本鲭(Scomber japonicus)繁殖群体连续6批取样的生物学测定数据,对其繁殖生物学特征进行了研究。结果表明,叉长340 mm以下群体中,雌雄比基本符合1∶1的性比关系;叉长340 mm以上群体中,雌鱼显著多于雄鱼(P0.05)。GSI随时间的变化结果显示,温台渔场日本鲭的主要繁殖期为3月中旬至4月中旬;不同时间段的雌鱼和雄鱼GSI均总体表现为雌鱼大于雄鱼(P0.05)。不同性腺发育阶段的平均摄食强度总体表现为雄鱼大于雌鱼。不同性腺发育阶段的雌性和雄性的肝指数均雌性显著大于雄性(P0.05)。绝对繁殖力范围为44 017~734 684粒/尾,平均值为(173 867±15 719)粒/尾,优势组为(10~30)×104粒/尾,占70.37%;相对繁殖力范围为187~1 403粒/g,平均值为(538±31)粒/g,优势组为(390~700)粒/g,占66.67%。卵径范围为0.27~1.22 mm,平均值为(0.86±0.01)mm,优势组为0.7~1.1 mm。温台渔场日本鲭的绝对繁殖力低于黄海北部而高于台湾海峡,相对繁殖力高于历史水平,平均卵径小于20世纪80年代,雌雄鱼的最小性成熟叉长均有一定程度的降低。以上结果都说明日本鲭为应对高强度捕捞和环境胁迫压力而采取增加相对繁殖力、减小卵径、提早性成熟等繁殖策略来维持种群数量和保证种群的延续。     

黄海北部日本鲭繁殖生物学特征的年代际变化

根据1986年和2010年在黄海北部取样测定的日本鲭(Scomber japonicus)产卵群体基础生物学数据以及怀卵量计数结果, 对其繁殖生物学特征的年代际变化进行了研究。结果表明, 在日本鲭产卵群体基础生物学特征方面, 1986年的叉长、体质量、纯体质量和性腺重这4项基本生物学指标的范围和平均值均明显大于2010年, 年龄结构从1986年由1⁺~7⁺龄组成, 2⁺龄和3⁺龄为优势组, 改变为2010年由1⁺~3⁺龄组成, 2⁺龄为优势组。在性腺成熟度组成和性腺指数(GSI)方面, 2次采样均发现日本鲭雌鱼性腺成熟度以Ⅳ期和Ⅴ期为主; 开始排卵前, GSI随性腺成熟度的增加而增加; 相同叉长组而言, 2010年平均GSI较1986年呈现增加趋势。相同叉长组的繁殖力分析表明, 相对于1986年, 2010年体质量相对繁殖力升高了11.93%, 而绝对繁殖力则下降了18.45%。这些繁殖生物学特征的变化可能是由于日本鲭群体年龄结构简单化、个体小型化、生长速度加快等原因造成的。为了今后更好地保护并可持续利用日本鲭资源, 在现有的围网休渔制度的基础上, 建议在东黄海日本鲭各主要产卵场及其产卵期制定其他相应的保护措施, 以限制其他捕捞网具对该物种产卵群体的过度捕捞。

     

Temperature conditions in the Argentine chub mackerel (Scomber japonicus) fishing ground: implications for fishery management

We describe the seasonal migrations of Argentine chub mackerel ( Scomber japonicus ) into the fishing ground in relation to sea surface temperature conditions and analyse the temperature evolution during the fishing season on the basis of 1955–97 time-series. The upper temperature limit for the presence of schools was around 19°C. At higher values, most schools leave coastal waters (< 50 m) for the shelf. An inverse relationship was observed between catches per unit of effort (CPUE) of the inshore fishery and sea surface temperature. The highest standardized CPUE values corresponded to temperatures lower than 19°C. Above this temperature, the probability of obtaining a standardized CPUE higher than 1 was extremely low, and the standard deviations were minimal. The economic benefit from catches was also analysed through the different months of the fishing season. It was found that the mean benefit corresponding to temperatures lower than 19°C exceeded approximately 15 times that obtained at higher temperatures. A simple fishing strategy was proposed to the commercial fleet in order to improve the economic benefit of the catches. The migratory pattern followed by mackerel during the spawning period was also analysed in relationship to other environmental factors like food availability. Zooplankton composition, size structure and abundance in coastal and shelf waters are described, and their implications for feeding ecology of larvae and adults of the species are discussed.     

