A Caribbean seahorse has been found a long way from home.

The lined seahorse was identified on the other side of the Atlantic in the Azores. And chances are it got there clinging on to a floating life raft of vegetation, perhaps a palm tree that blew down in a storm.

Lined seahorse (Hippocampus erectus). Photo by House photography.

It’s the kind of pan-oceanic wandering that researchers have suggested must go on from time to time in the seahorse world and it goes some way to explain how seahorses have made their way to far flung corners of the oceans – quite a feat considering adult seahorses have only meagre swimming skills and as newborn larvae they don’t drift far before settling down onto the sea bed.

It is also possible that someone in the Azores has been keeping these Caribbean Lined Seahorses as pets and decided to let one go in the wild. But I prefer the rafting theory.

Lined Seahorse. Photo by Brian Gratwicke

The finding was made by Lucy Woodall from Royal Holloway at the University of London who is part of the Project Seahorse team that I write about in my book Poseidon’s Steed.

In chapter two, I write about genetic studies that hint at the seahorses’ long distance migrations. Scientists have interpreted molecular messages in the seahorses’ DNA which tell us that individual pregnant males (yes, that’s right, males) occasionally hook their strong, prehensile tails onto a clump of marine tumbleweed that drags them off to a distant shore where they pioneer a new seahorse population.

This new discovery in the Azores seems to back up those ideas.

But whether this was a intrepid pregnant male Lined seahorse they found so far from home, the researchers don’t say. They certainly don’t seem to think this species is about set up home in the Azores.

In detail:

• Lined seahorses, Hippocampus erectus, are normally found in the West Atlantic, all along the eastern seaboard of North America (up as far as Nova Scotia), through the Caribbean Sea and down to the east coast of South America, possibly as far south as Uruguay.
• They grow up to 19 cm from head to tail tip, making them one of the larger known seahorses, especially compared to a bunch of new pymgy seahorses discovered recently.
• See fishbase for more info.

As their name suggests, Goliath Groupers are really very big indeed. The largest known have been around 2.5m long, or 8 feet.

They are undeniably fully-fledged members of the marine megafauna.

But these big fish are in big trouble and they need your help.

Goliath Grouper. Photo by pony 33406

Because it’s become more and more difficult to spot one of these giants, the fish formerly known as jewfish. Being so very huge made them an irresistible target for fishers. Over the last few decades goliath groupers have been fished so heavily from their reefy and rocky homes on both sides of the Atlantic, in the Caribbean and the eastern reaches of the Pacific Ocean, that they are now labelled as being Critically Endangered.

In days gone by, a common place to spot a goliath grouper was strung up on a quayside alongside a grinning recreational fisher. So many goliath groupers were caught by sport and commercial fishers that their populations became economically extinct: it made no sense to try and catch them if you wanted to make money.

Goliath grouper catch from 1950s Florida. Photo from Florida Keys Public Libraries

Goliath grouper catch from 1950s Florida. Photo from Florida Keys Public Libraries.

Good news is that since the 1990 it’s been illegal to catch goliath groupers in US waters. And a fishing ban on them has been in place across the Caribbean since 1993. As a result, populations of these enormous fish have been slowly recovering.

The problem is they have apparently been recovering a bit too well for some people’s liking. There is growing pressure to lift the fishing ban in Florida, one of the only places where scuba divers have a good chance of meeting these kings of the reef. Do we really want to relive a time when killing such magnificent fish was all the rage? Couldn’t we move on from that?

In early December the Florida Fish and Wildlife Conservation Commission will decide on whether to stick to the goliath grouper fishing ban or open these beasts up once again to human exploitation.

The Floridian scuba diving and conservation community are lobbying politicians hard in the hope they will hear a unified and loud voice of reason. An online petition to keep the fishing ban is gathering support and they hope to reach at least 1000 signatures.

So, do your bit and sign up. Because wouldn’t it be a crying shame if these spectacular beasts were once again allowed to be caught to make a bit of money or just for the fun of it.

