SEGH Articles

Otoliths: The little “White” box recorders of the fish world

01 February 2013
The use of fish otolith (ear bone) microchemistry has enabled scientists understand better fish migratory patterns and stock identification


Andy Marriott is in his final year studying for a PhD in the use of biogeochemical tags (primarily otoliths) to determine the origins and movement patterns of fishes. This NERC-funded research project at Bangor University, North Wales is supervised by Dr. Ian McCarthy and Prof. Chris Richardson of the School of Ocean Sciences at Bangor University, Dr Simon Chenery at the British Geological Survey and Dr Mike Armstrong (Case partner) from the Centre for Environment, Fisheries and Aquaculture Science.


Since graduating from Bangor University in 2007 where Andy studied the population biology of the red gurnard (Chelidonichthys cuculus) in inshore waters of Eastern Anglesey his interest in fish otoliths, or ear stones as they are more commonly known, has grown. Otoliths are paired calcified structures, situated in semi-circular canals either side of the brain and are used by the fish as auditory and/or balance organs. Their use as indicators in identifying the age of fish has been well documented with the first observations of otolith growth increments “annuli” by Reibisch in 1899. These annuli grow throughout the life of the fish creating banding patterns and can be a reliable way of estimating daily, weekly, monthly and yearly growth patterns. However, it is their use as an environmental recorder and biogeochemical tag which has accelerated the use of these metabolically inert structures during the last decade. The use of otolith microchemistry has enabled scientists to get a better understanding of fish migratory patterns, stock identification and the detection of Diadromy (fish moving between fresh and marine waters) with the reconstruction of temperature and salinity histories.

Variations observed in the chemical composition of fish otoliths, such as changes in trace elements incorporated within the otolith matrix, has enabled the discrimination between the life histories of fish species which spend some part of their life residing in water bodies which differ in their chemical composition. For example, moving between marine and freshwater (in either direction), or moving between bodies of water in either the marine or freshwater environment with distinct (natural or anthropogenic) water chemistry. These elemental tags may provide valuable information on movement patterns of larval and juvenile fish, may enable the identification of distinct “groups” of fish based on spawning or nursery location and allow the study of connectivity and habitat utilisation in fish populations.

Working with the BGS, one part of Andy’s PhD project has been to examine whether otolith microchemistry can be used to identify the rivers of origin of juvenile brown trout parr (Salmo trutta) collected from 36 rivers in NW England, Wales, Isle of Man, SW Scotland and the east coast of Ireland which drain into the Irish Sea. The ultimate aim of this research being to determine whether river- or region-specific chemical tags exist in the otoliths which may be used to identify sea-caught sea trout (the form of S. trutta that migrates to sea to feed) back to their region or river of origin.

Otoliths removed from trout parr have been analysed using solution-based inductively-coupled plasma mass spectrometry (sb-ICP-MS) to measure the element: Ca ratios of Mg, Mn, Sr and Ba and data analyses are currently underway to determine whether these biogeochemical tags can be used to classify the trout parr back to source. Relating the otolith chemical tag in a given catchment to the underlying geological bedrock formations and water chemistry may also assist in our understanding of why the trout parr are being classified back to particular locations. “Otoliths may be acting as little “white box recorders” of the entire life history of the fish with the differences in ambient water and various environmental conditions experienced by the fish all stored within the calcified structures. The exciting bit is trying to untangle the secrets held within the otoliths to tell us the life story of that fish”.


Future work involving the analysis of otoliths collected from adult sea trout may allow the identification of those adults back to their regions (or even rivers) of origin using the chemical tags identified in the juvenile trout parr. The validity of using trace elements as biogeochemical tags found within fish otoliths of brown trout parr may also assist in future conservation and management planning for this species.

Andy Marriott, 

Nuffield Fish Laboratory, Bangor University, UK.




Marriott, A. L., Latchford, J. W. and McCarthy, I. D. 2010. Population biology of the red gurnard (Aspitrigla cuculus L.; Triglidae) in the inshore waters of Eastern Anglesey and Northwest Wales. Journal of Applied Ichthyology. 26, 504-512.

Keep up to date

Submit Content

Members can keep in touch with their colleagues through short news and events articles of interest to the SEGH community.

