7 Things we learned about sharks this year

As the year 2017 draws to a close, we examine some of the most interesting finds made about sharks around the world.

1. Many sharks are probably older than we think
Aging sharks is long done by counting growth rings in their vertebrates, as we do with trees. But according to a 2017 review by Alastair Harry, this most common method used for aging sharks actually underestimates the true age. The availability of new techniques allows for the validation of counting rings as a method, suggesting that age underestimation is likely a systemic issue associated with the current methods and structures used for aging. Read more

2. Seeing sharks in an aquarium reduces fear of them
An article by Pepin-Neff & Wynter explains how public feelings toward sharks are influenced by exposure to sharks in aquariums. It even states that seeing sharks in the tank can effectively reduce the fear of sharks and change the emotion and opinion people have about shark bite incidents. This has great implications for shark conservation work, as it shows the importance of proper education. Read more

3. Sharks can extrude foreign objects from their body
This year, shark scientist Steve Kessel et al. recorded the observation how a lemon shark expelled a swallowed stringer, a loop-shaped, stainless steel tools used by spear fishermen. Taking more than a year to do so, the stringer was pushed through the stomach lining of the shark and eventually totally expelled. The finding is a true testament to the unique healing abilities of sharks. Read more

4. New species described
There are >500 shark species and >600 skate and ray species described in science, with the number growing yearly. Not because more species are evolving, but because we are developing more and better ways to find and record them, especially species living in deeper water. The team from the California Academy of Sciences alone described 10 new shark species in 2017, from  “Austin’s guitarfish” to the “Long-nosed African spurdog,”. Another shark that was discovered around Hawaii this year is a new species of lantern shark that glows in the dark. Read more

5. Sustainable shark fisheries could benefit conservation 
The co-chairs from the IUCN Shark Specialist Group, Colin Simpfendorfer and Nick Dulvy, wrote an article arguing that moving to sustainable fishing, as opposed to prohibiting sharks fisheries altogether, is a feasible solution to thwart the elevated risk of extinction that many species have. Indeed, there already are some places where sharks are being fished sustainably, which provide a good example for others to follow. Read more

6. Shark diversity can be assessed without actually seeing the sharks
A pioneering study by Judith Bakker and colleagues published in Nature this year shows how the presence of sharks can be inferred just from looking at water samples. The detection of DNA traces found in the seawater called environmental DNA (eDNA), which come from the dead skin cells and feces of animals, can provide new insight into populations of otherwise elusive shark species. Read more

7. Sharks are eating things you wouldn’t expect 
Scientists have discovered some pretty amazing eating habits of sharks this year. For example, bonnethead sharks (a type of hammerhead shark) from the eastern Gulf of Mexico were found eating seagrass as a significant part of their diet. And tiger sharks from South Africa had penguins and porcupines in their stomachs. New surprising predators of sharks were also found, such as freshwater alligators in America. Read more


By Linda Planthof