Fishy logic

My parents are out of town this weekend and they need me to feed their fish. My dad has a large aquarium with plecostomus and albinos little shark looking fish and well, all fish large and small. I haven’t really named them or anything. I just feed them.

But if I don’t feed them, what happens? I ask my dad.
They’ll eat each other, my dad replies.
But they have plants right? They can’t nibble on that for a day or two?

So it got me thinking tonight. About the fish brain and the fish code of ethics. If given the choice, will fish first choose plants or their own kind?

Let’s say they choose the fish first.
Do you think they feel any sense that they’re doing something wrong when they eat a tankmate? The child of a tankmate? Maybe their own child?
Do they feel any sense of remorse afterwards? If they do, why would they do it?

If they feel no remorse, what’s to stop them from just eating everything smaller than them in the tank? Food comes from the top. I want that food. You’re stopping me from getting that food. I’ll eat you.
You swam too close to me. I’ll eat you.
You’re looking at me funny. I’ll eat you.

How can a fish society live like that?
But also, would that mean they view the situation logically and not emotionally? It’s me or the guppie and I’m bigger. OK then. But if they were logical, wouldn’t they choose plants first? More than enough to go around.

Now when I say “emotion” I don’t mean the fish are writing sonnets in the tank. Just whatever the fishy equivilant of “guilt” might be. And when I say “logical” I don’t mean they’re writing geometric proofs on the glass with their fins. Just, you know, whatever serves as fishy logic.

And in a larger sense, there’s a question I suppose as to why some animal societies (i.e. fish or lobster or even kangaroo) will kill their young when confronted with a lack of food, but others will fight literally to their own death to raise their young. If animals have logic, why does it differ so drastically from one species to the next?

I know, these are extremely stupid questions. But tonight they intrigued me. Tonight I find them endlessly more fascinating than the war in Iraq and filibuster debates.

The thing to realise is that fish are incredibly dumb. They are barely a step above insects in terms of higher brain function, and that makes them little more than sophisticated machines. A fish receives a stimulus and that elicits a response. They can modify that response somewhat in repsonse to previous experience but not much.

So the whole question makes no sense. It’s like asking if the algorithm in a computer game feels guilt about shooting another algorithm. Such emotional responses simply aren’t party of the equation. The fishy brian receive a stimulus of lowered energy reserves and it responds to that by eating anything that moves. When the stimulus is removed as a result of that action then it stops eatingthings. There’s no cognition involved and very litle learning. There sure as hell ain’t no guilt.

Hungry fish won’t eat plants for the same reason that you won’t eat grass next time you get hungry. Plants are totally indigetsible to the vast majority of fish, which are carnivores. Moreover most plants poisonous.

As for why they don’t routinely eat other fish, that’s because of the energetic cost an the risk. Hunting uses energy and there is always the risk of being injured if the prey figs back. It’s last ditch survival mechanism for many species, not a routine. Just as you won’t go out and strangle a stray dog when you get peckish but would do so if you were starving.
You really do need to understand that fish, and indeed most animals, aren’t miniature people. They aren’t even likebaby humans. They are totally alien mentally and behave more like machines than even an infant human. They have no capacity for self-relfelction or reasoning and generally only a the most basic aversion reward type of learning capacity.

Trying to attribute their actions to higher brain functions as you have done is wrong on so many levels. You need to think of them as machines programmed by natural selection and then their bahviour makes perfect sense

Well first off kangaroos never kill their young when confronted with a lack of food. Some species will resorb an embryo or but that’s about it. Fish and lobsters also won’t kill their young. They may utilise them as a food source but they don’t just kill them for the hell of it. The only species that routinely kills its young in response to alack of food is humans.

And the answer to the question of why the effort put into caring for young varies so much can once again be found by viewing these animals as machines rather than adaptable intelligent entities.

Different species live in different environments with different resources and different reproductive patterns. Their behaviour to raising offspring will vary accordingly depending on what strategy has been proven by evolution to produce the greatest numbers of survival. It’s that simple. There’s no thought goes into this for 99.9% of animals, no decisions get made. It’s all pre-programmed.

For many species the actual cost of producing young is relatively small. A mouse is only pregnant for a matter of days. If the mother experiences a shortage of food the best strategy is abandoning the young or more often simply using them as food. Their little point is risking her own life to save the offspring for the loss of a few weeks pregnancy when she can produce another 50 young afterwards if she survives herself. And since that is the case those mice whose programming led them to behave in this way produced more young and the modern mouse behaviour evolved. The same basic pattern is seen in most fish and so forth.

