Thunnus thynnus, Atlantic bluefin tuna, are a top predator
of the ocean that are highly migratory predators. Atlantic bluefin tuna (BFT) have
two populations found within the Atlantic Ocean and both stocks are known to
have slow maturation and long-life cycles. The two stocks are large populations
of BFT that spawn in the Mediterranean Sea known as the eastern stock and the
smaller population that spawns in the Gulf of Mexico known as the western
stock. Both stocks feed on similar feeding grounds and the populations are known
to mix. BFT population abundance in the Mediterranean Sea has fluctuated since
the 16th century due to different pressures like overfishing and
climate change. This study looked at BFT contemporary DNA, 2009 to 2012, and
archival DNA, 1911 to 1926. SNP genotyping was used to compare archival DNA to
modern DNA to see if the pressures of industrial fishing have influenced the genetic
diversity of BFT. There were 92 SNP loci that were used to differentiate the
loci of the populations and their biological function. It is known that the
pressures of overfishing have direct influence on the abundance of BFT
populations, but the evolutionary potential and resilience the genetic change has
little information. The results found no significance in the differences of the
genetic diversity from the SNP. Overfishing does not appear to create
bottlenecking or allele loss in BFT populations, but this could also be due to
high spawning rates for generations even during significant decreases in biomass,
which makes it difficult to see trends of bottlenecking. The unknown stock
mixing of eastern and western stocks in possibly new Atlantic spawning grounds
leaves an unknown gene flow, which is not the same for all species. The SNP
loci might not have shown changes in genetic diversity due to BFT having large
population sizes of two different stocks as well as a slow maturation rate. BFT
also have a long life-cycle meaning mature BFT will be able to spawn many
generations year after year creating similar generations BFT.
https://www.nature.com/articles/s41598-021-99708-9.pdf
https://www.nature.com/articles/nmeth0508-447
https://www.edf.org/oceans/overfishing-most-serious-threat-our-oceans
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