Elevated manganese concentrations at the cores of clupeid otoliths: possible environmental,physiological, or structural origins

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used to investigate the distribution of manganese (Mn) in Atlantic herring (Clupea harengus L.) otoliths. An unusual pattern of Mn concentration, which has not previously been reported in fish otoliths, was observed. Time-resolved plots (time roughly equivalent to ablation depth) of the Mn signal recorded in the ICP-MS detector during ablation of otoliths contained a distinct peak, suggesting that elevated Mn concentrations were specific to certain regions. Ablation inside and outside of the otolith core revealed that the region of high Mn concentration coincided with the ablation of the core. It was initially suggested that Mn from the gravel substrate on which herring eggs are incubated is incorporated into the otolith core, producing elevated Mn concentrations in this region. It was hypothesised that otoliths from fish whose eggs are not incubated in gravel will not contain high Mn concentrations at the core. To test this, otoliths of sprat (Sprattus sprattus), which have a pelagic embryological stage, and from reared herring, which were incubated on glass plates, were analysed using LA-ICP-MS. Peaks in the Mn signal were observed during the ablation of cores from some sprat and reared herring otoliths, indicating that incubation on a gravel substrate is not necessary for the accumulation of Mn at the otolith core and that otoliths from both pelagic and demersally spawning fish species can contain elevated Mn concentrations. The results suggest that Mn concentrations at the otolith core do not reflect the external environment of the developing embryo. Two other hypotheses are considered. A dramatic increase in Mn concentrations in the egg, associated with embryological development, may produce elevated Mn levels at the otolith core. Alternatively, the high levels of Mn observed at the otolith core may reflect spatial variation in the crystal structure of the calcium carbonate portion of the otolith. The possible influence of physiological or structural factors on the chemical composition of the otolith core may confound the environmental signal in this region of the otolith. This has important implications for the interpretation of otolith chemistry data.Communicated by J.P. Thorpe, Port Erin     

Exploring the potential of otolith microchemistry to enhance diet analysis in pinnipeds

Increasing the scope and accuracy of information about pinniped diets obtainable from non-invasive techniques is increasingly important, particularly in cases where pinniped species are threatened or endangered. This study is the first to explore the potential for using elemental analysis of the otoliths found in scat to enhance the information available for diet analyses. We investigated the effects of pinniped digestion on otolith microchemistry using laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). We compared the elements contained in the edges (adult stage) and cores (larval/juvenile stage) of otoliths from Pacific herring (Clupea pallasii), Atka mackerel (Pleurogrammus monopterygius), and Walleye pollock (Theragra chalcogramma) recovered from the scat of captive Steller sea lions (Eumetopias jubatus) to elements in a sample of pristine (undigested) otoliths. We found that digestion had a significant effect on four of the six sampled combinations of species and otolith region (herring edges and cores, mackerel edges, and pollock cores), and that Rb most frequently showed significant differences in concentration after digestion. We could significantly discriminate among species of both pristine and digested otoliths using either otolith edges or cores with the elements Ba, Rb, Sr, Y, and Mg. When compared to previously identified digested otoliths, unknown samples of the three species of digested otoliths could be discriminated with 55–100% accuracy depending on species and otolith region. When compared to a library of previously identified pristine and digested otoliths, unknown samples of digested otoliths could be discriminated to species with 65–88% accuracy. When the group of unknown digested otoliths was compared to known pristine otoliths, discrimination ranged from 45 to 65%. These results indicate that elemental analysis could be used to supplement visual identification of otoliths from scat. However, further research is required to determine whether elemental analysis of digested otoliths could be useful for prey fish population studies.     

