Otolith Elemental Composition Research Articles

Connectivity within estuaries: An otolith chemistry and muscle stable isotope approach

Understanding whether fish move among estuarine areas and habitats or show high site fidelity has major implications for habitat conservation and the safeguard of estuarine ecological integrity. Muscle stable isotopes (δ13C, δ15N) and otolith elemental composition (Li:Ca, Mg:Ca, Mn:Ca, Cu:Ca, Sr:Ca, Ba:Ca and Pb:Ca) were used to evaluate connectivity between two separate estuarine nursery areas in summer and autumn for juvenile age-0 Dicentrarchus labrax and Pomatoschistus microps. Distinct isotopic ratios and otolith elemental signatures were found between areas for D. labrax and P. microps, and in both sampling times. High classification accuracies to collection sites were achieved via otolith elemental signatures (80–94%), and a combined analysis using both muscle stable isotopes and otolith chemistry resulted in increased accuracy with no classification errors. Overall, low site connectivity was found for both species. The use of two distinct natural tags provided corroborative and complementary information on fish movement and intra-estuarine habitat use at different temporal scales, whilst elucidating distinct ecological and environmental linkages. Ultimately, the combined use of distinct natural tags showed great promise to unravel intra-estuarine connectivity patterns.

Latitudinal variation of migratory life histories of riverine Galaxias maculatus in Chile (36°- 47°S)

Event Abstract Back to Event Latitudinal variation of migratory life histories of riverine Galaxias maculatus in Chile (36°- 47°S) Konrad Górski1, 2*, Evelyn M. Habit2 and Aliro J. Manosalva2 1 Universidad Católica de la Santísima Concepción, Departamento de Ecología, Chile 2 Universidad de Concepción, Facultad de Ciencias Ambientales, Chile A relationship between life histories and increasing latitude has been described for Northern Hemisphere riverine fish, whereby life cycles that complete most of the growth in the ocean are favoured at higher latitudes. In the riverine ecosystems of the Southern Hemisphere many species of galaxiids display highly flexible migratory life histories and the mechanisms driving employment of different strategies remain unclear. Our objective was to assess the mechanisms driving the selection of migratory strategies of Galaxias maculatus from rivers across a gradient of latitude. Fifteen fish from three size classes as well as water samples were collected from upper, middle and lower sections of 10 river systems in Chile across latitudes 36°- 47°S. Otoliths and water samples were analysed for a suite of trace elements using Laser Ablation Inductively Coupled Plasma Mass Spectrometry. Otolith elemental composition was analysed through depth profiling to assess the frequency of marine migrations in each section of each river. The propensity of marine migrations was strongly related to latitude as well as flow and temperature dynamics of each river system. Fish in river systems at higher latitudes more frequently displayed use of marine and brackish habitats, potentially enabling them to maximise foraging opportunities and increase recruitment success. River systems originating from large Andean lakes with more predictable flow pattern (large scale spring floodplain inundations and therefore more predictable food supplies) accommodated more resident individuals with no marine signatures even at higher latitudes. Therefore, climate as well as both longitudinal (headwaters-estuary) and lateral (main channel-floodplains) hydrologic connectivity seem to govern migratory strategies of riverine Galaxias maculatus. Consequently, management strategies that promote both lateral and longitudinal connectivity within riverine ecosystems are crucial to maximise habitat availability for this native fish species. Acknowledgements Financial support: Fondecyt 3130690, DIUC 213.310.063-1AP Keywords: Fish migration, Diadromy, LA-ICP-MS, Otolith microchemistry, Puye, īnanga Conference: XV European Congress of Ichthyology, Porto, Portugal, 7 Sep - 11 Sep, 2015. Presentation Type: Oral Presentation Topic: Otoliths as a tool to study fish life cycles Citation: Górski K, Habit EM and Manosalva AJ (2015). Latitudinal variation of migratory life histories of riverine Galaxias maculatus in Chile (36°- 47°S). Front. Mar. Sci. Conference Abstract: XV European Congress of Ichthyology. doi: 10.3389/conf.fmars.2015.03.00031 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 23 Oct 2015; Published Online: 04 Nov 2015. * Correspondence: Dr. Konrad Górski, Universidad Católica de la Santísima Concepción, Departamento de Ecología, Concepción, Chile, konrad.gorski@uach.cl Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Konrad Górski Evelyn M Habit Aliro J Manosalva Google Konrad Górski Evelyn M Habit Aliro J Manosalva Google Scholar Konrad Górski Evelyn M Habit Aliro J Manosalva PubMed Konrad Górski Evelyn M Habit Aliro J Manosalva Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Extent of mangrove nursery habitats determines the geographic distribution of a coral reef fish in a South-Pacific archipelago.

