Fishing for uncatchable fish is all part of the game. There are some fish you remember simply because you failed to catch them and the memory never dims.

Circa 1974 I tried every trick in my book to catch an enormous trout from North Elmham mill pool. It was the size of a decent leopard and it never fell for my flies, lures, worms, sticklebacks, gudgeon, bullhead, loach or dead frogs.

We fished in less caring times then, of course, and the only bait that nearly deceived it was a dead mouse twitched back across the surface of the pool.

The fish came at it gills flaring, but its eyes were as big as globes and it saw something wrong, backed off and that was the end of that.

Mullet, those that live wild in the creeks, have always stumped me, as they have everyone else I know.

I've fished and failed with sea bass in the crystal waters around Blakeney Point until I've wanted to throw myself in.

And as for crucian carp, well I could catch them in the 70s and even the 80s, but I've lost the knack now. Or not quite. After three sessions of trying I finally got one on Sunday from a tiny mere-like pool the size of a tennis court. I've done all the checks and it is a true crucian with not a hint of hybrid so I don't give a hoot it was three ounces not three pounds. I got one and that was all that mattered. Yes, I've become that desperate.

This time of the season my favourite fish has to be the tench and they are the biggest conundrum of them all. I have access to some 15 tench waters and I rate them 1 to 10, 1 being gobsmackingly easy and 10 simply impossible. I'm very precise about my ratings. They are based on number of tench caught per rod hour, but methods and weather conditions are also scrupulously taken into account. You'd think I would know why one water is a 4, for example and another is an 8, but I don't. Even seemingly obvious factors like numbers of, size of lake and amount of natural food don't always make the sort of sense you'd think they would.

I've only ever had one venue rated 1. That lake held swarms of tench a few inches long that in 30 years never even made a pound.

Fishing was an annihilation, a perfect pond for a seven-year-old. Sadly, the whole lot of these little beauties was consumed by a cormorant plague a couple of winters back. They have never returned. It was one of the unremarked tragedies these voracious birds visit upon us with sickening regularity.

I've never had a 10, but blooming nearly. You can't call Lost Lake impossible because we have had very, very rare fish from there, but a bite is a momentous event.

It has to come in at a head scratching 9.9, but why? There are loads of fish there - you can see them in the crystal water in their droves. They are obviously drawn down on the bait in a trice and they bubble till the water is turned to foam. Float? Feeder? Method feeder? Big hooks, small hooks? Line as light as you can get away with? Boilies of any sort? Pellets the same? Corn and maggots both real and plastic? Lobs and red worms and anything that wriggles? Bloodworm even and caddis grubs? Dawn, dusk and daytime? Nothing seems to make an iota of difference. I've seen Professors of Tench Studies go away broken men and women. If any reader thinks they can crack this terror of tench waters, then you know you can get in touch through this paper or by looking at my website. If I think your idea can crack this piscatorial puzzle, I'll not only give you a session but I'll come and pick you up into the bargain.

It is now agonisingly close to the opening of the river season and I'm already in a lather of excitement. I know, though, that if the rivers run low and clear there will be chub impossible to fool. There will be barbel impossible to locate because they are rare as tench teeth and because they make ghosts look OTT extrovert. If you find a decent river roach, you'll wave your rod at it and it will be in the next parish before the bait hits the water. But isn't that how it should be? We all groan at the cliche it is fishing, not catching but there is a dollop of common sense and wisdom in it. Imagine a fishing world with no challenges, waters where fish flocked in a queue for the net. Wouldn't it be like hell to catch the same species and same size of fish one sickening cast after another? Or at least that's what I tell myself at Lost Lake when the tench are cackling with glee at our failure.