Science in the News

Latest on-line papers from the SEGH journal: Environmental Geochemistry and Health

  • Date palm waste biochars alter a soil respiration, microbial biomass carbon, and heavy metal mobility in contaminated mined soil 2017-04-19


    A 30-day incubation experiment was conducted using a heavy metal-contaminated mined soil amended with date palm feedstock (FS) and its derivative biochars (BCs) at three pyrolysis temperatures of 300 (BC-300), 500 (BC-500), and 700 °C (BC-700) with different application rates (0.0, 5, 15, and 30 g kg−1) to investigate their short-term effects on soil respiration (CO2–C efflux), microbial biomass carbon (MBC), soil organic carbon (SOC), mobile fraction of heavy metals (Cd, Cu, Pb, Zn, Mn, and Fe), pH, and electrical conductivity (EC). The results showed that FS and BC-300 with increasing addition rate significantly reduced soil pH, whereas SOC, CO2–C efflux, and soil MBC were increased compared to the control. On the contrary, BC-500 and BC-700 increased soil pH at early stage of incubation and have small or no effects on SOC, CO2–C efflux, and MBC. Based on the results, the date palm biochars exhibited much lower cumulative CO2–C efflux than feedstock, even with low-temperature biochar, indicating that BCs have C sequestration potential. Applying BC-700 at 15 and 30 g kg−1 significantly reduced cumulative CO2–C efflux by 21.8 and 45.4% compared to the control, respectively. The incorporation of FS into contaminated soil significantly increased the mobile content of Cd and Mn, but decreased the mobile content of Cu. However, BC-300 significantly reduced the mobile content of Cd, Cu, Pb, and Zn. It could be concluded that low-temperature biochar could be used as a soil amendment for reducing heavy metal mobility in mining contaminated soil in addition to minimize soil CO2–C efflux.

  • Historical record of anthropogenic polycyclic aromatic hydrocarbons in a lake sediment from the southern Tibetan Plateau 2017-04-17


    High-altitude lake sediments can be used as natural archives to reconstruct the history of pollutants. In this work, the temporal distribution of polycyclic aromatic hydrocarbons (PAHs) was determined in a sediment core collected from the southern Tibetan Plateau (TP), which was dated by using the 210Pb dating method and validated with the 137Cs fallout peak. The concentrations of the anthropogenic PAHs (Σ8PAH) in the sediment core ranged from 0.83 to 12 ng/g dw, and the fluxes of the Σ8PAH were in the range of 2.1–27 g/cm2/year. The temporal variations in the concentration and input flux of anthropogenic PAHs were low with little variability before the 1950s, and then gradually increased from the 1950s to the 1980s, and an accelerated increase was observed after the early 1980s. The content of total organic carbon played an insignificant role in affecting the time trends of PAHs in the sediment core. Diagnostic concentration fractions of PAH components indicate PAHs in the lake sediment of the southern TP which are mainly from biomass burning and/or from long-range atmospheric transport.

  • Determination of the potential implementation impact of 2016 ministry of environmental protection generic assessment criteria for potentially contaminated sites in China 2017-04-12


    The Ministry of Environmental Protection of China issued a 3rd draft edition of risk-based Generic Assessment Criteria (the MEP-GAC) in March 2016. Since these will be the first authoritative GAC in China, their implementation is likely to have a significant impact on China’s growing contaminated land management sector. This study aims to determine the potential implementation impact of the MEP-GAC through an in-depth analysis of the management context, land use scenarios, health criteria values adopted and exposure pathways considered. The MEP-GAC have been proposed for two broad categories of land use scenarios for contaminated land risk assessment, and these two categories of land use scenarios need to be further delved, and a MEP-GAC for Chinese cultivated land scenario ought to be developed, to ensure human health protection of Chinese farmers. The MEP-GAC have adopted 10−6 as the acceptable lifetime cancer risk, given the widespread extent and severe level of land contamination in China, consideration should be given to the decision on excess lifetime cancer risk of 10−5. During risk assessment process in practice, it is better to review the 20% TDI against local circumstances to determine their suitability before adopting it. The MEP-GAC are based on a SOM value of 1%, for regions with particularly high SOM, it might be necessary to develop regional GAC, due to SOM’s significant impact on the GAC developed. An authoritative risk assessment model developed based on HJ25.3-2014 would help facilitate the DQRA process in practice. The MEP-GAC could better reflect the likely exposures of China’s citizens due to vapour inhalation by using characteristics of Chinese exposure scenarios, including China-generic building stock, as inputs into the Johnson and Ettinger model as opposed to adoption of the US EPA parameters. The MEP-GAC once implemented will set the trajectory for the development of the investigation, assessment and remediation of land contamination for years.