Goliath grouper catch. Photo from Florida Keys Public Libraries.

It’s been well proven that big fish like the goliath grouper are far more vulnerable to extinction than smaller fish. In a twist of nature, it’s the bigger animals that grow more slowly and take longer to reach maturity (5 or 6 years for goliath groupers). So, if someone asks you to take a guess at which species are most at risk, whether they live in the sea, on land, or in freshwater, all you need do is pick out the biggest ones and you won’t go wrong.

In detail:

• Goliath groupers or jewfish (Epinephelus itajara) can live for nearly 40 years if we let them.
• They commonly grow to 1.5m from head to tail.
• Young goliath groupers live in mangrove forests, giving us yet another vital reason to care about and protect these habitats that are so often overlooked and cleared away.

This week an extract of my book Poseidon’s Steed was published in the Guardian, and the book is now available to buy in Europe from various online booksellers. So I thought it was time I blogged about my favourite fish.

One of the questions I get asked a lot is ‘Are seahorses endangered?’. And my answer is, sadly, yes they are.

Seahorses around the world are not only taken from the oceans (both deliberately and accidentally) in scarily high numbers, but they also suffer from the breakdown of their fragile habitats – especially coral reefs, seagrasses and mangroves.

So, what can we do about it? Well, here are my top ten tips for doing your bit to save the seahorses:

1. Don’t buy dead seahorses

This may sound a little odd. Why would you want a dead seahorse?

Because they live inside a coat of bony plates – which take the place of a more conventional suit of fishy scales – seahorses maintain much of their delicate and intricate shape after they die.

Obviously, it’s not quite the same, but much of the seahorses’ beauty lives on after death and there is something to be said for having your very own magical seahorse sitting on your desk (I must admit I have one on my desk, in a little cardboard jewelry box, given to me by a friend who’d had it for years – it must be a long time dead).

Dead seahorse by luv life

But don’t forget it is just the dead body of a fish that once led a quiet, gentle life on the sea floor.

Picking up a dead seahorse from the beach isn’t so bad. But the ones on sale in seaside souvenir shops will almost certainly have been taken live from the sea. So please, don’t buy them. The seahorses will thank you.

2. Make sure your pets were born on a farm

Following the publication of an extract of my book in the Guardian, a few readers have commented that keeping endangered seahorses might not be such a good idea. Have a read of chapter 5 of the book and you’ll find details of modern seahorse farms where seahorses are being bred for the aquarium trade.

Baby seahorses. Photo by pixiesticks23♥ (real busy)

So these days there is no excuse. Anyone who wants to keep these cute animals at home can do so without taking them from a wild.

In the book I also go through some of the pros and cons of keeping seahorses: for you, for seahorses, and for the environment. It’s not up to me to say if people should or shouldn’t keep seahorses – although I can see how lovely it would be to have live, beautiful seahorses in my life every day.

But if you want to keep them, make sure you go to reputable suppliers. Or check out online forums: home aquarists are often giving away spare baby seahorses that were born in their tanks. And this doesn’t just apply to seahorses; always choose captive bred not wild critters for your tank.

3. Don’t buy seahorse medicines

Again, this might sound odd.

Especially to anyone who isn’t familiar with the popular practice in various countries of using seahorses as an ingredient in traditional medicines.

Traditional Chinese medicine texts dating back 500 years prescribed seahorses for all sorts of medical conditions from broken bones and bed wetting, to skin rashes and even a flagging libido. Global demand for seahorse medicines is a driving force behind a growing market in seahorses taken from the sea – at least 25 million of them every year.

Dead seahorses on sale in a medicine shop in Vietnam. Photo by Helen Scales.

Especially worrying is the growing popularity of pre-packaged, off-the-shelf seahorse medicines that use weeny, dark-coloured seahorses that traditional Chinese medicine doctors normally don’t bother with. This means that now any seahorse, no matter what size or colour, can now be used in traditional medicines.

So, if you do use traditional medicines and can afford to buy seahorses (they aren’t cheap), then think about engaging your compassion for the natural world and choose an alternative that doesn’t include endangered species. Because there are lots of alternatives.

