This video from the USA says about itself:
Jonathan joins a group of volunteer divers as part of an international event called the Great Annual Fish Count to take a census of marine life across the globe. His mission: dive the chilly waters of Massachusetts with a pencil…and count fish!
JONATHAN BIRD‘S BLUE WORLD is an Emmy Award-winning underwater science/adventure program.
Dear Kitty. Some blog 
I knew people were catching fish and counting birds. This is something new to me. Thanks for the info.
LikeLike
The video was recorded in 2013, and biologists have counted fish for longer.
Fish are counted, eg, to see whether conservation measures work.
LikeLike
Pingback: Five ‘fish’ that aren’t fish | Dear Kitty. Some blog