Stesimo,

Did you plumb the depth?  If you have loads of small perch around I've always found it better to fish at dead depth (exactly the depth of the water) or with just an inch or two of my hooklength on the bottom if there is a bit of a tow on the water (drift).  If you are fishing with too much of your hooklength on the bottom the perch has a chance of really gorging the bait before it moves away and you see the bite.  Fishing at dead depth or just a little overdepth should see little perchy make an indication on your float before he has had a chance to deep hook himself.  Make sure your 'tell-tale' shot is no more than 8 inches from your hook.

It's always sad when a fish dies but the guys are right - it's happened to us all. The best we can do is to try to minimise the chance of this happening. 

It is vitally important to plumb the depth and im surprised it took so long before anyone mentioned it,Phils advise is spot on.

An easy way to plumb up is to use a couple of heavy shot, position your tell tale shot the required distance from the hook,eg no 8  4 inches above hook,then lightly pinch a couple of ssg directly above the no 8, cast in and if your float sinks its set to shallow if it lies flat its to deep, move float up or down accordingly, your float should be undershotted during this processs eg 3bb float locked with 2bb add the final bb after depth is found.

This method causes a lot less disturbance to your swim than using a heavy plummet,and you can tie a hook on after youve plumbed up if you leave enough line below your telltale shot, this means once you find the depth at the distance you intend to fish you can overcast and find depth changes/features without snagging your hook up, i dont think i even own a plummet anymore, hope you can understand this, in practise its very easy.  steve