4. Protect the seahorses’ world

All sorts of human activities threaten the shallow coastal habitats that seahorses call home including coral reefs, seagrass meadows, mangroves, and estuaries. The list of problems is long and growing and includes pollution, habitat destruction, climate change, and ocean acidification.

And these are all things to worry about and take action over. Especially important is the creation of many more marine reserves or marine protected areas or marine parks or whatever you want to call them. Essentially these are places where the destructive influence of humankind is minimised, by banning fishing, extraction, direct input of pollutants and so on. Some strict marine reserves ban people altogether.

Healthy coral reef. Photo by Jiangang Luo Marine Photobank

There are obvioulsy problems that do not respect the boundaries of marine parks. But we know that protected habitats on the whole are healthier and can cope better when more insidious problems like climate change come along.

Currently less than 1% of the oceans are offered protection from human activities. That number needs to go up – a lot.

You may not have the power to set up your own marine reserve (who does?) but public support of local, regional, national and international campaigns to protect the oceans is vital for action.

5. Stamp out destructive fishing

A major threat to seahorses comes from trawl boats that plough through their habitat. Shrimp trawl boats don’t only catch shrimp but they also scrape up millions of seahorses every year (most seahorses made into traditional medicines are picked out of trawl nets), devastating their fragile habitats in the process. This insensitive, unselective form of fishing has to stop.

Trawl bycatch. Photo from Marine Conservation Cambodia/Marine Photobank

Do your bit by not buying fish that were caught in trawlers. How do you know, you cry? Well, you can ask. More and more these days, supermarkets and restaurants are giving customers information about how their fish is caught. If they don’t say and won’t tell you, then don’t buy.

Check out Monterey Bay Aquarium’s new Super Green List of fish that are good for you and not so bad for the oceans.

6. Take a stand against climate change

We may be releasing carbon dioxide into the atmosphere above our heads, but an awful lot of it ends up dissolved in the oceans where it’s already starting to wreak a particular brand of marine catastrophe. The oceans are becoming more acidic. And the seahorses – along with so many other marine creatures – are going to get hit hard, mainly because lots of them live in habitats that may soon be gone: coral reefs.

So don’t ignore the goings on in Copenhagan next month, because this really matters. Especially if you like the idea of a world with seahorses and coral reefs and other beautiful extraordinary wildlife.

And we can all do our bit to help. Switch off lights, turn down thermostats, insulate your house, recycle, drive less, fly less, ride your bike more. Get involved in campaigns like 350.org. And think of the seahorses while you do it.

7. Go see the seahorses

Aquariums around the world are home to thousands of seahorses and more of them than ever are bred in captivity and not taken from the wild (many aquariums swap baby seahorses when they have too many, which is often the case for the seahorses species that breed happily in tanks).

Seahorse and shrimp fish in an aquarium. Photo by Cal_gecko

Stop for a few minutes and watch the seahorses doing their seahorse thing, and let your thoughts wander off. When they come back, you’ll have your own personal seahorse moment to carry with you and remind you about these amazing creatures and the wild world they live in.

And have a read of the information boards at the aquarium. You never know what you might learn about the world of seahorses.

There’s a great new Secret Lives of Seahorses exhibit at the Monterey Bay Aquarium. But fear not, if you aren’t in California there are seahorse exhibitions all over the place.

8. Go dive for seahorses

If you are an addict of the underwater world like me, then there are heaps of places to go see a seahorse. Well, you can try anyway: they are extremely tricky to spot, with their cunning camouflage and shy nature.

Plus they are naturally rare creatures. You’ll not spot a big herd of them galloping by, but maybe – if you’re lucky – you might catch sight of a solitary seahorse grasping onto a blade of seagrass or coral branch. (Although, a friend of mine has just been diving in Indonesia and swears she saw a sea fan covered in dozens of pygmy seahorses. I’m not sure if she wasn’t just suffering from a case of nitrogen narcosis).