Environmental effects on recruitment and productivity of Japanese sardine Sardinops melanostictus and chub mackerel Scomber japonicus with recommendations for management

We compared a wide range of environmental data with measures of recruitment and stock production for Japanese sardine Sardinops melanostictus and chub mackerel Scomber japonicus to examine factors potentially responsible for fishery regimes (periods of high or low recruitment and productivity). Environmental factors fall into two groups based on principal component analyses. The first principal component group was determined by the Pacific Decadal Oscillation Index and was dominated by variables associated with the Southern Oscillation Index and Kuroshio Sverdrup transport. The second was led by the Arctic Oscillation and dominated by variables associated with Kuroshio geostrophic transport. Instantaneous surplus production rates (ISPR) and log recruitment residuals (LNRR) changed within several years of environmental regime shifts and then stabilized due, we hypothesize, to rapid changes in carrying capacity and relaxation of density dependent effects. Like ISPR, LNRR appears more useful than fluctuation in commercial catch data for identifying the onset of fishery regime shifts. The extended Ricker models indicate spawning stock biomass and sea surface temperatures (SST) affect recruitment of sardine while spawning stock biomass, SST and sardine biomass affect recruitment of chub mackerel. Environmental conditions were favorable for sardine during 1969–87 and unfavorable during 1951–67 and after 1988. There were apparent shifts from favorable to unfavorable conditions for chub mackerel during 1976–77 and 1985–88, and from unfavorable to favorable during 1969–70 and 1988–92. Environmental effects on recruitment and surplus production are important but fishing effects are also influential. For example, chub mackerel may have shifted into a new favorable fishery regime in 1992 if fishing mortality had been lower. We suggest that managers consider to shift fishing effort in response to the changing stock productivity, and protect strong year classes by which we may detect new favorable regimes.     

Changes in the expression of pituitary gonadotropin subunits during reproductive cycle of multiple spawning female chub mackerel Scomber japonicus

The endocrine regulation of reproduction in a multiple spawning fish with an asynchronous-type ovary remains largely unknown. The objectives of this study were to monitor changes in the mRNA expression of three gonadotropin (GtH) subunits (GPα, FSHβ, and LHβ) during the reproductive cycle of the female chub mackerel Scomber japonicus. Cloning and subsequent sequence analysis revealed that the cDNAs of chub mackerel GPα, FSHβ, and LHβ were 658, 535, and 599 nucleotides in length and encoded 117, 115, and 147 amino acids, respectively. We applied a quantitative real-time PCR assay to quantify the mRNA expression levels of these GtH subunits. During the seasonal reproductive cycle, FSHβ mRNA levels remained high during the vitellogenic stages, while GPα and LHβ mRNA levels peaked at the end of vitellogenesis. The expression of all three GtH subunits decreased during the post-spawning period. These results suggest that follicle-stimulating hormone (FSH) is involved in vitellogenesis, while luteinizing hormone (LH) functions during final oocyte maturation (FOM). Both GPα and FSHβ mRNA levels remained high during the FOM stages of the spawning cycle and increased further just after spawning. Thus, FSH synthesis may be strongly activated just after spawning to accelerate vitellogenesis in preparation for the next spawning. Alternatively, LHβ mRNA levels declined during hydration and then increased after ovulation. This study demonstrates that chub mackerel are a good model for investigating GtH functions in multiple spawning fish.     

