how do they know

i have often wondered how do bottom feeding fish tell the difference between all the rubbish that they suck in from the bottom of lakes and what they want to swallow as food,how do they know what to keep and what to blow back out? some baits such as boilies are simalar to small stones,some food items such as shrimp, bloodworm and small snails must get sucked in with other stuff like stones, leaves, silt and sticks, how do they know?

Cos they is clever.....

Seriously:
Bear in mind fish don't have hands to sift through the silt etc, bottom feeders mouths have evolved to give them extraordinary dexterity, therefore the ability to swallow or eject items as they please.

This noticable must if comparing a true bottom feeder like tench and an opportunist bottom feeder, such as a chub.
Chub will often mouth the item of percieved food a couple of times then take it properly in its mouth.
Where as tench suck (unless weary) in all percieved items of food and sort through them in their mouths, finally ejecting what they don't want.

It is this sifting and sorting process that bottom feeders use, that at times gives the necessity for critically balanced baits etc, to counter the weight of the hook, so not alerting the fish to something not being right.

The trait of opportunist feeding of chub is well shown by their lack of interest in picking up food from the river bed within a short period of time but when presented with a constant stream of maggots flowing past their noses mid-water, they just gorge themselves.

Regards food recognition, taste or smell many will debate but either or, it all leads to the same end.
Without which, any/all species would starve.

When you buy a meat and potato pie from the chip shop and start eating it, you sometimes find alien objects in the pies, least you do round here, these range from false nails, eye lashes to false teeth, we tend to eject these as usually they taste and feel unedible, whilst in some cases the entire pie is unedible, except for the likes of Deanos or somebody from wigan of course. Fish behave in much the same way although don`t generally eat meat and potato pies, or at least not from round here, which just goes to show how clever fish really are

I am no scientist but fish must have senses that we really don't have or understand apart from the ones we do have and understand. They must be able to smell things, taste things, sense things and they have sight, they must taste things in the water that are quite a distance from them as well, how else are they attracted to loose feed? They can hear perfectly well because they can be frightened by noise alternatively they are attracted by the sound of food hitting the water.

Combine all those faculties plus some we don't know about and it isn't surprising that they can pick out food from rubbish on the bottom is it?

What we describe as rubbish may just be gravy to fish.

The Monk's post is a simplified way of describing it and he has years of experience of eating rubbish like meat and potato pies!!!

By the time they get the food item into their mouths, most fish will have smelled it out and decided it's worth eating. Next test is to mouth it to find out if it's digestible and that's when you normally hook them except chub, which have devised the canny knack of doing this with their lips the crafty little b*****ds.

If it's loose feed then the mouth of many fish can sort out the good bits from the bad, blow out the bad and swallow the good, as the good Monk says. No doubt that many a time though, a fair bit of muck, silt, bits of leaves etc. is swallowed with the good, but what the hell.

Test: drop a piece of well buttered toast on the soil in the garden and watch you pet dog pounce on it and devour it regardless of how much muck is stuck to it. We have become too selective over the years and time we started eating more dirt!

1000's and 1,000,000's of years of evolution must play a bloody large part in all of this, not as stupid as they first look some of these fish.

Jeff Woody said:

We have become too selective over the years and time we started eating more dirt!

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You wouldn't say that if you had experienced my wife's cooking.

Seriously though, If you watch carp or tench feeding they pull in a large amount of detritus when they suck up their food, I have always thought of them as like vacuum cleaners that can finely tune the level of suck and blow to select the food items. I don't think they taste every morsel but select what they retain by it's density.

Ray Roberts said:

Seriously though, If you watch carp or tench feeding they pull in a large amount of detritus when they suck up their food, I have always thought of them as like vacuum cleaners that can finely tune the level of suck and blow to select the food items. I don't think they taste every morsel but select what they retain by it's density.
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Carp certainly are vacuum cleaners that cause water to go turbid. They will often dig deep into the silt with their tails up.

Tench are more bottom pickers and generally don't cause water to become turbid.

