Transcript of AE 1172 - The Goss: Aussie Eels Found to Travel 3000kms! But Why?!

G'day, you mob! Pete here, and this is another episode of Aussie English, the number one place for anyone and everyone wanting to learn Australian English. So today I have a Goss episode for you where I sit down with my old man, my father, Ian Smissen, and we talk about the week's news, whether locally down under here in Australia or non locally overseas in other parts of the world. And we sometimes also talk about whatever comes to mind, right? If we can think of something interesting to share with you guys related to us or Australia, we also talk about that in the Goss.

So these episodes are specifically designed to try and give you content about many different topics where we're obviously speaking in English and there are multiple people having a natural and spontaneous conversation in English. So it is particularly good to improve your listening skills. In order to complement that, though, I really recommend that you join the Podcast Membership or the Academy Membership at www.aussieneligsh.com.au where you will get access to the full transcripts of these episodes, the PDFs, the downloads, and you can also use the online PDF reader to read and listen at the same time. Okay, so if you really, really want to improve your listening skills fast, get the transcript, listen and read at the same time. Keep practising. And that is the quickest way to level up your English. Anyway, I've been rabbiting on a bit. I've been talking a bit. Let's just get into this episode, guys. Smack the bird and let's get into it.

Dad, what's going on?

Eels.

Eels. Have you ever eaten an eel?

I have.

I don't think I ever have. Is it any good?

Yeah.

Just fish.

It's fish, but it's. It's sort of oily and it's a, it's a, it's a weird one because it's a strong taste, but not an offensive one. But it's, they're very oily.

I always remember every time someone talks about eating eel, I remember that Friends episode. You know which one I'm talking about?

Yeah.

Unagi.

Yes.

I think it's where Ross is, like, obsessed with eel sushi or something. And he keeps saying like, "Unagi!". And then Rachel comes in and he's like, "Salmon skin roll!". Yeah, just making fun of him. Anyway, so we got this story here. "Freshwater Eel Research by Arthur Rylah Institute Reveals Marathon Journey to the Coral Sea to Breed." So- I love these sort of opening lines in articles.

Yeah.

"How far would you be willing to wander for a date? Probably not as far as this aquatic animal."

It depends on how attractive the date was.

Well, I was thinking. I met my wife through the internet and she was more than 3000 kilometres away.

Yeah, actually, she was two and a half. She was around about the same place that these eels go-.

Yeah, to the Coral Sea, right? Yeah. So she was in Townsville. "Long and short finned eels travel more than 3000 kilometres from waterways across Victoria to the Coral Sea. And for the first time researchers have been able to officially pinpoint where the eels breed. Scientists hoped a better understanding of migratory patterns would help reverse the species declining population. The recent discovery came amid a research project." Yep, "20 transmitters were attached to freshwater eels in 2019 at the start of the project and the tags- tagged eels were tracked over the course of five months and were seen moving all the way from south west Victoria to the Coral Sea near New Caledonia."

So that is what, off the coast of Cairns..

.. north coast of Queensland.

Yeah. Okay. So that's the Coral Sea of Cairns and Queensland there. There are so many things about this that blow my mind. Like besides the fact that you have a small animal. Well, at least like compared to us, right, a fish travelling that far to breed. I always love thinking about like, how the fuck did this evolve?

I know, I know.

How the fuck did you have an eel that obviously-.

Migrating animals-.

You would- you would think the thing originally evolved in the ocean then and was laying eggs in the ocean somewhere, and maybe around the Coral Sea, and somehow they found they've, they've travelled all the way, you know, somewhere and found a freshwater stream or something to go up to then live its life and then they have to go all the way back home.

But it's like- and that's insane, for them to actually have to transition from saltwater-.

.. changed their physiology completely.

Yeah. To be able to manage the lack of salt in freshwater, and then go back and forth like salmon, right?

Yeah.

And not only that, but they somehow end up with these huge distances because you're kind of like, okay, I could get it if it was the Coral Sea and then they end up in some river outside of Cairns.

Yeah, yeah. Like..

.. like 10 kilometres away.

... head west, until we get to a freshwater gradient and then we just follow this gradient up into a freshwater stream.

But you're like, how the hell do these things not get picked off?

Yeah.

Like I feel like if I were..

And why aren't they in Sydney?

Yeah.

We're in south west Victoria- they're in south east Victoria.

Yeah.

Where we have plenty of rivers but they're not. So, maybe they were, hundreds of years ago.

Yeah. Um..

Well they could have been hunted out by the indigenous people who..

