Like all tunas, the Atlantic Bluefin tuna (Thunnus thynnus) are one hell of an ocean predator. They are both fast and agile, adapting their hunting technique to catch their often equally fast moving prey.  They are also quite tasty to us humans, and just like the tuna, humans are very adept predators.  Out of the 8 species of true tuna, 5 are listed in the IUCN Red List as threatened (broken down into critically endangered, endangered, and vulnerable) or near threatened.  Bluefin tuna has perhaps received the most media attention, with both Eastern and Western Atlantic Bluefin tuna stocks currently listed as critically endangered.

Atlantic Bluefin fisheries are managed by ICCAT – the International Commission for the Conservation of Atlantic Tunas.  This is an inter-governmental fishery organization which -amongst other management actions - sets annual quotas for all its member states.  ICCAT has come under fierce criticism for failing to heed scientific advice when deciding on management measures like quota setting – even from its own scientists who have previously called for a moratorium on catching the tuna to allow the populations to rebuild.  To boot the management that is put in place, say some, is weak and ineffective.

According to ICCAT, under the current management the chances of the Eastern stock recovering by 2022 lies at 60%.  There is a problem with this.  The recovery probability estimate is only based on known catches; It forgets the ones that aren’t recorded through normal channels…illegal catches.  Illegal, Unreported and Unregulated (IUU) fishing is believed to be a huge business on a global scale.  No one can say with 100% accuracy what the scale of IUU fishing is, but it is considered to be a threat to marine biodiversity, ecosystems, and sustainable fishing.  In a new open access paper, Antonius Gagern from the Institute of Environmental Science and Technology in Spain, and colleagues, has taken a look at illegal fishing of the Eastern Atlantic Bluefin tuna.

Illegal fishing of this species on the edge is thought to be a large problem, particularly in the Mediterranean.  But just how large is it?  The researchers used a whole bunch of metrics to try gain an accurate assessment of illegal take.  These include comparing reported imports with corresponding reported exports, recreational fishing, and some fancy calculations around the weight of live tunas destined for ranching (essentially holding pens where they are fed till they get fat…. Yes think Hansel and Gretel and your there) and the final weight that comes out of the ranches.  I’ll just pop a quote from the abstract here that neatly summarise their findings…

“Basing our calculations on 25 countries involved in [the Eastern Bluefin Tuna fishery], we estimate that between 2005 and 2011, allowable quotas were exceeded by 44 percent. This gap between catch and quotas has slightly increased over past years, leading to estimated excess catches of 57 percent for the period between 2008 and 2011.”

Those are no small figures, and are likely to significantly alter recovery chances.  By just how much the authors don’t say, but hopefully it will result in ICCAT decision makers taking another look at their sums.

Estimating IUU fishing is very difficult, and the authors have noted down some potential sources of errors – many of which were centered around insufficient data.  As an example, one potential error on the data side was the exclusion of all landings in countries that do not possess quota from ICCAT, for which there simply isn’t the records to make any calculations from.  On balance, the authors feel that they have been conservative enough in their approach to prevent gross over-estimations of likely illegal catch.

The paper is published in the open access journal PLoS ONE

To read more about ICCAT check out their home page.

Some of the fiercest criticism of ICCAT has come from environmental NGOs.  Here’s one example from Greenpeace (open access).  Criticism has also been levied from the science community through more formal channels – here’s a paper that appeared in the science journal ‘Marine Policy‘ (you will need a subscription or to pay to view this).

The IUCN Red List for Atlantic Bluefin tuna also provides some interesting information.

To read more about IUU have a look at here.