Age compositions of flatfish stocks as determined by a new otolithometric method,its application in the estimation of growth,spawning potential and fisheries management

We developed an ageing methodology and examined age composition of three flatfish stocks inhabiting the Seto Inland Sea, Japan. Ages were difficult to determine for three-lined tongue sole (Cynoglossus abbreviates) and ridged-eye flounder (Pleuronichthys cornutus) because the first year annulus ring was often indistinct; therefore, we used directional change in otolith growth to distinguish it. Sectioning and etching methods were powerful tools for identifying annual checks for red tongue sole (Cynoglossus joyneri). Using these ageing methods, we determined age–length relationships and growth curves. The age composition of the populations studied and of the landings showed that a large proportion of the latter consisted of individuals under the mean age of sexual maturity, thereby reducing the percent spawning potential ratio (%SPR) to ≈ 20% for all species. These findings suggest that fishing pressure on immature fish is leading to overfishing of these flatfish stocks.     

Intra- and interspecies comparison of energy flow in North Atlantic flatfish species by means of dynamic energy budgets

The quantitative aspects of growth and reproduction in four flatfish species (plaice, flounder, dab, sole) in terms of energy flow are described on the basis of a dynamic energy budget (DEB theory). This theory consists of general assumptions about energy uptake, storage and utilisation and describes an individual by two state variables: structure and reserve, whereby body size exerts its influence through the ratio between surface area and volume. Comparison between model estimates and field data shows that the DEB model successfully describes the energetics of growth and reproduction in a number of flatfish species. Differences between species could be captured in the same model using different parameter values. Intraspecific differences in growth between males and females are mainly caused by differences in maximum surface area-specific ingestion rates. Differences between species are reflected in the surface area-specific maximum ingestion rate, the energy partitioning over growth and reproduction, and in egg volume. According to these parameters at 283 K (10°C), the species could be ranked as follows: surface area-specific maximum ingestion rate (W m⁻²) plaice: 56.6; flounder: 54.5; sole: 45.1 and dab: 36.1 W m⁻². Fraction of energy allocated to reproduction (–): flounder: 0.35; plaice: 0.15; dab: 0.15 and sole 0.10. As a consequence of these differences in surface area-specific maximum ingestion rate and in the fraction of utilised energy allocated to reproduction, the gonad masses (g) of females of 0.5 kg wet mass differ considerably: flounder: 149 g; plaice: 86 g; sole: 70 g; and dab: 69 g. However, due to differences in egg size between species, the potential annual egg production shows a completely different pattern: dab: 2200 10³; flounder: 1560 10³; sole: 343 10³ and plaice: 130 10³ eggs.     

10 个半滑舌鳎家系 MHC IIB 基因多态性初步研究

为检测10个半滑舌鳎(Cynoglossus semilaevis)家系MHCⅡB(Cyse-DAB)基因的多态性水平、MHCⅡ类B位点数目以及平衡选择的作用,作者利用多聚酶链式反应(PCR)和直接测序的方法对10个半滑舌鳎家系MHCⅡB基因位点遗传变异和平衡选择进行了研究。用特异性引物和PCR扩增的半滑舌鳎MHCⅡB基因片段大约397 bp,包含一部分第一外显子,全部第一内含子和全部第二外显子。10个半滑舌鳎家系中,每家系选取5个体,每个体5个克隆序列分析发现60个不同序列,代表60个等位基因,其中有28个是新发现的,已提交到Gen Bank。同源分析表明60个等位基因相似性为89.36%。共50个个体中,有6个存在5个不同等位基因,表明在半滑舌鳎至少存在3个座位。有9个家系的MHCⅡB序列多肽结合区(PBR)的非同义替换(dN)显著高于同义替换(dS)。     

A comparative analysis of recruitment variability in North Atlantic flatfishes — testing the species range hypothesis