Ron The Hat Clay said:

arp certainly are vacuum cleaners that cause water to go turbid. They will often dig deep into the silt with their tails up.

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I watched one feeding close in the margins last week, it was standing on it's head in about 3 feet of water. Once the fish started to feed it clouded the water in no time. It's amazing how they can suck in and swallow food items that vary in size from bloodworm to 22mm boilies

Hi All,

I once had this thought whilst fishing for barbel on the Severn near Bewdley.

I have fish tanks at home and i remember feeding the fish in there the flakes from the tubs you buy (can't remember the proper name) and was amazed at the process. The "flakes" that weren't taken immediately off the top sank through the water and landed on the bottom of the tank which was covered in decorative little stones. I stayed and watched the fish and saw one of them, although it is a tropical fish, suck the "flake" and 2-3 stones into its mouth. After siphoning the dirt out through his gills that was on top of the stones, he spat the stones back out and swam off. I began to watch this fish over a period of about a week to try and work out if there was a method which might help me to hook wearier fish. The process was always the same; suck stones in, siphon dirt out throught gills, spit stones out then digest food and swim away. I found that when i had bites on a commercial, that when the float rose out the water and dipped twice, to leave it alone. Once the float rose again and dipped, that was the time to strike. May i also inform you that this helped me catch my PB Tench of 8lb 10oz.

Barla

I have a feeling that roach do not eat whole maggot, caster or corn, but crush them and extract the soft liquid nutrition from them before ejecting the less digestible husk. Bread I think they suck in whole or in small bits but only when it is the softest mush possible which is why some anglers succeed with breadflake, and some struggle - creating any hard lumps seems to result in difficult to hit bites with the fish blowing the bread in and out. I have never actually observed what is going on directly, so this is all pure conjecture

However, I can tell you exactly how perch eat lobworms having recently witnessed one fish after the other take them in the same fashion in gin clear water.

They will rush up to it in small packs or groups, the first fish to get there is the winner, no other fish will contest the prize no matter how much larger it is. The fish then tilts upwards and sucks the worm in inch by inch until it is completely engulfed and then it will sit there for a few seconds and mull things over before deciding that it is good to eat, and then, and only then, will it move away.

The time to strike, is of course, when the whole worm is in. The only trouble is, in coloured water you will only get the smallest indications on the float, like crucian bites, as the fish takes the worm in bit by bit and by the time you get the sail away indication of a fish moving away, the fish has the worm in its gut and you are bound to throat hook it.

Now, if I am perch fishing, I strike gently at the smallest bites because doing so does not put the fish off at all , it simply makes them more curious about the worm.

The Monk said:

When you buy a meat and potato pie from the chip shop and start eating it, you sometimes find alien objects in the pies, least you do round here, these range from false nails, eye lashes to false teeth, we tend to eject these as usually they taste and feel unedible, whilst in some cases the entire pie is unedible, except for the likes of Deanos or somebody from wigan of course. Fish behave in much the same way although don`t generally eat meat and potato pies, or at least not from round here, which just goes to show how clever fish really are

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Ha ha, brilliant.

---------- Post added at 16:18 ---------- Previous post was at 16:17 ----------

rufus said:

However, I can tell you exactly how perch eat lobworms having recently witnessed one fish after the other take them in the same fashion in gin clear water. They will rush up to it in small packs or groups, the first fish to get there is the winner, no other fish will contest the prize no matter how much larger it is. The fish then tilts upwards and sucks the worm in inch by inch until it is completely engulfed and then it will sit there for a few seconds and mull things over before deciding that it is good to eat, and then, and only then, will it move away. The time to strike, is of course, when the whole worm is in. The only trouble is, in coloured water you will only get the smallest indications on the float, like crucian bites, as the fish takes the worm in bit by bit and by the time you get the sail away indication of a fish moving away, the fish has the worm in its gut and you are bound to throat hook it. Now, if I am perch fishing, I strike gently at the smallest bites because doing so does not put the fish off at all , it simply makes them more curious about the worm.

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That is very interesting, cheers Rufus.