

18 Jul 2026 · 15m · 5 chapters

Marine scientist Marah J. Hart argues that ocean animals’ reproductive strategies are “funky” and that human actions are interrupting them, affecting food, health, reefs, and shorelines. She highlights sex-changing fish, lobster mating, and deep-sea reproduction, then links disruption to fishing rules, climate change, pollution, and potential deep-sea mining.
Marah J. Hart is a marine scientist; her TEDx Mile High (2019) talk is republished as this TED Talks Daily episode.
Fishing minimum size rules can remove all males of sex-changing species; ocean chemistry changes from climate change can scramble chemical mating signals; pollution can damage sensory receptors; deep-sea mining could destroy eggs and sponges.
parrotfish sex change (female to male); clownfish (male to female); Maine lobster urine “love potion” that calms aggressive males; anglerfish male fusion into a sperm-producing attachment; newly discovered deep-sea octopus eggs on sponge-rocks over 2.5 miles deep.
Written by AI. May contain mistakes.
Exploration of the surprising sex lives of fish and marine creatures.
“You're listening to TED Talks Daily, where we bring you new ideas to spark your curiosity every day.”
Detailed discussion on how different fish reproduce and the impacts of human behavior.
“Subject to credit approval, Apple Card is issued by Goldman Sachs Bank USA, Salt like City Branch Terms and more at applecard.com.”
Insight into the elaborate mating strategies of lobsters and anglerfish.
“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.”
Exploration of how human activities disrupt marine reproductive processes.
“To survive, he has to find a female fast.”
Learn about the importance of safeguarding ocean life for future sustainability.
“one that recognizes and respects the enormous diversity of life and its limitations.”

