Natural Tags Research Articles

The Mangrove Nursery Paradigm Revisited: Otolith Stable Isotopes Support Nursery-to-Reef Movements by Indo-Pacific Fishes

Mangroves and seagrass beds have long been perceived as important nurseries for many fish species. While there is growing evidence from the Western Atlantic that mangrove habitats are intricately connected to coral reefs through ontogenetic fish migrations, there is an ongoing debate of the value of these coastal ecosystems in the Indo-Pacific. The present study used natural tags, viz. otolith stable carbon and oxygen isotopes, to investigate for the first time the degree to which multiple tropical juvenile habitats subsidize coral reef fish populations in the Indo Pacific (Tanzania). Otoliths of three reef fish species (Lethrinus harak, L. lentjan and Lutjanus fulviflamma) were collected in mangrove, seagrass and coral reef habitats and analyzed for stable isotope ratios in the juvenile and adult otolith zones. δ13C signatures were significantly depleted in the juvenile compared to the adult zones, indicative of different habitat use through ontogeny. Maximum likelihood analysis identified that 82% of adult reef L. harak had resided in either mangrove (29%) or seagrass (53%) or reef (18%) habitats as juveniles. Of adult L. fulviflamma caught from offshore reefs, 99% had passed through mangroves habitats as juveniles. In contrast, L. lentjan adults originated predominantly from coral reefs (65–72%) as opposed to inshore vegetated habitats (28–35%). This study presents conclusive evidence for a nursery role of Indo-Pacific mangrove habitats for reef fish populations. It shows that intertidal habitats that are only temporarily available can form an important juvenile habitat for some species, and that reef fish populations are often replenished by multiple coastal habitats. Maintaining connectivity between inshore vegetated habitats and coral reefs, and conserving habitat mosaics rather than single nursery habitats, is a major priority for the sustainability of various Indo Pacific fish populations.

A Comparison of Otolith Geochemistry and Stable Isotope Markers to Track Fish Movement: Describing Estuarine Ingress by Larval and Post-larval Halibut

Estuarine recruitment of fishes is a potential bottleneck in the life cycle of many coastal species. We investigated patterns of size-at-ingress for larval and post-larval California halibut entering the Punta Banda Estuary (PBE), Mexico, using both otolith geochemistry and carbon stable isotope ratios (SIR). Juvenile halibut (n = 126; 38–163 mm standard length [SL]) were collected from inside PBE and the adjacent exposed coast during the fall of 2003, and otoliths (geochemistry) and muscle tissues (SIR) were analyzed to reconstruct the environmental histories of individuals. Based on geochemical analyses, nearly all fish collected from PBE were characterized by a non-estuarine signature (e.g., low Mn and Ba) in the otolith growth bands deposited when fish were <30 mm SL. Although fish collected from the coast retained that signature throughout their lives, fish collected within PBE showed elevated concentrations of Mn and Ba in the otolith growth bands deposited once halibut were 30–70 mm SL, thereby recording ingress. Carbon SIR of juvenile halibut prey also differed between the estuary and coast. Muscle δ 13C values of halibut captured along the coast were consistent (ca.−15‰), while those captured in the estuary were variable and generally more enriched in 13C (−16‰ to −11‰). Both natural tagging approaches agreed that most halibut (~75 %) enter PBE long after settlement (> > 8–12 mm SL), although size-at-ingress estimates were significantly larger (mean difference = 27 mm; p < 0.001) when derived via carbon SIR than with otolith geochemistry. Potential explanations for the differences in size-at-ingress estimates involve the magnitude of isotopic and trace element gradients at this ocean–estuary boundary, the temporal resolution of environmental tags stored within otoliths and soft tissues, and the size-at-capture or somatic growth rate of juvenile halibut. We conclude by discussing the relative merits of otolith geochemistry and SIR as natural tags, and by considering the implications of secondary dispersal into estuaries by post-larval fish.

