The Mystery of Sea Creatures (4/5): Are we interrupting the kinky sex lives of fish? | Marah J. Hardt

**Elise Hu** (0:00)
It is summer where I live, and luckily, I live near the Pacific Ocean. As the weather continues to heat up, I'm spending more time at the beach. It always makes me wonder, what's going on under the water? From the deep sea to the shoreline, the ocean is teeming with creatures that are stranger, smarter and more surprising than most of us could ever dream up. For July's TED Talks Daily playlist, we have gathered five of our favorite talks that dive into the awe-inspiring and occasionally mind-bending creatures from orcas to kinky fish that live beneath the waves. Happy listening.
You're listening to TED Talks Daily, where we bring you new ideas to spark your curiosity every day. I'm your host, Elise Hu.
It turns out the ocean plays host to some of the wildest, weirdest and most surprisingly consequential sex lives on the planet. Yes, you heard me right. And most of us have no idea. In this talk, marine scientist Marah J. Hardt takes us deep into the reproductive strategies of everything from parrotfish to lobsters to anglerfish and makes the case that understanding them isn't just fascinating, it's urgent. Because human behavior is quietly disrupting these intimate affairs in ways that affect our food, our health and our shorelines. It turns out your own wellness depends, at least in part, on the healthy sex lives of fish. That's coming up right after a short break.
And now, our TED Talk of the day.

**Marah J. Hardt** (1:38)
Right now, beneath a shimmering blue sea, millions of fish are having sex.
And the way they're doing it and strategies they're using looks nothing like what we see on land. Take parrotfish. In this species, all fish are born female. Then later in life, she can transition into a male. But it's not just a spectacular wardrobe change. Her body can reabsorb her ovaries and grow testes in their place. In just a few weeks, she'll go from making eggs to producing sperm. It's pretty impressive. And in the ocean, it's also pretty common. In fact, I bet nearly all of you have at some point had a seafood dish made of an individual that started life as one sex and transitioned to another. Oysters, grouper, shrimp. Seeing some heads, nodding, yeah. But not all fish that change sex start as females. Those clownfish we know from Finding Nemo, they're all born male. So in the real world, when Nemo's mother died, Nemo's dad Marlin would have transitioned into Marlene, and Nemo would have likely mated with his father-turned-mother. You can see... You can see why Pixar took a little creative license with the plotline, right? So sex change in the ocean can happen in either direction, and sometimes even back and forth. And that's just one of the many amazing strategies animals use to reproduce in the ocean. And trust me when I say, it's one of the least surprising. Sex in the sea is fascinating. And it's also really important. And not just to nerdy marine biologists like me, who are obsessed with understanding these salty affairs. It matters for all of us. Today, we depend on wild-caught fish to help feed over two billion people on the planet. We need millions of oysters and corals to build the giant reefs that protect our shorelines from rising seas and storms. We depend on medicines that are found in marine animals to fight cancer and other diseases. And for many of us, the diversity and beauty of the oceans is where we turn for recreation and relaxation and our cultural heritage. In order for us to continue to benefit from the abundance that ocean life provides, the fish and coral and shrimp of today have to be able to make fish and shrimp and coral for tomorrow. To do that, they have to have lots and lots of sex.
And until recently, we really didn't know how sex happened in the sea. It's pretty hard to study. But thanks to new science and technology, we now know so much more than even just a few years ago. And these new discoveries are showing two things. First, sex in the sea is really funky. Second, our actions are wreaking havoc on the sex lives of everything, from shrimp to salmon. I know, it can be hard to believe. So today, I'm going to share a few details about how animals do it in the deep, how we may be interrupting these intimate affairs, and what we can do to change that. So, remember those sex-changing fish? In many places in the world, we have fishing rules that set a minimum catch size. Fishers are not allowed to target tiny fish. This allows baby fish to grow and reproduce before they're caught. That's a good thing. So fishers go after the biggest fish. But in parrotfish, for example, or any sex-changer, targeting the biggest fish means that they're taking out all the males. That makes it hard for a female fish to find a mate, or it forces her to change sex sooner, at a smaller size. Both of these things can result in fewer fish babies in the future. In order for us to properly care for these species, we have to know if they change sex, how and when. Only then can we create rules that can support these sexual strategies, such as setting a maximum size limit in addition to a minimum one. The challenge isn't that we can't think of these sex-friendly solutions. The challenge is knowing which solutions to apply to which species, because even animals we know really well surprise us when it comes to their sex lives. Take Maine lobster.