Spatial variation of otolith elemental signatures among juvenile gray snapper (<Emphasis Type="Italic">Lutjanus griseus</Emphasis>) inhabiting southern Florida waters

Juvenile gray snapper, Lutjanus griseus, are believed to use bays and estuaries in southern Florida as nurseries before moving out to the adjoining reef tract as adults. Using high-resolution sector field-inductively coupled plasma-mass spectrometry (SF-ICP-MS), the elemental chemistry of the otoliths of juveniles from five nursery regions was resolved by establishing elemental “signatures” for each region. In this study we simultaneously analyzed 32 elements including a suite of rare earth elements. A stepwise variable selection procedure retained a subset of eight elements that contributed substantially to separating otolith samples, including two rare earth elements; this is one of the first studies in which rare earth elements in otoliths have contributed to separation of fish stocks. The classification success rate in assigning fishes to the correct region of origin was 82%. Resolution of sites less than 10 km apart suggested high site fidelity in juvenile gray snapper and little mixing of water masses between sites. The juvenile nursery signatures will be used to determine the relative contribution of different nurseries to the adult population on an adjoining reef tract.     

Scales of variation in otolith elemental chemistry of juvenile staghorn sculpin (<Emphasis Type="Italic">Leptocottus armatus</Emphasis>) in three Pacific Northwest estuaries

Although distinct otolith elemental signatures are often observed in fish collected from different estuaries, significant differences are also observed among sites within estuaries. Variation at these smaller spatial scales is not well quantified and has the potential to lead to inappropriate interpretations of otolith elemental data. To quantify variation at multiple scales, the otolith elemental composition (Mg:Ca, Mn:Ca, Sr:Ca, Ba:Ca, and Pb:Ca) of juvenile staghorn sculpin (Leptocottus armatus Girard, 1854) collected from five sites within three estuaries, the Columbia River (two sites) and Coos Bay (one site), Oregon, and Humboldt Bay, California (two sites), was examined. Using laser ablation-inductively coupled plasma mass spectrometry, each otolith was sampled at three zones: (1) within the primordium, which represents the egg and early larval periods; (2) at the outer edge, which represents the juvenile period just prior to collection; and (3) midway between the primordial and edge samples, which represents the late larval and early juvenile period. There were significant differences in otolith metal-to-calcium ratios at all scales examined. Using multi-element otolith signatures, fish were classified to estuary and site within estuary with relatively high levels of accuracy (av = 70–90%). The largest differences in metal-to-calcium ratios were observed between sites within estuaries (<5 km apart) and the smallest differences were observed among otolith zones. Variation in otolith chemistry may be used to provide information on probable habitat use by estuarine fish but studies must be carefully designed. Electronic supplementary material  Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Population structure and life history of orange roughy (Hoplostethus atlanticus) in the SW Pacific: inferences from otolith chemistry

We examined site differences in the elemental composition of the primordium and ontogenetic variability of Sr in otoliths of fish from Australia and New Zealand and, as an out-group, the North Atlantic. Differences among sites in primordium composition are slight, but significant for all five elements assayed (Sr, Pb, Cu, Zn and Hg), but principally reflect differences between the North Atlantic and SW Pacific specimens, do not replicate for independent samples in the SW Pacific and constitute a poor “natural tag” in roughy, with <25% of fish successfully assigned to source location. However, mean Sr weight-fractions at the primordium showed similar latitudinal variation across sites in Australia, New Zealand and the Tasman Sea, indicating both spatially structured populations and a common structuring process across the region. Comparisons of ontogenetic variability of Sr in otoliths from juveniles and young adults within and between sites in the SW Pacific strongly support the hypothesis that variability in this element is site-specific and environmentally sensitive, although the environmental factors involved are not obvious. The otolith analysis confirms previous suggestions that juvenile and adult Hoplostethus atlanticus are relatively sedentary, but also indicates that the population sub-structuring by age within sites is more complex and there are likely to be more spawning areas in Australian waters than previously thought. More broadly, although single point analysis of otolith composition at the primordium resolves a population structure in roughy, alone it is not precise enough to test hypotheses about the processes causing this structure. Ontogenetic variability in Sr provides better resolution of spatial structure, even in a relatively homogenous marine environment like the deep ocean, and also provides insight into behavioural and ecological factors. Ontogenetic analyses of Sr in otoliths are expensive to obtain, require more effort in specimen preparation than single point analyses, and are difficult to compare statistically, but the increased information they yield warrants their broader consideration in marine species.     

