22 August: Salmon

In the French Revolutionary Calendar, today was the day of the Salmon. Here are a few things you might not know about these fish:

1. The name salmon comes from the Latin word salmo or salire, meaning “to leap”.
2. Most people know salmon are born in fresh water, migrate to the sea to spend most of their adult lives, and then return to the river to spawn. There is a word for fish which do this - anadromous.
3. Salmon have an excellent sense of smell, better than that of a Dog. Scientists believe they use this sense to find their way back to the spawning grounds by following an olfactory trail. Ocean currents, tides and the gravitational pull of the Moon also help them navigate.
4. We don't know how many salmon there are in the world, because their wide range of habitats makes it impossible to count them. Scientists have observed that numbers of salmon making their way up the Colorado river have declined over the years.
5. The female salmon makes a depression in the riverbed with her tail in which to lay her eggs. When the eggs have been fertilised, she covers them up. She may lay up to 7,000 eggs in up to seven depressions. There is a name for these nests of salmon eggs - a redd.
6. Newly hatched salmon are called alevins. They live under rocks and absorb nutrients from their attached yolk sac until they grow into "smoult". After a year or so, they will follow the river to the sea. Before they can enter the ocean they have to adjust to life in salt water, a chemical process called "smoulting". When they return to spawn, they have to spend some time in the same spot to readjust to living in fresh water.
7. Salmon can travel up to 3500 miles to spawn. On the way, they will have to negotiate obstacles like waterfalls which can be as high as four metres. They may have to make several attempts to get over these.
8. Salmon do not eat while travelling upstream, but use reserves of body fat for energy. Many of them die after spawning, although if they do survive they can spawn two or three more times. An exception is the Kokanee salmon which do not make the trip at all - they stay in rivers and lakes their whole lives.
9. The largest salmon on record caught by fishing rod in the UK was caught on the River Tay by Georgina Ballantyne and weighed 64lb.
10. There is an Irish legend called Finn and the Salmon of Knowledge. It concerns a salmon which lived in the water under the tree of knowledge - a hazel tree in this story - and ate the nuts which fell from the tree thus gaining all the wisdom of the universe. It was said that whichever human ate the salmon would gain the knowledge, too. Naturally, many tried and failed to catch it, until a poet named Finnegas having spent seven years fishing the Boyne caught it. Finnegas asked his apprentice to prepare and cook the fish, with strict instructions not to eat a single morsel of it. The lad obeyed, but then he burned his thumb on the cooking fire and did what anyone would do - put his thumb in his mouth to ease the pain and thus acquired all the knowledge of the universe. Finnegas could see something different about his apprentice and asked if he'd eaten the fish. The boy swore he hadn't, but had to admit to his accident. The boy was Finn MacCumhaill, who, thanks to the wisdom of the salmon, grew up to become leader of the Fianna, the famed heroes of Irish myth.