In contrast with humans and large mammals the cost of reproduction is high and opportunities are few. A human female can only really have one child every 3 years and might only sustain that for 20 years. That means that a person only has the opportunity for 7 offspring. Similar numbers are seen for cows which might produce only 1 offspring a year for 10 years.

When the loss of any one young represents the loss of 10% or more of an individual’s reproductive potential it’s well worth risking your own life even if you die 9% of the time. And as a result large mammals do indeed risk their own life routinely for their young. In contrast a mouse litter probably only represents 1% of the individual’s reproductive potential so almost any risk isn’t worth it.

Basically it all comes down to what evolution has directed as being the best survival strategy. What the actual animals feel is open to debate and in most species they don’t; ‘feel anything’, but the behaviour is simply what is successful.

I have had guppy after guppy that ate its own young despite ample food and space.

I’ll deal with the cognitive functions in a bit.

I think fish in a fishtank are different from fish out in the wild. Out in the wild it is indeed not cost efficient, energywise, to try to eat everything out there. You can’t swallow the whole ocean! But here in the tank there are a limited number of fish. More importantly, there’s a limited amount of space so the chase won’t go on too long. It’s the limited amount of space that I would assume makes them more likely to think “other fish = my supper”

Another of your arguments is that some plants are poisonous and thuse aren’t eaten. But the plants in the tank aren’t poisonous and they’re the only ones the fish know. Besides, many fish are poisonous but that doesn’t stop fish from eating each other.

Now seguing from poison to cognitive ability, many species know what they can eat and what they can’t eat. Trial and error, certainly, but also from communication. They’re able to pass information such as “don’t eat the brown tablets” onto others. Surely this takes some form of intelligence, not only to communicate but also to understand and to store that information.

Finally, scientists are discovering new cognitive abilities for animals previously believed to not have any. Octopi play! Or so claimeth Discover. They seem to like bouncing colored barrels near a jet stream for no purpose other than to go out and chase it.
The fish in my dad’s tank gang up against an albino fish. The little thing likes hiding out in the corner and three of the larger fish who roam in a pack continually come up and bash him against the side then swim away. They don’t try to kill him. They don’t try to eat him. They just enjoy harassing him.
What purpose does this serve an analog brain stem with fins?

But more than all that, I was just sort of asking a philisophical question. Do androids dream of electric sheep? Do fish in my fishtank feel guilt?

Some facts first:
Fish have a preferred diet, plant or animal. Some will only eat a certain food, some are more omnivorous.

Unless there is a great size disparity, it is unlikely fish will start to eat others over the course of a weekend. The first fish to appreciably weaken after going without food will become a target, though. If the fish isn’t a plant eater (such as a barracuda), no amount of hunger will get it to think of plants as food, except on an evolutionary time scale. There’s likely not a great size disparity, otherwise the smaller, swallowable fish would already have been eaten.

Fish brains are not developed enough to feel emotions. They have patterned responses (tank hood opens, food comes in, go to surface to eat - not much different than seniors flocking to the Old Country Buffet as soon as it lays out its dinner items). That should not be mistaken as recognition of the owner.

Like most animals, including the human one, the fish will choose the diet of least resistance. They don’t have to chase flakes; flakes won’t fight back.

Lobsters have even less of a developed brain and no, or almost no, cerebrum. Mammals have a more highly developed brain (except for humans), and are much better at learning responses versus parroting behavior. Part of the learned behavior is how to keep the species alive. Some mammals need to be much more protective of their offspring than others; those that weren’t have died out.

I’d like to see a reputable cite for this.

I have no reputable cites offhand though I do recall seeing it in my high school science books back in the day. Birds were referenced there.
Bees can communicate too. It’s clear enough that their patterns inside the hive tell others where to find nectar.

But have you ever seen Mom and Dad save the World? The entire alien planet is filled with idiots. Complete and total morons. And one of the most effective fighting pieces of technology is a light grenade that instantly destroys anyone who touches it. So how do you get someone to touch it? You put a sign on it that says “pick me up!” and one by one an entire army will do just that.

How long would a species last that had no ability to learn “red berry = bad,” and no way to communicate that to others? One by one by one they’d all die out.

