Here’s how to use DNA to find elusive sharks
Genetic traces in seawater reveal an unseen ‘dark diversity’ that divers and cameras miss
SHARK SIGNS A baited camera lures a tiger shark and gray reef shark into view, as part of a test to compare what works better to census the elusive fishes: cameras, divers or collecting DNA from seawater.
Laurent Vigliola/IRD
Pulling DNA out of bottles of seawater collected from reefs has revealed some of what biologists are calling the “dark diversity” of sharks.
Physicists have their dark matter, known from indirect evidence since humans can’t see it. Dark diversity for biologists means species they don’t see in some reef, forest or other habitat, though predictions or older records say the creatures could live there.
That diversity showed up in a recent comparison of shark sampling methods in reefs in the New Caledonian archipelago, east of Australia. An international team analyzed results from three approaches: sending divers out to count species, baiting cameras and analyzing traces of DNA the animals left in the environment.
Environmental DNA revealed at least 13 shark species — at least six of which failed to show up in the other surveys, the team reports May 2 in Science Advances
