SmartDots – creating a link between fish ageing and stock assessment modelling

WGSMART present at the 7th International Otolith Symposium in Chile.
Published: 21 November 2023

​​​​​​​​​Estimating the age composition of a fish stock is fundamental to the evaluation of its status as age data underpins growth and mortality rates, maturity patterns, and eventually stock size. 

Routine ageing is conducted in age reading laboratories across the globe to deliver age data for stock assessment purposes, for a set of samples that are representative of survey and commercial catches. Fish age is commonly estimated from the observed patterns of the growth structures laid down in hard structures like otoliths or scales. Age estimation is a subjective process and thus variance between and within readers is expected, this can potentially lead to bias and imprecision in the estimated age composition of a population. 

Stock assessment

ICES SmartDots platform was developed in 2018 as a tool to support quality assurance procedures aimed at achieving a high level of age data quality. SmartDots age calibration events are image-based interactive exercises that can be accessed online by multiple expert and trainee age readers. All registered data is available in a standardized format in the connected reporting environment with R-scripts producing statistical outputs indicating levels of age reader accuracy and precision. Recent efforts have been focused on incorporating the output (either the raw empirical data or the so-called Age Error Matrices [AEM]) from these exchange events into the stock assessment process.

Currently, three of the most widely used stock assessment models in ICES community - SAM, Gadget, and SS3 - are capable of incorporating ageing error information. The ultimate aim of an ICES SmartDots event is to improve the reliability of the stock assessment. Various fora, from workshops and exchanges to working groups, have identified the need for cross-disciplinary cooperation between age readers, data-quality managers, stock assessors, and model developers as being necessary if this goal is to be reached. Several studies are underway.​


The Working Group on SmartDots Governance (WGSMART) continues to develop the SmartDots quality assurance platform so that outputs can be used by the relevant assessment working groups. It focuses on the dissemination of results and cooperation across expert groups who provide feedback and input.

Members of WGSMART organized a workshop on SmartDots and how it is being used by ICES community for data quality assurance at the 7th International Otolith Symposium in Chile, 9–13 October 2023. They also presented the SmartDots challenge, giving otolith enthusiasts from around the world an opportunity to test their skills against a group of expert age readers.

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WGSMART members, 2023 meeting, San Sebastian, Spain.​.

Julie Coad Davies, co chair of WGSMART, at the 7th International Otolith Symposium.
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SmartDots – creating a link between fish ageing and stock assessment modelling

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