Shark, Blue

Prionace glauca

Method of production — Caught at sea
Capture method — All applicable methods
Capture area — North East Atlantic (FAO 27)
Stock area — North East Atlantic
Stock detail — All Areas
Picture of Shark, Blue

Sustainability rating five info

Sustainability overview

Blue sharks are a long-lived, relatively slow-growing species. They travel with oceanic currents over huge distances each year. Though they are not considered to be overfished, or undergoing overfishing in this region, there are considerable issues with the stock assessment and current management in place. The catch data for the species are considered to be “highly unreliable” and underestimated. Discards go unreported and blue sharks are often reported under a general sharks category “sharks nei”. Finally, there is “substantial occurrence of finning over parts of the time series”.

Biology

Blue sharks are fast oceanic predators that specialise in feeding on mackerel and other pelagic fish and squid, although there is evidence they are opportunistic and do occasionally feed nearer the seabed on demersal species and occasionally eat sea birds. Blue sharks are long lived and females will give birth to up to 135 pups in a litter after a 9- 12 month gestation period.

Stock information

Criterion score: 1 info

Stock Area

North East Atlantic

Stock information

Blue shark is listed as Near Threatened by the IUCN and the most recent stock assessment concluded that the stock was “unlikely to be overfished, nor subject to overfishing.”

The North Atlantic Blue shark stock was assessed by ICCAT in 2015 using two different approaches: the Bayesian Surplus Production Model (BSPM) and Stock Synthesis (SS3) model (based on length-based age-structured models). The BSPM estimated that the stock was not overfished (B2013/BMSY=1.50-1.96) and that overfishing was not occurring (F2013/FMSY=0.04-0.50). The SS3 model concurred, where B2013/BMSY=1.35-3.45 and F2013/FMSY=0.15-0.75. There is considerable uncertainty in both models, which should be interpreted with caution. The catch data are incomplete and underestimated, and there is a high level of uncertainty (WG2017).

Management

Criterion score: 1 info

There are insufficient management measures to adequately protect the species in this area and better monitoring standards are required. Though the stock is not considered to be overfished, or undergoing overfishing, there are considerable issues with the stock assessment and current management in place. For example, catch data are “highly unreliable” and underestimated: There are some time-series based on Catch-Per-Unit-Effort but there is much variance within the time-series. Further research has been advised to explain downward trends in CPUE and to collect better on blue shark mortality. Discards go unreported and underreported and Blue sharks are often reported under a general sharks category “sharks nei”. There is a lack of fishery-independent data for blue sharks from this area. Finally, there is “substantial occurrence of finning over parts of the time series” (WG2017).

Capture Information

Criterion score: 1 info

The Blue shark is a productive shark and therefore, it has the capabilibity of being relatively more resilient to overfishing compared to other shark species. However, it is a common bycatch in tuna and billfish fisheries, particularly on longlines and there is a lack of data to determine the effect of fishing on the population. There is also “substantial occurrence of finning” and a general lack of management to protect the species. Therefore, they are a red-rated species.

Alternatives

Based on method of production, fish type, and consumer rating: only fish rated 2 and below are included as an alternative in the list below. Click on a name to show the sustainable options available.

Basa, Tra, Catfish or Vietnamese River Cobbler
Bass, seabass (Farmed)
Bream, Gilthead (Farmed)
Cod, Atlantic Cod
Cod, Pacific Cod
Coley, Saithe
Haddock
Hake, Cape
Hake, European
Pollock, Alaska, Walleye
Sturgeon (Farmed)
Tilapia

References

ICES. 2017. Report of the Working Group on Elasmobranchs (2017). 31 May-7 June 2017, Lisbon, Portugal. ICES CM 2017/ACOM:16. 1018 pp.