Understanding the drivers of species' geographic distribution has fundamental implications for the management of biodiversity. For coral reef fishes, mangroves have long been recognized as important nursery habitats sustaining biodiversity in the Western Atlantic but there is still debate about their role in the Indo-Pacific. Here, we combined LA-ICP-MS otolith microchemistry, underwater visual censuses (UVC) and mangrove cartography to estimate the importance of mangroves for the Indo-Pacific coral reef fish Lutjanus fulviflamma in the archipelago of New Caledonia. Otolith elemental compositions allowed high discrimination of mangroves and reefs with 83.8% and 98.7% correct classification, respectively. Reefs were characterized by higher concentrations of Rb and Sr and mangroves by higher concentrations of Ba, Cr, Mn and Sn. All adult L. fulviflamma collected on reefs presented a mangrove signature during their juvenile stage with 85% inhabiting mangrove for their entire juvenile life (about 1 year). The analysis of 2942 UVC revealed that the species was absent from isolated islands of the New Caledonian archipelago where mangroves were absent. Furthermore, strong positive correlations existed between the abundance of L. fulviflamma and the area of mangrove (r = 0.84 for occurrence, 0.93 for density and 0.89 for biomass). These results indicate that mangrove forest is an obligatory juvenile habitat for L. fulviflamma in New Caledonia and emphasize the potential importance of mangroves for Indo-Pacific coral reef fishes.

Amphidromy and marine larval phase of ancestral gobioids Rhyacichthys guilberti and Protogobius attiti (Teleostei: Rhyacichthyidae)

Even if amphidromous fish species contribute most to the diversity of fish communities in the tropical insular rivers, their biological cycle remain poorly known. For the first time, the otolith elemental composition and microstructure of two ancestral gobioids, Rhyacichthys guilberti and Protogobius attiti, were investigated to describe their biological cycle and pelagic larval duration (PLD). The otolith analysis using a femtosecond laser ablation coupled to an inductively coupled plasma–mass spectrometer (fs-LA-ICP-MS) revealed an amphidromous life history for R. guilberti and it suggested a progressive habitat shift from a marine habitat to a freshwater environment for P. attiti. For the first time, an endemic species, P. attiti, showed longer and more variable PLD (55.2 ± 13.5 days) than did a widespread one (R. guilberti: ~30 days). These results need to be confirmed by analysing more samples but suggest that factors other than the PLD control endemism and dispersal processes. In association with this first description of the biological cycle for both species, such an approach is a prerequisite for the management and conservation of both patrimonial species.

Evidence for meta-population structure of Sardina pilchardus in the Atlantic Iberian waters from otolith elemental signatures of a strong cohort