The hypothesis that recruitment variation in flatfishes should be most variable at the northern edge of the species range, least near the centre of the range, and intermediate near the southern limit was tested using stock and recruitment data generated from sequential population analysis for several different flatfish stocks involving four species (plaice Pleuronectes platessa, sole Solea vulgaris from the eastern Atlantic, American plaice Hippoglossoides platessoides, and yellowtail flounder Limanda ferruginae from the western Atlantic). Several groundfish species have been found to conform to this so-called species range hypothesis with the suggestion that density-independent processes predominate at the edges of the distributional range and density-dependent processes dominate in the centre of the range. Our results were generally inconsistent with the hypothesis: the coefficient of variation (CV) of recruitment for plaice in the eastern Atlantic was independent of latitude, the CV of recruitment for sole exhibited a dome-shaped relationship with latitude with the highest CVs occurring at the mid-point of the range, and the CV of recruitment for the western Atlantic stocks exhibited a monotonic decrease with latitude. We extended our latitudinal analyses by assessing both the degree of dependency of recruitment on spawning stock biomass and the spatial and temporal scales of variability in recruitment and pre-recruit survival for the eastern Atlantic stocks. In general our analysis revealed no evidence of a strong stock and recruitment relationship for any of the stocks examined, and previously published analyses revealed no such patterns with latitude. Analysis of both de-trended recruitment and pre-recruit survival time series over the species ranges of sole and plaice revealed strong positive correlations among adjacent stocks and inverse correlations among stocks at the extremes of the range. Recruitment variation in the flatfish stocks examined appears to be dominated by density-independent factors, operating at a local scale, on the egg and larval stages.     

半滑舌鳎(Cynoglossus semilaevis)幼鱼生长性状和底色的表型和遗传参数估计

半滑舌鳎是重要的经济鱼类,已经被广泛推广养殖,致力于养殖方面的研究开展了很多工作,但是对半滑舌鳎生长性状进行准确遗传评估的研究还未见报道。为了对生长性状进行准确的遗传参数估计,本次研究以80个半滑舌鳎家系为研究对象,对半滑舌鳎早期生长性状（包括个体全长、体宽和体质量）进行分析。另外还将鱼体底面纯白与否（命名为底面颜色）作为一个性状进行研究。结果表明,四个性状都属于中等遗传力（全长为0.210、体宽为0.259、体质量为0.268、底面颜色为0.362）。三个生长性状之间具有很高的遗传相关性（0.913-0.959）,表明如果三个性状进行间接选择的话,将会取得较好效果。底面颜色性状与三个生长性状均为正遗传相关,相关系数在0.241-0.353之间,由此可知,对底面颜色进行选择时,可以加强生长性状的选择效果。通过家系育种值排序,初步筛选出了生长性状优良遗传背景丰富的16个全同胞家系,将作为亲鱼繁殖后代。本研究为半滑舌鳎优良品种的成功培育提供了重要基础资料。     

Mesh selection studies on flatfish in relation to the Otago trawl fishery

Cod‐end mesh selection experiments were conducted on three species of flatfish (common or English sole Peltorhamphus novaezeelandiae, lemon sole Pelotretis flavilatus, and sand flounder Rhombosolea plebeia) trawled off the Otago coast. It is suggested that better yields would be obtained from stocks of these fish if the minimum cod‐end mesh size was increased from 10.2 cm (4 in.) to 11.4 cm (4.5 in.).     

温度对半滑舌鳎的生长、生化组成和能量收支的影响

研究了不同温度(16,19,22,25,28和31 ℃)对半滑舌鳎(Cynoglossus semilaevis Günther)幼鱼的生长、体成分组成和能量收支的影响.结果表明,随温度的升高,半滑舌鳎幼鱼生长率总体呈现先升高后降低的趋势.其中,在19～25 ℃温度范围内,半滑舌鳎幼鱼的特定生长率相对较高,在16和28 ℃下则有所降低,而在31 ℃下,半滑舌鳎幼鱼特定生长率则显著降低.本研究表明半滑舌鳎幼鱼特定生长率与温度符合二次曲线模型.半滑舌鳎摄食量随温度升高而逐渐增大,但在31 ℃时显著减小,饵料转化率则随温度的升高而降低.鱼体脂肪与能值均随温度升高而降低,蛋白质含量受温度影响不显著.温度对半滑舌鳎的能量收支影响显著,其中,生长能和代谢能主导半滑舌鳎的能量分配,生长能占摄食能比例则随温度的升高而降低,呼吸能占摄食能比例则随温度的升高而升高.本研究表明,半滑舌鳎幼鱼(13～37 g)适宜生长温度范围为18～25 ℃,而不同温度导致的半滑舌鳎摄食量和能量收支的差异可能是温度影响其生长的主要生理生态学机制.     

