Helen Scales says in a way there's no such thing as a fish, just hundreds of thousands of creatures that are excellent at swimming.
Scales is a marine biologist and author of "Eye of the Shoal: A Fishwatcher's Guide to Life, the Ocean and Everything."
Scales said that while it's true all fish are technically related to each other on the evolutionary tree of life, they're so varied and different, it's hard to lump them all into one category.
"It'd be like saying spiders and octopuses are related because they both have eight legs," she said in an interview with A Beautiful World.
She reasons that some people have a problem with the identity of fish because as vertebrates we are basically highly-evolved fish — mammals, reptiles and amphibians all evolved from fish.
"At some point hundreds of millions of years ago, a fish basically upped and left the ocean and lived on land and they gave rise to us," she said. "So, we are basically highly-evolved fish and I'm fine with that."
Fish not just a menu option
Scales loves fish. She loves watching them and studying them.
Woven throughout her book are vignettes of her own aquatic explorations: eerie nighttime dives with glowing fish, close encounters with giant manta rays and floating in the middle of a swirling shoal as she was watched by thousands of inquisitive eyes.
She hopes to connect her readers with fish beyond menu items on their dinner plate.
"People often don't have a strong connection to fish, because they're not really in our daily lives. People don't see fish, we don't encounter them apart from as food," she said.
"It's really hard to connect things that we eat, to beautiful, fascinating wildlife. There's a barrier that comes down between us and our food," she added. "I wanted to push through that and share with people my experience with seeing this enormous diverse extraordinary group of animals, watching them and really getting to know them in different ways."
There are 28,000 named species in the world and Scales said she hopes we will not only start to think of fish as wildlife, but as wildlife that demands our attention and protection.
She said that starts with choosing the type of fish we eat more carefully.
One way to do that is to download a sustainable fish app and use it make dinner choices wisely. One, she recommended, is the Good Fish Guide, so you can make dinner choices wisely.