Traditionally, fishing for pike has pretty much always been a winter pursuit. In general terms, the pike ‘season' begins 1 October and runs until the close of the river coarse fishing season on 14 March.
Why the tradition?
The reason for this traditional pike ‘season' is perhaps lost in the annals of time. Maybe it's just that other fish species become harder to catch so historically people used to divert their attention to pike? It could be down to a view that pike do not respond well to being caught in the warmer months suffering from a build up of lactic acid after a titanic struggle. Or perhaps there are more selfish reasons at play ie. it's the lure of catching a pike when they are at their fattest and heaviest prior to spawning in the spring? After all, a big female pike may weigh 5 or 6lb more due to the weight of spawn.
Seasons and locations
There are of course lots of casual pike anglers who target the species at all times of the year. The current popularity of lure fishing has also meant pike see an anglers bait throughout the year. Personally, I would suggest the die-hard pike angling enthusiast ought to consider a self-enforced closed season for pike fishing. In other words, only fishing for them in the autumn/winter period.
Pike and oxygen
It is true that pike do suffer when oxygen levels are low, which they often are in the heat of summer. In fisheries which suffer from low dissolved oxygen it is usually the pike that will show signs of distress first, even in some cases being the only fish to succumb.
Of course, there are many varied fisheries all over the country and they will have different environmental factors influencing them. A shallow, non-navigable canal will heat up quickly in the summer compared to a commercial freight waterway in the north of the country. The weir pool of a large lowland river will be highly oxygenated and have cooler water than a shallow pond or lake.
Bite indication and handling
In the warmer months a fish's metabolism speeds up. They are also quicker to pick up and swallow baits. For this reason, any angler bait fishing needs to be on the ball. Accurate bite indication is a must and any take should be struck at immediately. If a take is not actioned instantly deep hooking is likely. This is not good for a pike at any time and is especially dangerous in high temperatures as this will put further stress on the fish.