Researchers have been working on a new model to estimate the population of Atlantic bluefin tuna. The reason why this new model is so revolutionary is because the data included, accounts for the population overlap of eastern and western bluefin.
There are three major sources of data being observed. The first is the tracking tag that sends data corresponding with the fish's geographical location and migration (read more about it in my blog on Tuna Tagging). Secondly the scientists will be studying earbone microchemistry, explaining that it is similar to a birth certificate; explaining the origin and family of specimen. Lastly, fisheries' data will be taken into account to discover how many tuna are surviving to adulthood versus being caught.
Not much is known about bluefin tuna because they are a pelagic, migratory species - meaning they don't spend much time where people can observe their behaviour. Although we do know that bluefin tuna can live to 35 years old and weigh over 1500lbs. This study has also introduced scientists to the fact that bluefin born in the Mediterranean have a significantly lower age of reproduction than their Gulf of Mexico-counterparts.
Originally it was believed that most bluefin caught in the west, were born and lived out their lives there, and visa versa in the east. But, this study has brought to light that as much as 50% of bluefin caught in the west were spawned in the Mediterranean. The highest fish mortality rates in the Med, took place in 1998 and 2007 - we now know that this is a direct cause of a decrease in populations in the western Atlantic.
The catch in the east has been cut by about half, so it is possible this trend will invert. Since the decline of fishing in the wes, the eastern bluefin population can bounce back relatively quickly due to its early age of sexual maturity. Whereas the populations on the west will take at least 15 years to bounce back, that is if efforts remain and continue to repopulate bluefin tuna.