But you are still making the mistake of treating the fish as little humans rather than what they more truly are, sophisticated machines. A fish that has evolved not to habitually eat other fish because of the energy cost in the ocean is the same machine even when placed in a fish tank. To ask why this behaviour hasn’t change just because the fish is in a tank is like asking why a lawnmower attempts to tear up my carpet just because I’m stupid enough to start it in my loungeroom. These are machines. They have limited if any control over their behaviour. A change in the operating environment may make the behaviour less appropriate but it can’t alter the behaviour because it’s hardwired into the machine.

How do you know they aren’t poisonous? To me the fact that they haven’t all been eaten is all the proof I need that they are indeed poisonous. Remember that most plants are poisonous like lawngrass, not poisonous like hemlock. Routine eating of them will be fatal but occasional nibbling never is.

Can you please tell us how you ascertained that these plants are not poisonous to those fish?

Well, no. Many fish are not poisonous. A tiny minority of fish are poisonous, and most of them advertise the fact quite blatantly. Not at all comparable to plants.

I’ll second the call for a reputable reference for this. I know of some highly debatable evidence of this in primates but certainly the vast majority of species show no such ability. A horse placed in poison pasture with a dozen horses who were born there and learned to avoid the poison plants inevitably gets poisoned. I have never known a dog in Australia that has not tried at leats once to try to eat toads even if they have been raised by their own parents.

I look forward to a reference of even one animal species communicating danger avoidance in this manner. Certainly it not a trait of many species and personally I think it is a trait of only one species, our own.

Could we also have a reference for the claim that it was once believed that octopuses were once believed not to have such abilities. Who believed that, and when did they believe it? I don’t believe any such belief was ever held.

Oddly coloured animals almost always suffer this sort of behaviour. The problem is that lacking colouration they also lack the ability to communicate. Most fish have chameleon abilities that they use to communicate. In this case the albino fish probably lacks the ability to produce ‘submission’ colouration. As a result the alpha fish will attack him until he shows submission by retreating. The poor thing is probably firing all the right nerves for ‘submission’ but because the pigment cells are colourless the others get no response.

The fish don’t enjoy harassing him, they are simply responding to stimulus. The program runs:
See rival.
Initiate dominance display.
If rival shows submission colouration then end dominance display.
If no submission colouration initiate violence until rival retreats.

The problem here is that with no ability to produce submission colouration the program has to move onto violence. That’s because the fish are complex machines, not thinking entities. There’s no enjoyment ion the part of the attacker. A fish can’t experience any such emotion any more than a lawnmower can.

The display also doesn’t serve any purpose in an artificial environment with an amelanistic fish. That’s a mistake you will continue to make until you realise that this is hardwired behaviour. It can be highly inappropriate outside the environment it evolved in but because fish are just machines and not thinking entities they can’t actually modify it.

Philosphically the answer is of course “A tree”.

In the real world the answer is “No”. Fish can’t experience those sorts of emotions any more than a lawnmower can. You might just as well ask if your washing machine feels guilt.

I recall seeing lots of crap in HS text books. That doesn’t make it correct. Certainly I can show you numerous examples of chickens (which are a type of bird) being poisoned by foods that local chickens have learned to avoid. I can also list numerous bird specie sin Australia that still suffer mortalities from toads poisoning.
So clearly this isn’t a trait common to birds. As far as I can tell no species aside form humans exhibit such a trait.

Nobody disputes that animals can communicate what to do. All species that engage in sexual reproduction have some ability to communicate what to do. However that is very, very different to your claim that any species but man has the ability to communicate what [I[not to do*. That is much harder to achieve and so far there is no evidence that it is capable of existing outside a species with complex language and abstract thought.

No they wouldn’t. That’s because plants don’t evolve deadly poisons of that type. It’s waste of resources. Plants and animals are in an arms race and plants only evolve the bare minimum toxicity needed to make them unpleasant to eat, not deadly. As a result almost no plants are fatal in normal doses, even to non-target species.

As a result in the real world we see the situation we see when the cane toad reaches new environments. A tiny minority of species do indeed succumb universally and become extinct. The vast majority of species suffer some losses but mostly just get ill individually and learn. Next generation they all learn all over again.