The European sardine is one of the most important clupeoid fish captured by the Portuguese and Spanish purse-seine fleets in the Atlantic waters of the Iberian Peninsula. Despite the importance of this species, and substantial decrease in catches over the last two decades, knowledge about sardine movements and connectivity between their juvenile recruitment areas and the adult fishing grounds is scarce. In this study otolith elemental fingerprints (both whole and core) of juvenile recruits (ages 0+ and 1+) and adults (age 3+) collected along the Portuguese coast (North, Central and South regions) were used to demonstrate regional population structure. The whole and otolith core analyses represented the entire life-history prior to capture and the larval/recruitment phases (first 2 months of life), respectively. Molar ratios of Sr/Ca, Mg/Ca, Mn/Ca and Ba/Ca provided location-specific elemental signatures, although otolith elemental compositions were not temporally stable within a year-class, particularly for Mg/Ca and Ba/Ca. Classification accuracy rates obtained from quadratic discriminant function analysis of core and whole otolith chemistry data of adults were relatively high (63% and 79% mean accuracy percentages, respectively). The results support the hypothesis of meta-population structure of the sardine stock in the Atlanto-Iberian waters. However, because there was evidence of some mixing among adult aggregations, and adult aggregations were largely derived from a common northern juvenile recruitment area they cannot be classified as entirely separate stock units for fisheries management purposes. The maximum likelihood analysis suggested for the 2004 cohort that replenishment of adult populations of sardine along the Portuguese coast was mostly derived from a single northern recruitment area.

Otolith elemental and Sr isotopic composition as a natal tag for Biwa salmon Oncorhynchus masou subsp. in Lake Biwa, Japan

We examined the elemental and Sr isotopic composition of otoliths from Biwa salmon Oncorhynchus masou subsp., an endemic subspecies of the O. masou complex in the Lake Biwa (Japan) water system, to evaluate the usefulness of otolith chemistry as a natural tag for studying homing and migration history. Fish and water samples were collected from 5 major spawning rivers and 2 hatcheries. The elemental content relative to calcium (Na/Ca, Mg/Ca, K/Ca, Mn/Ca, Sr/Ca, and Ba/Ca) and Sr isotopic ratio ( 87 Sr/ 86 Sr) of the samples were analyzed using laser abla- tion inductively coupled plasma mass spectrometry and thermal ionization mass spectrometry, respectively. Significant variations in otolith and water sample chemistry were detected. We also observed significant relationships between the Sr/Ca, Ba/Ca, and 87 Sr/ 86 Sr ratios of otoliths and those of ambient water samples from which the fish were collected. The other elemental ratios and all elemental concentrations in the otoliths showed variations independent of water chemistry. Jackknife cross-validation using quadratic discriminant function analysis showed that otolith ele- mental composition could classify Biwa salmon juveniles by sampling location, with a high level of accuracy (mean 79%). The mean accuracy increased to 89% when Sr isotopic ratios were com- bined with elemental data. This study thus demonstrated the suitability of otolith chemistry for determining fish distribution. Otolith chemistry successfully revealed the natal (hatching) loca- tions of individual fish, facilitating further understanding of migration history and habitat use, which are essential for establishing effective fishery management strategies for this Near Threat- ened subspecies.

Species and Life History Affect the Utility of Otolith Chemical Composition for Determining Natal Stream of Origin for Pacific Salmon

AbstractTo test the utility of otolith chemical composition as a tool for determining the natal stream of origin for salmon, we examined water chemistry and otoliths of juvenile and adult Chum Salmon Oncorhynchus keta and Coho Salmon O. kisutch from three watersheds (five rivers) in the Norton Sound region of Alaska. The two species are characterized by different life histories: Coho Salmon rear in freshwater for up to 3 years, whereas Chum Salmon emigrate from freshwater shortly after emergence. We used laser ablation (LA) inductively coupled plasma (ICP) mass spectrometry (MS) to quantify element: Ca ratios for Mg, Mn, Zn, Sr, and Ba, and we used multicollector LA‐ICP‐MS to determine 87Sr:86Sr ratios in otolith regions corresponding to the period of freshwater residence. Significant differences existed in both water and otolith elemental composition, suggesting that otolith composition could be used to discriminate the natal origin of Coho Salmon and Chum Salmon but only when 87Sr:86Sr ratios were included in the discriminant function analyses. The best discriminant model included 87Sr:86Sr ratios, and without 87Sr:86Sr ratios it was difficult to discriminate among watersheds and rivers. Classification accuracy was 80% for Coho Salmon and 68% for Chum Salmon, indicating that this method does not provide sufficient sensitivity to estimate straying rates of Pacific salmon at the scale we studied.