鱼类耳石元素指纹研究进展

耳石是沉积在真骨鱼类内耳中的一种矿物结构,其主要成分是碳酸盐.在鱼类的生活过程中,水环境中的化学元素经过代谢稳定地沉积在耳石上,由于生活水域化学环境的差异,鱼类耳石的元素组成或含量存在一定的差异,而使耳石上的元素指纹成为一种天然标志,记录了鱼类所经历的生态环境及其变化.耳石元素指纹研究主要包括同位素成分分析、锶钙比率研究(Sr/Ca)以及一些痕量元素分析等,这些可以用于鱼类种群识别、生活史研究、生活环境重建,以及高龄鱼的年龄鉴定,在鱼类生态学和渔业资源学研究中具有广泛的应用前景.参57     

Population structure and connectivity of the European conger eel (Conger conger) across the north-eastern Atlantic and western Mediterranean: integrating molecular and otolith elemental approaches

Genetic variation (mtDNA) of the European conger eel, Conger conger, was compared across five locations in the north-eastern Atlantic (Madeira, Azores, South Portugal, North Portugal and Ireland) and one location in the western Mediterranean (Mallorca). Genetic diversity of conger eel was high, and differentiation among regions was not significant. Additionally, comparisons of element:Ca ratios (Sr:Ca, Ba:Ca, Mn:Ca and Mg:Ca) in otolith cores (larval phase) and edges (3?months prior to capture) among the Azores, North Portugal, Madeira and Mallorca regions for 2?years indicated that variation among regions were greater for edges than cores. Therefore, while benthic conger may display residency at regional scales, recruitment may not necessarily be derived from local spawning and larval retention. Furthermore, data from otoliths suggest a separated replenishment source for western Mediterranean and NE Atlantic stocks. The combination of genetics and otolith chemistry suggests?a population model for conger eel involving a broad-scale dispersal of larvae, with limited connectivity for benthic juvenile life stages at large spatial scales, although the existence of one or multiple spawning grounds for the species remains uncertain.     

Changes in otolith strontium:calcium ratios in metamorphosing Conger myrisaster leptocephali

Content ratios of strontium (Sr) to calcium (Ca) in the otolith of Conger myriaster metamorphosing leptocephali and elvers increased with increasing increment number from the core to the 110th increment and subsequently decreased. The otolith region from the 110th increment to the edge corresponded to the metamorphic stage. The Sr:Ca ratios in otolith edges of metamorphosing leptocephali were inversely related to metamorphic stage, suggesting that the changes in otolith Sr:Ca ratios were influenced by some physiological factor(s) rather than by environmental factors. Sr concentration in leptocephalus somatic tissues was high and decreased as metamorphosis progressed until the late metamorphic stage when the preanal myomere to total myomere ratio was 0.4. Ca concentration was constant throughout ontogenesis. Body Sr:Ca ratios markedly decreased as metamorphosis progressed. Decrease in somatic Sr concentration and the consequent decrease in body Sr:Ca ratios seemed to be associated with the breakdown of glycosaminoglycan (GAG) in gelatinous matrix, which is the major constituent of soft tissue in leptocephali. Catabolism of GAG may also cause a decrease in otolith Sr:Ca ratios during metamorphosis. In leptocephalus otoliths, Sr:Ca ratios may change in association with the synthesis and breakdown of GAGs during ontogeny. Received: 29 November 1996 / Accepted: 6 January 1997     

Chemistry of tuna otoliths: assessment of base composition and postmortem handling effects