盐度突变对半滑舌鳎血浆渗透压和鳃丝Na+/K+-ATP酶活性的影响

研究了半滑舌鳎(Cynoglossus semilaevis)由盐度30突变至0、1O、20、35和40盐度后血浆渗透压和鳃丝Na+/K+-ATP酶活性的变化.结果表明,盐度对半滑舌鳎血液渗透压和鳃丝Na+/K+-ATP酶活性均有显著影响(P＜0.05).盐度突变后,各处理组的血液渗透压和鳃丝Na+/K+-ATP酶活性...     

半滑舌鳎肾脏组织结构与细胞种类研究

半滑舌鳎(Cynoglossus semilaevis)是中国重要的海水养殖鱼类品种,目前对于其肾脏结构与细胞种类的研究较少。本研究以半滑舌鳎肾脏为研究对象,通过切片技术、免疫组织化学与显微镜观察,描述半滑舌鳎肾脏结构与细胞分布情况。结果显示,半滑舌鳎的肾脏可以分为头肾与体肾两部分;头肾较小,具有独立的结构,位于肾脏前部,靠近脑,形态上呈分叉状;头肾由淋巴髓样细胞构成,无肾小球等分泌结构,免疫细胞丰富,包括淋巴细胞、单核细胞、颗粒细胞,是半滑舌鳎免疫细胞的主要生发部位之一,是免疫系统的重要组成;半滑舌鳎的体肾与头肾后部分叉处相连,呈纺锤状,紧贴腹腔背部,向后延伸;体肾主要由肾单位组成,有丰富的肾小囊、近曲小管、远曲小管和集合管结构,表明其具有排泄功能。     

Greenland halibut diet in the Northwest Atlantic from 1978 to 2003 as an indicator of ecosystem change

The Northwest Atlantic marine community underwent dramatic changes during the last 30 years, including the collapse of many groundfish stocks and an increase in shrimp populations. Greenland halibut Reinhardtius hippoglossoides is an important commercial species and one of the top fish predators in this system. It is a large, wide-ranging flatfish that is found at depths up to 2200 m and it has an opportunistic diet which makes it a potential candidate for an ecosystem indicator. Analysis of stomach contents of Greenland halibut between 1978 and 2003 indicates that diet composition reflects the major changes in community structure. Over the entire period there was a clear increase in the importance of invertebrates, particularly after 1992. This change was associated with a higher importance of Pandalus shrimp and Gonatus squid and a protracted reliance on zooplankton by predators under 25 cm length. Capelin Mallotus villosus was the dominant prey between 1978 and 1992 for predators in the 12–63 cm range, but its importance dropped off drastically in the mid 1990s. Levels of main prey in the diet of Greenland halibut correlated well with fishery-independent surveys. Greenland halibut sample capelin well, compared to bottom trawl surveys and acoustic surveys. Greenland halibut consumed small shrimp which are not routinely caught by surveys and may be important in deriving information on year classes and growth of shrimp. Our results suggest that Greenland halibut's diet is a useful tracker of ecosystem change.     

