We’ve all heard the story about the goldfish with a three-second memory, rediscovering a brand new world with each lap of its bowl. But behavioural science is challenging this perception of fish as dim-witted swimming robots – with important implications for the conservation of fisheries.
After fifty years of industrial fishing, the United Nations estimates that three quarters of the world’s 400 commercial fish stocks are at risk of collapse.
While fish are the only wild animals that we hunt for food on an industrial scale, very little is known about the ecology and behaviour of most species.
Over the last decade, an undercurrent of research reveals that fish are intelligent social animals that learn from direct experience and by watching how other fish behave.
Using complex communication systems, they enjoy long memories and pass cultural knowledge between generations.
Catalyst visits two young Australian scientists whose work adds new meaning to the idea of ‘schools of fish’.
Dr Culum Brown There are 32,000 plus species of fish. We know almost nothing about their behaviour and ecology.
Each fish is an individual, just like people, you have these aggressive individuals, shy retiring individuals, you have bold individuals.
They have fantastic learning and memory capabilities.
A lot of people think that fish behaviour is totally inflexible, like little swimming robots, but that’s absolutely not the case.
They can learn all sorts of things and adjust their behaviour, if only we give them the chance to do it.
Mark Horstman We don’t tend to regard fish as animals, do we?
Dr Culum Brown No, it’s an odd thing, I mean, how many vegetarians do you know that say, I’m a vegetarian, but I eat fish!
Narration Fish are the only intelligent wild animals that we hunt for food, on an industrial scale.
The problem is how much we take them for granted.
The ones we don’t want are dumped over the side as by-catch.
Many of their coastal habitats are degraded by pollution.
Some fishing methods are highly destructive.
If we want fish in the future, we have to give them a fighting chance.
Before dawn each morning at the Sydney fish market is a passing parade of the best our oceans have to offer.
Mark Horstman Every day, 50 tonnes of 100 marine species come through this market. But how much do we really know about how fish behave?
Now new research is showing us that there’s more learning going on in schools of fish than we ever expected.
Narration The less we understand about fish behaviour, the more their populations are at risk from overfishing.
Dr Culum Brown They just can’t cope with the huge amount of predation pressure we’re putting on them. The gap between their ability to respond to predators and our ability to catch them as predators, that gap is widening hugely.
Narration As a result, after fifty years of industrial fishing, three quarters of the world’s 400 commercial fish stocks are at risk of collapse.
We still don’t really know how many are removed each year, nor how many remain.
While we’re good at exploiting the behaviour of fish to catch them, we’re blind to the social lives they need to survive.
It’s a mindset that behavioural ecologist Culum Brown wants to change.
Dr Culum Brown They call me the fish whisperer, yes… you have to think like a fish, definitely, get inside their heads.
Narration These are rainbow fish. Culum uses simple principles of animal psychology to test their learning and memory.
Dr Culum Brown What they do is, they make an association between the light and food delivered down the tube…
Mark Horstman Like Pavlov’s dogs?
Dr Culum Brown Exactly like Pavlov’s dogs.
Narration It doesn’t take them long to figure out that where’s there’s a light, there’s food.
Dr Culum Brown It takes only six or seven exposures, so it’s pretty rapid learning.
Narration What happens if you add fish that know about the light, to a school that’s never seen it before?
Dr Culum Brown These pre-trained individuals could be put in with naďve ones, and the rate of learning is rapidly accelerated.
Narration When he did this with some juvenile wild fish, he found they learned twice as fast from each other. The same applies to most things that fish learn.
Dr Culum Brown This is a fairly straightforward experiment where we teach them that this is a scary thing, simply by taking this and physically chasing them around.
Narration Whether it’s a plastic toy or a real predator, the principle remains the same.
Dr Culum Brown If you train them to recognise and respond to predators, we’ve shown in controlled experiments that dramatically increases their chances of survival.
Narration That’s important for fish reared in hatcheries. Before they’re released to the wild, they can be taught what to eat and when to swim away.
Dr Culum BrownThere’s no way a fish could survive in the real world, with that many challenges, if they didn’t remember things. That’s exactly the sort of thing we’re simulating here. It’s not inbuilt, it only comes from experience.
Narration And here might lie an answer to overfishing.
Dr Culum Brown As we’re increasingly removing fish from the wild, what we’re trying to do now is actually put some back.
Narration On the Georges River south of Sydney, fisheries scientist Matt Taylor is putting these ideas into action.
He’s towed this tank from a hatchery 250 kilometres away to release baby mulloway, or jewfish. It’s the only marine restocking project in NSW.