Protocols used to collect and prepare otoliths for chemical analysis may result in either contamination or loss of elements, thus biasing population studies in unknown ways. We evaluated precision and bias associated with collection and cleaning procedures for three Atlantic tuna species: Atlantic bluefin tuna (Thunnus thynnus), yellowfin tuna (T. albacares), and blackfin tuna (T. atlanticus). Elemental concentrations were measured using solution-based inductively coupled plasma mass spectrometry and atomic absorption spectrophotometry. Seven elements were present above detection limits in all samples (Na, Mg, K, Ca, Mn, Sr, Ba). Mean concentrations of all seven elements were statistically indistinguishable in fresh pairs of otoliths of T. thynnus (mean error 5%, range 2-8%) and T. albacares (mean error 5%, range 3-7%); no indication of a left versus right otolith effect was observed. Otolith elemental concentrations were size dependent and significant inverse relationships were observed for Mg, Na, and K. Deliberate contamination of previously cleaned samples using a 10-ppm solution of a mixture of elements demonstrated that otoliths easily acquire surface contamination. Recleaning contaminated otoliths restored elemental concentrations to levels similar to control otoliths. Precision of paired comparisons between cleaned otoliths and those exposed to contamination and recleaned was high (mean error 6%). The effects of storage at two temperatures (7 days at -20°C, 3 days at 1°C) were investigated. For K, Ca, Sr, Mn, and Ba, variation between control (removed immediately) and treatment otoliths (in situ freezing or chilling) was similar to variation observed within fresh otolith pairs (mean error: fresh vs frozen 5%, fresh vs iced 5%). Statistically significant but small (<10%) postmortem storage effects were observed for Na and Mg. Estimates of error indexed to natural ranges in otolith chemistry of T. thynnus and T. albacares from different geographic regions in the Atlantic and Pacific showed that error values of several elements (Mg, Mn, Ba, Na, K) accounted for a small proportion of the natural range, suggesting levels of precision achieved in this study are suitable for the purpose of stock delineation.     

Effects of specimen handling and otolith preparation on concentration of elements in fish otoliths

The use of otolith chemistry as a tool for analysing the biology of fishes assumes that the procedures used to collect and prepare otoliths for analysis do not alter their composition. With otoliths of Nemadactylus macropterus, Hoplostethus atlanticus, and Rhombosolea tapirina, we show that this assumption is not valid for the elements that can be detected using electron-probe microanalysers (those present at concentrations greater than ≃100 parts per million): all six elements routinely measured using these techniques were affected by at least one post-mortem procedure tested. Measured concentrations of calcium and strontium were relatively insensitive to most procedures tested, whereas concentrations of sodium, potassium, sulphur and chlorine were affected substantially by many commonly used procedures. The ease with which otolith composition could be modified post-mortem suggests that apparent geographic, habitat-specific or ontogenetic differences in otolith composition should be interpreted with extreme caution because of easily induced artefacts and the problem of pseudo-replication associated with the ways otoliths are sampled and prepared for analysis. Received: 23 September 1996 / Accepted: 11 April 1998     

Isolation of Atlantic cod (<Emphasis Type="Italic">Gadus morhua</Emphasis>) nursery areas

This study examines the degree of isolation among 0-group Atlantic cod in a region where a number of resident adult congregations have been found. The location of key nursery areas in Scottish coastal waters was identified from trawl surveys of settled 0-group cod around the Scottish coast. Segregation among four of these key areas; within the Clyde, Shetland Isles, Moray Firth and Buchan was investigated using otolith elemental composition. Isotope concentrations in the otoliths of cod were analysed by solution-based inductively coupled plasma mass spectrometry of the whole otolith. Discriminant analyses showed a clear separation between nursery areas based on the concentrations of three elements (manganese, barium and magnesium). The concentration of these elements was not affected by the age or size of individuals. Classification accuracy exceeded 90% for all four sites. Evidence of temporal persistence in the relative spatial differences in elemental concentrations between two sites for 2 year-classes was found. The results suggest limited exchange between sites during some period of the early life history. The significance of this limited exchange is discussed in relation to recent evidence for adult fidelity and the utility of closed areas for protecting nursery grounds.     

Population structure of red drum (<Emphasis Type="Italic">Sciaenops ocellatus</Emphasis>) as determined by otolith chemistry

To examine current genetic-based paradigms pertaining to the structure and possible philopatry of red drum populations, we used solution-based inductively coupled plasma-mass spectrometry (ICP-MS) to analyze the otolith chemistry of juvenile red drum (Sciaenops ocellatus) from eight different estuaries in the Gulf of Mexico (Gulf) and the North Atlantic Ocean. One estuary (Tampa Bay, Fla.) was sampled in three different years. Analyses of variance for five elemental ratios (Mg/Ca, Mn/Ca, Zn/Ca, Sr/Ca, Ba/Ca) were all significantly different between estuaries, as was a multi-element signature (MANOVA, Pillais trace F _{50, 1020}=19.41, P<0.0001). We also found that red drum from the Gulf could be distinguished from those taken from the Atlantic Ocean with 99.5% accuracy, likely due to differences in water chemistry between these water masses. A discriminant function developed using these elemental ratios was more than 80% accurate in assigning juvenile red drum to their natal estuary, or in the case of Tampa Bay, to the correct year of spawning. We also used laser ablation ICP-MS to examine the otolith core chemistry of adult red drum collected from spawning aggregations near Tampa Bay. Using a discriminant function analysis with a calibration data set derived from juvenile signatures, we found that 75% of the adult cores matched the juvenile signal established for Tampa Bay 1982. Although preliminary, the results presented here suggest that red drum may return to their natal estuary to spawn, which has been postulated from genetic data.Communicated by P.W. Sammarco, Chauvin     

