This project aims to set up a monitoring programme to increase our knowledge of bluefin tuna migrations with special reference to their residency in Irish coastal waters and specific use of these habitats, reasons for their presence after more than a decade of near absence up to 2015 and establish whether they are likely to remain as persistent migrants in coming years. Bluefin tuna have appeared regularly and in significant numbers in recent years, off the coast of Ireland often coming within hundreds of meters from the shore. This may be linked to changing ocean conditions influencing bluefin tuna migration.
Atlantic bluefin tuna (ABFT) are currently managed by the International Commission for the Conservation of Atlantic Tunas (ICCAT) as two populations separated by the 45° meridian. Given the perceived recovery in Atlantic Bluefin Tuna populations since 2016, the Long Term Recovery Plan in place for Atlantic Tuna since 2006 has now been replaced by a Management Plan from 2018 on. The key tasks associated with these objectives are to reduce uncertainty in the current stock assessment and to provide robust management advice into the future. A well-designed international tagging programme, developed over a schedule of several years and with a progressive methodological approach, will therefore be important in improving the understanding of the bluefin tuna ecology and ethology and for developing better stock assessment methods. Use of electronic tagging and receiver platforms negates the need for intensive ship surveys which are expensive, resource intensive and time consuming. Data obtained from electronic tagging improves modelling of key life history parameters including maturation, growth, natural and fisheries mortality. Using electronic tagging to reduce the uncertainty in these parameter estimates is vital to improving new assessment models and projecting accurate biomass assessments of each population, and this ultimately improves new efforts to develop operating models.
There is currently no monitoring programme to assess MSFD and OSPAR indicators for exploited deep-water species; this has been identified as a gap in the last review of the Irish monitoring programme. This project will contribute to the National reporting obligations for management of large pelagic fish species in Irish waters. This proposal is to use biologging techniques to measure residency time, spawning behaviours and life history such as natural mortality, one of the most difficult parameters to estimate in fishery stock assessments, by using electronic tags placed on BFT taken in Irish waters. The main objectives are to extend the electronic tagging efforts on bluefin tuna initiated by the Marine Institute 2019-2022 and use these data to provide empirical data that advance the MSE operational modelling, which is used to establish the status of the stocks and set international quotas to bluefin tuna fisheries as well as to estimate the residency time of bluefin tuna in Irish coastal waters since their re-establishment in 2015 and consistency of this residency in the future.
The project has a 1 year duration and runs in 2023
- Database on the stock origin of bluefin tuna, size range, oceanic migrations and residency time in Irish waters.
- Migration models and forecasting of bluefin tuna presence in Irish waters.
- Provision of data to ICCAT for ongoing stock assessments and stock evaluation.
- These data sets will expand on the existing 2016 to 2022 data from electronic tagging time-series and inform changing migration patterns of large pelagic marine species. Note - These migration datasets can only be collected as described in this project using electronic tagging techniques.
Reports and publications
- A preliminary report submitted to the MI following tagging procedures with numbers of bluefin tuna tagged including length, weights and other biological characteristics.
- On recovery of tag information following one year of attachment to the migrating fish, a complete report submitted six weeks after the final tags has transmitted information outlining the oceanic migration of each tagged animal and interactions with fisheries and other man-made and oceanic features.
- A final synthesis report with results from all tagged fish for the period to be provided 2 months after the final tag has transmitted information
- A migration model indicating depth, temperature and range preferences associated with key oceanic features such as currents, upwelling’s, seamounts etc.
- A data package complying with ICCAT requirements for data-reporting templates and standards and for use in ongoing MSE processes and quota setting at an international level. This will include all tracks, depth and temperature information and associated data.
- A package containing images of all tracks obtained during the programme and associated depth, temperature data.
- Collaborative scientific peer review publications on aspects of catch and release mortality and oceanic migrations of bluefin tuna.
- This project will contribute to the National reporting obligations for management of large pelagic fish species in Irish waters and to assess MSFD and OSPAR indicators for exploited deep-water species;
- Set up a monitoring programme to increase our knowledge of bluefin tuna migrations with special reference to their residency in Irish coastal waters and specific use of these habitats, reasons for their presence after more than a decade of near absence up to 2015 and establish whether they are likely to remain as persistent migrants in coming years.
- Use of electronic tagging and receiver platforms negates the need for intensive ship surveys which are expensive, resource intensive and time consuming. Electronic tagging is less complex and is not affected as much by adverse weather conditions.
- Improved the understanding of the bluefin tuna ecology and ethology and for developing better stock assessment methods
- Contribute to updating bluefin tuna instantaneous rates of survival, a critical parameter in stock assessment models.