Persistence of a southern Atlantic salmon population: diversity of natal origins from otolith elemental and Sr isotopic signatures

We investigated the use of Sr:Ca, Ba:Ca, and87Sr:86Sr ratios as natural tags for determining the natal origins of juvenile and adult Atlantic salmon (Salmo salar) from 12 tributaries in the Adour basin (southwestern France) and estimated homing on a tributary scale. Geochemical signatures from core regions of the otolith were also used to identify fish from hatchery or naturally spawned sources. Quadratic discriminant function analysis (QDFA) was on average 80% successful at classifying juveniles according to their natal rivers. Adults of unknown natal origin were assigned to their natal rivers using the juvenile fingerprints from QDFA approach. Only 18 adults originated from streams not included in the juvenile database. Although most of the adults showed a marked homing instinct, homing was not perfect, and some wild fish strayed into non-natal spawning areas. Returns of hatchery-reared fish as adult spawners represented 10% of the total sampled fish. Allocation of fish to natal tributaries or hatcheries illustrated the abundance and relative contributions of natal sources, important for the recovery of Atlantic salmon in this area.

Otolith geochemistry discriminates among estuarine nursery areas of Solea solea and S. senegalensis over time

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 452:193-203 (2012) - DOI: https://doi.org/10.3354/meps09621 Otolith geochemistry discriminates among estuarine nursery areas of Solea solea and S. senegalensis over time S. E. Tanner1,*, P. Reis-Santos1, R. P. Vasconcelos1, S. França1, S. R. Thorrold2, H. N. Cabral1 1Centro de Oceanografia, Faculdade de Ciências da Universidade de Lisboa, Campo Grande, 1749-016 Lisbon, Portugal 2Biology Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA *Email: setanner@fc.ul.pt ABSTRACT: Otolith geochemistry is used increasingly as a natural tag to retrospectively determine habitat use in marine fishes. It is necessary to first conduct a thorough assessment of spatio-temporal variability before attempting to use the approach to determine estuarine residency or natal origins. In particular, knowledge of temporal variation at different scales is important when such variability may confound spatial discrimination. We assayed elements and calculated the elemental ratios to Ca (Li:Ca, Mg:Ca, Mn:Ca, Cu:Ca, Sr:Ca, Ba:Ca, Pb:Ca) in otoliths of juvenile Solea solea and Solea senegalensis, collected over several months in 2006 and 2009 in Portuguese estuaries, using laser ablation inductively coupled plasma mass spectrometry (LA ICP-MS). The elemental compositions of the otoliths varied significantly between and within years in both of the species, although the within-year variability did not interfere in spatial discrimination. The overall classification accuracy of juveniles to their estuaries of origin varied among the years and species, ranging from 71.0 to 80.1%. Established elemental signatures constitute the baseline data for future assessments of connectivity between juvenile and adult populations of the 2 sole species. KEY WORDS: Otolith chemical composition · Temporal variability · Soleidae · Connectivity · Natural tags Full text in pdf format PreviousNextCite this article as: Tanner SE, Reis-Santos P, Vasconcelos RP, França S, Thorrold SR, Cabral HN (2012) Otolith geochemistry discriminates among estuarine nursery areas of Solea solea and S. senegalensis over time. Mar Ecol Prog Ser 452:193-203. https://doi.org/10.3354/meps09621 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 452. Online publication date: April 25, 2012 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2012 Inter-Research.

Validation of Oligohaline Elemental Otolith Signatures of Striped Bass by Use of In Situ Caging Experiments and Water Chemistry