东海日本鲭繁殖群体生物学特征的年代际变化

利用1960–2012年间3个时间段共1054尾东海日本鲭(Scomber japonicus)繁殖群体的基础生物学数据,对其群体组成、肥满度、性比、性成熟长度等繁殖特征的年代际变化进行了研究。结果表明,随着时间的推移,东海日本鲭繁殖群体的年龄结构和优势年龄组、肥满度指数、最小和平均性成熟长度都呈现出逐渐下降的趋势。各年代的性比均符合1∶1关系(P0.05),但呈现升高的趋势。与前2个年代相比,21世纪初期有大量1龄鱼加入繁殖群体,这有助于提高繁殖群体的数量。各年代的雌雄鱼性成熟长度之间无显著性差异(P0.05),但最小和平均性成熟长度均表现为雄鱼略大于雌鱼。面对近50年来不断增强的捕捞压力,日本鲭主要采取降低性成熟年龄、提高性腺指数、增加群体中的雌性比例、提高相对繁殖力和减小卵径等自身调节机制来保持种群的延续。针对上述日本鲭繁殖群体的生物学长期变化特征,为了保持该鱼类资源的种群平衡和渔业可持续利用,文章提出了3点渔业管理建议,分别是控制中上层渔业捕捞努力量并制定渔船及网具标准、在主要产卵场设立产卵亲体保护区及在幼鱼索饵场设立特殊禁渔期、针对日本鲭渔业实施TAC管理制度。     

Seasonal variation in quality and chemical composition of the muscles of the spotted mackerel Scomber australasicus and Pacific mackerel S. japonicus

Fisheries Science - The quality of fish muscles is known to vary with the season. The characterisation of such seasonal variations is important for the development of fish products of high...     

Stock size fluctuations in chub mackerel (Scomber japonicus) in the East China Sea and the Japan/East Sea

The stock size of chub mackerel (Scomber japonicus) in the East China Sea and the Japan/East Sea has shown a continuous decrease, with fluctuations, from 1975 to 1990. After a remarkable increase in 1992–96, the stock size fell to its lowest level in 1997–99. The spawning success (number of recruits/spawning biomass) fluctuates periodically with a period of several years, although there are no clear relationships between the spawning biomass and the number of recruits. Spawning success was inversely correlated with sea surface temperature (SST). On the contrary, the catch amount and the catch per unit effort (CPUE) of spotted mackerel (Scomber australasicus) has increased since 1997.     

东、黄海日本鲭种群鉴定和划分的研究进展

分布于东、黄海的日本鲭(Scomber japoncus)在我国海洋渔业中具有重要的地位,随着中韩、中日渔业协定的生效,开展日本鲭等重要经济鱼类的种群归属研究显得尤为重要。关于东、黄海日本鲭种群划分,20世纪中日两国学者利用标志放流和渔业调查数据分别进行了研判,但中日间以及国内对其种群划分存在不同见解。21世纪以来,中国一些研究者利用形态框架法和分子遗传学方法对前辈的种群划分进行了验证并提供了一些证据,但分析结果值得商榷。总结相关研究结果,多数中国学者将分布于东、黄海的日本鲭划分为东海西部种群、五岛西部种群和闽南—粤东地方种群,也有中国学者将其划分为东海群系和闽南—粤东地方种群;日本学者将分布于东海不同越冬场日本鲭归属为对马暖流群系,也有日本学者将分布于东、黄海和日本海西部的日本鲭划分为九州西部群系和东海西部群系。针对东、黄海日本鲭种群划分存在的不同观点,今后研究者应同时利用目前较为先进的、相对可操作的鱼类框架形态和分子遗传等判别技术,增加产卵场样本采集覆盖面,以获得判别东、黄海日本鲭种群相对最为科学的证据。     

基于Catch-MSY模型的西北太平洋日本鲭资源评估及敏感性分析

为了解日本鲭(Scomber japonicus)的资源状况,利用北太平洋渔业委员会(NPFC)统计的1995—2019年渔获量数据和生活史信息,基于Catch-MSY模型估算了西北太平洋日本鲭最大可持续产量(maximum sustainable yield, MSY),评价了渔业管理策略,同时对该模型开展了敏感性分析研究。根据不同模型参数先验分布、不同时间序列渔获量数据及过程误差设立了16个情景进行敏感性分析,考虑各因素对模型评估结果的影响。结果表明：1)基准方案情景S1A中,日本鲭MSY估计值为49.62×10⁴ t (38.72×10⁴ t～60.52×10⁴ t);情景S1B中,日本鲭MSY估计值为49.47×10⁴ t (38.51×10⁴ t～60.43×10⁴ t); 2)与参数内禀增长率r相比,环境容纳量K具有相对较窄的后验分布,lnK随着lnr的增加呈逐渐减小的趋势,MSY的值与r先验分布的下限呈正相关关系;3) MSY值的估算结果对渔...     