Get the gist, explore an idea or ask about something said.
On TED Talks Daily, what are the key points of this episode?
Automatic transcript. May contain errors.
0:00It 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.
0:38You'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 Mara J. Hart 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.
1:19It 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.
1:32This episode is sponsored by Kohler Smart Toilets. The objects we interact with most are often the ones we notice least. But what if the most overlooked space in your home could be the most considered? Kohler Smart Toilet challenges that assumption. Their Veil Smart Toilet is a sculptural silhouette that isn't just intentional, it's a philosophy. That design changes everything. The Kohler Veil Smart Toilet is sleek with a rounded shape that's more like architecture than just plumbing. And it goes beyond looks. The touchscreen controls and customizable cleansing features offer a level of comfort and cleanliness that exceeds expectations.
2:07It's all about elevating those ordinary daily rituals into something extraordinary through thoughtful design. Kohler has been pushing these boundaries for over 150 years, mastering that balance of stunning form and high-performance function. That's a long time to get it right, and it shows in every detail. Experience the difference of Kohler Smart Toilets. Find out more at Kohler.com.
2:53and hello to more free time because you finished your work faster. Complete your setup with savings on select monitors and more must-have electronics and accessories. Limited time deals and free shipping on PCs and more await you at dell.com slash deals. That's dell.com slash deals.
3:15This message is brought to you by Apple Card. Apple Card puts the power of titanium in the palm of your hand. What does that mean? It means the power to earn unlimited daily cash back on your purchases every day. It means a materially different credit card accepted anywhere in the world. MasterCard is accepted. Ditch the plastic. Upgrade to titanium. Apply in the wallet app on iPhone today. Subject to credit approval, Apple Card is issued by Goldman Sachs Bank USA, Salt like City Branch Terms and more at applecard.com.
3:48And now, our TED Talk of the day. Right now, beneath a shimmering blue sea, millions of fish are having sex.
4:03And 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 up of an individual that started life as one sex and transitioned to another.
4:50Oysters, 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 Marlon would have transitioned into Marlene, and Nemo would have likely mated with his father-turned-mother. 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.
5:47And 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.
6:38In 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.
7:22I 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.
8:05That 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.
8:47Take Maine lobster. They don't look that romantic or that kinky. They are both.
8:58During mating season, female lobsters want to mate with the biggest, baddest males. But these guys are really aggressive, and they'll attack any lobster that approaches male or female. Meanwhile, the best time for her to mate with the male is right after she's molted. when she's lost her hard shell. So she has to approach this aggressive guy in her most vulnerable state. What's a girl to do? Her answer? Spray him in the face, repeatedly, with her urine. Under the sea, pee is a very powerful love potion. Conveniently, lobsters' bladders sit just above their brains, and they have two nozzles under their eye stock, which they can shoot their urine forward.
9:51So, the female approaches the male's den, and as he charges out, she lets loose a stream of urine and then gets the hell out of there. Only a few days of this daily dosing is all it takes for her scent to have a transformative effect. The male turns from an aggressive to a gentle lover. By the week's end, he invites her into his den. After that, the sex is easy. So, how are we interrupting this kind of kinky courtship? Well, the female's urine carries a critical chemical signal that works because it can pass through seawater, and lobsters have a smell receptor that can detect and receive the message.
10:38Climate change is making our oceans more acidic. It's the result of too much carbon dioxide entering seawater. This change in chemistry could scramble that message. Or it could damage the lobster's smell receptors. Pollution from land can have similar impacts. Just imagine the consequence for that female if her love potion should fail. These are the kinds of subtle but significant impacts we're having on the love lives of these marine lives. And this is a species we know well. lobsters live near shore in the shallows, dive deeper, and sex gets even stranger. Fanfin anglerfish live at about 3 ,000 feet below the surface in the pitch black waters, and the males are born without the ability to feed themselves.
11:28To survive, he has to find a female fast. Meanwhile, the female, who is 10 times bigger than the male, 10 times, she lets out a very strong pheromone with which to attract mates to her. So this tiny male is swimming through the black waters, smelling his way to a female. And when he finds her, he gives her a love bite. And this is when things get really weird. That love bite triggers a chemical reaction, whereby his jawbone starts to disintegrate. His face melts into her flesh, and their two bodies start to fuse. Their circulatory systems entwine, and all his internal organs start to dissolve, except for his testes.
12:24His testes mature just fine and start producing sperm. In the end, he's basically a permanently attached on-demand sperm factory for the female. It's a very efficient system. But this is not the kind of mating strategy that we see on a farm, right? I mean, this is weird. It's really strange. But if we don't know that these kind of strategies exist or how they work, we can't know what kind of impacts we may be having, even in the deep sea. Just three years ago, we discovered a new species of deep-sea octopus where the females lay their eggs on sponges attached to rocks that are over two and a half miles deep.
13:09These rocks contain rare earth minerals, and right now there are companies that are building bulldozers that would be capable of mining the deep-sea floor for those rocks. But the bulldozers would scrape up all the sponges and all the eggs with them. knowingly and in many cases unknowingly we are preventing successful sex and reproduction in the deep and let's be honest dating and mating is hard enough without somebody coming in and interrupting all the time right i mean we know this so today while i hope you will leave here with some excellent bar trivia on fish sex I also ask that you remember this.
13:54We are all far more intimately connected with the oceans than we realize, no matter where we live. And this level of intimacy requires a new kind of relationship with the ocean, one that recognizes and respects the enormous diversity of life and its limitations. We can no longer think of the oceans as just something out there, because every day we depend on them for our food security, our own health and wellness, and every other breath we take. But it is a two-way relationship, and the oceans can only continue to provide for us if we, in turn, safeguard that fundamental force of life in the sea, sex and reproduction.
14:43So, like any relationship, we have to embrace some change for the partnership to work. The next time you're thinking about having seafood, look for sustainably caught or farmed species that are local and low on the food chain. These are animals like oysters, clams, mussels, small fish like mackerel. These all reproduce like crazy, and with good management, they can handle a bit of fishing pressure. We can also rethink what we use to wash our bodies, clean our homes, and care for our lawns. All those chemicals eventually wash out to sea and disrupt the natural chemistry of the ocean. Industry also has to play its part and take a precautionary approach, protecting sexual activity where we know it exists, and preventing harm in the cases where we just don't yet know enough, like the deep sea.
15:37And in the communities where we live, the places we work, and the country in which we vote, we must take bold action on climate change now.
15:56That was Mara J. Hart at TEDx Mile High in Denver, Colorado in 2019. This talk was originally published in May of 2020. If you're curious about TED's curation, visit ted.com slash curation guidelines. And that's it for today. TED Talks Daily is a podcast from TED. This episode was produced and edited by our team, Martha Estefanos, Oliver Friedman, Lucy Little, Emma Taubner, and Tansika Sungmarnivong. Additional support from Daniela Ballarezzo, Christopher Fazey-Bogan, Valentina Bohanini, Banban Chang, Brian Green, and Lainey Lott. Learn more at podcasts.ted.com. I am Elise Hu. Thanks for listening.
16:50Marah J. Hardt: On the under$3 menu at McDonald's, a McChicken is$1.50. Because when you're craving a McChicken, you deserve a McChicken. And now that McChicken is just$1.50 with McValue. Limited time only. Prices and participation may vary. Prices may be higher for delivery.
The ocean plays host to a peculiar party of wild, marine sex life that's perhaps quirkier (and kinkier) than you can fathom. But is human behavior interrupting these raunchy reproductive acts? Take a deep dive with marine biologist Marah J. Hardt to discover what exactly goes down under the sea -- and why your own wellness depends on the healthy sex lives of fish.
(This episode originally aired in 2020.)
Hosted on Acast. See acast.com/privacy for more information.