Bluefin tuna catch. (Photo: AZTI)

Eastern Atlantic and Mediterranean bluefin tuna recovery still uncertain

A new stock assessment of eastern Atlantic and Mediterranean bluefin tuna conducted by the International Commission for the Conservation of Atlantic Tunas (ICCAT) concludes that it is too early to determine this once severely depleted population has been fully rebuilt.

The NGO Pew Charitable Trusts states that ICCAT’s determination comes as many groups had expected to be celebrating a full recovery of the stock, which had improved after less than a decade of science-based fishery management policies.

For eastern bluefin, scientists have competing theories on how to forecast how many young fish in the population will survive to age 1—a calculation called future recruitment.

For the assessment, the scientists ran high, medium, and low recruitment scenarios and noted that, if the high scenario is correct, the stock could still be considered overfished. If the low or medium calculation is accurate, the stock may already have recovered.

Pew ensures that while the new assessment was meant to resolve a large amount of scientific uncertainty over the stock status, it was arguably the most complicated assessment ever undertaken for any bluefin species.

In the organization’s view, ICCAT scientists were unable to address many of the outstanding issues and remain concerned that their estimates of the stock’s abundance could be overly optimistic.

The NGO says that this stems from questions about the accuracy of newer data sources, such as a new survey of larval bluefin in the Mediterranean Sea, which is driving much of the assessed population growth, coupled with worry that the estimate was further skewed by a single strong year of bluefin reproduction.

Pew adds that other concerns are that they included data only through the 2015 fishing season; vessels landed much higher catches in 2016 and this year, which almost certainly affected the eastern population overall. And, as always, scientists’ future projections carry even more uncertainty than does their estimate of the current status.

According to the organisation", of most concern are signs that ICCAT may be returning to a riskier management approach, first by agreeing in 2014 to increase the eastern bluefin quota by 72 per cent (to 23,155 metric tons) over three years, and then by voting last year to raise it an additional 500 metric tons, again pushing the quota above the scientifically advised limit.

In addition to the pressure that a sudden spike in catch can place on the stock, a new economic analysis indicates that raising bluefin quotas can also be bad for business: When the global supply of bluefin and its market substitutes, such as fresh bigeye tuna, goes up, the price of all of those species drops.

Further, for several tuna products, the decrease in price is greater than the increase in supply, meaning that even if those fishermen can sell more fish, their overall revenue would decrease.

While ICCAT scientists are meeting in Madrid through October 6 to develop their advice for 2018 and possibly beyond, governments already have key information to help them form their management positions this year: Scientists have not confirmed the recovery of eastern bluefin; the assessment results are highly uncertain and likely overly optimistic on population estimates, and tuna prices have suffered due to the significant increases in eastern bluefin catch in recent years.

Pew states that while the scientific advice provides the bounds for quota negotiations, it is the responsibility of fishery managers to protect the full recovery and long-term health of Atlantic bluefin and related fisheries.

"This year, the science and economics clearly point to the need for a conservative approach to management, including setting quotas for the coming years that are based on a precautionary interpretation of the scientific advice, while also making progress on the development of harvest strategies, an innovative system of fisheries management that will transition ICCAT to a more effective, predictable, and stable approach to bluefin in the future," concludes Amanda Nickson, The Pew Charitable Trusts’ global tuna conservation work director.

 
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