AbstractThe spatiotemporal variability in strontium (Sr), barium (Ba), magnesium (Mg), and manganese (Mn) elemental signatures of water and fish otoliths was assessed from July to October 2008 across river habitats of Albemarle Sound, North Carolina. We examined whether relationships in these signatures exist and the potential of otoliths to serve as innate chemical tags. Hatchery‐reared age‐0 striped bass Morone saxatilis were placed in cages at four different locations to test development of habitat‐specific otolith signatures. Dissolved elemental water and otolith signatures exhibited spatial variability but did not vary temporally. Chemical water signatures classified habitats with 76–81% accuracy, and otolith signatures of caged fish displayed 59–63% total classification accuracy depending on the classification method used. The elements Sr, Ba, and Mn were the main habitat discriminators, as their concentrations in otoliths were significantly correlated with concentrations in the water. Otolith Mg was not related to water chemistry and did not vary among habitats. Natural physiochemical gradients, geochemical processes, and possibly anthropogenic inputs influenced the trace elemental signatures of Albemarle Sound habitats. The unique chemical signals of the sound's river habitats validate the use of otolith signatures for determining striped bass habitat utilization in this system. Use of otolith elemental signatures as natural tags provides a quantitative method to determine the proportion of juvenile striped bass recruiting to the adult spawning stock from specific habitats, thus aiding resource managers in identifying habitats that should receive priority in restoration and conservation decisions.Received June 11, 2010; accepted September 12, 2011

Use of a Natural Isotopic Signature in Otoliths to Evaluate Scale‐Based Age Determination for American Shad

AbstractWe used δ18O signatures in otoliths as a natural tag for hatch year to evaluate the scale‐based age determination method used for adult American shad Alosa sapidissima in the York River, Virginia. Juveniles of the 2002 year‐class exhibited high δ18O values in otolith cores that identified adult members of the cohort as they returned to spawn. Recruitment of the 2002 cohort was monitored for three consecutive years, identifying age‐4, age‐5, and age‐6 individuals of the York River stock. The scale‐based age determination method was not suitable for aging age‐4, age‐5, or age‐6 American shad in the York River. On average, 50% of the individuals from the 2002 year‐class were aged incorrectly using the scale‐based method. These results suggest that the standard age determination method used for American shad is not applicable to the York River stock. Scientists and managers should use caution when applying scale‐based age estimates to stock assessments for American shad in the York River and throughout their range, as the applicability of the scale‐based method likely varies for each stock. This study highlights a promising new direction for otolith geochemistry to provide cohort‐specific markers, and it identifies several factors that should be considered when applying the technique in the future.Received March 21, 2011; accepted August 18, 2011

Natural trace elemental markers for adult red rock lobsters Jasus edwardsii vary among replicate distinct water masses

In order to determine the potential utility of trace elemental natural tags to resolve fine-scale stock structure and residency patterns in adult crustaceans, we investigated whether concentrations of trace elements in exoskeleton could be used to resolve capture sites of red rock lobsters Jasus edwardsii. Using inductively coupled plasma mass spectrometry, we measured ratios of Li, Mg, Mn, Ba and Sr to Ca in samples of exoskeleton from 4 pairs of inner fjord and outer coast sites in Fiordland on New Zealand's southwest coast. Water column salinity structure was characterised at these 8 sites from a 12 yr series of conductivity, temperature and depth casts. Information on capture site, sex, carapace length and moult stage was used in an information theoretic framework to assess the degree to which capture site could be statistically discriminated using trace element signatures of exoskeleton. Using a permutational multivariate analysis of variance, we found significant differences in trace elemental signatures of exoskeleton at the scale of 10 to 20 km for 2 of the 4 fjords. In these same 2 fjords, we found persistent differences in water column salinity structure between sites. A multivariate permutational assignment test (canonical analysis of principal coordinates) successfully reclassified individuals from all 4 pairs of sites better than chance. These results indicate that trace elements can effectively be used to discriminate capture sites of adult rock lobsters between regions with different water mass characteristics. Within these limits, trace elements of exoskeleton may prove effective as natural tags to provide valuable information on fine-scale stock structure and residency patterns for rock lobsters.

