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Adult plaice in the Irish Sea have distinct traits that reflect the spawning locations that could suggest a number of different populations. However, do connectivity pathways support this concept? Different tools are directed at measuring exchange or connectivity between different life‐history stages, and the challenge is to integrate the signals to obtain full life‐cycle estimates. Collectively, the different methods reveal stable connectivity between known spawning and nursery grounds, with sufficient exchange to maintain a single population with weak genetic structure. [ABSTRACT FROM AUTHOR]

Fish otoliths have provided biologists with a treasure-house of valuable life history information across levels of biological organization from individuals to ecosystems. Otoliths have long been used to provide the age and growth estimates which are basic data that underpin scientific fisheries and fisheries ecology. The traditional use of calcified tissues (CS) has been augmented by new applications to address questions of population connectivity, migration, and trophic ecology. These tools have become increasingly important in meeting the demands for spatially explicit and ecosystem- level management tools. Analysis of CS is now extended to applications related to spatial use (essential habitats) and as a record of past and present environmental conditions. This special volume of the ICES Journal of Marine Science contains contributions from the 5th International Otolith Symposium (IOS 2014), an ICES Science Symposium held in October 2014, in Mallorca, Spain. IOS 2014 is a continuation of a series of symposia that started in 1993 to encourage the exchange of information and expertise and to promote the development of new techniques and applications for otolith-based analysis in ecology, management, and conservation. IOS 2014 was the largest meeting to date, with 329 participants from 45 countries. The aim of IOS 2014 was to explore the use of CS as tools to support management and define indicators at environmental, community, population, and individual levels. This international forum is the centre for the exchange of information about developments in the field. New techniques of analysis, statistical treatment, and indeed new areas of application are all presented in this forum. Regular attendees are often the prominent users of otolith analyses in their home institution, and many are active in ICES work. This is also a premier venue for interaction between ICES scientists and those working in other parts of the world. North America, Japan, Taiwan, and Australia are particularly active in advancing otolith techniques, and exchange of ideas and information is crucial to improving the science in the ICES community. [ABSTRACT FROM AUTHOR]

Fish otoliths are comprised primarily of Ca CO3 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. [ABSTRACT FROM AUTHOR]

Abstract: Otolith microchemistry is a powerful tool for fisheries biology, but many applications stretch the limits of analytical techniques. Sources of measurement error were evaluated with a methodological comparison of solution and laser ablation inductively coupled plasma mass spectrometry at two laboratories, using otoliths and certified reference materials NIES-22 and FEBS-1. The intercalibration exercise was effective for Na, Ca, Zn, Cu, Sr, Ba, and Pb. Measurements of Sr were most robust, i.e. sensitivity, accuracy, and precision were least affected by laboratory, technique or sample type. Calcium and Ba measurements varied more between laboratories than between techniques. Lead and Cu measurements were more dependable across laboratory and technique while Zn measurements were more sensitive to these effects. Because the measurement of otolith elements may vary with methodology, it is imperative to consider the sensitivity, accuracy and precision for each application as the suite of elements of interest may differ. The development of reference materials has been the first step in standardization of the procedures, but there is a need for wider ranging calibration and comparison studies. [Copyright &y& Elsevier]

Geffen, 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. [ABSTRACT FROM PUBLISHER]

Therkildsen, N. O., Nielsen, E. E., Hüssy, K., Meldrup, D., and Geffen, A. J. 2010. Does DNA extraction affect the physical and chemical composition of historical cod (Gadus morhua) otoliths? – ICES Journal of Marine Science, 67: 1251–1259.Archived otoliths constitute an important source of historical DNA for use in temporal genetic studies, but such otoliths are also valuable for other research applications, e.g. growth or microchemistry studies, where information about the past is of relevance. Consequently, there are potentially conflicting interests regarding how the limited and irreplaceable otolith collections should be used. To resolve this, it is important to find out whether DNA extraction damages otoliths such that they can no longer be used for other research purposes or whether individual otoliths can be used in multiple applications. We examined the effects of three different DNA extraction methods on the elemental composition, the morphology, and the clarity of annual growth increments for successful age estimation of Atlantic cod (Gadus morhua) otoliths that had been archived for 0–31 years. The three extraction methods yielded DNA of comparable quality, and none of the methods caused major damage to the otoliths. Of the element concentrations measured, only Mg and Rb showed considerable changes resulting from DNA extraction. The physical properties of the otolith (morphology and clarity of annual growth increments) were not affected. Hence, cod otoliths can be used for several research purposes after DNA extraction. [ABSTRACT FROM PUBLISHER]

The article presents a study which classifies the fingerprint of a harvest location of individual cod Gadus Morhua L. in the northeast Atlantic. The study used a combined approach to classification, such as otolith microchemistry, otolith shape analysis, and body morphometry, which found more powerful than any single technique. It also determined that based on binomial and multinomial logistic regression analyses, cod from widely separated origins were classified with high placement success. It noted that focusing on the placement of individual fish, the study represents a decisive advance toward identifying fish harvested from protected populations.

The article discusses research on the connectivity and microchemical variation between juvenile Solea solea otoliths and adult fish habitats in the North Sea. It states that the study provides an important contribution to effective fisheries management. It stresses that geochemical or genetic techniques are indirect methods for quantifying connectivity. It depicts that laser-ablation inductively-coupled plasma mass spectrometry was used to measure the elemental composition of otoliths from juvenile sole Solea solea collected at four sampling locations in the Southern Bight of the North Sea.

Sagittal otoliths of Coryphaenoides rupestris(roundnose grenadier), Helicolenus dactylopterus(bluemouth) and Merluccius merluccius(European hake) were collected using a variety of handling and storage treatments and their elemental composition was examined using inductively coupled plasma mass spectrometry. Some differences between element concentrations were identified between the control and treatment groups, most notably for the element Li. For H. dactylopterus and M. merluccius, Li concentrations were significantly higher in the otoliths extracted with metal forceps and stored in paper envelopes (treatment), compared to those from the same fishes that had been extracted using plastic forceps and stored in polyethylene vials (control). Lower concentrations of Ba and Cr were found in M. merluccius otoliths extracted from fish that had been stored frozen. The presence or absence of elemental concentrations above the instrumental limits of detection was noted, but no significant differences were identified between otolith pairs for any of the treatments. The differences between otolith pairs attributable to storage and handling effects are small compared to between-area differences. [ABSTRACT FROM AUTHOR]