Temporal stability of otolith elemental fingerprints discriminates among lagoon nursery habitats

The chemical composition of fish otoliths reflects that of the water masses that they inhabit. Otolith elemental compositions can, therefore, be used as natural tags to discriminate among habitats. However, for retrospective habitat identification to be valid and reliable for any adult, irrespective of its age, significant differences in environmental conditions, and therefore otolith signatures, must be temporally stable within each habitat, otherwise connectivity studies have to be carried out by matching year-classes to the corresponding annual fingerprints. This study investigated how various different combinations of chemical elements in otoliths could distinguish, over three separate years, between four coastal lagoon habitats used annually as nurseries by gilthead sea bream (Sparus aurata L.) in the Gulf of Lions (NW Mediterranean). A series of nine elements were measured in otoliths of 301 S. aurata juveniles collected in the four lagoons in 2008, 2010 and 2011. Percentages of correct re-assignment of juveniles to their lagoon of origin were calculated with the Random Forest classification method, considering every possible combination of elements. This revealed both spatial and temporal variations in accuracy of habitat identification, with correct re-assignment to each lagoon ranging from 44 to 99% depending on the year and the lagoon. There were also annual differences in the combination of elements that provided the best discrimination among the lagoons. Despite this, when the data from the three years were pooled, a combination of eight elements (B, Ba, Cu, Li, Mg, Rb, Sr and Y) provided greater than 70% correct re-assignment to each single lagoon, with a multi-annual global accuracy of 79%. When considering the years separately, discrimination accuracy with these elemental fingerprints was above 90% for 2008 and 2010. It decreased to 61% in 2011, when unusually heavy rainfall occurred, which presumably reduced chemical differences among several of the lagoons. This study highlights the need for multi-annual sampling, and multi-elemental analysis, when developing otolith microchemical fingerprints to explore nursery habitat use in coastal fishes.

Effects of temperature, salinity and water composition on otolith elemental incorporation of Dicentrarchus labrax

Elemental composition of fish otoliths provides a valuable means to retrospectively determine a fish's environmental history over time. However, to reconstruct the patterns of fish movement and migration using otolith chemistry it is essential to establish the link between changing environmental variables, in particular, temperature, salinity and elemental concentration, and the concentration of elements within otoliths. Using a controlled laboratory experiment we investigated how otolith chemical composition of Sr:Ca and Ba:Ca was affected by temperature, salinity and ambient elemental concentration in juvenile sea bass Dicentrarchus labrax. A total of 18 treatments representing all combinations of temperature (21, 25°C), salinity (10, 20, 30) and ambient water concentrations (Low, Medium, High) were assessed. Otolith elemental composition of Sr:Ca and Ba:Ca were positively related to ambient water concentration. Consistent interactions between salinity and concentration were found for otolith composition, as well as elemental incorporation, for both elements. Positive effects of temperature on elemental composition and incorporation were also detected. The partition coefficient of Ba (DBa) initially decreased with increased water concentration but increased at the highest level of added elemental concentration. Across salinity gradients, DBa increased whilst distinct patterns in variation of DSr occurred within water concentration treatments. Our data highlight the importance of validation experiments to decipher species-specific patterns in otolith chemistry, particularly if the goal is to reconstruct fish life histories and determine fish movement patterns and habitat use.

Influence of the limit of detection on classification using otolith elemental signatures

Otolith elemental composition is a commonly used tool in the classification of fish stocks. Lower detection limits associated with trace element analysis techniques are the source of much debate among fisheries biologists. Using empirical data from Atlantic herring (Clupea harengus) from two separate origins in the British Isles, we addressed methods of treating data at or falling below detection limits and the implications of each treatment for discrimination and classification analysis. Estimating actual values of non-detected concentrations, through imputation, is now a plausible and simply applied strategy and should be considered as an alternative to constant replacement. We compare a robust regression approach to estimating values for non-detects alongside a variety of constant replacement methods. We also show the value of a highly censored variable in understanding population discrimination; despite 40% of readings for one element being non-detects, we found that its removal was detrimental to the discriminatory power of the analysis.

