A new study from the Simon Fraser University (SFU) warns that one of the most distinctive marine species -- sawfish -- are at real risk of extinction due to overfishing.
Sawfishes have already disappeared from roughly half of their known range, the authors report, as overfishing is driving their numbers into the ground. The species used to be quite a common sight for around 90 coastal countries around the globe, but are now one of the most threatened family of ocean fish and presumed extinct in 46 of those nations. A further 18 countries presume at least one species of sawfish to be locally extinct, while 28 others presume at least two.
A fish in need
"Through the plight of sawfish, we are documenting the first cases of a wide-ranging marine fish being driven to local extinction by overfishing," says Nick Dulvy, one of the two authors of the paper.
"We've known for a while that the dramatic expansion of fishing is the primary threat to ocean biodiversity, but robust population assessment is difficult for low priority fishes whose catches have been poorly monitored over time. With this study, we tackle a fundamental challenge for tracking biodiversity change: discerning severe population declines from local extinction."
Sawfishes get their name from the highly distinctive rostra they sport. These are long and narrow noses lined by teeth, making them very similar to sawblades. According to the International Union for Conservation of Nature (IUCN) Red List of Threatened Species, three of the five species of sawfish alive today are critically endangered, with the other two being endangered.
According to the authors of this study, overfishing is to blame. The animals' long rostra and the teeth they sport can easily become entangled in fishing nets. They can fetch a high price on the market as their fins are among the most pricy shark fins. Rostra can also be sold for a variety of reasons, from folk medicine and novelty to spurs used in cockfighting.
Although we have no reliable global account of sawfish numbers, Dulvy says that the data we do have paints a very bleak picture. Unless an effort is made to stop overfishing and protect the habitats these species live in, there's a very real risk of them going completely extinct.
In regards to solutions, the team recommends a concerted international conservation project focusing on Cuba, Tanzania, Columbia, Madagascar, Panama, Brazil, Mexico, and Sri Lanka, where such efforts are likely to see the greatest payoff. Fishing restrictions in these countries could also help. Australia and the United States both have solid protections already in place and retain populations of sawfish -- they should act as "lifeboat" nations to ensure the species doesn't go the way of the dodo.
"While the situation is dire, we hope to offset the bad news by highlighting our informed identification of these priority nations with hope for saving sawfish in their waters," says Helen Yan, the paper's other co-author.
"We also underscore our finding that it's actually still possible to restore sawfish to more than 70 percent of their historical range if we act now."
The paper "Overfishing and habitat loss drive range contraction of iconic marine fishes to near extinction" has been published in the journal Science Advances.