They could have been.

Ate a lot of them.

They did.

And that was the other part of the story. But yeah, it just- that aspect of migratory animals always blow my mind because there are so many aspects to it. Often they're changing environments completely. There's how do they navigate from one end, one place to the other? And also, what are the, what are the triggers?

Well, that was, that was what this research was about, is what are the cues that say 'it's time for you to leave your freshwater environment and swim 3000 kilometres to breed'. And I'm assuming I, I'm not a fish biologist, but I think I know enough about this species.

Is it ichthyologist?

Ichthyologist. Very good. Um, I think that they only breed once. That these adults will swim out of their, the Hopkins River, and out into the ocean at Warrnambool and end up all the way up the east coast of Australia and out into the Coral Sea. They will breed out there. And then the elvers, the little baby eels, will, at some stage during their life cycle, wind their way back and find themselves back in the rivers in south west Victoria..

And they're gonna be eaten by someone.

Yeah, well they'll be eaten a long way along the way, but, um. And they'll stay there for the rest of their lives.

Yeah.

Until they were mature enough. And then they get this signal that says, oh there's, there's a flood here or whatever. And I think that was the, the finding of this article, was the, that-.

Seasonal changes.

The seasonal changes. But how do you- I don't think they're one year old when they go. They're probably there for ten years by the time they grow up and go, all right, it's time to go. When do we go? When there's a flood! Which is makes perfect sense when you get that, because you don't want to be trying to make your way through shallow water that's not moving.

I guess that'd be a..

.. certainly a ..

.. La Nina, too, right?

Yeah. Yeah. And it may well have something to do with water temperatures in the Coral Sea and then clearly not going to know what that is. But, you know, go, oh, this is a good thing to move now because La Nina is here. And that means there are changes in weather patterns and so on. It probably means there are changes in currents. So it's easier to swim north because the majority of the currents in eastern Australia are going south. So all of that stuff is probably..

Just lines up.

Tied up, tied up and they end up there. But the interesting part I think is the physiology. How do you go from being a little baby fish out in the marine environment and then decide, oh, I'm going to swim up a freshwater stream and and completely flip my physiology. Because the basic problem is to do with water and salt.

Yeah.

Moving across your skin surface. So obviously in a marine environment you've got a, the concentration of salts outside your body is higher.

Yeah.

So you're losing water constantly and gaining salt and you've got to have a way of getting rid of the salt and retaining water. And then you switch it over and you're into freshwater as a fish. You have your concentration of salt inside your body is higher, so you're absorbing water and yeah..

Yeah, yeah, I've got to get rid of that..

.. and you're losing salt. So that physiology switch is just bizarre.

What does it say here that- so yeah, the process is called osmosis, right? Regulating the amount of water on either side of a cell membrane so that it's effectively equal based on the concentrations. Right. But two organs do the work of shuttling salt ions in and out of a fish's bodies to counteract osmosis, the gills and the kidneys. Saltwater fish need to take in water to replenish the fluids in their bodies. But that means they're also taking..

Taking in salt, taking it to get rid of it.

Yeah. So that was the little snippet here from one of these articles, but I'm not sure. I guess that would mean that they just have either the gills or the kidneys changing the way in which they deal with these salt..

Yeah, they'll be really developing..

Pumping them out, moving them in..

In their, in there, as they're ageing, that changes their physiology. But that in itself is..

Yeah.

Interesting.

Well, and yeah. How do you suddenly change it if you're an adult, you've grown and then you suddenly decide to go back into the saltwater. Right. And you've been in freshwater for decades. Yeah, that must be a shock. But I would love to know how the hell they they. Okay, would they get the trigger of 'we need to go'. But then how do they know where to go?

They decide that they've all got to swim north east?

Yeah, yeah. And again, what are you following? The stars, the moon, you know, like magnetic fields?

And yeah, that- those, the evolution of those migratory patterns is sort of really interesting because clearly there is something about the, you know, that Southern Pacific Ocean that, you know, it'll be environmental as to right amount of food available, water temperature and all those sort of things to breed. But there are plenty of other fish, freshwater fish in those rivers that breed in that freshwater in that temperature, you know. Why does this particular species need to do that?

Well, that's where I would say, as an evolutionary biologist, it's- evolution isn't about finding the most efficient thing, but it's about using what works.

And what you've got.

And so obviously, if they're already able to breed readily in the Coral Sea and physically, they can make that distance and travel that distance, then they're going to do it as opposed to. And there's no evolutionary pressure if they're able to do that easily, for them to find somewhere else locally to breed. Obviously, if they were to randomly stumble upon that, then that population would be at a great advantage of like, well, we just lay our eggs right here.