Mammalian Sialyltransferase ST3Gal-II: Its Exchange Sialylation Catalytic Properties Allow Labeling of Sialyl Residues in Mucin-Type Sialylated Glycoproteins and Specific Gangliosides

While glycosyltransferases are known to display unidirectional enzymatic activity, recent studies suggest that some can also catalyze readily reversible reactions. Recently, we found that mammalian sialyltransferase ST3Gal-II can catalyze the formation of CMP-NeuAc from 5'-CMP in the presence of a donor containing the NeuAcα2,3Galβ1,3GalNAc unit [Chandrasekaran, E. V., et al. (2008) Biochemistry 47, 320-330]. This study shows by using [9-(3)H]- or [(14)C]sialyl mucin core 2 compounds that ST3Gal-II exchanges sialyl residues between CMP-NeuAc and the NeuAcα2,3Galβ1,3GalNAc unit and also radiolabels sialyl residues in gangliosides GD1a and GT1b, but not GM1. Exchange sialylation proceeds with relative ease, which is evident from the following. (a) Radiolabeleling of fetuin was ~2-fold stronger than that of asialo fetuin when CMP- [9-(3)H]NeuAc was generated in situ from 5'-CMP and [9-(3)H]NeuAcα2,3Galβ1,3GalNAcβ1,3Galα-O-Me by ST3Gal-II. (b) ST3Gal-II exchanged radiolabels between [(14)C]sialyl fetuin and [9-(3)H]NeuAcα2,3Galβ1,3GalNAcβ1,3Galα-O-Me by generating CMP-[(14)C]- and -[9-(3)H]NeuAc through 5'-CMP; only 20.3% (14)C and 28.0% (3)H remained with the parent compounds after the sialyl exchange. The [9-(3)H]sialyl-tagged MN glycophorin A, human chorionic gonadotropin β subunit, GlyCAM-1, CD43, fetuin, porcine Cowper's gland mucin, bovine casein macroglycopeptide, human placental glycoproteins, and haptoglobin were analyzed by using Pronase digestion, mild alkaline borohydride treatment, Biogel P6, lectin agarose, and silica gel thin layer chromatography. Sulfated and sialylated O-glycans were found in GlyCAM-1 and human placental glycoproteins. This technique has the potential to serve as an important tool as it provides a natural tag for the chemical and functional characterization of O-glycan-bearing glycoproteins.

Elemental fingerprints of southern calamary (Sepioteuthis australis) reveal local recruitment sources and allow assessment of the importance of closed areas

Movement of individuals over a range of temporal and spatial scales is a critical process in determining the structure and size of populations. For most marine species, a substantial amount of movement that is responsible for connecting subpopulations occurs when individuals are too small and numerous to be tagged using conventional methods. Using the elemental fingerprints of the statoliths of the squid Sepioteuthis australis and a robust machine learning classification technique, this study determined that newly hatched squid had elemental signatures that exhibited sufficient spatial variation to act as natural tags for natal origin and that elemental signatures can be used to allocate adult squid back to their natal site. Between 55% and 84% of the adult squid caught throughout the east and southeast of Tasmania, Australia, were classified back to an area that is closed to commercial fishing over much of the peak spawning period, and this was the only location with substantive evidence of natal recruitment. Although many studies have demonstrated the potential of this approach to discern connectivity between population units, few studies have successfully done so by then examining the trace element profiles of adults in addition to those of hatchlings as we have demonstrated with S. australis.

Spatial and temporal trends in stable carbon and oxygen isotope ratios of juvenile winter flounder otoliths