And you don’t have to venture to the tropics to see seahorses. Contrary to popular belief, seahorses inhabit shallow seas along virtually every coastline, tropical and temperate (but they don’t like really cold, icy waters, so don’t bother looking there).

Me and a seahorse. Photo by Steve Trewhella 2009.

A few weeks ago, I saw my first British seahorse off the beach at Studland in Dorset. Yes, that’s right. A British seahorse. There are two species on our fare but chilly shores.

Divers can play an important role in proving that a seahorse is worth more in the water than out. So, go out and support dive operations that care about their local seahorses.

And if you do spy a seahorse, try not to hassle it, poke it, prod it, or blind it with camera flash.

In this picture I am holding onto Troy (or rather, he is holding on to me), but I must point out, I was diving with a licensed seahorse handler (the UK species are now protected). We were conducting a survey, taking down this guy’s vital statistics, and stopped just quickly for an unmissable photo opportunity!

Check out chapter 6 of Poseidons’ Steed for more seahorse spotting tips.

9. Send in your seahorse sightings

Do your bit for seahorse research by getting involved with local seahorse spotting projects. The British Seahorse Survey collects reports of seahorse sightings from across the British Isles – and that goes for live seahorses in the water and dead seahorses too.

Get your seahorse spotting reports in!

10. Spread the seahorse love

And finally… (as they say on the news)

Recycled cashmere seahorse by snaulkter

Raspberry seahorse by snaulkter

I recently discovered these gorgeous cuddly seahorses made from recycled materials by a brilliant artist/designer snaulkter.

They are simply the most adorable – and accurate – depictions of seahorse in fabric that I’ve seen (and trust me, over my years of being a seahorse fanatic friends have given me virtually every beanie baby and cuddly seahorse ever made!). And I love that they are made from reused fabrics. Perfect!

So go get the kids hooked on seahorses, or indulge a grown up’s passion. Each seahorse is a unique critter, and each one is beautiful. Go see for yourself…

So… there you have my top 10 suggestions of how to help save seahorses. I’d love to hear you thoughts of any other things we can do.

Tonight it was the turn of fish to take centre stage on the BBC’s Life. And what an episode it was… absolutely, by far the best yet.

Clown fish. When the head female of an anemone dies, the biggest male has a sex-change & becomes the new dominant female. Photo by ecatoncheires.

Honestly. Trust me. You have to see this one. The early episodes had moments of eyebrow-raising novelty and breathtaking beauty, but so far none of them have truly enthralled me from start to finish. Until now.

And yes, it was about fish, so I’m a bit biased. But really, if anything, I was more likely to say “seen it” to whatever the BBC marched out on my screen.

What we see is scene after scene of surprises, extraordinary behaviour, and frankly stunning spectacles. We have freshwater barbel fish picking the muck off herds of grateful hippos. I never knew this sort of thing went on. Cleaning wrasse and shrimp oncoral reefs, sure. But hippos? Really! The hippos even open up those lethal jaws of theirs and have themselves a fastidious tooth clean.

Then there are the gobies that use their lips to climb up vast, roaring Hawaiian waterfalls. A few of the bravest individuals make it to glorious mountainous pools – fishy heaven. Only, their babies get swept back down the waterfall and out to sea, and the whole, exhausting process starts over again.

There are gorgeous slow motion shots of flying fish. Seeing these guys in real life is such a treat and wierder than you can ever imagine. But why not? Some birds swim don’t they? So why shouldn’t fish take to the air?

But crazier still is when the flying fish start getting together to make more flying fish. On camera, they cast their prodigious eggs and sperm onto a floating palm frond (which I suspect the film crew put there): so much that some of the fish start getting stuck in it and die. Yuck!

Flying fish eggs as sushi. Apparently some people like to eat this stuff. Photo by Roger Jones.

Imagine if you will, that when these fish start getting it on, they can produce enough gametes to sink a boat! The “behind the lens” section at the end of the programme showed a worried captain heaving a massive lump of sticky orange fish goo off the deck after the fish started spawning on his boat. The film crew make a hasty exit. (Also catch the hilarious scenes where the flying fish fly right into the camera team on their little boat).

