Learn French: J'ai beau utiliser cette canne à pêche, le poisson ne mord pas. - I use this fishing rod in vain, the fish are not biting.

The expression avoir beau is always conjugated (here as J'ai beau) and followed directly by an infinitive verb (here, utiliser). It means doing an action without getting the desired result. You can translate it as doing something in vain, or by saying no matter how much I use this fishing rod, the fish are not biting.

Why do we use à in cette canne à pêche instead of de?

The preposition à is often used in French to describe an object's purpose or what it is designed for. A canne (rod or cane) designed for pêche (fishing) becomes une canne à pêche. You also see this in everyday words like une brosse à dents (a toothbrush) or un verre à vin (a wine glass).

The English translation says the fish are not biting (plural). Why is le poisson singular here?

When talking about catching fish in general, French uses the singular le poisson to refer to them as a collective group or resource. You are not talking about one specific fish, but rather the fish in the water as a whole.

Does the verb mordre only apply to fishing?