Isotopic ratios of fish otoliths have been used in numerous studies as natural tags or markers to aid in the study of connectivity among fish populations. We investigated the use of spatial and temporal changes in the stable carbon and oxygen isotope ratios of otoliths to differentiate juvenile habitats of winter flounder (Pseudopleuronectes americanus). Young-of-the-year (YOY) juvenile winter flounder were collected annually over a three-year period from 18 stations along the coast of Rhode Island, USA. Sagittal otoliths were removed from fish and analyzed for stable carbon (13C/12C or δ13C) and oxygen (18O/16O or δ18O) isotope ratios using continuous flow isotope ratio mass spectrometry. Differences in isotope ratios were observed among stations and along salinity gradients in the Narragansett Bay estuary and an estuarine river system (Narrow River). Overall, the isotope ratio patterns observed among stations were consistent over the three sampling years; however, differences were noted in isotope ratios and the magnitude of the isotope ratio gradients among years. Significant positive correlations were noted between salinity and δ13C for two of the three years. For each of the three years sampled there was a highly significant positive correlation (2002, r = 0.93, P < 0.01; 2003, r = 0.85, P < 0.01; 2004, r = 0.97, P < 0.01) between δ18O and the salinity of the collection site. Also, there was a significant negative correlation between the number of months of above average river flow and δ18O for the three sampling years (r = 0.99, P < 0.05). These findings suggest that yearly changes in the volume of freshwater inputs to these estuarine habitats may be related to the differences observed in otolith δ18O isotope ratios. Because of these year-to-year differences, sampling of each cohort may be necessary in order to use this isotopic technique for winter flounder connectivity studies.

Resolving natal tags using otolith geochemistry in an estuarine fish, rainbow smelt Osmerus mordax

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 433:195-204 (2011) - DOI: https://doi.org/10.3354/meps09178 Resolving natal tags using otolith geochemistry in an estuarine fish, rainbow smelt Osmerus mordax Ian R. Bradbury1,4,*, Claudio DiBacco2, Simon R. Thorrold3, Paul V. R. Snelgrove4, Steven E. Campana2 1Fisheries and Oceans Canada, Science Branch, 80 East White Hills Road, PO Box 5667, St. John’s, Newfoundland and Labrador A1C 5X1, Canada 2Fisheries and Oceans Canada, Bedford Institute of Oceanography, PO Box 1006, Dartmouth, Nova Scotia B2Y 4A2, Canada 3Biology Department, MS #50, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA 4Ocean Sciences Centre and Biology Department, Memorial University of Newfoundland, PO Box 4200, St. John’s, Newfoundland and Labrador A1C 5S7, Canada *Email: ibradbur@me.com ABSTRACT: Dispersal and connectivity are central to stability and persistence in natural populations. The use of otolith composition as geo-referenced tags may provide unparalleled resolution of spatial movements in marine and anadromous fish, although these geochemical signatures remain largely undescribed and the factors influencing otolith composition poorly understood. We examined spatial variation in the otolith geochemistry of juvenile rainbow smelt Osmerus mordax using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and isotope ratio monitoring mass spectrometry to evaluate its potential as a natural tag to resolve fine-scale geographic patterns and dispersal of estuarine early life history stages. Otolith element ratios (Mg:Ca, Mn:Ca, Sr:Ca, Ba:Ca) and isotope ratios (δ13C, δ18O, 87:86Sr) varied significantly among locations (n = 9) and provided 83% cross-validated accuracy using a quadratic discriminant function analysis. Assignments based only on the 3 isotope variables resulted in the highest rates of correct assignment (87%), largely driven by a significant increase (~11%) in correct assignments at nearby locations (<20 km distant). Five of the 7 elements examined were significantly correlated with each other, consistent with a common response to estuarine differences. We also observed a significant effect of habitat on assignment success, in that sites with partially restricted marine access (i.e. sand bars) assigned correctly at significantly higher rates. This study demonstrates that geochemical otolith signatures are intimately linked to estuarine structure, which in turn directly influences assignment power. It also demonstrates that assignment over fine spatial scales (<20 km) can be maximized by the examination of isotope signatures and sampling of specific habitat types. KEY WORDS: Otolith chemistry · Rainbow smelt · Connectivity · Population structure · Elemental fingerprint Full text in pdf format Supplementary material PreviousNextCite this article as: Bradbury IR, DiBacco C, Thorrold SR, Snelgrove PVR, Campana SE (2011) Resolving natal tags using otolith geochemistry in an estuarine fish, rainbow smelt Osmerus mordax. Mar Ecol Prog Ser 433:195-204. https://doi.org/10.3354/meps09178 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 433. Online publication date: July 18, 2011 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2011 Inter-Research.