The plant availability of auto-cast platinum group elements

The introduction of automobile catalysts has raised environmental concern, as this pollution control technology is also an emission source for platinum group elements (PGE). The main aim of this study was to assess soil and grass PGE concentrations in soils adjacent to five road networks. The soil and grass samples were collected from four distances at each site; they were 0, 1, 2 and 5 m from the road edges. The maximum soil Pt, Rh and Pd concentrations were measured at the road perimeters. Pd concentrations were much higher than Pt or Rh, possibly due to differences in its use, emission and/or soil chemistry. Rh and Pt soil concentrations accounted for 66 and 34% (P < 0.01) of the variability observed, respectively, in their plant concentrations. Grass Pd concentrations had no relationship with its total soil concentrations.     

Variation in concentrations of trace elements in otoliths and eye lenses of a temperate reef fish, Parma microlepis, as a function of depth, spatial scale, and age

 Territorial Parma microlepis (Günther) (Pomacentridae) were collected at different depths, at three sites in each of four estuaries near Sydney, Australia. Element concentrations were measured by induc- tively-coupled–plasma mass spectrometry. Significant differences in concentrations of Mn and Ba were found in the otoliths of fish sampled in different depth strata, with concentrations generally greatest in fish found in water <4 m deep. Depth-related differences varied among estuaries (e.g. 0 to 1.2 μg Ba g⁻¹ otolith). In most estuaries there was a negative linear relationship between concentrations of Mn and Ba in otoliths and actual depth. Great variation was found within an estuary among sites separated by 0.5 to 3 km. In the eye lenses, concentrations of Rb differed according to depth of capture of fish. The age of fish (1+ to 34 yr) had no influence on the concentrations of elements in otoliths or lenses. Multivariate comparisons of elemental composition (= fingerprints) detected significant differences among depth strata. Fish collected from shallow water had the clearest multivariate classification according to depth. There was a close match between our shallow strata and the average depths reached by low-salinity/high-temperature estuarine plumes. The element composition of whole otoliths and lenses represents average concentrations experienced by the fish. The temporal resolution of differences in ambient conditions is likely to be coarse in the fish (i.e. months to years). Received: 9 April 1999 / Accepted: 29 February 2000     

Confirmation of longevity in Sebastes diploproa (Pisces: Scorpaenidae) from 210Pb/226Ra measurements in otoliths

Fish ages are often estimated by assuming an annual frequency of the band-like, growth-zones recorded in the largest of their otoliths, the sagittae. The total number of growth-zones are normally determined either by counting external growth-zones (whole otolith technique) or by examining otolith cross-sections (otolith section technique). The two techniques do not always yield the same age, however, particularly in older specimens of certain fishes. To resolve this problem, otoliths of the splitnose rockfish Sebastes diploproa were examined morphologically and were assayed for their natural radionuclide concentrations. Four age groups of otoliths were identified based on growth-zone counting; in the first three, whole otolith and otolith section age estimates agreed, while in the fourth, the otolith section age substantially exceeded the whole otolith age. Radiometric analysis demonstrated that all otoliths were deficient in ²¹⁰Pb activity relative to ²²⁶Ra activity with the deficiency decreasing with increasing number of growth-zones. The magnitude of the ²¹⁰Pb/²²⁶Ra radioactive disequilibrium in each otolith group, when compared to the number of growth-zones and the otolith weight histories derived with the two techniques, identifies the growth-zones revealed by otolith sections as annual features. Thus when otolith section age exceeds whole otolith age (usually occurring after 20 to 25 yr of age for this species), the otolith section technique is the correct method of age determination. Estimates of longevity in the genus Sebastes near 80 yr are therefore confirmed.     

