The seven threatened species are southern bluefin tuna, Atlantic bluefin tuna, bigeye tuna, blue marlin, white marlin, and two species of Spanish mackerels. Graves says two main factors contribute to these fishes' troubled status: the tunas' high dollar value leads to heavy fishing pressure, and all the species are slow to reach sexual maturity, prolonging any recovery from over-fishing.
The proportion of threatened tuna and billfish species is higher than that of most other groups of marine bony fishes, with values closer to those recorded for other valuable and slow-reproducing species such as sharks. A previous IUCN study led by VIMS emeritus professor Jack Musick found that 17 to 33% of shark, skate, and ray species are in the threatened category.
Graves and his co-authors write that the quickest road to recovery for the most-depleted stocksSouthern and Atlantic bluefin tunasis to ban harvesting of these fishes until their populations can rebuild to healthy levels. They recognize that this would cause economic hardship and increase the incentive for illegal fishing, and thus call for strong deterrents such as controlled international trade through a listing of these species on the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).
The scientists note several examples where strict monitoring and compliance measures have led to successful recovery of tuna, mackerel, and billfish species.
Refining the IUCN criteria
The IUCN Red List process provides a useful worldwide standard for assessing and comparing extinction risks among all organismsboth marine and terrestrial. But Graves and other memb
|Contact: David Malmquist|
Virginia Institute of Marine Science