Dr Matt Taylor We’ve got about 8500 mulloway or jewfish, between 80 mm and 150 mm in length. It’s an important fish on the Georges River, with such a high concentration of anglers around this estuary, being in the heart of Sydney …they’re a difficult one to catch, but few anglers that catch a jewfish ever forget it.
Narration Usually restocking means backing up to a boat ramp, tipping out bucketfuls of fingerlings, and hoping for the best.
But Matt’s approach is different. He releases mulloway in areas selected for their carrying capacity. It’s based on their key habitat, their appetite, and the abundance of food.
Dr Matt Taylor You targeting mulloway?
Fishermen That’s the name of the boat, we wish we could.
Dr Matt Taylor Well we’re out stocking them today, we’ve got a couple of thousand on the boat here with us.
Mark Horstman How many young mulloway do you reckon you’ve released in your life?
Dr Matt Taylor Since 2003, about 250,000. Mark
Mark Horstman Quarter of a million!
Dr Matt Taylor Yeah, up and down the coast. Gone into half a dozen estuaries from the border down to Sydney.
Mark Horstman There you go fellas, live long and prosper.
These young mulloway experienced live prey and predators while growing up in the hatchery.
Mark Horstman So how many of these are going to survive?
Dr Matt Taylor Hopefully all of them, but realistically, probably about 50 percent will die before they reach the fishery, that’s my best guess.
Narration When the monitoring is complete, he expects a better survival rate than the usual ten percent or less.
Dr Matt Taylor Depending on the species, fish education can play a huge role in the survival of your released fingerlings.
Mark Horstman What’s your dumbest fish?
Dr Matt Taylor We’re only stocking mulloway, so it’ll have to be mulloway, won’t it.
Mark Horstman Smartest fish? Mulloway!
Narration But restocking the sea, even with smart fish, is only part of the solution to overfishing.
Dr Matt Taylor If you start throwing fish into the open ocean waters you’ve got to be very sure where the currents are going to take them or where they’re going to migrate by the time of harvest.
Narration Nevertheless, Culum Brown sees untapped potential in their talents for social learning.
Dr Culum Brown Training fish en masse, and releasing them in the real world. That’s the next step, and we’re pretty confident it’s going to work.
Narration He herds his schools of experimental rainbow fish behind a wall to record how long it takes them to find the way out.
Dr Culum Brown The idea of this experiment is to teach the fish to escape from, well it used to be a trawl net but we’ve modified it somewhat.
Mark Horstman It’s a symbolic trawl net.
Dr Culum BrownIt’s a symbolic trawl net, with a nice pink escape route, which is a little bit terrifying for them.
Narration Fish learn to escape by watching others do it, a lot quicker if their teachers are already trained. And with similar species he found they remember the lesson for at least a year.
Mark Horstman That’s a long time in the life of a fish.
Dr Culum Brown These fish live only 2 or 3 years in the wild. That’s a third or half of their lifetime, for fifteen minutes of training, that’s pretty astonishing.
Dr Culum Brown Not only are they learning from their individual experiences, because they’re keeping track of what others are doing, they gain a lot of information just by watching and learning from others.
Mark Horstman That suggests then that fish have culture?
Dr Culum Brown Yes certainly.
Narration And that means cultural knowledge can be lost when the big old fish with all the wisdom get dragged out of the school.
Like the infamous North Sea cod fishery, which collapsed because too many mature fish were taken. Now the cod no longer migrate to the same places to feed and breed.
Dr Culum Brown Not only have we messed with their biology…now the juvenile fish effectively have to figure it out for themselves. That’s pretty devastating, there’s no doubt about that. There’s some debate about whether those stocks will ever come back because we’ve messed with that culture.
Narration Culum suggests keeping the middle-sized individuals and leaving the old ones alone.
And he goes one step further: why not help fish bridge the technological gap, by training them to avoid trawlers?
Dr Culum Brown Yeah certainly that would be the ultimate aim, if you could teach them to avoid trawlers, which some fish do learn, they can recognise the noise of trawlers.
Mark Horstman The fishing industry might see you as a dangerous man if you go out and talk to too many fish.
Dr Culum Brown Yes possibly, but I’ve always been a keen fisherman myself.
Dr Culum Brown What we need to do is really concentrate on putting the ecology and behaviour back into fisheries management, particularly hatcheries.
- Reporter: Mark Horstman
- Producer: Mark Horstman
- Researcher: Holly Trueman, Amy Johnston
- Camera: Underwater: Richard Smith
Kevin May, Geoff Lye
- Sound: Nick Wood, Richard McDermott
- Editor: Ted Otton
Dr Culum Brown
Department of Biological Sciences
Macquarie University, Sydney NSW
Dr Matt Taylor
Fisheries & Marine Environmental Research Facility
School of B.E.E.S.
University of NSW