桁拖网渔具刚性栅栏对鱼类的分隔效率研究

东海捕虾桁拖网选择性能不佳,对渔业资源的保护和渔业的合理管理带来了负面的影响.刚性栅栏是实现拖网渔具种类选择性捕捞的主要装置,本文根据在吕四渔场开展刚性栅栏海上生产试验,结合SELECT模型分析不同栅条间距(15、20和25mm)的刚性栅栏对短吻舌鳎、小黄鱼和棘头梅童鱼的分隔效率.结果表明,随着栅条间距的增大,栅栏对鱼类的重量分隔率逐渐减小,分隔栅栏对鱼类的50%选择体长(L50S))逐渐增大;对于短吻舌鳎,个体接触分隔栅栏的概率可使用常数来表示,即接触概率与个体尺寸无关,接触概率在0.2-0.4之间,并随着栅条间距的增大而增大(不显著,P>0.05):对于小黄鱼和棘头梅童鱼,所有进入网囊的个体都将接触刚性栅栏;不同鱼类接触栅栏概率的显著差异说明不同鱼类在网囊中的不同行为习性.     

半滑舌鳎(Cynoglossus semilaevis)GnRHR基因全长cDNA 的克隆与组织表达分析

采用同源克隆和末端快速扩增(RACE)方法, 克隆了半滑舌鳎中 GnRHR 全长 cDNA。通过基因全长以及推断的氨基酸序列分析, 得知该序列包含一个 7tm-1 保守结构域, 为 G 蛋白偶联受体家族成员。利用 PHYLIP 3.5c 邻位相连法以及 DNAstar 中的 CLUSTAL W 方法对相应的氨基酸序列进行了聚类分析和序列相似度分析。结果表明, 半滑舌鳎 GnRHR 鳉 与鲈鱼、琥珀鱼、虹鳟以及青 等鱼类中的 GnRHR聚为一支, 亲缘关系较近, 且相似度较高, 分别为 90.1%、 89.7%、 79.0%以及 78.3%, 而与高等哺乳动物人、小鼠相似性仅分别为 18.8%和 16.2%, 亲缘关系较远。应用半定量 RT-PCR 技术分析其组织表达, 发现 GnRHR 广泛表达于各个组织, 但表达量差异较大, 在性腺、脑和肾中表达量较高, 其它组织较弱。     

Estimated intensity needed for sampling flatfish assemblages in reference areas of tidal mud flats systems may be disproportionately costly and deleterious

Beam trawl surveys were carried out in a tidal stream system of the German Wadden Sea on two to three successive days of comparable weather conditions in three summers. The variability in time and space detected for plaice (Pleuronectes platessa), flounder (Platichthys flesus), dab (Limanda limanda), sole (Solea solea) and lemon sole (Microstomus kitt) was considerable even for species with a very high abundance. Other flatfish species such as turbot (Scophthalmus maximus) and brill (Scophthalmus rhombus) occurred only occasionally in the catches. Sampling effort calculated to detect a 50 or 20% difference between the surveys caused by immigration, emigration or mortality appears to be disproportionate. It is argued that such a major sampling effort of reference areas in tidal mud flat systems is likely to influence the results, to harm the environment, and to be very expensive.     

半滑舌鳎(Cynoglossus semilaevis)Patched 1基因的克隆和表达分析

Hedgehog(Hh)信号通路在脊椎动物和非脊椎动物发育过程中细胞信号传导方面发挥重要的作用。Patched 1 (Ptc1)基因是Hh的受体,通过和Hh配体结合调节Hh信号通路。本研究克隆和鉴定了半滑舌鳎的Ptc1基因(csptc1),该基因cDNA全长为5212 nt,编码蛋白包括1543个氨基酸残基,序列比对和进化分析显示该蛋白在进化过程中较为保守。荧光定量显示该基因在脑,肝脏,心脏,鳃,肠,脾脏、肾脏和性腺组织中普遍表达,在精巢中的表达水平显著高于卵巢。精巢中的原位杂交信号主要位于该基因主要在初级精母细胞,次级精母细胞和支持细胞中,而在卵母细胞中的信号较弱。Csptc1基因在卵巢中的甲基化水平高于在雄鱼和伪雄鱼精巢中。这一研究结果可能说明csptc1基因参与了 Desert Hedgehog (DHH)基因维持雄鱼和伪雄鱼的生殖细胞系以及精子发生等生物学过程。     