This episode was especially poingnant for me, because I might have been involved in filming it. I’m not disgruntled that I didn’t get a chance to hob-knob with BBC film crews (although that would I’m sure have been a blast). But I’m miserable because the fish I wanted to take the BBC to film have apparently all gone.

For my PhD I studied I huge species of coral reef fish called the Napoleon wrasse or humphead wrasse (Cheilinus undulatus).

A fully grown male Napoleon wrasse. Photo by bananeman.

These are probably the biggest bony fish that live on tropical reefs and can grow up to nearly 2m long – it would tricky fitting one in a bath tub.

In this episode of Life we see snappers spawning in huge aggregations (these particular aggregations in the Caribbean attract whale sharks who come to feed on the resulting egg soup). Napoleon wrasse do this too. Or at least they used to at a site in the Spratly Islands in the South China Sea where I studied their spawning aggregations.

Every day when the aggregation formed, I went a long to film these giant fish. Then later on, back in Cambridge, I studied the footage and identified individual fish returning to the site day after day, recognising them from the unique patterns of scribbles and lines each one has on its face. Napoleon wrasse, as I discovered, come stamped with an individual faceprint.

Napoleon wrasse scribbles, like a human fingerprint. Photo by Peter Nangle.

Then, after I’d finished my PhD, a few years ago now (that’s how long it takes to film these series) I was contacted by a member of the Life team who suggested we go to the remote island where I did my PhD to film the spawning wrasse once again – this time with proper cameras, and not the sony handicam I used for my research.

It was all looking good until an email came through saying he’d heard that the wrasse were all gone: rumour had it that they’d been taken away to be sold in expensive Asian restaurants, another subject I studied for my PhD.

After following the intimate love lives of individual, gorgeous fish, my Napoleon wrasse have all gone.

Napoleon wrasse eye. Photo by tetzi.

So, all in all, I love this episode of Life. It reminds me why I do what I do. The oceans are beautiful and staggering and still, after all these years that I’ve got to know them, they can take my breath away.

But they also can make me very, very sad.

At least there were some beautiful dancing dragons to help cheer me up.

Oh, and how could I forget. They showed footage of a fish called the sarcastic fringehead. For real.

Today the BBC screened the first episode of their latest landmark wildlife series. This time around they’ve called it, quite simply, Life.

I must admit that back in 2006 when trailers for Planet Earth came out I was a little skeptical that we were really about to witness ‘planet earth as we’ve never seen it before’ as was promised. Surely we’ve seen it all by now?

But no. I was swept away from the opening scene to the closing credits. Planet Earth is undeniably stunning and when I watch it again and again on DVD there are still bits of my mind that get blown away.

And now we have Life. Once again, a little part of me is whispering ‘we’ve seen it all before, we’ve seen it all before’.

And once again, I have to admit that we obviously haven’t seen it all before.

Take, for example, the giant pacific octopus.

Perhaps I should already have known this, but the pregnant female finds herself a safe crevice deep down somewhere out of sight, lays a hundred thousand eggs and slowly starves as she tends and cares for them. By the time the tiny, spotty babies hatch, mother octopus has passed away. Yes it does sound a little sad, but that’s semelparity for you.

Giant Pacific Octopus (Enteroctopus dolfeini)

The first episode offers up other oceanic treats like bottlenose dolphins stirring mud rings off the Florida coast and extraordinary slo mo shots of flying fish as they try to escape sailfish (with footage that for the first time convinces me where the sailfish get their name from). These guys alone are definitely worth tuning in for (it’s on again tomorrow and on Saturday) or watching again on BBC iplayer.

This episode did feel a little bit like a quick fire round.  We see a carnival of snippets without going into too much detail. For example we whiz through madagascar and catch a tantalizing glimpse of a leaftail gecko’s foot with no mention of who it belongs to.

Mossy leaftail gecko from Madagascar. Helen Scales.