Like evolution doesn't create enough. Well, there haven't been mutations to allow them to do that yet.

Yeah.

That have been exposed to the selective pressures.

Yeah. Because there must be huge things too, perhaps there's much higher a hurdle evolutionarily for them to be able to evolve eggs that can handle freshwater compared to saltwater.

Yeah.

And that's, you know, how would you- you'd have to be living somewhere where there is constant fluctuations in salt levels, right from freshwater to saltwater for there to be an evolution of eggs that could then handle..

.. less, in your environments.

Yeah.

And look, who knows, maybe this- and these are reasonably ancient animals. So maybe over a period of 100 million years, there has been sufficient changes in water temperature, as an example, that they used to be able to do it from just travel from that freshwater thing, just whip out into the ocean for, (makes funny sound) lay your eggs and then..

See yah!

And then you're gone. And then when your babies, you go, 'Yeah, this is all right, but we'd be better off up that freshwater stream.'

So we get away from the predators.

Exactly. We'll head up there. But that- then just became impossible with the water's cooling in the Southern Ocean and so on. So who knows? I mean, that's quite possibly the way it goes that but it's a bizarre one from that sense. Because most other migratory animals are migrating to retain a constant environment.

Yeah.

Rather than...

So they change..

Deliberately change.

This place is going to winter so we need to go somewhere else..

We got to have continuous summer.

Yeah.

And there's, we have migratory shorebirds that come to Southern- well, they come to all over Australia.

You wonder how many..

.. come from..

.. how many million..

.. Siberian Alaska.

How many millions of years it's been since they've seen winter.

Yeah. Well exactly.

Because they're just constantly chasing summer, right?

Yeah. They, they in this particular, in the case of some of our shorebirds, they come to Australia for our summer to feed and they breed in the northern hemisphere in Siberia and Alaska. Other birds like our shearwaters, the mutton birds do the reverse. They come to Australia to breed and then they just go up to the northern hemisphere in their summer to feed.

And for each you would probably think 'If you guys wanted, there would probably be somewhere for you to both breed and eat.'.

Yeah, just hang around in the tropics. Yeah, yeah. That's that's probably there's surely got to be somewhere closer by that you can eat or mate.

Yeah although..

.. that's amenable.

Although the, in the case of say the shorebirds, and for pelagic birds like shearwaters as well, they're eating specific things that are, in the case of shorebirds, in sand flats and mudflats that only occur in cool temperate environments.

Yeah.

So they're restricted to eating in those environments. Those sorts of things just simply don't occur in the tropics. And so you get those environments, but the food is different. And so they go through, have a bit, you know, don't like this, keep going south.

Yeah.

And the same thing I suspect for the pelagic birds like shearwaters where they're feeding on fish at sea and they've evolved to feed on cool temperate fish. So, or even in the case of moving to the Arctic. Yeah, cold water fish. But...

Yeah.

It's bizarre.

Back to the, um, the eels though. It was really cool reading about the Indigenous people. So the importance, the importance food sort- important- importance food source for night..

(mumbling) Yeah.

Yeah. Okay.

It's a badly written article.

It may be 'important food source for First Nations'. "The research is in collaboration with the region's traditional custodians, the Gunditjmara people," and that's spelt Gunditjmara, if you guys want to check it out.

So, "Gunditjmara man and World Heritage Park Ranger at Gunditj Mirring Traditional Owners Aboriginal Corporation, Tyson Lovett-Murray, said it can be overstated how culturally significant the eels were to the south-west Victorian Indigenous people. Traditionally..

Hardly overstated.

Yeah, sorry, it can't- it can't be. Traditional- "traditionally, for thousands of years it was a food source and led to the Gunditjmara community engineering a really big landscape around short finned eels."

Yeah.

"There are 350 recorded stone house sites on the cultural landscape and they're all attached to huge swamps that were formed by the eruption of Budj bim, formerly known as Mount Eccles."

Yeah.

So yeah, it's cool place, right? Where it's in-

It's southwestern Victoria.

Yeah. I'd have to learn more about the stone houses, but looking them up, they, they create these kind of like ring stone walls that are a few feet high, maybe, you know, one and a half, two feet high.

And then they have a sort of timber branch structure over the top with bark so that they can obviously live in these sort of small houses. And I wonder if the rocks stay there permanently and they can just come back with..

I would suspect so..

And just recreate them each season when..