Polychaete assemblage as surrogate for prey availability in assessing southeastern Bering Sea flatfish habitat

The flatfish yellowfin sole (Limanda aspera), northern rock sole (Lepidopsetta polyxystra), and Alaska plaice (Pleuronectes quadrituberculatus) in the southeastern Bering Sea prey mainly on infauna. Spatial correspondence between their stomach contents and infauna assemblages across habitat types was examined to identify indices of prey availability for flatfish habitat characterization and quality assessment. Benthic samples and flatfish stomachs were collected in 2009 near the Alaska Peninsula in the southeastern Bering Sea. Polychaetes and bivalves were the most dominant infauna groups, each comprising 35–60% by weight in each infauna sample. These two were also the only prey groups that frequently averaged > 50% of stomach content by weight. Bivalves dominated the infauna biomass on the relatively sandy inner shelf (0–50 m depth). The muddier middle shelf (50–100 m) had the highest infauna biomass, which was dominated by polychaetes. Diet compositions of the flatfish varied spatially in correspondence with the infauna assemblage. Polychaetes were prevalent in all flatfish diets on the middle shelf, even yellowfin sole whose typical primary prey are amphipods and bivalves. Polychaete-rich habitats are potentially prime for flatfish as polychaetes are readily utilized where available and generally have high nutritional value. Flatfish did not select for specific polychaete taxa, so an index of habitat quality could be based on the biomass of aggregate polychaetes or on dominant polychaete families of the region. Under normal environmental conditions, the three flatfish have slightly-offset spatial distributions, enabling each to utilize different infauna assemblages across the shelf. However, during cold phases in the Bering Sea ecosystem, as when this study was conducted, a cold pool of < 2 °C bottom water from the spring ice melt extends over the middle shelf in summer. This physiological barrier displaces all three flatfish to the inner shelf, intensifying competition for prey resources.     

Effect of native and invasive cordgrass on Macoma petalum density, growth, and isotopic signatures

Ecosystem engineers can influence community and ecosystem dynamics by controlling resources, modifying the flow of energy or biomass, or changing physical characteristics of the habitat. Invasive hybrid cordgrass (Spartina alterniflora × Spartina foliosa) is an ecosystem engineer in salt marshes in San Francisco Bay, California, U.S.A. that raises intertidal elevations and may be either increasing C₄ plant carbon input into food webs or tying up carbon in a form that is not usable by consumers. A manipulative experiment compared abundance, growth, and stable isotope (δ¹³C and δ¹⁵N) composition of the clam Macoma petalum (=M. balthica) among native marsh, hybrid Spartina, and mudflats in central San Francisco Bay. We found higher densities (individuals m⁻²) of M. petalum on mudflats compared to either native or hybrid Spartina (p < 0.001). Macoma petalum shell growth was significantly greater in mudflats than in either vegetation type in 2002 (p = 0.005) but not 2003. Differences in shell growth between native and hybrid Spartina were not significant. Stable isotope results showed differences between habitats in δ¹³C but not δ¹⁵N. Carbon signatures of M. petalum placed in Spartina were much more depleted than the isotopic signature of Spartina. Neither native nor hybrid Spartina appears to be a significant carbon source for M. petalum in San Francisco Bay, and we found no evidence that hybrid Spartina contributes carbon to M. petalum beyond what is provided by S. foliosa, despite the hybrid's much greater biomass. Our results show that loss of mudflat habitat, rather than increased input of C₄ carbon, is the greatest effect of the invasion of hybrid Spartina on M. petalum.     

