'Salar the salmon ' , a novel written by the great naturalist Henry Williamson, is one of my favourite books and I recommend it to readers.

Atlantic salmon have been swimming up our rivers for some weeks, intent on arriving at the shallow upper reaches where they will spawn from November until February.

But the aptly named 'king of fish' is in trouble for a number of reasons with only a very small proportion of those hatched returning safely to breed years later, compared with many more a decade or so ago. Furthermore, any that do make it are much smaller than those in the past.

One factor concerning their decline involves overfishing with commercial trawlers hoovering up  vast quantities of small fish and sand eels on which salmon feed in the north Atlantic. The catch is then processed into fishmeal for use in fish farms. Those farms, with hundreds  of caged salmon swimming in close contact with one another create food waste and pollution surrounding the farms and can also pass on disease and sea lice when escaping and coming onto contact with wild salmon in the river estuaries as they travel upstream.

Other problems involve climate change causing prey fish to move northwards; illegal  poaching; netting in the estuaries and at sea; damming of rivers for hydroelectric schemes preventing salmon moving upstream to spawn.

Problems enough for our declining 'king of fish' to cope with.