There are more than 34,000 species of fish on our planet. It can be tricky to tell the age or sex of a fish, but biologists have come up with a few different ways to find out.
My friend Paul Wheeler, a fish biologist at Washington State University, told me all about it.
There are also some outward characteristics that help us tell the sex of a fish. Wheeler is very curious about salmon. He said male salmon get darker and their colors are more intense than females. The males also have a big hook on their jaw and sharp teeth.
“It requires taking a little piece of their fin and the fins grow back. It’s like taking a little piece of fingernail,” said Wheeler.
We have to rely on outward characteristics or analyze fish scales to determine age. Biologists use scales of a fish that form yearly rings to count their age. It’s a lot like counting the rings of a tree.