But perhaps this was a starter show parading things we’ll see later in the series. We’ll see next week.

And there were a couple of things that I’m sure we have seen before, like the poison arrow frog carrying its tadpoles one-by-one up a tree and plopping each one in a different water-filled bromeliad. These guys hopped through another BBC show a while back I think. But nevertheless they are still quite extraordinary.

We get some gnarly scenes of a leopard seal eating young chin strap penguins, flinging them about like rag dolls. But we are left with the oh-so-cute images of a baby orang utan with its mum while David Attenborough reminds us what life is all about.

So, in my humble oppinion, Life was good. I wonder if next week will be even better. I look forward to finding out.

This week is European Shark Week run by the Shark Alliance.

The idea is to spread the word about the many species of shark, ray and chimera that live in European waters, and highlight the problems they are all facing.

The Save Our Seas Foundation is running a great blog throughout the week. Offerings over the weekend include the announcement by three major european supermarkets that they plan to stock only shark products from non-threatened species. It’s a step in the right direction, but how about not selling any sharks at all?

Shark fins without the bodies they came from. Jessica King/Marine Photobank.

Shark Week has just begun and already there is one piece of encouraging news for European sharks.

It’s been announced that shark finning will be affectively banned in the UK. The plan is to close a loophole in existing legislation by no-longer giving fishermen permits to bring back fins that have been separated from sharks at sea. Hopefully this will turn the pressure up on Spain and Portugal, the two main shark-finning nations in Europe, to do something similar.

So, do look out for more European shark news this week.

And you can spread the word a little further yourself by sending out  Shark Week e-cards to your friends (check out the theme music!).

Could this be the end of the Chinese paddlefish?

This extraordinary aquatic giant wasn’t seen once during an intensive 3-year survey of the upper Yangtze River in China.

The Chinese paddlefish. A fish no more?

The last official reported sighting of the Chinese paddlefish was back in 2003. So, have they all gone now?

This bizarre species looks (or at least it did) a lot like a sawfish (a close relative of sharks and rays) with a huge long saw-like snout, or rostrum.

Chinese paddlefish have been measured at 3m long, while unconfirmed reports claim a 7m (22 feet) specimen weighing half a ton was found (that’s longer than three very tall men lying head to foot). Maybe they do grow that big, maybe they don’t. We may never know.

Because sadly we may never know much about Chinese paddlefish. They remain tremendously illusive with very few details uncovered about their habits. But it is thought that they probably spent time both in the sea as well as in rivers.

Overfishing and habitat destruction are named as the main culprits behind the demise of the Chinese paddlefish.

There was a possible sighting reported in Chinese newspapers earlier this year. But even so, with a team of keen-eyed scientists making every effort to find one – and failing – in the stretch of river they were most likely to hang out in, there is little doubt that there are hardly any of these magnificent beasts left in the wild.

If there are a few still hiding from us, there can’t be many.

And there aren’t even any in captivity.

What to do? Wave farewell?

Does this make the Chinese paddlefish the next on the list of species we have witnessed vanish, hot on the heals of the its former river-mate the Yangtze River dolphin?

If so, is there really anything we can do about it?

Scientists are talking about trying breeding programs, even artificial parthenogenesis. If only they could find a single, live female. Decide for yourself whether or not you think we should go to such extreme lengths to stop a single doomed species from being pushed over the edge.

A tiny part of me clutches onto a sliver of hope that there will still be Chinese paddlefish in the world in years to come. Just like I refuse to believe that I will one day wake up to the news that there are no more tigers or black rhinos or Philippine mahogany trees or any of the other critically endangered species there are.

But I’m afraid the pessimist in me seems to be winning on this one. I can’t really see how there is much chance the Chinese paddlefish will be with us for much longer, if indeed there are any out there right now. There are so many pressures crashing down on these fish – and many others species that live in the Yangtze. I just think we might be too late.

Flip side?

Is there a positive side to look on? Well, maybe.