Effect of low salinity on the expression profile of Na+/K+‐ATPase and the growth of juvenile chub mackerel (Scomber japonicus Houttuyn)

Chub mackerel (Scomber japonicus Houttuyn) is one of the most commercially important scombroid fish used as a food resource. Recently, there has been a demand for efficient rearing methods of this fish for a full‐life cycle aquaculture. In the present study, we evaluated the physiological responses in the juvenile S. japonicus to different ambient salinities. A significantly higher gain of the body mass was observed in the juveniles reared in 24 g/L and 13 g/L seawater than in those reared in natural seawater (34 g/L) within 40 days of the experimental period without affecting mortality. A principal enzyme for osmoregulation, Na⁺/K⁺‐ATPase, was expressed in the ionocytes located in the gill filaments of the juveniles. The number and the cell size of ionocytes and the enzymatic activity of Na⁺/K⁺‐ATPase in the gills decreased within 10 days after the low‐salinity challenge, which implies the reduction of the energy‐consuming active ion secretion under the low‐salinity environment. The physiological capacity for adaptation to low‐salinity seawater in chub mackerel could be basic knowledge to carry out culturing of these fish in coastal sea pens where ambient salinity fluctuates. The improvement of the growth performance by rearing in low‐salinity seawater will contribute to the efficient production of the seed juveniles for aquaculture.     

Shading of net cage is an effective control measure against skin fluke Neobenedenia girellae infection in chub mackerel Scomber japonicus

The skin fluke Neobenedenia girellae has become a serious problem in Japan since the 1990s. Present control methods focus on the removal of the attached parasite and these post-infection treatments are often labor intensive, time consuming, and/or stressful to fish. Chub mackerel Scomber japonicus are highly susceptible to N. girellae. However, because of their sensitive nature, bath treatments may cause mortality. In this study, we investigated the efficacy of cage shading to reduce skin fluke infection and the frequency of conventional post-infection treatments. Juvenile mackerel were reared in cages with or without shade for 3 months and their skin fluke infections were monitored. We performed either freshwater baths or oral administration of praziquantel if fluke intensity exceeded the given criteria. In unshaded cages, 3 total bath treatments or 6 total drug treatments were conducted. In contrast, no treatment was required for the shaded cage. The overall fluke intensity in the shaded cage was less than half that of the unshaded cages, despite the lack of treatments. This study demonstrated for the first time the practical use of shading in fish farms to reduce skin fluke infection.     

我国东、黄海鲐鱼灯光围网渔业CPUE标准化研究

日本鲐是我国近海重要的中上层鱼类资源之一,评估其资源量需要对单位捕捞努力量渔获量（CPUE）进行标准化。影响CPUE标准化的因素很多,包括季节、区域和海洋环境等。本文利用广义线型模型（GLM）和广义加性模型（GAM）,结合时空、捕捞船、表温等因子,对1998-2006年东、黄海大型灯光围网渔业鲐鱼CPUE进行标准化,并评价各因子对CPUE的影响。首先应用GLM模型评价时间、空间、环境以及捕捞渔船参数对CPUE的影响,并确定显著性变量。其次,将显著性变量逐一加入GAM模型,根据Akaike信息法则（AIC）,选择最优的GAM模型。最后,利用最优的GAM模型对CPUE标准化,并定量分析时间、空间、环境以及捕捞渔船参数对鲐鱼CPUE的影响。GLM模型结果表明：8个变量对CPUE有重要影响,依次为年、船队、船队与年的交互效应、月、船队与月份的交换效应、经度、纬度和海表温。根据AIC,包含上述8个显著性变量的GAM模型为最优模型,对CPUE偏差的解释为27.78%。GAM模型结果表明：高CPUE分别出现在夏季海表温为28～31 ℃的东海中部和冬季海表温为12～16 ℃的黄海;1998-2006年,标准化后的CPUE呈逐年下降趋势,与持续增长的捕捞努力量有关。     

