For the first time, all scombrid species (tunas, bonitos, mackerels and Spanish mackerels) and billfishes (swordfish and marlins) have been assessed for the IUCN Red List of Threatened Species. Of the 61 known species, 7 are thought to be at serious risk of extinction and are classified in a threatened category.
The situation appears particularly grim for tunas – three of the eight species are now classified in a threatened category, including the Critically Endangered southern bluefin tuna and the Endangered northern bluefin tuna, while two species are classified as Near Threatened.
Three species of billfishes were classified in threatened or Near Threatened categories; the blue marlin and the white marlin are both Vulnerable, while the striped marlin is Near Threatened.
“This is the first time that fishery scientists, ichthyologists and conservationists have come together to jointly produce an assessment of the threats facing a commercially important group of fishes,” said Dr Bruce B. Collette, Chair of the IUCN Species Survival Commission’s (SSC) Tuna and Billfish Specialist.
This new information will be invaluable in helping governments make decisions which will safeguard the future of these species, many of which are of extremely high economic value.
Fishing pressure causing collapse
There is growing concern that many scombrid and billfish species are being heavily overfished, and that there is a lack of resolve to protect against overexploitation because of the high prices they fetch at markets.
“All three bluefin tuna species are susceptible to collapse under continued excessive fishing pressure. The southern bluefin has already essentially crashed, with little hope of recovery,” says Dr Kent Carpenter, Professor at Old Dominion University and manager of the IUCN’s Marine Biodiversity Unit.
Most of the long-lived economically valuable species are considered threatened. They mature later than short-lived species and they reproduce slower, meaning recovery from population declines takes more time.
As these scombrids and billfishes are at the top of the marine food web, population reductions of these predators may cause negative effects on other species that are critical to the balance of the marine ecosystem and that are economically important as a source of food.
Ban on fisheries
The future of these threatened fishes is reliant on fishing nations to properly manage their populations. However, southern and northern bluefin tuna populations have been so reduced that scientists now believe the most efficient way to avoid their extinction is to shut down fisheries until their populations recover, although this would cause substantial economic hardship and increase the incentive for illegal fishing.
“Temporarily shutting down tuna fisheries would only be a part of a much needed recovery programme. In order to prevent illegal fishing, strong deterrents need to be implemented,” says Jean-Christophe Vié, Deputy Director, IUCN’s Global Species Programme.
“This new study shows that there is an urgent need for effective management. Scientific findings should not be discarded in order to maintain short-term profit. Marine life and jobs for future generations are both at stake.”
Alex Royan, ARKive Scientific Text Author