鱼耳石微化学特征在湖库水质评价中的标型意义——以河北白洋淀和北京密云水库野生鲤鱼为例

对河北白洋淀和北京密云水库的野生鲤鱼耳石和水体中的微量元素进行了定量分析。白洋淀鱼耳石中诸微量元素含量均高于密云水库的鱼耳石,反映了白洋淀各水体较密云水库水体的环境复杂,污染程度高。统计分析结果表明,在鱼耳石中大致存在两类生物地球化学习性不同的元素,水体中第一类元素的变化不会引起耳石中相应元素的响应,如Au、K和Na;第二类元素的变化会引起耳石中相应元素的强烈响应,如As、Ba、Co、Cr、Fe、Sr和Zn。诸微量元素在耳石中富集的强弱顺序为,Zn>Sr>Se>Fe>As>Ba>K>Co>Au>Na>Cr。通过相关性分析发现,白洋淀和密云水库的鱼耳石和水体中对应微量元素平均含量的自然对数值之间均存在良好的线性关系。     

Otolith shape as a stock discrimination tool for ling (Genypterus blacodes) in the fjords of Chilean Patagonia

ABSTRACT

Genypterus blacodes, in terms of its fishing history and local economic importance, is an emblematic species harvested in Chilean Patagonia (41°00’–57°00’S). Most of the current fisheries and biological knowledge of this species come from the open ocean, whereas information about the species in fjords and inner channels is fragmentary. In 2018, two research surveys targeting G. blacodes were conducted in the fjords and inner channels of Chilean Patagonia. A total of 253 pairs of sagittal otoliths were sampled at three different localities, and their contours were modelled using wavelet analysis as a tool for stock discrimination. Contours were compared using canonical analysis, and classification was performed using linear discriminant and Random Forest analyses. The results indicated that the wavelet method is efficient in modelling otolith contours, and the discriminant analyses showed differences among fishing grounds across the latitudinal gradient, thus confirming the hypothesis that G. blacodes conform to at least two separate stock units in Chilean Patagonia. Fishing grounds that were closer in space showed higher levels of misclassification. The discussion focuses on how environmental variables and the geography of fjords shape stock differences and how this information can be used for the sustainable management of G. blacodes.     

Carbon stable isotopes in estuarine sediments and their utility as migration markers for nursery studies in the Firth of Forth and Forth Estuary, Scotland

The stable carbon isotope ratios (δ¹³C) of the organic fraction of intertidal sediments in the Forth Estuary and the Firth of Forth, Scotland, were measured to determine if terrestrially derived carbon was present in the estuarine sediments. It was hypothesised that differences in the inputs from marine vs. terrestrial sources to the organic carbon of estuarine and marine sediments, as well as differences in ambient seawater stable oxygen isotope (δ¹⁸O) ratios between the estuary and the Outer Firth, would allow the use of these two stable isotopes as habitat markers for juvenile plaice (Pleuronectes platessa), to allow determination of nursery habitats. Muddy and sandy sediments from the estuary and sandy sediments from the Outer Firth were sampled and δ¹³C measured. Juvenile plaice were caught at two estuarine sites and at two Outer Firth sites and otoliths were removed for δ¹³C and δ¹⁸O analysis. The sandy sediments in the estuary showed a strong gradient of δ¹³C enrichment with distance down the estuary, while the muddy sediments showed a much shallower gradient. δ¹³C and δ¹⁸O measured in the carbonate of juvenile plaice otoliths showed no clear difference between otoliths of fish caught at one of the estuarine sites and at the two Outer Firth sites. However, the isotope ratios of both carbon and oxygen in plaice otoliths from the other estuarine site showed the expected trend of depletion in the heavier isotopes. While the measurements recorded here did not conclusively distinguish between otoliths from juveniles caught in the estuarine site and those caught in the other three sites, they show that stable isotopes have potential to distinguish between estuarine habitats with terrestrial carbon inputs, and coastal marine habitats with predominantly marine carbon inputs.     

