It has been claimed that owning salmon fishing is twice as expensive as keeping a mistress, and just as frustrating. I make no comment, but the pursuit of this deeply desirable fish for sporting and culinary purposes has certainly spawned a vast literature, much of it outlandish or brimful with mumbo-Macjumbo. As well as rod and line, the salmon has had to run the gauntlet of spears, nets, poison and various ‘fixed engines’, and these days faces further threats from habitat degradation, global warming, and infections from fish farms. And yet the silver tourist survives, not quite an endangered species but certainly in fragile populations.

Admirers of his bestselling memoir The Longshoreman will know that fisheries scientist Dick Shelton is no slouch with his pen. Here he writes of the mysterious creature whose anadromous lifestyle (which begins and ends in fresh water, but has a crucial and still mysterious marine phase) has made