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Features
05 Jun 2017
by Simon Blanford
The clever fish?
Biologist and carp fanatic, Simon Blanford poses the question: are carp clever? Find out his thoughts...

All fishing used to be about food. At least all documented fishing used to be about food. That’s not to say that Eric the Slightly Deranged didn’t occasionally take his hazel-stick rod and horsehair line out (in between taking care of his farm, fighting off marauding Vikings/wolves/Welsh) purely for the pleasure of doing so. But recreational fishing as a pastime, as an approved way of interacting with the country and its watery wildlife, didn’t really get going until the 16th century. Subsequently, famous authors like Walton, Bickerdyke, Sheringham and many modern others reinforced the view that fishing is good and that any sensible folk should take it up for their physical and mental well being.

Across the centuries of this angling activity a huge amount of information has had time to accumulate and all that knowledge has allowed us to improve our kit. As big-brained apes we are good at the technology stuff: greenheart to cane to solid glass to fibreglass to carbon: horsehair to gut to nylon to monofilament. And that’s just the start. Look at all the gizmos Korda and Fox have in their respective catalogues, the myriad items from little plastic beads to shelters you can live in. One might reasonably ask why there is so much tackle, so many different ways of putting what effectively comes down to a hook on the end of a line to catch a fish. One obvious, and perhaps slightly ungenerous answer, has to do with marketing and profits. Fishermen, whatever their chosen quarry and whatever their favourite technique to catch that quarry, are inveterate magpies, quite happy to pass over hard-earned readies for ‘shiny-shiny’ new tackle. No profit-orientated company is going to miss out on the possibilities afforded here, a kind of avarice on both sides of the shop counter.

Izaak Walton thought the carp the “most subtle of fishes”

The more generous explanation is that we are in a continual arms race with carp: the wisest, the most cautious, most intelligent of fish. As we adapt our tactics so do they. We originally received this view of carp as the clever fish from those early writers. According to them, and as we saw in last month’s article, carp were likened to freshwater foxes, their brains were larger than any other fish, and anglers who tried to catch them developed a “strange look in their eyes.”

Then along came Richard Walker riding the post-war technology boom who, along with equally able but less celebrated anglers, wondered what all the fuss was about and claimed, sacrilege of sacrileges, that carp really aren’t that bright. Walker was using (in fact creating much of it himself) more advanced fishing technology than his predecessors. His view may also have been coloured by the fact that he was deploying this arsenal against carp that had, by modern standards, seen very little angling pressure. Either way, the former acceptance of carp as the professorial fish they were once considered to be was challenged. Carp aren’t clever, they aren’t intelligent, they don’t have the fishy equivalent of PhDs, they haven’t written learned theses on “Post-Industrial Fishing Techniques of Western Europe”. They do everything by simple instinct. They are, not to put too fine a point on it, not much more advanced than the classic trope of the aquarium goldfish and its three-second memory. As an example we have last month’s thoughts from the veteran angler and columnist here on CARPology, Ian Chillcott, who stated, “I have no wish to keep on talking about how intelligent carp are, I think that any reader of this column would know, I credit them with none whatsoever.” So there.

Andy Bell with an immaculate common. But, if they’re that clever how do we manage to catch them?

Trouble is anglers, like many others, aren’t very good about judging this sort of thing. We lack any formal training on how to interpret fish behaviour in an unbiased manner. So it’s worth noting that while modern carp anglers have been downgrading the intelligence of carp, those who spend time studying fish behaviour and their cognitive ability have been trending the other way. Here’s an introduction to a recent book all about the topic. “[G]one (or at least obsolete) is the image of fish as drudging and dim-witted pea brains, driven largely but “instinct” with what little behavioural flexibility they possess being severely hampered by an infamous “three-second memory.” The passage concludes by saying, “Although it may seem extraordinary to those comfortably used to pre-judging animal intelligence on the basis of brain volume, in some cognitive domains, fishes can even be favourably compared to non-human primates.”

That last sentence is telling. On CARPology’s website a regularly recycled question is “Are carp clever?” The most erudite response comes not from the carp experts but from a Facebook commenter who simply asked, “compared to what?” Compared to what indeed. It’s a reasonable and actually quite fundamental question. Compared to a worm, deep down in the dark? A bird, quick and light among the branches of a tree? Or compared to us with our abundance of cerebral matter but tenuous grasp of the lives of other animals? Its bad enough trying to understand other people let alone a completely different animal whose life is spent in an alien environment. We are told to “think like a carp” to better find and fool them into taking our bait. But in reality we can’t. Wittgenstein (one of those clever philosopher types) once said, “if a lion could talk, we could not understand him.” The lives of lions are so different to ours, the way they monitor and experience their environment so at odds with our own that should a lion turn round and speak to you in English, you still might not understand a word they were saying. And a lion is a terrestrial mammal, not an aquatic teleost.

