Much has changed since PETA two decades ago first introduced Fish Amnesty Day; did you miss it Saturday?

Since then science has shown us that every fish is someone — a “who,” not a “what.” Fish feel pain, form friendships, have unique personalities, develop cultural traditions, use tools, get depressed, eavesdrop on other fish and more. Yet despite our growing awareness of fish sentience and suffering, our treatment of them remains abysmal.

Let’s reconsider our treatment of these sensitive animals.

PETA’s motto — “Animals are not ours to experiment on, eat, wear, use for entertainment, or abuse in any other way” — applies to fish, as they’re used and abused in all four ways and more.

They’re genetically manipulated by experimenters to develop cancerous tumors and poisoned to death with harmful chemicals in archaic toxicity tests.

Humans kill them by the trillions for the dinner table and to feed to their dogs and cats. Gelatin from fish swim bladders (called isinglass) is used to filter beer and wine, and fish oil is falsely marketed as a cure-all. Designers use their skins for bags and belts.

Well-meaning parents condemn them to barren glass bowls as “starter pets” for their children. “Sport” fishers pierce them through the lip for fun and mount their bodies on the wall as trophies. I could keep going.

Did you know that fish form emotional attachments and become depressed when they lose their mates? Like apes and orcas, they can recognize themselves in a mirror (a classic test of self-awareness). Researchers in Japan recorded tiny cleaner wrasses (a type of coral reef fish) attempting to scrape off marks that had been placed on their throats or heads while they looked at their own reflections. Studies have shown that brainy wrasses use tools and work with other species of fish to obtain food.

Fish have excellent long-term memories, are savvy social learners, pass on knowledge to other fish and like to play. They’ve been observed riding bubble streams — just for fun — rearranging the plants and toys in their dull aquariums and even playing ball.

They live in complex social groups, can count and tell time, think ahead and “talk” to one another underwater. Catfish warn each other about predators by making squeaking sounds. Pearlfish use oyster shells as speakers to help amplify the volume of their communications.

In other words, fish are every bit as complex as the cats and dogs so many of us dote on.

It’s time for a sea change. The PETA International Science Consortium is working hard to replace the use of fish in experiments — pushing researchers to switch to sophisticated computer models and in vitro (test tube) screening methods.

Its international affiliates create eye-catching ads and hold colorful demonstrations against recreational fishing. (Google “Keep Hookers Off the Pier!”)

And you can make a difference for fish as well, simply by leaving them off your plate.

Let’s vow to treat all living beings — from cats to catfish — with compassion and respect.

Paula Moore is a senior writer for the PETA Foundation.