Training courses

Intro to tag-recapture campaigns

​Introduction to large-scale tag-recapture campaigns and their potential role in the management of fisheries resources

4-8 October 2021
Online course

Registration has closed.
​​​​​​In the context of fisheries stock assessment, tag-recapture data have the potential to improve identification of stock structure and estimate key parameters, including migration/movement rates, natural mortality, selectivity, and growth. Tagging data can be processed on their own, to provide estimates that are independent of the stock assessment process, or they can be incorporated directly into the stock assessment estimation framework using integrated stock assessment models.

The basic principle of tag-recapture is straightforward. Animals are marked in some way and released into the wild again. Prior to release, the animals are typically measured, sexed (if possible) and weighed. When these animals are subsequently recaptured, a wealth of useful scientific information about their population dynamics and the fishery dynamics becomes available.

The course instructors worked on the implementation of the Atlantic Ocean Tropical tuna Tagging Programme (AOTTP)​ between 2015 and 2021. Their experiences rolling out and managing that project will underpin this course.


  • How to set up a large-scale tag-recapture project and what pitfalls to avoid
  • Reviewing the information content and quality of tagging data – simple calculations and visualizations in R (e.g., time at liberty, distance travelled) using real tag recapture data
  • Estimating growth, selectivity and mortality from tag-recapture data outside of the stock assessment model
  • Insights into stock structure, behaviour, movement, and migration provided by all types of tag-recapture data (i.e., both conventional and electronic tags)
  • Integrating tag-recapture data into stock assessment models (the case of the Northeast Atlantic Mackerel, and other examples in Stock Synthesis)
All worked examples and homework will be based on R scripts and real tag-recapture data.


The course is organized as online teaching on 4-8 October 2021, over Microsoft Teams.  Participants will follow an online session 4 hours each day from 12 – 16 CET. Participants prepare for the online session by doing exercises intersessionally. 

Instructions on how to install the required software (free and open source) and background reading materials will be distributed prior to the course.

Requirements for attending

Participants should have basic knowledge of R and population dynamics/stock assessment theory. Prior experience with stock assessment models is helpful but not required.​


Registration deadline is 20 September 2021. Go to registration.

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​Aita Fraxku - pole and line boat tagging and releasing fish during AOTTP. Photo: AZTI​

Lisa Aillouad, NOAA, USA
Doug Beare, International Commission for the Conservation of Atlantic Tunas (ICCAT), Spain

​Course fee:

750 Euros for ICES member country affiliated participants

1250 Euros for non-member country affiliated participants​

​Atlantic Ocean Tropical tuna Tagging Programme (AOTTP)

AOTTP focused on tropical tuna species in the Atlantic Ocean, which were mostly tagged and released by commercial pole and line fishers. AOTTP was an integrated tag-recapture programme exploiting the pros and cons of different types of tag. 120,000 fish were tagged and released with conventional plastic dart tags and, to date, around 17,000 have been recovered and reported. Conventional tags are relatively cheap (about 2 euros each) but only provide information on release location, size and timestamp and, if found and reported, recovery location, size and timestamp. These tags do not provide any information on the whereabouts and behaviour of the fish between the point of release and recovery. An additional 600 fish, were therefore tagged with electronic tags (both pop-up which report to satellites and internal archival, which must be found and reported for the data to be recovered). Electronic tags are expensive (1,000 to 4,000 euros) but potentially provide more detailed information on the fishes' behaviour (e.g. vertical migration, habitat association) and movement.
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Intro to tag-recapture campaigns

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