Genetic study provides data for improved bluefin tuna conservation and management

Bluefin tuna swimming.

The results of a study on bluefin tuna genetics, intended to support better conservation and help aid in the creation of effective management plans, recently appeared in the scientific journal Molecular Ecology.

AZTI Technological Centre, an organization that specializes in marine and food research, led the study and said the results will support sustainable management plans that better anticipate when changes in abundance or distribution occur.

The study included more than 500 individual Atlantic bluefin tuna from different spawning grounds and aimed to determine the number of genetically distinguishable bluefin tuna populations and the ways in which distinct populations are connected. One of the three spawning grounds studied was discovered in 2016 in the northeast U.S. and has little data otherwise associated with it.

"For all these years, we have assumed that bluefin tuna, despite their ability to make large migrations within the Atlantic Ocean, remain loyal to spawning at the same area where they were born. However, spawning activity has recently been detected in an area off the northeastern United States that had not been included in previous genetic studies and whose origin was unknown," AZTI Fisheries Genetics Researcher Natalia Díaz-Arce said.

The study was able to identify that tuna in this newly identified spawning ground were coming from the Mediterranean and the Gulf of Mexico, and in another first, the study found tuna from the Mediterranean spawning in the Gulf of Mexico. Through the study’s genetic testing, traces of the albacore tuna genome were found in the genome of Mediterranean bluefin tuna, implying the two species hybridized at some point.

Because this was the first analysis of Atlantic bluefin tuna genetics to include all three known spawning grounds, the research will help develop more accurate fish stock assessments and inform management plans.

"These findings shows that although they tend to return to the area where they were born, what were thought to be two reproductively isolated populations (those that spawn in the Mediterranean and the Gulf of Mexico, respectively), are not only demographically connected, but they also mix in the spawning ground in the northeastern United States," Díaz-Arce said.

Along with a better understanding of the health of specific bluefin populations, identifying the connectivity of the Mediterranean with the other two spawning areas will help scientists and fisheries managers understand the potential genetic homogenization of bluefin tuna globally and how that may affect the resilience of bluefin tuna to ecological changes, according to Díaz-Arce.

The project received funding from the Basque government in Spain and from the International Commission for the Conservation of Atlantic Tunas (ICCAT), a commission which develops management plans for Atlantic bluefin tuna.

Photo courtesy of AZTI


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