While there may be not much hope for this particular species, I think we all need to reflect deeply on the possibility of another species lost. Stand (in your mind) on the banks of the River Yangtze, peer into the murky waters, and bid farewell to another creature gone, another fabulous product of natural selection.

It seems we never learn from our mistakes. But perhaps the story of the Chinese paddlefish could be one more reason to change that.

Because we’ve really got the stop this from happening. And not just for individual, charismatic species that we can admire and relate to, but for all creatures, great and small (as we used to sing in primary school assemblies), the species we may never meet and those we rely on in ways we may never know.

2010 is the year we said we’d reverse the tide of species loss. We’ve obviously not quite managed that yet. But I don’t think it’s time to give up.

In Detail:

• The Chinese paddlefish (Psephurus gladius) is one of only two known paddlefish, the sole members of the family Polyodontidae. The other species, the Mississippi paddlefish (Polyodon spathula) lives, as you might imagine, in rivers of southern United States.
• Photo of a tiny juvenile Chinese paddlefish.
• Link to paper: Zhang et al 2009.

On this week’s Naked Scientists we had behavioural ecologist Rebecca Kilner in the studio telling us about the extraordinary things cuckoos get up to. Duping other species into rearing your babies for you is undeniably a crafty way of going about life. But it’s not just cuckoos that do it, she told us. Fish do it too.

Namely the cuckoo catfish, a beautiful spotty fish from Lake Tanganyika.

Cuckoo Catfish. Photo by Johnny Jensen

Obviously, its name is a bit of a giveaway. And yes, technically this is a freshwater species – not an ocean inhabitant – but I was so amazed when I found out more about this fish that I decided they deserve space on wild ocean blue (and don’t they look a bit like goat fish?).

For starters, cuckoo catfish hang around cichlids, those famously diverse inhabitants of the great lakes of the African Rift Valley. And they get rather excited by the sight and smell of mating cichlids. So excited in fact, that male and female catfish rush in and cast their own eggs and sperm among the cichlid eggs on the lake floor (where they live as far down as 100m below the surface). The catfish also gobble up a few of the cichlid eggs while they are at it.

Lake Tanganyika as seen from space

The unlucky cichlids are mouth brooders, which means that seconds after the eggs are fertilized the female cichlid slurps them all up and incubates them inside her mouth. Cichlids can’t distinguish their own eggs from the impostors’ so they all get scooped up together.

Can she still eat with a mouth full of growing babies? Apparently not very well. By the time the babies have vacated their mother’s mouth, they  leave her underweight and hungry.

And it is not simply that the wily catfish leave their young in the care of the cichlids. They go one step further.

The cuckoo catfish young have evolved to hatch earlier than the cichlids. When they do, they instinctively eat the cichlid eggs and any cichlid fry that have hatched, eventually leaving nothing but catfish fry in the duped cichlid’s mouth.

The cichlid mother is so oblivious to the fraudsters she is nurturing that she will suck the young catfish back into her mouth if they wander outside.

Cuckoo Catfish. Photo by Johnny Jensen

Cuckoo catfish are popular with aquarium keepers, who have discovered that they don’t have to pass their eggs on to cichlids. Their eggs get on perfectly well if they are simply laid on their own on the tank floor.

why, why, why?

It might like seem like a foolish plan to trust your offspring to a total stranger. Imagine the human equivalent! But it obviously does make sense because so-called brood parasitism has evolved in several different groups of animals.

And the reason it works is because for many animals raising youngsters is difficult and costly: feeding them, keeping them safe without risking your own neck, all sorts.

So even if you occasionally get caught out, it can pay off in the long run to palm your babies off on someone else while you head off and make more babies elsewhere.

I give you the cuckoo catfish. All in all, a crazy and wonderful animal. And yet another perfect example of natural selection driving the evolution of something brilliantly adapted to a certain way of life.

In detail:

• Cuckoo catfish, Synodontis multipuncata, can live for up to 15 years.
• Females grow bigger than males, up to about a foot long.
• They are the only fish known to be brood parasites.
• Fishbase entry