Spatial and temporal variations in otolith chemistry and relationships with water chemistry: a useful tool to distinguish Atlantic salmon Salmo salar parr from different natal streams

Otolith elemental (Sr:Ca, Ba:Ca, Mn:Ca, Mg:Ca and Rb:Ca) and isotopic (⁸⁷Sr:⁸⁶Sr) profiles from several annual cohorts of juvenile Atlantic salmon Salmo salar were related to the physico-chemical characteristics (chemical signatures, flow rate, temperature and conductivity) of their natal rivers over an annual hydrological cycle. Only Sr:Ca, Ba:Ca and ⁸⁷Sr:⁸⁶Sr in otoliths were determined by their respective ratios in the ambient water. Sr:Ca ratios in stream waters fluctuated strongly on a seasonal basis, but these fluctuations, mainly driven by water flow regimes, were not recorded in the otoliths. Otolith Sr:Ca ratios remained constant during freshwater residency at a given site and were exclusively related to water Sr:Ca ratios during low flow periods. While interannual differences in otolith elemental composition among rivers were observed, this variability was minor compared to geographic variability and did not limit classification of juveniles to their natal stream. Success in discriminating fish from different sites was greatest using Sr isotopes as it remained relatively constant across years at a given location.

Resiliency of juvenile walleye pollock to projected levels of ocean acidification

As atmospheric concentrations of CO2 rise, the pH of high-latitude oceans is pre- dicted to decrease by 0.3 to 0.5 units by 2100. Several biological consequences of ocean acidifica- tion across this pH range have already been documented in invertebrates and tropical marine fishes. However, little work has been done examining potential responses of the temperate and boreal marine fish species that support major fisheries. In 2 experiments, we examined the growth responses of juvenile walleye pollock Theragra chalcogramma at ambient and 3 elevated CO2 lev- els. In a short-term experiment with yearlings, CO2 treatment had no significant effect on growth or condition after 6 wk of rearing. Elevated CO2 levels (>450 µatm) increased the rate of otolith deposition, but did not affect otolith elemental composition. In a second experiment, growth in length of sub-yearlings over 12 wk at 8°C was 7.2% faster in the 2 higher CO2 treatments (>1200 µatm) than in the lower CO2 treatments (<900 µatm). Growth of sub-yearlings measured during 11 subsequent weeks of rearing at 2.5°C did not differ among CO2 treatments. There was no effect of CO2 treatment on condition factor following either phase of the experiment. Sub- yearling consumption rates were not directly affected by CO2 treatment, confirming that growth at elevated CO2 levels is not maintained through compensatory feeding. While not exhaustive of potential interactive environmental factors, these experiments demonstrate a general resiliency of growth energetics in juvenile walleye pollock to the direct effects of CO2 changes predicted for the Gulf of Alaska and Bering Sea in the next century.

Preliminary indication of ontogenetic and spatial variations in the whole otolith isotopic and elemental signatures of &lt;i&gt;Solea solea&lt;/i&gt; in the Gulf of Lions (NW Mediterranean)

Knowledge of fish life cycles is important for exploited species. In the Mediterranean Sea, catches of common sole ( Solea solea ) have fluctuated widely since the 1970s. Solea solea displays an ontogenetic shift in habitat: sole larvae are marine, juveniles inhabit shallow marine waters and coastal lagoons and adults inhabit deeper marine waters. Although the results of this study were obtained using only a small set of individuals, the otolith elemental composition and isotopic ratios were investigated for the three life stages (post-larval, juvenile and adult) in order to acquire a better knowledge of the variability in environmental conditions experienced by the common sole at each life stage in the NW Mediterranean. Moreover, this study provides the first evaluation of the potential of whole otolith microchemistry for investigating habitat connectivity in sole populations from the Gulf of Lions. The elemental and isotopic signatures of otoliths of post-larvae captured in various environments appear to show variations related to the River Rhone inputs (high Ba/Ca and low Sr/Ca ratios). Juveniles appear to show significant variations in otolith elemental and isotopic compositions depending not only on the physico-chemical properties of water in the nurseries they inhabit (Rhone River, Thau or Mauguio lagoons), but also as a result of variations in the chemical composition of their surrounding sediments and in their benthic prey. Adults exhibit otolith differences for isotopic ratios only, which is probably linked to the River Rhone inputs. Finally, several significant relationships were observed between otolith elemental composition and fish size in specimens captured at the River Rhone mouth. However, these variations seem to be an indication of the composition acquired in each environment rather than a sign of ontogeny.