Biology of the redspotted tonguesole Cynoglossus zanzibarensis (Pleuronectiformes: Cynoglossidae) on the Agulhas Bank,South Africa

The biology of the redspotted tonguesole Cynoglossus zanzibarensis, a common African cynoglossid inhabiting the Agulhas Bank, South Africa, is described. Growth studies based on sectioned sagittal otoliths revealed that C. zanzibarensis is relatively fast-growing and long-lived, attaining ages >8 years. Growth in length was rapid in immature fish, fish attaining 56% of their maximum size within their first year. By sexual maturity, fish had attained 28% of their maximum age and 68% of their maximum length. Total length-at-age was best described by the Von Bertalanffy growth model with combined-sex growth described as L_t = 354.78(1?e^{?0.43 (t+1.17)}) mm TL. Sexually dimorphic growth patterns were evident, females attaining larger lengths, but at a slower growth rate than males. Despite the similar mean size of adult fish, the trawl-sampled adult population was dominated by females, with a sex ratio of 1 male:2.4 females. Female C. zanzibarensis mature in their second year of life (275 mm TL), after which they spawn small, pelagic eggs throughout the year. Approximations of the rates of total, natural and fishing mortality were estimated to be 0.62, 0.48 and 0.14 year^?1 respectively.     

Age verification,growth and life history of rubyfish Plagiogeneion rubiginosum

Age verification of rubyfish (Plagiogeneion rubiginosum) was sought using the bomb radiocarbon chronometer procedure. Stable isotopes were investigated for life history characteristics. Radiocarbon (¹⁴C) and stable isotope (δ¹⁸O and δ¹³C) levels were measured in micro-samples from five otoliths that had been aged using a zone count method. All the core ¹⁴C measurements were ‘pre-bomb’ indicating ages of at least 45 years, and the ¹⁴C measurements across the otolith sections suggested that the zone-count ageing method described herein is not biased. Maximum estimated age was 100 years. There was no significant between-sex difference in the von Bertalanffy growth curves. The δ¹⁸O values indicated that rubyfish are near-surface as juveniles, and move deeper with age. Adults appear to reside in 600–1000 m; this is deeper than most trawl-capture data suggest, but not implausible, and has stock assessment implications. The δ¹³C values reflect fish metabolic rates, trophic feeding levels and oceanographic conditions. The stable isotopes record the environmental life history of each fish, and have value in distinguishing stocks and/or indicating vertical and latitudinal migratory patterns.     

Distribution, condition, and growth of newly settled southern flounder (Paralichthys lethostigma) in the Galveston Bay Estuary, TX

Several flatfish species, including southern flounder (Paralichthys lethostigma) recruit to estuaries during early life. Therefore, evaluation of estuarine sites and habitats that serve as nurseries is critical to conservation and management. The present study used density data in conjunction with biochemical condition and growth measurements to evaluate settlement sites used by southern flounder in the Galveston Bay Estuary (GBE). In 2005, beam-trawl collections were made in three major sections of the GBE (East Bay, Galveston Bay, West Bay). Three sites were sampled in each bay. Within each sampling site, replicate collections were taken from three habitats: 1) marsh edge (< 1 m depth), 2) intermediate zone (10–20 m from marsh interface;  1 m depth), and 3) bay zone (typically > 100 m from marsh interface; depth > 1 m). Average size of southern flounder collected was 12–19 mm standard length, and peak densities occurred in January and February. Catch data indicated that densities of southern flounder were significantly greater in East Bay (2.75 per 100 m²) than in Galveston Bay (0.91 per 100 m²) or in West Bay (0.45 per 100 m²). Densities were statistically similar among habitats. Otolith-based estimates of age indicated that the majority of southern flounder collected were 35–45 days old and derived from early December to early January hatch-dates. Growth rates were similar among bays and among habitats, with the average growth rate being 0.40 mm day^− 1 (range: 0.21–0.76 mm day^− 1). RNA:DNA was above the established baseline value for nutritional stress, indicating that newly settled southern flounder in the GBE were in relatively high condition. Habitat-specific differences in RNA:DNA ratios were not observed; however, ratios were significantly lower in West Bay (average 8.0) than in East Bay (average 9.5) or in Galveston Bay (average 9.8), suggesting the condition of new recruits may vary spatially within the GBE. Findings from the current study suggest density and condition of newly settled southern flounder vary at the bay scale, suggesting that parts of GBE do not function equally as nurseries.