Bluefin Tuna Project Update

The Bluefin Tuna project is the only focused research project at SOCIB. The project started in 2010 following a long tradition at IEO and is led by Dr. Alemany also from IEO. The main objectives (already included in SOCIB implementation plan approved in 2012, pgs. 115-150) are understanding the inter-annual variability of Bluefin Tuna spawning sites and the application of operational oceanography to the conservation and management of tuna species in the Balearic Sea. The main activities have focused on the development of predictive models of Bluefin Tuna spawning locations using the different SOCIB observing systems (including R/V cruises).

Figure 1 (from Reglero et al, 2012). Thunnus thynnus, T. alalunga, and Auxis rochei. Conceptual figure summarizing results, showing the spawning geography of the 3 species of tuna associated with their plausible migration pattern, for the large migratory Bluefin tuna (black solid line), the Mediterranean albacore (grey solid line), and the coastal bullet tuna (black dotted line). 

The results, obtained from the collaboration between SOCIB, IEO and IMEDEA (CSIC-UIB), have demonstrated the dependence of Bluefin Tuna spawning ecology on the regional oceanography (Reglero et al, 2012). Other species of tuna in the area that do not migrate long distances do not show this dependency. These results verify the possibility of developing operational models of spawning areas for this emblematic species using environmental satellite data and oceanographic models. The value of these sources of information was evident during the field campaigns carried out in 2011 and 2012. The application of real time data from the modeling, drifters and satellite facilities during these two years has been the key to find locations, associated with the Modified Atlantic waters inflows, where thousands of larvae and eggs of Bluefin Tuna were found. These larval densities had never been reported in any other place in the world for this species. (Fig. 2, Fig.3). Different samplings carried out using Mocness nets have provided essential data on the vertical stratification of these larvae in the water column. This data will be a key input for future larvae survival studies. 

Figure 2: Sea surface salinity from the SOCIB Wmop prediction model of 01/07/2012 and sea surface temperature from satellite data of 11/07/2012 showing the inflow of Atlantic waters through the Ibiza channel, where abundance records of Bluefin Tuna larvae were measured during the 2012 field campaign. 
Figure 3. Eggs of Bluefin Tuna (Thynnus thynnus) collected during the field sampling. 

Relevant results of this project are also emerging from the existing international collaborations. Research developed with NOAA teams allowed testing the possibility of evaluating the stock of Bluefin from larvae data. These techniques provide an evaluation of the Bluefin spawning stock biomass (SSB) independently of the fisheries data. Researchers from IEO and SOCIB visited Oregon State University in Corvallis (USA), where together with NMFS/NOAA researchers they have been working on the development of new methods of analysis to include information from the oceanographic models and satellite data into the prediction models of spawning areas.

Figure 4. Temporal evolution of Northern Bulefin tuna catches (mtn) since 2000 at three scales, Global, European Union and Spanish fleets (Source data: ICCAT).

Results of the BLUEFIN project were presented on September of this year at the V Scientific meeting of Bluefin Tuna organized by the Balfego Co., showing to tuna fisheries related stakeholders the advances on applying new scientific knowledge and technologies for the sustainable management of this species. Techniques for calculation of larvae indices in the Balearic Sea were also presented at the 18th Special Meeting of the International Commission for the Conservation of Atlantic Tunas, (ICCAT). This commission is the responsible for the conservation of tunas and tuna-like species in the Atlantic Ocean and its adjacent seas. The Standing Committee on Research and Statistics (SCRS) from this commission found a possible improvement in the east Atlantic and Mediterranean stocks of Bluefin Tuna deciding not to reduce Bluefin tuna quotas for next year (read more). Quotas were strongly reduced in 2010 from 32000 to 13500 mtn and the possibility of suspension of the fishery was pending on 2010-2012 statistics (data from Mylonas et al. 2010). Regulations are relevant for both stock recovering and evolution of the fishery industry, that during last years has experimented a relevant fallout at global, European and national level (Figure 4). The commission specifically highlighted the importance of science-base management for establishing quotas that ensure the sustainability of this resource. 

Finally, it is also important to emphasize the work carried out since 2010 by the SOCIB data center that is working on providing public access to the data collected during the Bluefin tuna field surveys and the standardization of historical data of larvae of Thunnus thynnus in the Balearic Sea.

  • References
  • Reglero P, Ciannelli L, Alvarez-Berastegui D, Balbín R, López-Jurado JL, Alemany F (2012) Geographically and environmentally driven spawning distributions of tuna species in the western Mediterranean Sea. Mar Ecol Prog Ser 463:273-284 (
  • Mylonas,C.C., De La Gandara,F., Corriero,A. & Rios,A.B. (2010) Atlantic Bluefin Tuna (Thunnus Thynnus) Farming and Fattening in the Mediterranean Sea. Reviews in Fisheries Science, 18, 266-280.