The first annulus of otoliths: a tool for studying intra-annual growth of walleye pollock (Theragra chalcogramma)

We quantified the growing season of yearling walleye pollock (Theragra chalcogramma) and related it to annual cycles of water temperature and day length. The study was restricted to members of the 2000 year class and thereby controlled for inter-annual variability. Juveniles were sampled from the year class during 10 cruises in the western Gulf of Alaska (GOA). Fifty percent of juveniles exhibited an annulus on 16 March 2001 (± 11 days 95% confidence interval). No regional difference was detected in the timing of annulus formation or in post-annulus growth trajectories. A model, derived from growth trajectories, estimated that the growing season lasted 204 days (22 March to 13 October 2001) and that growth rate peaked at 0.59 mm day−1 on 2 July 2001. Growth rate increased with day length and water temperature during spring and decreased in late summer possibly due to thermal stress. Secondarily, we explored the utility of otolith size at the first annulus as a natural tag to identify nursery area, but this potential was curtailed by overlap in length among regions. Our results indicate that the first annulus can be used to advance our understanding of climate forcing on marine fish growth by providing fine temporal resolution of the growing season.

Tracking Baltic hypoxia and cod migration over millennia with natural tags

Growing hypoxic and anoxic areas in coastal environments reduce fish habitat, but the interactions and impact on fish in these areas are poorly understood. Using "natural tag" properties of otoliths, we found significant correlations between the extent of Baltic Sea hypoxia and Mn/Ca ratios in regions of cod (Gadus morhua) otoliths corresponding to year 1 of life; this is associated with elevated bottom water dissolved manganese that increases with hypoxia. Elevated Mn/Ca ratios were also found in other years of life but with less frequency. We propose that cod exhibiting enhanced Mn/Ca ratios were exposed to dissolved manganese from hypoxia-induced redox dynamics in nursery areas. Neolithic (4500 B.P.) cod otoliths (n = 12) had low levels of Mn/Ca ratios, consistent with low hypoxia, but a single otolith dated to the younger Iron Age had a distinct growth band with an elevated Mn/Ca ratio. Sr/Ca patterns reflecting changes in environmental salinity and temperature were similar in both modern and Stone Age otoliths, indicating consistent migration habits across time, and Ba/Sr ratios in modern cod otoliths indicate increasing use of a more saline habitat with age. Using elemental ratios, numerous existing archival collections of otoliths could provide the means to reconstruct hypoxia exposure histories and major patterns of fish movement near "dead zones" globally.

Fin Ray Chemistry as a Potential Natural Tag for Smallmouth Bass in Northern Illinois Rivers

ABSTRACT Natural chemical markers in otoliths and fin rays have proven useful for describing environmental history of fishes in a variety of environments. However, no studies have evaluated smallmouth bass (Micropterus dolomieu) pectoral fin ray chemistry as a non-lethal alternative to otolith chemistry. We evaluated the trace element composition of smallmouth bass fin rays collected from northern Illinois rivers and determined the accuracy with which fish could be classified to their environment of capture using pectoral fin ray strontium: calcium (Sr:Ca) and barium: calcium (Ba:Ca) ratios. Fish were collected from nine sites during summer 2008. Fin ray Sr:Ca differed among some sites, reflecting previously observed differences in water and otolith chemistry for other fish species. Fin ray Ba:Ca did not differ among sites. Classification accuracy for individual fish to location of capture based on fin ray Sr:Ca was relatively poor when data from all nine sites in different watersheds were included. However, individual fish captured from the upper Illinois River watershed were accurately assigned to the river in which they were collected when data were restricted to these sites. Natural chemical signatures in fin rays will likely be effective for reconstructing environmental history of smallmouth bass when spatial differences in water chemistry are present, enabling investigations of stock mixing and recruitment sources for this species.

