Up close and personal with pike on canal

I HAVE spent several days this autumn travelling on the Grand Canal in my boat.

In some stretches where the canal cuts through peat bogs the water is quite opaque. But in others it’s as clear as bottled water and on certain days when the sun is at the right angle, and there is no breeze, a remarkable thing happens.

You can look over the side of the boat and the whole underwater world is revealed as clearly as if you were floating over a giant aquarium.

I find this fascinating, but it’s also slightly dangerous if I happen to be steering the boat at the same time, because I tend to get engrossed by what I’m seeing and this can result in a minor shipwreck.

Watching fish is one of the main attractions, trying to guess what species they are, which is often difficult when you’re looking at them from above. Telling a roach from a rudd is almost impossible under these circumstances, but perch are quite easy to distinguish. When it comes to larger fish I can now tell bream from tench most of the time and eels, of course, are easy — though there aren’t as many of them as there used to be.

The other unmistakable species is the pike. Their long, streamlined shape and alligator jaws are impossible to confuse with any other Irish freshwater fish. The big ones tend to shoot off before the boat arrives, leaving a big boil in the water. But the smaller ones hide in the marginal weeds and then the water displaced by the boat sweeps the weeds away and leaves them on show.

There are two reasons why smaller pike hide in the weeds along the edge of the canal. The first is that they are ambush hunters. Excellently camouflaged they have the ability to hide in a weed-bed, motionless, apart from the occasional twitch of a couple of fin rays to keep them in position. Then, when prey appears within range, they can accelerate with blinding speed from a standing start and grab it in alligator jaws.

They can sense the impending arrival of the prey, even in cloudy water, by using a series of specially modified scales along their flanks and around the head called the lateral line. This registers the slight turbulence created by something swimming towards it.

This prey is normally another fish which is grabbed across the middle of the body, squeezed between rows of large teeth to subdue it and then turned and swallowed head first. But small pike also eat a lot of water insects and other invertebrates and larger ones will occasionally eat frogs, rats or water birds. I know of a case where a very large pike took and swallowed a cygnet.

And there is a second reason why those small pike were hiding in weed-beds. Pike are cannibals. They were trying to avoid being eaten by the larger pike. These may well be their mothers or their sisters because all large pike are females. It is very unusual for a male pike to exceed 4 kilos in weight, whereas females can reach 20 or even 25 kilos.

This fact makes mating a very dangerous business for males. Usually several follow the female from behind. They have to get to close quarters to fertilise eggs and typically they have to do this several times. Often one of them is rewarded for his attentions by being eaten.

Mating occurs in shallow water in spring when the water temperature gets to be around 8 or 9 degrees. Pike can reach 30 years of age, though five to 15 is more normal.

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