If this ability to communicate what is poisonous is as vital as you suggested it should be ubiquitous. And yet you can’t provide even one reference for it occurring on the planet while I can name a hundred provable examples of animals who clearly can’t communicate in this manner. So how do you explain those cases? How do these species that I can prove don’t have any such ability survive if having this ability is necessary for survival?

The rest of your post I understood, and it was very informative.

This statement, however, causes me to go “Huh?”

I can’t think of any widespread child killing where food is scarce. Did I miss a memo?

Sorry I hadn’t gotten back to this thread earlier. No internet at work. Le sigh…

Unfortunately I don’t have much more information than I had last night. The article on the Octopus is in the October 2003 issue of Discover but I can’t seem to find my copy right now. It’s in the attic somewhere and I’m sure I’ll find it eventually. It was an interesting read though.

Some of the other claims I’ve made I know need cites. Don’t have them. Sorry.

Look, I know the brain function of a fish is quite limited. I get that I’m anthropomorphizing these critters even asking the question. Yet fish can act logically even if they don’t comprehend the concept of logic. It’s just a question of degree. Could emotion be the same? It occurred to me last night. What if? That’s all I was asking. What if? To what degree?

I really just meant this thread to be a silly diversion into philosophy to break the minutia of GD. Alas. I failed spectacularly on that account.

No, youprobably just missed this thread ( ) where I gave a reference that included numerous other references to the near universal practice of infanticide in human cultures.

Unfortunately I can’t link to that article anymore because it no longer appears to be functional. But that thread contains a small excerpt.

Naturally fish act logically, just as a computer acts logically or a washing machine acts logically or a lawnmower acts logically. It’s an inherent part of being a machine. They act logically by default. The tricky part, and what nobody has succeeded in doing so far, is to create a machine that can act illogically as humans and higher animals do. That appears to be an emergent process or some higher intelligence.

The difference between emotion and acting logically is that acting logically is simply an action, a process. Emotion is a subjective experience. They’re quite separate things.

Making a machine that responds to stimulus X with behaviour Y is simple. Making a machine that has emotions requires at least a modicum of self-awareness, at least to the degree of understanding that how it feels now is not how it felt then and is not how it will feel in the future. As you can imagine that requires a lot more programming and of course a lot more memory capacity.

The extent to which fish might experience the rudiments of emotion can never be absolutely certain of course because emotion is subjective. However the best neuroscience we have says that fish can’t even feel pain, much less emotion.

Yes, I did miss that. Thanks for the link. Although in some ways I wish I hadn’t read it - it’s put a bit of a downer on this Friday afternoon.

In my experience as a fish keeper, fish will eat anything they can. Herbivorous fish, that get fed plenty of good, well-balanced foods will still eat any plants in the tank. It doesn’t matter how much you feed them, or don’t feed them. This is why you don’t keep silver dollars in planted tanks. It is expected that fish will nibble on plants in the tank, so I don’t imagine anyone would keep poisonous plants with their fish.

The same with carniverous fish. They will pretty much eat any smaller fish they can fit into their mouths, no matter how recently or how much they have been fed. Basically, if they were going to eat each other they would have done so already.

Most ornamental tropical fish can go quite a while without food with no ill effects. If I were leaving for up to a week, I probably wouldn’t get anyone to feed my fish for me. There is more of a danger in overfeeding than in leaving them with no food.

I don’t really know how much, if any, emotion they feel. None of my fish have ever shown any signs of feeling guilty about anything, even though sometimes I think they should. I like to think some of them seem happy to see me, even though I know it’s probably more due to anticipation of food than any actual attachment to me.

That’s certainly been my experience, as well, but I think that all that it proves is that:

1.) Guppies are blatantly unsentimental creatures.

2.) A goodly percentage of all baby guppies end up as food for somebody, so why shouldn’t the chef get to lick the spoon once in a while? :wink:

3.) Fishtanks don’t provide enough baby-guppy-hiding habitat, and they are small enough (despite “ample space” by fishtank standards) and protected enough (for the adults) that the adults don’t have anything to distract them from chowing down. They are also short on the kind of currents which would probably serve to quickly disperse the young in the wild, making them less convenient to eat. Finally, I’m guessing that the confined spaces of the fishtank increase the odds of a guppy eating it’s OWN young as opposed to someone else’s.

Presumably, the large numbers of baby guppies in each “litter” (spawning?) allows for a great deal of loss before maturity.