Spatial and ontogenetic variability in the chemical composition of juvenile common sole ( Solea solea) otoliths

A description of variations in the chemical composition of fish otoliths at different spatial scales and life history stages is a prerequisite for their use as natural tags in fish population connectivity and migration studies. Otolith geochemistry of juvenile common sole ( Solea solea), a marine migrant species collected in six Portuguese estuaries was examined. Elemental ratios (Mg:Ca, Mn:Ca, Cu:Ca, Sr:Ca, Ba:Ca, Pb:Ca) were analysed in two zones of the right otolith (corresponding to late larval and juvenile stages) using laser ablation inductively coupled plasma mass spectrometry (ICP-MS). Stable carbon and oxygen isotopes (δ 13C and δ 18O) were determined in left otoliths using isotopic ratio monitoring mass spectrometry (irm-MS). Significant differences in otolith geochemical signatures were found among estuaries, among sites within estuaries and between otolith zones. Several elemental ratios (Mg:Ca, Mn:Ca, Cu:Ca and Sr:Ca) showed consistent patterns between otolith zones and were likely influenced by environmental factors and ontogenetic effects associated with physiological changes during metamorphosis. Assignment of individuals to their collection estuary based on the otolith geochemical signatures was more accurate at the site level (81%) than among estuaries (69%). Site temperature was not correlated with any of the elemental or isotope ratios, but salinity was significantly correlated with Ba:Ca, δ 13C and δ 18O. Observed spatial variations among estuaries and sites within estuaries indicate that geochemical signatures in otoliths are accurate natural tags of estuarine habitat in common sole. Nevertheless, the significant variations observed between otolith zones should be taken into account in the design of population connectivity studies.

Distinguishing Wild from Hatchery‐Produced Juvenile Red Snapper with Otolith Chemical Signatures

AbstractOtolith chemical signatures were evaluated as natural tags to distinguish wild from hatchery‐produced juvenile red snapper Lutjanus campechanus. Otoliths were sampled from 59 hatchery‐reared fish and 146 wild fish collected over the continental shelf from northwest Florida to Texas. One sagitta from each fish was cleaned, dissolved in ultrapure nitric acid, and analyzed with sector field inductively coupled plasma mass spectrometry to test for differences in otolith element:Ca ratios (Ba:Ca, Li:Ca, Mg:Ca, Mn:Ca, and Sr:Ca) between wild and hatchery fish. The second sagitta was cleaned, ground to a fine powder, and analyzed with stable isotope ratio mass spectrometry to test for differences in delta (δ) values of the stable isotopes 13C and 18O. Significant differences existed in otolith chemical signatures between hatchery and wild juveniles (multivariate analysis of variance, Pillai's trace: P &lt; 0.001). Jackknifed classification accuracies from linear discriminant function analysis indicated that hatchery fish could be distinguished from wild fish with 100% accuracy based on otolith chemical signatures. The most important otolith chemistry feature in distinguishing hatchery from wild fish was δ13C, with the mean difference in δ13C between hatchery and wild fish (−2.6‰) being similar to the mean difference in δ13C between hatchery feeds and the predominant food of wild juveniles (−2.8‰). Overall, results suggest that otolith chemical signatures may be employed as effective natural tags for mass marking of future stockings of red snapper or other marine fishes to estimate the hatchery contribution to wild populations.

Limited diversity in natal origins of immature anadromous fish during ocean residency

Variable migration patterns can play a major role in promoting diverse life history traits among populations. However, population and stage-specific movement patterns are generally unknown yet crucial aspects of life history strategies in many highly migratory species. We used a natural tag approach using geochemical signatures in otoliths to identify natal origins of 1-year-old anadromous American shad ( Alosa sapidissima ) during ocean residency. Otolith signatures of migrants were compared with a database of baseline signatures from 20 source populations throughout their spawning range. Samples were dominated by fish from only two rivers, while all other potential source populations were nearly or completely absent. These data support the hypothesis that American shad exhibit diverse migratory behaviors, and immature individuals from populations throughout the native range do not all mix on northern summer feeding grounds. Rather, our results suggest populations of anadromous fish are distributed heterogeneously at sea in the first year of life and thus may encounter different ocean conditions at a critical early life history stage.