If it is impossible to think like a carp and very difficult to read its mind, no matter. Scientists have examined fish’s intelligence by actually looking at what they can do. Solving mazes is old hat (fish can form and hold mental maps and visualise short cuts without physically following them). Fish can also tell each other apart and judge and remember the social status of the friends (yes, some do seem to form ‘friendships’) and how good their enemies are in a fight. Some can count and do addition, appreciate classical rather than pop music, use tools and even tell us humans apart. There are Grouper, the large predatory marine fish, who ask Moray eels to come and help them get at prey in particularly difficult bits of coral. Then there are cod.

In Norway they were training cod to use a self-feeder. The self-feeder is basically a length of string with a bead on the end that dangles down into the water of the fish’s tank. The cod fairly quickly learnt to take the bead into their mouths and pull on the string, which in turn releases a set number of food pellets. Hey presto, self-feeding. But every now and then a cod would get caught up in the string. Each fish had a tag in its back so it could be identified by sight. The tag sat proud of the back an inch or so. It was this tag that sometimes got caught up in the bead and string set up.

No it doesn’t just have a three-second memory

At first ‘hooked’ fish struggled frantically until they had managed to extricate themselves. After a while however, the researchers noticed that some of the cod had reversed their behaviour. They were still swimming up to the string, but instead of taking the bead into their mouths some were deliberately hooking their tags onto the bead. They would then give a quick, whole body tug before releasing themselves from the bead with a deft twist and swimming over to grab some pellets. Why do this? They did it because by hooking themselves via their tag, instead of pulling on the bead with their mouths, they could get to the released pellets faster and not find them all scoffed by their tank mates. They had somehow learnt (and presumably spent some time practising) how to change an unpleasant experience into a profitable one and used a tool to do so. That’s some mental muscle for a fish.

Grouper seek out and ‘ask’ Moray eels to help them hunt

As background, these examples (and there are many more) are interesting but cod are not carp and pulling on beads or asking eels out for an evening hunt don’t tell us about our fish’s approach to baits and rigs. Scientists have examined carp of course but more often they have been studied for their use as a food animal or an invasive pest. Nevertheless, there has been some interest in looking at the extent to which carp learn to avoid being caught.

Enter one J. J. Beukema, a Dutch biologist. He set-up some experiments by stocking previously uncaught carp into a number of ponds. After the fish had settled down and got used to their environment he invited anglers to fish for them. The anglers were free to choose their baits and tactics and most chose bread, followed by potatoes with a few anglers choosing worms or maggots. This was back in the late 1960s so no boilies and no Hair or bolt rigs. Over the two weeks of angling, the carp rapidly learned to avoid being caught. In fact, in just four days, catch-rates had crashed and recaptures were very few and far between.

Beukema established a ground zero for carp learning in response to angling. If you fish for them intensively, with relatively simple tackle and baits, they will rapidly ‘wise up’ and learn to avoid being caught. There’s nothing really new in these observations. Any angler fishing back in the pre-Hair rig days on hard fished waters knows this already (though for many younger anglers, educated fish are the norm and have been since they started fishing). Still, it is good to have the carp’s learning curve formally confirmed in an experimental setting. And there were a couple of other interesting points.

Beukema couldn’t account for the decline in catch-rates simply from those carp that were landed once learning not to be caught again. One suggestion was that a carp didn’t have to go through the whole catastrophe of being hooked, played and hauled ashore to learn to avoid anglers. Just feeling the hook and at most being played for a short time was a sufficient experience to make it unlikely they would be caught again. Another was that the carp learnt by watching each other. Animals are very good at watching. Carp can observe the behaviour of their neighbours and go on to copy the avoidance reactions shown by experienced fish without having to be caught themselves.

Cod. The really clever fish? Surely not

Beukema then added an interesting wrinkle. He went away for a year. When he came back he introduced some naive carp into the ponds that held the fish from the previous experiment and set about trying to catch both groups, the new fish and those caught and released a year earlier. As you’d expect the new, naive carp came out quickly. But the population that had been fished for in the past were still difficult to catch, less so than when he’d finished fishing the previous year but more so than when they were first introduced to the ponds and more than the new, naive fish. Some of those carp, even though they had only been caught once a year ago, still remembered and applied their experience twelve-months later. That’s quite some feat especially for a fish whose close orange relative is meant to have a three-second memory.