Accumulation of Mn, Co, Zn, Rb, Cd, Sn, Ba, Sr, and Pb in the otoliths and tissues of eel (Anguilla anguilla) following long-term exposure in an estuarine environment

Aiming at increasing the resolution of otolith tracers, we investigated the possibility to use Mn, Co, Zn, Rb, Cd, Sn, Ba, Sr, and Pb otolith composition to retrieve the movements of eels (Anguilla anguilla) in the lower Gironde watershed. Caging experiments were designed to validate the site specific otolith signatures. Individually identified eels were reared in cages in three locations along the estuarine and river gradient. Three trials were set up for successive periods of 3months and 6months. Water Mn, Co, Zn, Rb, Cd, Sn, Ba, Sr, and Pb concentrations were monitored. The eel otolith composition corresponding to the experimental period was measured with an ICPMS coupled with a femtosecond laser. Liver Cd, Zn and Pb concentrations were measured. For each caging experiments, we tested the influence of individual weight gain, caging site and trial on elemental otolith concentrations. Mn, Co, Zn, Rb, Cd, Sn, Ba, Sr, and Pb were detected in eel otolith above the detection limits. Otolith Sr and Ba concentrations significantly discriminated the caging sites for one trial. Individual weight gain did not have a significant influence on otolith elemental concentrations. Co, Rb, Cd, Sn, Zn, Sr and Ba otolith concentrations were significantly influenced by the trials. Water elemental composition was only partly reflected by otolith elemental composition. The results showed that otolith composition had a more integrative value than water composition. Complex elemental seasonal variations and individual eel incorporation potential complicated the interpretation of otolith composition. Liver and otolith Cd and Zn concentrations did not show a statistically significant correlation.

Taxonomic and geographic influences on fish otolith microchemistry

AbstractFish otoliths are comprised primarily of CaCO3 and grow throughout an individual's lifetime. The chemical composition of otoliths is often a distinctive characteristic of the populations that live in discrete areas, and as a result, it has been used for population classification studies, supporting ecological and fisheries research. However, the deposition of chemical elements in the otolith is influenced by both physiological and environmental factors. We review observed trends in otolith elemental composition and then test the taxonomic and geographical patterns, using marine species in European waters. anova comparisons and multivariate analyses revealed strong taxonomic signals in species inhabiting the same region. Variations in Sr, Mg, Mn and Ba concentrations were most often species specific; for example, multivariate analyses showed separation of cod (Gadus morhua) and herring (Clupea harengus) based primarily on Mg and Sr concentrations, while Mn and Ba concentrations separated bluemouth (Helicolenus dactylopterus) and sole (Solea solea). The relative contributions of taxonomic and regional factors varied between elements. For cod and herring, for example, species‐specific differences explain 75% of the variation for Mn, but only 50% of the variation in Sr. Although there are significant regional differences within a single species on both a restricted and extensive geographic scale, these regional patterns are not the same for each species. As the amount of otolith composition data increases, representing more species and regions, as well as longer time series, further analyses can provide a deeper insight into the predictability of using otolith data in fisheries ecology.