Otolith geochemistry does not reflect dispersal history of clownfish larvae

Natural geochemical signatures in calcified structures are commonly employed to retrospectively estimate dispersal pathways of larval fish and invertebrates. However, the accuracy of the approach is generally untested due to the absence of individuals with known dispersal histories. We used genetic parentage analysis (genotyping) to divide 110 new recruits of the orange clownfish, Amphiprion percula, from Kimbe Island, Papua New Guinea, into two groups: “self-recruiters” spawned by parents on Kimbe Island and “immigrants” that had dispersed from distant reefs (>10 km away). Analysis of daily increments in sagittal otoliths found no significant difference in PLDs or otolith growth rates between self-recruiting and immigrant larvae. We also quantified otolith Sr/Ca and Ba/Ca ratios during the larval phase using laser ablation inductively coupled plasma mass spectrometry. Again, we found no significant differences in larval profiles of either element between self-recruits and immigrants. Our results highlight the need for caution when interpreting otolith dispersal histories based on natural geochemical tags in the absence of water chemistry data or known-origin larvae with which to test the discriminatory ability of natural tags.

Ten Years of Global Evolution of the Human Respiratory Syncytial Virus BA Genotype with a 60-Nucleotide Duplication in the G Protein Gene

The emergence of natural isolates of human respiratory syncytial virus group B (HRSV-B) with a 60-nucleotide (nt) duplication in the G protein gene in Buenos Aires, Argentina, in 1999 (A. Trento et al., J. Gen. Virol. 84:3115-3120, 2003) and their dissemination worldwide allowed us to use the duplicated segment as a natural tag to examine in detail the evolution of HRSV during propagation in its natural host. Viruses with the duplicated segment were all clustered in a new genotype, named BA (A. Trento et al., J. Virol. 80:975-984, 2006). To obtain information about the prevalence of these viruses in Spain, we tested for the presence of the duplicated segment in positive HRSV-B clinical samples collected at the Severo Ochoa Hospital (Madrid) during 12 consecutive epidemics (1996-1997 to 2007-2008). Viruses with the 60-nt duplication were found in 61 samples, with a high prevalence relative to the rest of B genotypes in the most recent seasons. Global phylogenetic and demographic analysis of all G sequences containing the duplication, collected across five continents up until April 2009, revealed that the prevalence of the BA genotype increased gradually until 2004-2005, despite its rapid dissemination worldwide. After that date and coinciding with a bottleneck effect on the population size, a relatively new BA lineage (BA-IV) replaced all other group B viruses, suggesting further adaptation of the BA genotype to its natural host.

Uncovering a Latent Multinomial: Analysis of Mark–Recapture Data with Misidentification

Natural tags based on DNA fingerprints or natural features of animals are now becoming very widely used in wildlife population biology. However, classic capture-recapture models do not allow for misidentification of animals which is a potentially very serious problem with natural tags. Statistical analysis of misidentification processes is extremely difficult using traditional likelihood methods but is easily handled using Bayesian methods. We present a general framework for Bayesian analysis of categorical data arising from a latent multinomial distribution. Although our work is motivated by a specific model for misidentification in closed population capture-recapture analyses, with crucial assumptions which may not always be appropriate, the methods we develop extend naturally to a variety of other models with similar structure. Suppose that observed frequencies f are a known linear transformation f=A'x of a latent multinomial variable x with cell probability vector pi=pi(theta). Given that full conditional distributions [theta | x] can be sampled, implementation of Gibbs sampling requires only that we can sample from the full conditional distribution [x | f, theta], which is made possible by knowledge of the null space of A'. We illustrate the approach using two data sets with individual misidentification, one simulated, the other summarizing recapture data for salamanders based on natural marks.