产卵深度变动对东海日本鲭鱼卵仔幼鱼输运和存活率的影响

日本鲭(Scomber japonicus)是我国近海重要经济鱼种,海洋环境变动对鱼类生命周期中最为脆弱的鱼卵和仔幼鱼的生长、存活直至种群补充产生重大的影响,其中产卵深度变动对其是否会产生影响,目前尚不清楚。为此,本文拟采用FVCOM(Finite-Volume Coastal Ocean Model)物理模型来模拟三维物理场,使用基于个体模型IBM(individual-based model)参数化并模拟日本鲭的早期生活史,从而建立起基于物理-生物个体的东海日本鲭初期生态耦合模型,使用该耦合模型模拟了日本鲭产卵水深不同导致鱼卵仔幼鱼从产卵场向育肥场的输运过程中经历物理环境的差异对鱼卵仔幼鱼的输运分布以及存活率的影响。研究发现,产卵深度的变动,未对鱼卵仔幼鱼的输运分布产生明显影响,但在输运过程中所处水深和水温的微小差异却导致了变浅(5 m)和加深(15 m)产卵深度鱼卵仔幼鱼的存活率降低,正常产卵深度(10 m)是最佳的产卵水深。因此,研究认为产卵深度的细微变动将会对东海日本鲭鱼卵仔幼鱼的存活率产生影响,但对鱼卵仔幼鱼输运则影响不大。     

Effects of synthetic kisspeptin peptides and GnRH analogue on oocyte growth and circulating sex steroids in prepubertal female chub mackerel (Scomber japonicus)

In recent years, kisspeptin peptides, encoded by kiss genes have been used to manipulate reproductive processes in farmed animals, including fish. Our previous studies demonstrated that the chub mackerel brain expresses kiss1 and kiss2 and intramuscular injection of synthetic Kiss1 pentadecapeptide (Kiss1‐15) but not Kiss2 dodecapeptide (Kiss2‐12) accelerates spermatogenesis in prepubertal male chub mackerel (Scomber japonicus). In the present study, we evaluated their effects in prepubertal female chub mackerel. The gonadosomatic index (GSI) values of experimental fish did not show any significant changes. Condition factor (CF) values increased significantly in Kiss1‐15 treated fish, in comparison with control and GnRH analogue (GnRHa) injected fish. Histologically, only perinucleolar oocytes were found in all experimental fish. However, Kiss and GnRHa treated fish showed a significant increase in the perinucleolar oocyte diameter, in comparison with the control fish. Gene expression analyses revealed decreased expression of gnrh1 in the telencephalon‐preoptic region of the brain of Kiss2‐12 and GnRHa injected fish, in comparison with control fish. In contrast, GnRHa injected fish exhibited higher levels of fshβ in the pituitary, with no changes in the levels of lhβ among different treatments. Levels of circulating sex steroids, testosterone, and estradiol‐17β were significantly higher in Kiss1‐15 injected fish, in comparison with control fish. These results indicate that synthetic kisspeptin peptides and GnRHa can induce oocyte growth in prepubertal female chub mackerel.     

Dual effects of reversed winter–spring temperatures on year‐to‐year variation in the recruitment of chub mackerel (Scomber japonicus)

To clarify the effects of temperature on the recruitment of chub mackerel (Scomber japonicus) in the North Pacific, we investigated the influence of winter surface temperature (WST) on spawners at the time of maturity around the spawning grounds and the influence of ambient spring temperature on larvae using estimated temperature (ET) obtained from particle tracking experiments. We found a significant positive correlation between ET approximately 10 days following hatching and the recruitment per spawning stock biomass (RPS) after 2000. The closer (more meandering) the Kuroshio Current (KC) axis was in relation to the spawning ground, the higher (lower) the spring surface temperature and the higher (lower) RPS was in the spawning ground. In contrast, WST inside KC near the maturity/spawning ground was significantly negatively correlated with RPS. A significant negative correlation between the temperatures in winter and spring was detected in the area after 2000, when the conditions of the Pacific decadal oscillation index and the stability of the Kuroshio Extension were synchronous, indicating that KC shifted northward during this time. The reversed temperature pattern was consistent with the winter–spring movement of KC axis in the offshore direction and was correlated with the winter–spring difference in the intensity of the Aleutian low. These results suggest that the annual variation in chub mackerel recruitment after 2000 was strongly affected by the combined effects of ambient temperature because of the reversal of conditions that occurred between winter and spring around the maturity/spawning ground, which was related to the KC path.