But they also used to build eel traps.

Yeah. So.

.. when they come to.

.. build stone walls inside the stream.

Yeah.

Which narrows the, the stream width.

Mm hmm.

And then they used to build little wooden fish traps, and they would set them in the narrow gaps that they'd built.

Well, these things look like a sock, right, a long sock that would be made out of reeds or something, that would have the water funnelled. That would obviously allow the water to go in and through it. But the eel would get stuck.

.. eels would get stuck, yeah. So, so they'd capture these eels as they were heading downstream.

And that was about as, like advanced agriculturally, as the Indigenous Australians got right down here in south west Victoria, which is something we should probably be proud of geographically, that they created these stone complex- complexes. These structures that obviously were used by generation after generation. I think they were- I think we did an article on this a while back, where the data- back to like at least seven or 8000 years.

Ah, or 30,000 years.

Oh, was it even longer than that? Jesus, okay.

Well, certainly- I'm not necessarily the building of eel traps, but..

No, the stone structure.

Yeah, but the people living around Lake Condah, I think is, or what we call Lake Condah, I can't remember the indigenous name for it, but there has, there have been continuous occupation of that land for about 30,000 years.

Yeah, yeah. It's definitely thousands of years. I'm not sure exactly how long, but yeah, at this area, some of them, some of the things have been radiocarbon-dated to 7000 years..

Yeah, and it will be around that 6 to 7000 years because that's the, that they would have been trapping fish because that's when the land bridge was created between Victoria and Tasmania.

Yeah.

Which meant that it all disappeared, sorry, between Victoria and Tasmania.

True.

Which meant that we then had the shallow water Bass Strait that would have allowed those fish migrations to, to occur because before that, that area wouldn't have had the same level of estuarine environments to have those fish in it.

Well, it's crazy to think that Port Phillip Bay was originally just this massive green..

It's the Yarra River.

What was a- what would it have been like, an outlet..

It's a floodplain.

.. up the, right, floodplain with loads of kangaroos and it would have been like a hunting ground..

Yeah, a huge floodplain.

So it would have been crazy to think that there were probably people who migrated across from mainland Australia to Tasmania across that land bridge, you know, obviously if they had gotten there in the first place, but you wonder if they did that seasonally, you know, or had connections. And the number of places that must have had indigenous people living there that are now underwater, you know, you're kind of like it's sad that we won't probably ever know about all these locations that they would have frequented to to hunt, to live, to to love, to do all of those things.

And look, there are other migration things around that Bass Strait migration where you look at it now, if we have birds that- over winter in Victoria, that breed in summer in Tasmania.

Well, he's a swift parrot.

Well, swift parrots, orange bellied parrots. We have a lot of, you know, little tiny birds, little tiny bush birds that come from Tasmania in north to Victoria in the winter because it's just too cold for them, obviously..

When you..

.. in Tasmania.

You would guess that would have evolved..

And that would have evolved because they clearly would have just migrated up and down the coastline.

Yeah. Through the..

Or across the bush.

The land that was there originally.

Yeah. And then over a period of a few hundred years.

Yeah. Became islands..

It became islands and then it just became sea. And so now we have these, these birds that have to migrate across some of the most dangerous sea in the world from a point of view of storms and things, because it's it's stuck out into the Southern Ocean, but it's shallow water. So you get these storms and really big waves and all sorts of things in in Bass Strait.

But these little birds flying across it. And, you know, surely you can find somewhere in northern Tasmania, but it's just this evolutionary pressure that for tens or hundreds of thousands of years, their ancestors have just flown that far north and they keep doing it, even though now they have to fly 150 kilometres across the sea.

Yeah.

They might stop at King Island for a while, but it's yeah, it's a it's a bizarre one, but it's that evolutionary pressure of we've always done this, so we will keep doing it.

Well, and it's working. Yeah, we're still alive.

Well, it works until you get to the point at like swift parrots and orange bellied parrots. Two of the most endangered bird species in Australia. And part of that reason is, I suspect, is that they actually struggle with this migration. Now there's a whole lot of environmental reasons of, environmental destruction, habitat destruction. That means that they no longer have places to feed when they get here.

.. get already on the edge.

Exactly.

Then destroying the habitat that either they nest in or eat in is going to push them over. Well, that was a good episode. Just a quickie. Anything else to say?

No, having a drink. Sorry, you..

Could you..

.. drinking with my mouth full..

With your pants down?

Metaphorically.

All right. Well, thanks for hanging out, guys, and we'll chat to you next time.

Ciao!

See yah!