Comparative study on the fate of the polychlorinated biphenyl 2,4,5,2′,4′,5′-hexachlorobiphenyl and the polycyclic aromatic hydrocarbon phenanthrene in flounder (Platichthys flesus), determined by liquid scintillation counting and autoradiography

The otolith microstructure of juvenile starry flounders (Platichthys stellatus) sampled from a monitored environment was examined for evidence of lunar periodicity. Three types of biweekly cycles were observed in all of the flounder otoliths; two of the cycles were correlated with a tidal modulation of the environment. Through a multiple regression model, much of the day-to-day variability in increment width could be related to daily variations in temperature, salinity and tidal mixing. My results suggest that a 15-d increment width cycle was entrained by the interaction of a 15-d tidal cycle with temperature and salinity. The same tidal cycle/temperature interaction probably produced a biweekly pattern of increment contrast. However, the presence of otolith checks formed at weekly and/or biweekly intervals could not be so explained, although checks were consistently formed on the new and full moons.     

Within- and transgenerational effects of ocean acidification on life history of marine three-spined stickleback (Gasterosteus aculeatus)

Some studies have demonstrated that elevated CO₂ concentrations in ocean waters negatively impact metabolism and development of marine fish. Particularly, early developmental stages are probably more susceptible to ocean acidification due to insufficient regulations of their acid-base balance. Transgenerational acclimation can be an important mechanism to mediate impacts of increased CO₂ on marine species, yet very little is known about the potential of parental effects in teleosts. Therefore, transgenerational effects were investigated on life history in juvenile three-spined sticklebacks Gasterosteus aculeatus by acclimating parents (collected in April 2012, 55°03′N, 8°44′E) and offspring to ambient (~400 µatm) and elevated (~1,000 µatm) CO₂ levels and measured parental fecundity as well as offspring survival, growth and otolith characteristics. Exposure to elevated CO₂ concentrations led to an increase in clutch size in adults as well as increased juvenile survival and growth rates between 60 and 90 days post-hatch and enlarged otolith areas compared with fish from ambient CO₂ concentrations. Moreover, transgenerational effects were observed in reduced survival and body size 30 days post-hatch as well as in enlarged otoliths at the end of the experiment, when fathers or both parents were acclimated to the high-CO₂ environment. These results may suggest that elevated CO₂ concentrations had rather positive effects on life-history traits of three-spined sticklebacks, but that parental acclimation can modify these effects without improving offspring fitness. Although the mechanistic basis of such transgenerational acclimation remains unclear, selective gradients within generations seem to determine the direction of transgenerational effects.     

Oxygen and carbon stable isotopes in the otoliths of wild and laboratory-reared Australian salmon (Arripis trutta)

Australian salmon,Arripis trutta, collected from the east coast of Tasmania, Australia, in 1987, were weighed and measured and their otoliths marked by immersing fish in an oxytetracycline hydrochloride/seawater solution before placement in constant-temperature aquaria. Individual somatic and otolith growth rates were determined for input into mass balance models. Mass balance models were used to determine the oxygen and carbon isotopic composition of otolith material produced during captivity. There was a significant relationship between ¹⁸O measured in the otolith aragonite and ambient temperature (r ² = 0.77). The linear relationship between these data, where ¹⁸O = 6.69 – 0.326 (T, °C), was not significantly different from a relationship indicative of equilibrium deposition of oxygen isotopes in aragonite. Otolith carbon was significantly depleted in¹³C relative to equilibrium deposition, with depletions >6.0 at all temperatures. There was no relationship between ¹³C and temperature. It was estimated that >30% of the otolith carbon was from metabolically derived sources. Significant differences in otolith carbon isotopes among wild juvenile Australian salmon were hypothesised to be attributable to differences in diet. Levels of variability for both oxygen and carbon isotopes in laboratory-maintained and wild fish were similar to that found by other researchers for foraminifera and these results highlight the importance of large sample sizes when estimating environmental temperatures from oxygen isotopes measured in fish otoliths.