Assessing the usefulness of otolith elemental compositions for evaluating the population structure of the Pacific herring Clupea pallasii in northern Japan

The present study examined whether the elemental compositions of whole otoliths and chronological transect profiles of otoliths covering the complete life history are useful for evaluating the population structure of Pacific herring. Eight elemental ratios, Li:Ca, Na:Ca, Mg:Ca, K:Ca, Mn:Ca, Cu:Ca, Sr:Ca, and Ba:Ca, were measured in whole otoliths and in a series of ablations across the life-history transects by laser ablation inductively coupled plasma mass spectrometry. We studied fish from three sample groups collected from Lake Obuchinuma, Miyako Bay, and Akkeshi Bay of northern Japan from March to May 2008. Significant differences were found in the Na:Ca, Mg:Ca, P:Ca, K:Ca, Mn:Ca, and Ba:Ca ratios of the whole otoliths and in the Li:Ca, Na:Ca, K:Ca, Mn:Ca, Sr:Ca, and Ba:Ca ratios of the otolith core among the three sample groups. Therefore, the present study showed clear differences in elemental composition among the three sample groups from different locations, suggesting that otolith elemental compositions reflect the habitats experienced by individual fish.

Effects of water temperature and barium concentration on otolith composition along a salinity gradient: Implications for migratory reconstructions

Analysis of naturally occurring variation in otolith elemental composition has become a common approach for retrospectively determining migratory history in diadromous fishes. Environmental factors, such as temperature, salinity, and ambient water concentration, can independently, or in an interactive manner, affect elemental incorporation rates. Furthermore, the relative importance of kinetic and metabolic (or “vital”) effects on elemental incorporation remains unclear. In this study, a repeated measures design was used to: (1) quantify the effects of water temperature (9 °C, 12 °C, 15 °C) and freshwater Ba:Ca levels (low, intermediate, and high) on elemental partitioning and otolith composition (Mg:Ca, Sr:Ca, Ba:Ca) in juvenile Chinook salmon ( Oncorhynchus tshawytscha) along a salinity gradient (0, 5, 10, 14); and (2) estimate the lag time between physical exposure to chemically distinct water masses and changes in otolith composition. Additionally, relationships between elemental incorporation and somatic and otolith growth rates were evaluated across and within temperature treatments to identify potential rate effects. Otolith incorporation of Sr and Ba was positively related to water concentration whereas Mg incorporation was not. For Sr and Mg, there were significant interactions between temperature and salinity ( p ≤ 0.01). For Ba, there were complex interactions among temperature, water Ba:Ca values, and salinity ( p ≤ 0.01). In certain instances, interactive effects of temperature and salinity were large enough to confound interpretation of field data. Furthermore, there was evidence for negative effects of somatic growth rate on the incorporation of Ba that were consistent across temperatures ( r = − 0.32 to − 0.72). Observations were consistently contrary to expectations based on models of elemental incorporation for abiotic aragonite, highlighting the importance of vital effects and indicating that species-specific models of incorporation may be necessary. Changes in otolith composition were detected within 2–3 d of a change in water composition but otolith composition did not stabilize for 12–14 d, indicating that habitat transitions should be discernable in a short period of time but the otolith may not reflect ambient water levels for up to 2 weeks. These observations underscore the need to evaluate the effects of abiotic and biotic factors on otolith elemental incorporation in settings that mimic natural conditions to accurately interpret field data.

Characterization of herring populations west of the British Isles: an investigation of mixing based on otolith microchemistry

AbstractGeffen, A. J., Nash, R. D. M., and Dickey-Collas, M. 2011. Characterization of herring populations west of the British Isles: an investigation of mixing based on otolith microchemistry. – ICES Journal of Marine Science, 68: 1447–1458. Herring along the west coast of the British Isles are managed and assessed as a series of discrete stocks. The relationship between the spawning components, mixed (feeding) aggregations, and juveniles in nursery areas for these stocks was modelled by discriminant analysis and integrated stock mixture analysis based on otolith elemental composition data. The relative elemental concentrations produced otolith signals corresponding to three main groupings of nursery-ground fish representing the Irish Sea, Scottish sea lochs, and the Minch. There were significant differences among spawning groups in the otolith concentrations of Li, Na, Mg, Mn, Sr, and Ba. Inclusion of length-at-age information improved the classification rates, ranging overall from 35 to 100%. Spawning groups consist of individuals from a number of different nursery areas and originate from several different management areas. Each of the mixed aggregations contained at least three spawning components. Results suggest that most west coast herring belong to interconnected populations subject to mixing and that populations are not discrete, so the current practice of assessments based on individual spawning components will probably not provide sufficiently robust information for management advice. The complexity of herring populations needs to be considered for both fisheries and coastal-zone management.