Measurement of alkaline and earthy ions in fish otolith and sea water using a high performance ion chromatography

Fish growth and the relation between growth and environmental conditions offer a good opportunity for measuring alkaline and earthy ions in fish otoliths.The analytical method must involve high sensitivity when attempting to discriminate between fish growth and environmental conditions.The aim of this paper is to propose a chromatographic method, with low detection limits, as a new approach in determining some important micronutrients present in sea water and fish otoliths.The work samples are: coastal, off-shore and sediment waters and fish otoliths (Engraulis encrasicholus, Mullus barbatus, Umbrina cirrhosa, Sciaena umbra, Pagellus erythrinus) in the Adriatic Sea and the Canal of Sicily.The analytical method includes an IONPAC CS12A chromatographic column and a 18 mM methanesulfonic acid eluent.The detection limit readings obtained with this method, for one E. encrasicholus fish otolith, weighing 2.6 mg are equal or inferior to 0.1 μg/L for lithium (Li), 59 μg/L for sodium (Na), 46 μg/L for ammonium (NH₄), 23 μg/L for potassium (K), 13 μg/L for magnesium (Mg), 88 μg/L for manganese (Mn), 2.567 μg/L for calcium (Ca) and 13 μg/L for strontium (Sr).The HPIC method minimizes overlaps such as Na on Li, and NH₄ in seawater and Ca on Mg and Sr in fish otolith. These elements are an essential constituent present in otoliths when describing the relation between growth and environmental conditions.Good separation among analytes is achieved within 16 min.     

日本鳗鲡早期阶段耳石日生长轮形成的周期

于1990年4月从江苏太湖搜集日本鳗鲡亲鱼暂养在天津滨海虾场8t玻璃钢水槽中，经人工催熟催产后孵出仔鳗，对孵出仔鳗连续取样；于1989年4月在长江口采集白仔鳗，观察和比较二者的耳石生长轮形成。结果表明，（1）人工繁殖仔鳗耳石第一个生长轮是在孵出后第一天形成的，轮纹形成具有24h周期性；仔鳗孵出后生长天数与生长轮数关系的回归方程以y=0．23＋0．91x表示，其中，x为孵出后的天数，y为生长轮数;在人工繁殖仔鳗耳石上没有观察到“孵化标记”轮。（2）白仔鳗耳石中心核与“孵化标记”轮之间存在日生长轮。（3）人工繁殖仔鳗与白仔鳗耳石中心核同第一个生长轮比较表明，前者小于后者。     

Habitat selection and quality for multiple cohorts of young-of-the-year bluefish (Pomatomus saltatrix): Comparisons between estuarine and ocean beaches in southern New Jersey

In this study, seasonal and annual variability in the use of estuarine and ocean beaches by young-of-the-year bluefish, Pomatomus saltatrix, was evaluated by indices of abundance in coastal areas of southern New Jersey (1998–2000). Biological and physical factors measured at specific sites were correlated with bluefish abundance to determine the mechanisms underlying habitat selection. In addition, integrative and discrete indicators of bluefish growth were used to examine spatio-temporal dynamics in habitat quality and its effect on habitat selection by multiple cohorts of bluefish. Intra-annual recruitment to coastal areas of southern New Jersey was episodic, and resulted from the ingress of spring-spawned bluefish (hatch-date April) to estuarine beaches in late May to early June, followed by the recruitment of summer-spawned fish (hatch-date early July) to ocean beaches from July to October. Bluefish utilized estuarine and ocean beaches in a facultative manner that was responsive to dynamics in prey composition and temperature conditions. The recruitment and residency of bluefish in the estuary (1998–1999) and ocean beaches (1998), for example, was coincidental with the presence of the Atlantic silverside Menidia menidia and bay anchovy Anchoa mitchilli, the principal prey species for bluefish occupying these respective habitat-types. Bluefish abundance in the estuary (2000) and ocean beaches (1999–2000) was also correlated with water temperature, with the greatest catches of juveniles coinciding with their optimal growth temperature (24 °C). Bluefish growth, estimated as the slope of age–length relationships and daily specific growth rates, equaled 1.27–2.63 mm fork length (FL) d⁻¹ and 3.8–8.7% body length increase d⁻¹, respectively. The growth of sagittal otoliths was also used as a proxy for changes in bluefish size during and shortly before their time of capture. Accordingly, otolith growth rates of summer-spawned bluefish were greater at ocean beaches relative to the estuary and were explained by the more suitable temperature conditions found at ocean beaches during the mid- to late summer. Notwithstanding the fast growth of oceanic summer-spawned bluefish, individuals spawned in the spring were still larger in absolute body size at the end of the summer growing season (240 and 50–200 mm FL for spring- and summer-spawned bluefish, respectively). The size discrepancy between spring- and summer-spawned bluefish at the onset of autumn migrations and during overwintering periods may account for the differential recruitment success of the respective cohorts.