Many years after Beukema published his studies, a German research group decided to have another look at the question. This research group also fished for carp in small ponds but in addition included large tanks in the laboratory to better observe the fish’s behaviour. Being a recent study they chose to fish with corn on a Hair and bolt rig and fished not only during the day but for some of the night too, feeding them an hourly diet of free corn and carp pellets. The researchers also videoed some of the carp’s response in the laboratory tanks and an excerpt is available to watch on CARPology’s website along with a bit of text to explain what is going on. (Just go to CARPology.net and search ‘The Carp’). Go over and have a look, it’s a very interesting view of how angling and being caught dramatically changes the carp’s approach to bait.

The ponds the researchers used were a more complicated environment than the laboratory tanks. Murky water, other food sources, some variation in depth and bottom consistency (however slight for each) all influenced the way the carp behaved after fishing started and resulted in some differences in behaviours between carp in the pond and those in the laboratory. In the ponds they learnt to avoid the hookbait more slowly taking a week to ten days for catch-rates to decline to very low levels. They didn’t avoid the baited areas and there wasn’t any difference between the number of captures during the day or the night.

One question carp anglers ponder is how often carp are picking up the bait and dropping it without giving any, or only very slight indication of their interest on our bobbins and alarms. Should we be hitting those single beeps as some advocate we should? The researchers included this question in their study and found that in the ponds the carp appeared to avoid the hookbait more, the more experience they had of being caught. The number of times they picked up and tested the hookbait declined in line with the decline in the number of fish actually hooked and landed. The researchers did get done every now and then but the main effect was that the carp increasingly learnt to avoid the hookbait.

In the simple environment and clear water of the laboratory tanks the behaviour was quite different. Carp learnt how to avoid being caught very quickly and catch-rates crashed in just a couple of days. Unlike in the ponds the fish became much more wary around the baited areas (these were marked with a circle on bottom of the tank and can be seen on the video), visiting them less frequently and using shelter areas more often.

This helps inform another CARPology question: do the fish spook off baited areas? Here the answer was yes, to an extent at least. Their body language showed that they were much more wary of the bait generally and not just the bait on the hook. Another difference to the behaviour in the ponds was a clear difference in catch-rates between day and night, the carp in the tanks were caught more often during the night than during the day, albeit still at a low rate. Murky water and/or the dark make carp more vulnerable as they lose the opportunity to closely eyeball the bait. And also, unlike the ponds, rather than avoiding the hook bait the carp continually tested it. They got caught less often not because they completely avoided the bait (in a simple environment like these tanks and with no alternative food supply it’s not surprising they took more of an interest in the bait than in the ponds) but because they very quickly learnt how to test for the presence of a hook and get rid of it when one was found. It seems in clear water and when fishing for experienced fish, avoiding giving them any clue they can use to tell the hookbait from the free offering is important. In murky water and at night where visual inspection is severely limited this becomes much less important.

The author happy to have fooled one. Carp will always make mistakes. How often depends a lot on their individual foraging behaviour, their personality and their rearing background

So are carp intelligent? Are they clever? Yes, absolutely. But it is an intelligence of their own, expressed in an environment appropriate to them. To try and judge carp intelligence by our standards is silly. Carp clearly learn and adapt their response depending on the environment they are in (murky ponds versus clear laboratory tank) and the availability of alternative food drives the risks that they take with our hookbaits. They can clearly work out solutions to the problems we pose them and if they are not always successful, well, neither are we. In fact, that early comment about carp being the freshwater fox is not far from the mark. They are both extremely adaptable. They are both adept at exploiting different food supplies, are inquisitive, have excellent memories, know their way around their environment and can map and remember routes to food and areas of risk to be avoided. And they are both difficult to trap. Any of those traits indicate that the animal is adaptable and intelligent in its own world.

But they still make mistakes. In fact they seem to make odd mistakes. Why do those carp in the laboratory tank persist in testing the bait when they’ve learnt an unpleasant experience might follow? Why don’t they just eat the pellets and not the corn? They weren’t starved after all. Part of the answer here lies in the differences inherent between individual fish, the variation that exists between how bold or shy they are. Part of the answer has to do with where they come from, what strain they are and how they were reared. And part of the answer lies in the way carp feed. We’ll have a look at foraging behaviour and the personalities of carp in the next couple of articles.

-Read more

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