Fingerprints of lagoonal life: Migration of the marine flatfish Solea solea assessed by stable isotopes and otolith microchemistry

The commercially important marine flatfish common sole (Solea solea) facultatively uses NW Mediterranean lagoons as nurseries. To assess the imprint left by the lagoonal passage, muscle carbon (C) and nitrogen (N) isotope values of S. solea juveniles caught in Mauguio lagoon in spring (shortly after arrival from the sea) and in autumn (before the return to the sea) were compared with values of juveniles from adjacent coastal marine nurseries. In addition, in the lagoon, sole otolith stable isotope (C and oxygen (O)) and elemental (11 elements) composition in spring and autumn, and the stable isotope composition (C and N) of organic matter sources in autumn, were determined. Overall, our data indicate that a distinct lagoonal signature existed. Specifically, lagoon soles showed a strong enrichment in muscle tissue 15N (>6‰) compared to their coastal relatives, likely linked to sewage inputs (see below), and a depletion in 13C (1–2‰), indicative of higher importance of 13C depleted terrestrial POM in the lagoon compared to coastal nurseries. In addition, over the time spent in the lagoon, sole otolith δ13C and δ18O values and otolith elemental composition changed significantly. Analysis of the lagoon sole foodweb based on C and N isotopes placed sediment particulate organic matter (POM) at the base. Seagrasses, formerly common but in decline in Mauguio lagoon, played a minor role in the detritus cycle. The very strong 15N enrichment of the entire foodweb (+7 to +11‰) compared to little impacted lagoons and coastal areas testified of important human sewage inputs. Regarding the S. solea migration, the analysis of higher turnover and fast growth muscle tissue and metabolically inert and slower growth otoliths indicated that soles arrived at least several weeks prior to capture in spring, and that no migrations took place in summer. In the autumn, the high muscle δ15N value acquired in Mauguio lagoon would be a good marker of recent return to the sea, whereas altered otolith δ18O values and elemental ratios hold promise as long-term markers. The combination of several complementary tracers from muscle and otoliths may present the chance to distinguish between fish from specific lagoons and coastal nurseries in the future.

High-latitude climate variability and its effect on fisheries resources as revealed by fossil cod otoliths

Abstract Geffen, A. J., Høie, H., Folkvord, A., Hufthammer, A. K., Andersson, C., Ninnemann, U., Pedersen, R. B., and Nedreaas, K. 2011. High-latitude climate variability and its effect on fisheries resources as revealed by fossil cod otoliths. – ICES Journal of Marine Science, 68: 1081–1089. Cod (Gadus morhua) otoliths from archaeological sites in northern Norway were analysed to reconstruct the temperature regime and determine the age structure, growth, and population identity of the fish harvested. Otoliths were selected from late- and post-medieval sites (700–300 years ago) to evaluate historical changes in the geographic region that matches the present-day stocks of Northeast Arctic cod (NEAC) and Norwegian coastal cod (NCC). Seasonal temperature cycles were reconstructed from stable isotope (δ18O) measurements along transects representing fish ages 1.5–3 years old. Reconstructions of the size, age, and growth characteristics of individual fish were based on otolith growth increments. The geographical source and stock identity of the individuals were estimated based on otolith elemental composition and otolith growth features. Both NCC and NEAC fish were represented at Måsøy and Vanna. The results indicate that fishing at Vanna exploited NEAC during their spawning migration, compared with fishing at Måsøy, which was restricted to more coastal fish. Fish growth patterns appeared to be affected by changes in the temperature regimes as estimated from otolith δ18O and back-calculated fish length-at-age, with evident differences between pre- and post-1600 periods.